More 2.5 STI short block info...

here is a link to more info
http://www.i-speed.us/news/sti_block.shtml?s=3f201451459effff;act=ST;f=12;t=1 15

More Pics: http://www.i-speed.us/news/sti_parts.shtml

Also, we do not know if people are telling you this, but we have been told be several Subaru Reps and Subaru dealers that the 2.5 STI short block will ONLY work with the 2.5 STi heads. Well, that's not entirely true.
With the help of our engine builder, Crawford Performance, we can now get the new 2.5 STI block to work with USDM WRX heads! We keep the 2.5 STi turbo crank and rods and use special forged Crawford pistons. These Crawford pistons keep the proper compression ratios that the wrx heads need to operate effectively. Without specially designed pistons in place of the STI pistons…the 2.5 STI block will not work with the wrx heads.

http://www.I-club.com/forums/attachment.php?s=&postid=225896

Now, it's time to put that R/D on the street and then the DYNO:)

Chris
i-speedusa.com
cescamilla@i-speedusa.com

Link isn't working.

Just out of morbid curiosity can you confirm that the picture above is your custom piston setup installed in a 2.5L sti block?

Those pistons look like they have quite a bit of dish in the picture (could just be picture quality). Do they have more or less dish than the standard UDSM pistons?

Any chance you are willing to reveal dish volume?

correct link (http://www.i-speed.us/news/sti_block.shtml?s=3f201451459effff;act=ST;f=12;t=1 15)

nmyeti - yes it is our custom setup (2.5 STI block with Crawford custom pistons).
Yes, there is quite a bit of dish when compared to the stock STI pistons. And yes, we know the picture is not the greatest.
Sorry, not ready to divulge dish volume.


Chris
i-speedusa.com
cescamilla@i-speedusa.com

the 2.5 block will also work with the JDM STi heads as well btw :)

Could you clarify the "stockUSDM wrx heads won't work" statement.

Do you mean that with the stock heads and no change in piston you have excessive compression, or you get valve to piston interference or both.


Do your custom pistons return the engine to the stock (for the 2.5 STi) compression ratio, or did you choose a slightly different compression ratio to make the heads work?

Thanks for the info and pic's!!

Larry

Larry - Yes keeping the stock STI pistons with the USDM heads will get you "excessive compression". We also noted that you may have "valve to piston interference".
BTW: We did not test the interference theory. But other people are more than welcome to try it:)

"Do your custom pistons return the engine to the stock (for the 2.5 STi) compression ratio, or did you choose a slightly different compression ratio to make the heads work?"
We chose a different ratio

Chris
I-Speed USA
cescamilla@i-speedusa.com

So how much of an overbore is possible with this block? looks to be much more capible of mega displacement than the normal STi EJ20 block.

Originally posted by XT6Wagon
So how much of an overbore is possible with this block? looks to be much more capible of mega displacement than the normal STi EJ20 block.


how much more do you need? I speed already has a 2.8...:confused:

Can't wait for testing results

i thought the 2.5 STI blocks were closed deck? cuz it seems to me that, that looks open deck

or am i wrong in the defintion of what a closed deck is?

-thanks

Originally posted by BoostedAWD
i thought the 2.5 STI blocks were closed deck? cuz it seems to me that, that looks open deck

or am i wrong in the defintion of what a closed deck is?

-thanks

The new age sti blocks ej207/257 are not closed decks... they are reinforced decks. The older blocks ej20g,k? and the ej22t are semi closed decks. There are no closed decks from the factory

Originally posted by BoostedAWD
i thought the 2.5 STI blocks were closed deck? cuz it seems to me that, that looks open deck

or am i wrong in the defintion of what a closed deck is?

-thanks

The 2.5 STi block is "semi-closed".

http://www.uploadit.org/files/200803-sti%20forged%20pistons%202.JPG

thanks for the info.

Where can I get a set of those pistons? I need sety for a block I have sitting here.

Are normal people now able to get ej257 shortblocks through normal channels?

Let me say that i have personally dealt with Crawford Peformance and all i can say is that he knows alot. He knows his stuff. He also has been messing with subarus for years and lives and breathes motors. Anything from Crawford gets two thumbs up from me.

Nice! Time for me to start saving my duckets.

Not sure why you would want to waste your time running crap usdm wrx heads on a 2.5L block, unless you want a (small) stump puller that falls on its face at high rpm. If you want to do it, do it right the first time.

I'm not trying to run 9's like Nick is... I'd be really happy sticking the new forrester engine in my car :)

Whatever is cheaper, cuz I'm poor :(

I guess I could just get a 2.5 sticker.

“Where can I get a set of those pistons? I need sety for a block I have sitting here.”
We would need to know exactly (compression, material, size etc…) what you are looking for and the application you would be using them for. That would help us to help you better. Email me for details.

“Are normal people now able to get ej257 shortblocks through normal channels?”
I have no idea. Crawfords' Subaru connections run fairly deep. To be honest we all were surprised when we got what we asked for.

“Not sure why you would want to waste your time running crap usdm wrx heads on a 2.5L block, unless you want a (small) stump puller that falls on its face at high rpm. If you want to do it, do it right the first time.”
True the WRX heads may not be completely up to the 2.5 STi short block potential. However, getting the 2.5 STi short block to work with heads that most people seem to have is what we were after. In any case, this option now provides new avenues for people to mod their WRX. Where those people go from there is up to them and most often… their pocket book.

Chris
I-Speed USA
cescamilla@i-speedusa.com

Woops...forgot to answer this one

" So how much of an overbore is possible with this block? "
The overbore capability is 1mm. But in fact the overall thickness of the liner and casting is less than the 2.0.

Chris
I-Speed USA
cescamilla@i-speedusa.com

Well its just that some people seem to bore the EJ20 block out for 100mm pistons.... and since the inner AND outer diamiter of the "liners" is bigger in radius I figured that it could take a decent ammount of extra bore size.

I dont want to turn this thread into a bitch fest as I think there could be useful information gained from it but...

... the pocket book argument is ****ing weak when it comes to building a proper 2.5L stroker. If you are in the market for something like this, please do yourself a favor and atleast get cams to stand up to the task at hand.

I can't even afford brake pads, let alone cams right now. :banana:

Originally posted by I am mattjk
I'm not trying to run 9's like Nick is... I'd be really happy sticking the new forrester engine in my car :)

Whatever is cheaper, cuz I'm poor :(

I guess I could just get a 2.5 sticker.

from what ive been told the new forrester has the sti heads working avcs without the cams....;)

so....

So is your goal to simply provide information on the caveats of using a replacement USDM STi shortblock, to provide a piston package to enable the use of the USDM STi shortblock, or to sell a direct replacement USDM STi shortblock for those needing a slightly better shortblock to replace their broken one with?

Also, can you quantify the "excessive compression"?

There may not be much room to bore out more than 1mm, however when you are talking about a diameter that is already slightly larger, an increase in 1mm could be significantly larger than that of the EJ20. For example, boring out the EJ20 by 1mm increases displacement from 1994 cm^3 to 2082 cm^3 for a net increase of 88 cm^3. Boring out an EJ20 by 1mm increases displacement from 2457 cm^3 to 2557 cm^3 for a net increase of 100 cm^3.

-Jon

The 2.5 blocks themselves are cheap imho. You can get them for $1300-1400 from many dealers and they are starting to get them in. I have the block and a set of STI RA heads that I plan on using with the block and that will hopefully maintain the 8.2:1 compression ratio. I posed a question about that a few weeks ago and was told the US STi heads are the same as the JDM ones.

Then why wouldn't using the wrx heads on this engine flat out not work? I KNOW you can use wrx heads on an STi engine. And STi heads on an WRX engine (I've seen both). So why can't you use US wrx heads on this engine without doing this?

Somethings not making sense.

Originally posted by totoherbs
from what ive been told the new forrester has the sti heads working avcs without the cams....;)
Ummm... W T H does that mean?

I guess he means AVCS is working, without the STI cams... just standard duration.

Which makes sense the turbo forester falls on its face at about 5500rpm.

(HEY! I Just made specialist! After 8 engine swaps, 3 complete rebuilds, and unknown man weeks working on these cars, FINALLY Nasioc promotes me! LOL!)

Originally posted by DarthChicken
Which makes sense the turbo forester falls on its face at about 5500rpm.

:lol: :lol: i almost tossed my lunch i thought that was so funny:lol: :lol: ...maybe my day is super slow?

Originally posted by DarthChicken
(HEY! I Just made specialist! After 8 engine swaps, 3 complete rebuilds, and unknown man weeks working on these cars, FINALLY Nasioc promotes me! LOL!) Sponaugle is still a newbie, right? :lol:

Originally posted by Austin
Sponaugle is still a newbie, right? :lol:

Total n00b :lol:

-Jon

Wheeler - I live to serve :D

Coming from the land of high compression and boost (AFI), and knowing that the DOHC heads have smaller combustion chambers then the SOHC heads, I am really curious what your definition of what "excessive compression" is. The pistons that are on your page scream about 9.4-9.5:1 to me.

stimpy - "So is your goal to simply provide information on the caveats of using a replacement USDM STi shortblock, to provide a piston package to enable the use of the USDM STi shortblock, or to sell a direct replacement USDM STi shortblock for those needing a slightly better shortblock to replace their broken one with?"
The answer to the first three questions would be yes.

"Also, can you quantify the "excessive compression"?"
Excessive compression, per Crawford Performance, would be 10% higher than stock.

"There may not be much room to bore out more than 1mm, however when you are talking about a diameter that is already slightly larger, an increase in 1mm could be significantly larger than that of the EJ20. For example, boring out the EJ20 by 1mm increases displacement from 1994 cm^3 to 2082 cm^3 for a net increase of 88 cm^3. Boring out an EJ20 by 1mm increases displacement from 2457 cm^3 to 2557 cm^3 for a net increase of 100 cm^3."

Lastly, the comment on increasing the bore on the 2.5 by 1mm would increase the displacement from 2457 to 2557. Well, that didn't sound right. So we did some math.
a 99.5mm bore = 2457cc
a 100mm bore = 2482 cc
a 101mm bore = 2532cc
a 1mm increase = 50cc not 100cc

Chris
I-Speed USA
cescamilla@i-speedusa.com

Originally posted by I-Speed USA


"Also, can you quantify the "excessive compression"?"
Excessive compression, per Crawford Performance, would be 10% higher than stock.


Chris
I-Speed USA
cescamilla@i-speedusa.com

If that is excessive, wait till you see what I've gone and done.


-Nathan

12:1 is excessive to me. i wanted 10:1 with my set up but i decided to go with 9:1. 10% is nothing. good tuning, good gas, and a good set up makes good power. nothing wrong with 10:1 or less.

Originally posted by Austin
Ummm... W T H does that mean?

well mostly it was aimed at matt... just making sure he knows that slaping his heads on a 2.5 block will not make a forester motor.

I havent driven a forester yet... Does it it realy fall on its face at 5500? I know an the usdm sti head needs longer deration cams. ;)

so %10 more then...? I dont know the usdm sti C/R. But if crawford says its a bad idea I would be inclined to argee.

Here are some more pictures :)
http://www.i-speed.us/news/sti_parts.shtml

nmyeti - We are always interested in seeing what everyone else is up to.

Chris
I-Speed USA
cescamilla@i-speedusa.com

Originally posted by totoherbs


well mostly it was aimed at matt... just making sure he knows that slaping his heads on a 2.5 block will not make a forester motor.


Oh come on now... I didn't just come from the Ford Tempo Forums... :lol:

I'm perfectly happy with how my car is running right now. :)

Originally posted by I-Speed USA
"Also, can you quantify the "excessive compression"?"
Excessive compression, per Crawford Performance, would be 10% higher than stock.


Compression Ratio
Alright boys, let's get out of the speculation, and into the real technical discussion. I have a brand new US STI 2.5 block sitting here in front of me.

My first pass measurement, justa quick slap of the tool, shows the deck clearance is about .013" (.3mm), and the piston dish PLUS deck clearance volume is around 34-36ccs.

Just a quick shot of the math would show the following:

If the STI 2.5 Gasket is .8mm think (that is what the WRX one is), that gives you about 6.2cc of volume in the head gasket space.

The stock WRX heads have about 49cc of volume.

Total compressed volume would be 49+6.2+35 = 90.2ccs.
Total Swept volume is 614.28ccs.

Compression Ratio would be (614.28 + 90.2) / 90.2, which is
7.8:1.

I'm puzzeled about the higher compression comments? Can you clarify, or perhaps correct my measurements? I need to go back to really confirm these numbers, as the CC measurements were just a quick squirt of oil over a flat plate. It could be off by a lot.

Quench

The piston deck clearance is about .013", which is very close to the stock WRX at ~.015". Depending on the STI 2.5 gaskets, the quench depth should be very similiar.

Valve Interference

Not sure about this.. Doesn't look like it would interfere, based on how the JDM STI Pistons compare to the stock US ones. Have you guys seen the JDM STI pistons? The have a different top design, change in pin offset, and change in quench design, and they still clear the stock WRX heads just fine.

I'll post more detailed pictures soon.. However before anyone goes about saying you can/can't do something, we should flush out the technical details. We have the tools, block, etc. I've got STI RA, STI Export, and US WRX heads sitting here to try.

I realize you don't want to say about the piston dish volume, but could you share the math you used to show the compression problem in the first place?

Jeff Sponaugle

Originally posted by Austin
Sponaugle is still a newbie, right? :lol:
Yep. Now if the board only had a rating system of the value, not volume of posts. ;) ;) hahahhaaha

Anyone else have the new 2.5L blocks? Let's get these details worked out! I think this STI block would be a GREAT upgrade for lots of people.

Jeff

Originally posted by I-Speed USA
Lastly, the comment on increasing the bore on the 2.5 by 1mm would increase the displacement from 2457 to 2557. Well, that didn't sound right. So we did some math.
a 99.5mm bore = 2457cc
a 100mm bore = 2482 cc
a 101mm bore = 2532cc
a 1mm increase = 50cc not 100cc


I originally did it with .5mm radius increase for a total of 1mm increase. But then I thought that it could be 2mm total increase or 1mm radius increase (drastic, I guess, but thats just how I interpreted it). There was a little ambiguity about what was increasing by 1mm.

To correct, increasing entire bore by 1mm increases the EJ20 by 44cc and the EJ25 by 50cc.

-Jon

DarthChicken - "Then why wouldn't using the wrx heads on this engine flat out not work? I KNOW you can use wrx heads on an STi engine. And STi heads on an WRX engine (I've seen both). So why can't you use US wrx heads on this engine without doing this?"
You are correct. The swept volume on the 2.5 is greater than on the 2.0. That is why the cylinder head volume is greater on the 2.5 than the 2.0.
You can just bolt it all up (the stock STi Block and the WRX heads) if you don't mind the +10% increase in compression.
Mind you that the swapping of pistons is done to keep the compression lower than stock STi which in turn makes for safe and reliable power when using the USDM WRX heads. That's our main concern for this application...safe and reliable.

Chris
I-Speed USA
cescamilla@i-speedusa.com

I-Speed: Just a note, that the most likly place for error in my measurements is the piston dish (actually since I didn't pull the block apart, I was only able to measure the piston dish PLUS deck clearance volume.) I just did a quick pass with a squirter and a flat piece of plastic, and came up with 34-36ccs of volume total. Obsiously this number makes a big difference to the compression ratio. Since you have the piston pulled out, could you disclose what you measured the piston dish at (for the 2.5L STI)?

I'll spend some time tonight to make some more measurements.

(Also, note that I'm not against you or anyone else making upgrade parts, etc. I think it is great. I prefer to work with vendors who are as open as possible about the techincal details, at least when it comes to providing information about certain combinations not working.)

Thanks,

Jeff Sponaugle

I defer to Sponaugle at this point (even if he is a newbie, LOL)

This is good stuff, keep the information coming on this. I-Speed I think you'll sell a LOT of these if you can clear up some information for us, its just that the math doesn't quite work at this point.

Originally posted by I-Speed USA


nmyeti - We are always interested in seeing what everyone else is up to.

Chris
I-Speed USA
cescamilla@i-speedusa.com

Since you asked

http://www.turboxs.com/_images/flatpiston.JPG

i just keep learnin new stuff on this forum all the time :banana:

Sponagle,

The dish volume is 22cc. And the piston in my block is .015 below the deck.

Now do your math and we will see if I screwed up on mine.

I will return later tonight.

Quirt Crawford
Crawford Performance

Originally posted by Quirt
Sponagle,
The dish volume is 22cc. And the piston in my block is .015 below the deck.
Now do your math and we will see if I screwed up on mine.
I will return later tonight.
Quirt Crawford
Crawford Performance

Yikes! Like I said, the most likly place in error is the measurements I took. If you measured 22ccs of dish volume, and the deck clearance is .015, then that equates to a total dish + deck volume of:

(99.5/2)/^2*PI * 0.38mm /1000 = 2.95ccs deck volume,
which equates to 24.95ccs of total dish + deck.

My quick measurement was 35ccs, which appears to be way off! I'll do another measurement to be sure, but if you are pretty sure about the 22ccs on the stock STI pistons, then the 7.8CR figure will of course be way off!

Let's see how this looks if we use the 22ccs and .015 dc:

WRX Heads: 49ccs
Piston Dish: 22ccs
Deck Vol: 2.95ccs
Gasket Volume: 6.22ccs (assumes .8mm gaskets)
Swept Volume: 614.27ccs

Total Compressed Volume is: 80.17

CR = (Swept + Compressed) / Compressed
CR = 8.66:1

Keep in mind this is the static, not the dynamic compression ratio. For example, the US WRX motor's static compression ratio, based on the same measurements and estimates is about 8.2:1.

This nets approximatly a 5.6% increase in compression ratio. (based on the actual measured figures, not published numbers)

From what I have seen so far, 8.66:1 is well within a tolerable range if you have adaqute engine tuning. The stock JDM WRX (not STI) motor from Japan has the AVCS Heads and 9:1 CR stock.

I can fully understand and appreciate that making custom pistons with greater dish volume to bring the static CR back down to 8:1 or better can be helpful in many environment.

As far as valve interference, I'll have to take some measurements to be sure. I would guess it to be just fine based on looking at the location of the valve cuts, but I could be wrong. Really the best way would be to compare WRX/JDM STI heads to those of the US STI 2.5 heads. Anyone care to take the heads off their new STI?

But seriously, I don't mean to take over your thread, or make negative remarks about your products and your progress. I'm glad to see a vendor doing such R&D, and helping to get the ball rolling on the WRX 2.5 conversions.

Let's keep this conversation going and correcting itself. If it turns out that the 2.5 gaskets are a different thickness, or that the valves interfere, lets get that information out!

Thanks again for posting about your piston dish measurements and deck clearance.

Jeff Sponaugle

deck clearance volume = 2.96cc
dish volume = 22cc
.8mm gasket volume = 6.22cc
Total swept volume = 614.28cc

assuming that Jeff Sponaugle's information is right .....

US WRX heads volume = 49cc


then CR is:

(614.28 + (2.96 + 22 + 6.22 + 49)) / (2.96 + 22 + 6.22 + 49) = 8.66:1

and BTW the stock CR of the US 2.5 STi is 8.2:1, so that would be and increase of 5%.

EJ20K

Originally posted by EJ20K
deck clearance volume = 2.96cc
dish volume = 22cc
.8mm gasket volume = 6.22cc
Total swept volume = 614.28cc

assuming that Jeff Sponaugle's information is right .....

US WRX heads volume = 49cc


then CR is:

(614.28 + (2.96 + 22 + 6.22 + 49)) / (2.96 + 22 + 6.22 + 49) = 8.66:1

and BTW the stock CR of the US 2.5 STi is 8.2:1, so that would be and increase of 5%.

EJ20K

Like two ships in the night, with equal math! ;)
I didn't realize that Subaru specified that the stock STI is 8.2:1 CR. As I mentioned, the regular WRX comes in at 8.2:1 using the same measurements, etc. The Head volume at 49ccs comes from several places, including both my own and Cobb's measurements.

Jeff

http://alan.net/austin/Subaru/imp04spec.jpg

From the MY04 Impreza manuals.

Wow, that 8.66:1 compression ratio and the standard WRX heads would make an awesome auto-x/street motor - should be really peppy. This will be perfect if you were targeting to make only 300-325 whp (limited by the heads), perfect for the average stage 4+ car that needs a new shortblock. As long as you're not trying to make huge power, I don't see how the WRX heads would be any worse than they would be on a 2.0.

Kevin

Originally posted by totoherbs



how much more do you need? I speed already has a 2.8...:confused:

The 2.8 I saw.. are the bores siamesed? Any comments about cooling or hotspots with this particular setup?

Second.. I would love a 2.5 with the best (JDM STI?) heads and cams (JDM STI or JUN?). I would want a 8:1 CR. I am willing to live with a little lag and take up the slack with the turbo..

But, alas, I cannot contenance paying 10K for a motor before it is dropped in.. much less all the other stuff necessary to take proper advantage of this setup.. I figure at least 20k to do it all right. I think for me, the price point is 10k to the low teens for a complete engine, turbo, fueling, engine management, IC, exhaust setup. Basically this is putting another 10 to 12k in a 22k car. Perhaps too much to hope for but if the Subie boxer could become as common as the chevy v8........

Originally posted by tolnep




Second.. I would love a 2.5 with the best (JDM STI?) heads and cams (JDM STI or JUN?). I would want a 8:1 CR. I am willing to live with a little lag and take up the slack with the turbo..


Sometimes a little extra compression can actually help prevent detonation and you might want to make sure the 2.5L pistons mirror the combustion chamber found in the 2.0L STI as closely as possible.

When properly built, higher compression is only going to help you. Look at the EVO. We can run 23psi on 93 octane pump gas without detonation. The Evo is 8.8:1. It's all about combustion chamber design.

I am surprised no one has commented on my "excessive compression" pistons above ;)

Originally posted by nmyeti


Sometimes a little extra compression can actually help prevent detonation and you might want to make sure the 2.5L pistons mirror the combustion chamber found in the 2.0L STI as closely as possible.

When properly built, higher compression is only going to help you. Look at the EVO. We can run 23psi on 93 octane pump gas without detonation. The Evo is 8.8:1. It's all about combustion chamber design.

I am surprised no one has commented on my "excessive compression" pistons above ;)

Yes. I have a sportbike Y2k Yzf-r1 and I think it runs a fairly high CR as do most Japanese sport bikes. Is my understanding it is because the combustion chambers are optimized and small. Seems like I have heard that the smaller the head area, the less likely the detonation.

As to the CR, is just my experience. I had a built 240z with a custom built 280z turbo and I specified 8:1 CR which had some lag but ran pretty well. You can always add boost. To reduce CR you have to machine something(s). Also when I had this car, tuning was fairly primitive (butt tuning with someone who had broken a few motors before he got it right). Access to a dyno and someone with experience with your chosen setup (who you have confidence in) can make all the difference in the world in what you end up with.

Guys,

When I design a stock "type" replacement motor, I shoot for the original specks so it will work the best for most people.

When a customer asks for a "custom" setup the only problem that creates is a longer delivery time.

My personal car has a 2.8L with 9.4 to one compression and I run 24 LBS of boost. At times it is a real pain in the but.

If you want a special setup, just let us know the specs your looking for.

Quirt Crawford
Crawford Performance

Originally posted by nmyeti


Sometimes a little extra compression can actually help prevent detonation and you might want to make sure the 2.5L pistons mirror the combustion chamber found in the 2.0L STI as closely as possible.

When properly built, higher compression is only going to help you. Look at the EVO. We can run 23psi on 93 octane pump gas without detonation. The Evo is 8.8:1. It's all about combustion chamber design.

I am surprised no one has commented on my "excessive compression" pistons above ;)

Since you asked those pistons are sick. That looks to be 10:1 if I can see correctly.

Originally posted by nmyeti


Since you asked

http://www.turboxs.com/_images/flatpiston.JPG



:confused: :devil: nuts

So bolting up the 2.5 block to some RA heads would likely leave me with the same 8.6:1 CR? Since sponaugle's earlier post about block/head combinations showed the head volume the same between the STI motor and the US WRX ones. I think that coupled with a nice turbo would make a perfect autox motor, which is what I'm building the car for. I may be looking at going with a HKS 2835R turbo with this setup...

So does that mean the heads on the US WRX are different or maybe the 8.2:1 CR is similar to the way they state the US WRX as 8:1 and sponaugle's calculations show 8.24:1?

Originally posted by nmyeti


Sometimes a little extra compression can actually help prevent detonation and you might want to make sure the 2.5L pistons mirror the combustion chamber found in the 2.0L STI as closely as possible.

When properly built, higher compression is only going to help you. Look at the EVO. We can run 23psi on 93 octane pump gas without detonation. The Evo is 8.8:1. It's all about combustion chamber design.

I am surprised no one has commented on my "excessive compression" pistons above ;)

The 2.5STi piston doesn't look that bad .....

http://www.i-speed.us/images/sti_engine/sti-piston-ok_small.jpg

EJ20K

Not to derail this, but... it also does't look forged. Did anybody ever settle whether they are forged or cast?

Originally posted by nmyeti


Since you asked

http://www.turboxs.com/_images/flatpiston.JPG

Is that the finished product? Wouldn't softing the hard edges on the valve reliefs prevent a source of detonation?

Originally posted by EJ20K


The 2.5STi piston doesn't look that bad .....

http://www.i-speed.us/images/sti_engine/sti-piston-ok_small.jpg

EJ20K

The stock STI piston is "very" nice part.

Quirt Crawford
Crawford Performance

Originally posted by Quirt


The stock STI piston is "very" nice part.

Quirt Crawford
Crawford Performance

Then how about utilizing the stock pistons, and using slightly shorter rods to lower the compression?

why would u do that ?

You could always go for a thicker head gasket, like a 1.6mm one ..... and it is much cheaper too.

But if you really want to give some "xtra" strength to the engine I would ideally only replace the rods for stronger units.

EJ20K

The main reason would be the change to the squish area which would be negative to performance.

Another reason would be the rod ratio change which would enhance the bottom end and take away from the top end.

And last, pistons cost less than good rods.

Quirt Crawford
Crawford Performance

Originally posted by EJ20K
why would u do that ?

You could always go for a thicker head gasket, like a 1.6mm one ..... and it is much cheaper too.

But if you really want to give some "xtra" strength to the engine I would ideally only replace the rods for stronger units.

EJ20K

Well, if you went that thick of a gasket, you'd widen the engine a bit. That would affect the mounting of the manifold, posistion of the cam gears thus slightly altering cam timings, etc.

In theory, The shorter the rod ratio the is the more of a tractor motor it will be.

Also, the rod ratio is allready shorter in the 2.5 STI than the 2.5 n/a.

Quirt Crawford
Crawford Performance

So if what we were looking for was the simplest (and cheapest) way to end up with a WRX with better bottom-end might be getting shorter rods and a STi/Forester XT short block?

Assuming the goals are a reliable sub-to-near 300hp and to end up with a car whose mods are completely transparent (ie uses stock (reflash okay) ecu and keeps emissions equipment)?

Or would we still need something else?

You would probably be ok just bolting things right up. The STI pistons are not forged, they are hyperutectic, just like the V8 STI motors everywhere. It's in the JDM V8 literature.

Originally posted by dwx
So bolting up the 2.5 block to some RA heads would likely leave me with the same 8.6:1 CR? Since sponaugle's earlier post about block/head combinations showed the head volume the same between the STI motor and the US WRX ones. I think that coupled with a nice turbo would make a perfect autox motor, which is what I'm building the car for. I may be looking at going with a HKS 2835R turbo with this setup...

So does that mean the heads on the US WRX are different or maybe the 8.2:1 CR is similar to the way they state the US WRX as 8:1 and sponaugle's calculations show 8.24:1?

As for the STI heads, you are correct. I am just about to bolt up a set of V7 STI RA heads to the 2.5 block. As for the US WRX compression numbers, I believe it is just a difference between static and dynamic compression. Keep in mind while the JDM STI heads and WRX Heads are the same volume, the piston dish and deck clearance is different by a small amount.
Jeff

Originally posted by Quirt
In theory, The shorter the rod ratio the is the more of a tractor motor it will be.

Also, the rod ratio is allready shorter in the 2.5 STI than the 2.5 n/a.

Quirt Crawford
Crawford Performance

Quirt: You mentioned that the rods are a bit short? Could you post the measurement? I would save me from having to crack my block open! Thanks!!!
Jeff

Originally posted by dwx
You would probably be ok just bolting things right up. The STI pistons are not forged, they are hyperutectic, just like the V8 STI motors everywhere. It's in the JDM V8 literature.

Do we have any confirmation on this? Several US STI documents state the US STI 2.5 has forged pistons. The JDM V8 STI uses the hyperutectic, but I have not been convinced on the US STI.

Quirt can probably comment best since he has the pistons taken out. Do they look forged? Can you see the cast lines or are then flattened (typical of forged pistons)?

Jeff

The AVCS heads that I have here have a 1.4cc larger combustion chamber than the US 2.0 WRX head.

The rod in the STI is .0435 shorter than the 2.5 n/a rod.

The piston has the apperance of being forged but that is as far as I will go.

Quirt Crawford
Crawford Performance

Originally posted by cjm04WRX


Since you asked those pistons are sick. That looks to be 10:1 if I can see correctly.

Just under 9:1

The flat tops should help us quite a bit. In fact I’d be willing to bet a good deal of money that it will outperform a stock 8:1 compression WRX on pump gas.

The compression is only part of the story with that motor though; I’ll let my builder talk about the rest when he is ready.

-Nathan

Originally posted by Quirt
The AVCS heads that I have here have a 1.4cc larger combustion chamber than the US 2.0 WRX head.
The rod in the STI is .0435 shorter than the 2.5 n/a rod.
The piston has the apperance of being forged but that is as far as I will go.
Quirt Crawford
Crawford Performance

Thank you Quirt for the information!. I can believe that the AVCS STI JDM heads may have slightly more volume, as my measurement technique wasn't the greatest.

Hmm. So the rods are 131.19 - 1.1049mm = 130.0851mm.
(Assuming I have the 2.5NA rod lenght right. This is from the JE web site)

The WRX Rods are 130.43 RS Ratio 1.74.
The JDM STI Rods are 130.43 RS Ratio 1.74.
The 2.5 NA Rods are 131.19. RS Ratio 1.66.
The 2.5 STI Rods are 130.0851mm. RS Ratio:1.65

As a side note, if I have the 2.5na rod length right, and the deck clearance is .015" (.38mm), then the compression height of the STI 2.5 pistons would be:

201mm - 79/2 - 130.0851 - .38 = 31.0349mm.

WRX Comp Height: 32.69mm
JDM STI Comp Height: 31.59mm
2.5NA Comp Height: 29.51mm
2.5STI Comp Height: 31.0349mm

Jeff

Jeff,

You'r welcome.

Quirt

Originally posted by Coati
So if what we were looking for was the simplest (and cheapest) way to end up with a WRX with better bottom-end might be getting shorter rods and a STi/Forester XT short block?

Assuming the goals are a reliable sub-to-near 300hp and to end up with a car whose mods are completely transparent (ie uses stock (reflash okay) ecu and keeps emissions equipment)?

Or would we still need something else?

Yes it would work... but you might want to think about getting sti heads and keeping the stock rods. If your going to pull the block for a sawp you might as well do the whole thing, plus there will be a HUGE difference in performance. And theres no such thing as cheep when talking about transplants;)

So shorter rods + us heads = tractor motor? Would it work for autox? or would its power band be too narow?

Originally posted by Quirt


The stock STI piston is "very" nice part.

Quirt Crawford
Crawford Performance

Quirt,

Since you have had the block apart, could you give us a rough assessment of the quality and design of the component parts (rods/crank/pistons)? I'm getting an STi next week, just wondering how good the stuff in there is. There's been alot of rumors flying around that say the 2.5 sti motor is on the weak side, perhaps you can lay those to rest.

Thanks,

Kevin

If I add the STi heads, will I also need to get a STi ECU (for the AVCS? or something else?) which means getting the whole thing re-registered as a STi for smog purposes. Extra hassle?

Sorry for my questions: If I didn't want a wagon, I'd have already just bought a STi.:mad::(

Originally posted by totoherbs


Yes it would work... but you might want to think about getting sti heads and keeping the stock rods. If your going to pull the block for a sawp you might as well do the whole thing, plus there will be a HUGE difference in performance. And theres no such thing as cheep when talking about transplants;)

So shorter rods + us heads = tractor motor? Would it work for autox? or would its power band be too narow?

I can't see the appeal of using shorter rods. Using shorter rods instead of different dish pistons is worse because:

(A) you make the rs ratio worse, not better.
(B) the rods will cost you more
(C) changing the rods is much more work, and will require retorquing of the rod bolts, etc.
(D) using short rods will increase the quench space, which may cause more detonation in the first place.

If you want to use this block with your WRX heads, the best options are

(a) use it as it. Higher compression
(b) get the bigger dish pistons so you have the lower compression.

The STI Heads have very similar area, but since they flow more, they would probably be better suited. Or perhaps some better WRX cams.
Jeff

Originally posted by Coati
If I add the STi heads, will I also need to get a STi ECU (for the AVCS? or something else?) which means getting the whole thing re-registered as a STi for smog purposes. Extra hassle?

Sorry for my questions: If I didn't want a wagon, I'd have already just bought a STi.:mad::(

You can run the STI heads without the STI ECU, but you will not have AVCS. I'm running the STIRA ecu with the AVCS, and it helps spoolup quite a bit.

As far a smog goes, you would probably have to switch back to the stock ECU during the test period, as the JDM STI ECUS may not have all of the OBDII functions..

Originally posted by sponaugle


I can't see the appeal of using shorter rods. Using shorter rods instead of different dish pistons is worse because:

(A) you make the rs ratio worse, not better.
(B) the rods will cost you more
(C) changing the rods is much more work, and will require retorquing of the rod bolts, etc.
(D) using short rods will increase the quench space, which may cause more detonation in the first place.

If you want to use this block with your WRX heads, the best options are

(a) use it as it. Higher compression
(b) get the bigger dish pistons so you have the lower compression.

The STI Heads have very similar area, but since they flow more, they would probably be better suited. Or perhaps some better WRX cams.
Jeff

Points well taken, although you keep talking about the squish area. Seems to me (although hard to tell from the out of focus picture) that the STi piston is a dish design, and would not benefit in a tighter piston to head clearance.

Changing pistons does sound like a much better idea, just trying to throw some ideas out here.

Matt

Red Rocket,

The crank, rod and piston assembly, in my opinion are the best parts in the motor. The semi closed deck design is the weakest component .

I think that 400HP will not be a problem as long as the tune is good. But if it detonates, all bets are off.:)

Quirt Crawford
Crawford Performance

Originally posted by Quirt
Red Rocket,

The crank, rod and piston assembly, in my opinion are the best parts in the motor. The semi closed deck design is the weakest component .

I think that 400HP will not be a problem as long as the tune is good. But if it detonates, all bets are off.:)

Quirt Crawford
Crawford Performance

Can you guys finish this already and give us a price for the shortblock? My nuts are hangin low in anticipation!!! :)

Originally posted by I am mattjk


Points well taken, although you keep talking about the squish area. Seems to me (although hard to tell from the out of focus picture) that the STi piston is a dish design, and would not benefit in a tighter piston to head clearance.

Changing pistons does sound like a much better idea, just trying to throw some ideas out here.

Matt

Keep in mind the 'squish' is the area around the outside rim of the piston that comes up to the flat part of the head. In the JDM STI case, there is a flat rim around the outside of the piston that is level with the center rise, and what you would consider the top of the piston. The Piston then has two dish cutouts.

On the STI US pistons, the dish cutout is round, with a raise in the center. Still, there is a ring around the outside edge of the pistion that comes up to the head at a flat spot.

The purpose of the squish area is to provide a rapid compression wave that adds turbulence to the combustion. For that reason, changing the rod lenght without also changing the compression height (pin offset) is not a good idea. Same with using two head gaskets, etc. They all change the squish area, which alters the detonation resistance. The 'invention' of squish areas was a major advance in combustion and detonation prevention. (keep in mind I'm not expert on this area. There are plenty of people deeply involved in automotive design that can provide much more detail)

Jeff

Originally posted by sponaugle


Keep in mind the 'squish' is the area around the outside rim of the piston that comes up to the flat part of the head. In the JDM STI case, there is a flat rim around the outside of the piston that is level with the center rise, and what you would consider the top of the piston. The Piston then has two dish cutouts.

On the STI US pistons, the dish cutout is round, with a raise in the center. Still, there is a ring around the outside edge of the pistion that comes up to the head at a flat spot.

The purpose of the squish area is to provide a rapid compression wave that adds turbulence to the combustion. For that reason, changing the rod lenght without also changing the compression height (pin offset) is not a good idea. Same with using two head gaskets, etc. They all change the squish area, which alters the detonation resistance. The 'invention' of squish areas was a major advance in combustion and detonation prevention. (keep in mind I'm not expert on this area. There are plenty of people deeply involved in automotive design that can provide much more detail)

Jeff

I fully understand the theory of the squish area, and providing turbulence to enhance combustion... but the flat area on the dish style STi pistons seems too small compared to the flat spot on the WRX heads to make much difference. I'm sure I'm wrong... just my observation.

Now these guys did a good job matching up the flat areas of the WRX heads:
http://I-club.com/forums/attachment.php?s=&postid=225896

This is a cool piston design from JE, check out the dimples to create more turbulence.

http://www.chevyhiperformance.com/chevyhighperformance/techarticles/p173615_image_large.jpg :banana:

Anyone have an idea of what the rev limit would be on this block... I know the ej207s have been known to rev to 9000

Originally posted by totoherbs
Anyone have an idea of what the rev limit would be on this block... I know the ej207s have been known to rev to 9000

Another question is will the WRX valve train handle 9000rpm? :)

the wrx has vavle flot at 7500-8000 so no... not without work

Originally posted by totoherbs
the wrx has vavle flot at 7500-8000 so no... not without work

yeah, that was my point :)

Although, I think only you and I want to use the WRX heads with this block.

Originally posted by I am mattjk


yeah, that was my point :)

Although, I think only you and I want to use the WRX heads with this block.

Depending on what this setup would cost...

If its more then an ej257 block and some used jdm sti heads I wouldnt bother, but if its less It seems like a great place to start.

Originally posted by I am mattjk


yeah, that was my point :)

Although, I think only you and I want to use the WRX heads with this block.

:mad:

sinner

Any idea what the compression ratio would be using the 2.5 N/A heads?

Originally posted by I am mattjk

I fully understand the theory of the squish area, and providing turbulence to enhance combustion... but the flat area on the dish style STi pistons seems too small compared to the flat spot on the WRX heads to make much difference. I'm sure I'm wrong... just my observation.
Now these guys did a good job matching up the flat areas of the WRX heads:
http://I-club.com/forums/attachment.php?s=&postid=225896

Yes, those pistons look very nice! It is worth noting however that the JDM STI pistons, used in conjunction with the JDM STI Heads, also have about the same size squish area as this combo would have. (Actually, when I think about it, the 2.5STI is bigger, since it is about the same width, but farther out in a circle thus more area).

From my limited memory of engine dynamics in school, the squish area can be effective with only a small amount of exposed overlap. I have seen some piston designs with outer edge lips that are only a few mms wide.

Also, since I have yet to actually see the 2.5 STI heads, one might speculate that that with the JDM heads, the squish could be larger since the combuistion chamber might be a bit smaller. (this assumes that in the real 2.5 block 2.5 head combo that not all of the potential squish space is realized)

Either way, I think the best option is to give it a try. As soon as I get the 2.5 STI head gaskets (on order), I'll get it bolted up and we will see how it runs.

Jeff

Originally posted by SubaFastR
Any idea what the compression ratio would be using the 2.5 N/A heads?

It is easy to calculate:

From the JE site
DOHC 2.5 Head Volume: 48cc
SOHC 2.5 Head Volume: 51cc

From the previous post:
Piston Dish: 22ccs
Deck Vol: 2.95ccs
Gasket Volume: 6.22ccs (assumes .8mm gaskets)
Swept Volume: 614.27ccs


2.5 NA DOHC CR would be:
Compressed Volume: 48+22+2.95+6.22 = 79.17
CR: (79.17+614.27)/79.17 = 8.76:1

2.5 NA SOHC CR would be:
Compressed Volume: 51+22+2.95+6.22 = 82.17
CR: (82.17+614.27)/82.17 = 8.48:1

Originally posted by sponaugle




Either way, I think the best option is to give it a try. As soon as I get the 2.5 STI head gaskets (on order), I'll get it bolted up and we will see how it runs.

Jeff

Awesome! I always look forward to the work you do on your car!

this seems like a great replacement shortblock for us RS guys assuming the RS heads will work well w/ the block.

Originally posted by SubaFastR
Any idea what the compression ratio would be using the 2.5 N/A heads?

I found on one site that the DOHC heads were 46cc and the SOHC ones were 50cc. Using the above computations, the 46cc would result in ~8.95:1 and the SOHC would be ~8.56:1

Is it possible to bolt up the usdm STI 2.5 heads to the stock usdm 2.0 and work well without clearence issues. If so what would the compression ratio be and would it be worth doing?

Originally posted by Porkchop-WRX
Is it possible to bolt up the usdm STI 2.5 heads to the stock usdm 2.0 and work well without clearence issues. If so what would the compression ratio be and would it be worth doing?

We would have to know the head volume of the new STI heads. Anyone taken them off their engine yet?

Jeff

Originally posted by dwx


I found on one site that the DOHC heads were 46cc and the SOHC ones were 50cc. Using the above computations, the 46cc would result in ~8.95:1 and the SOHC would be ~8.56:1

I have seen several different numbers. Anyone with a set of heads laying around that can measure?
Jeff

Thats great news about the CR of the NA heads. Has anyone actually bolted these two pieces together yet? The STI block and the 2.5RS heads? Which gasket is required?

J

looks like I'll being doing it next week.....:banana:

I just purchased an STi short block... so basically the RS heads will bolt up to it an work well? Will the RS heads work with forced induction? I've always heard "no", but this thread is making me think otherwise...

By the way, this is some great information... keep up the good work guys.

Scott

where'd you get it and for how much? im very curious to kno...

Originally posted by Stime187
I just purchased an STi short block... so basically the RS heads will bolt up to it an work well? Will the RS heads work with forced induction? I've always heard "no", but this thread is making me think otherwise...

By the way, this is some great information... keep up the good work guys.

Scott


Most of the posts in this thread have been dealing with compression ratio and quench distances. There really has not been any substantial claims as to the effectiveness of the older NA 2.5 heads/cam and this bottom end. I'm not very familar with the older Subaru heads and cams, so I really can't comment on what would work well. Generally Cams for NA cars don't work that great on low compression turbo motors.

You might want to look around for some flow numbers. I thought someone had tested the SOHC 2.5 heads as well as the WRX heads.

Just knowing that the compression and interference doesn't have problems does not equate to the heads 'working well'

Jeff

Originally posted by sponaugle



Most of the posts in this thread have been dealing with compression ratio and quench distances. There really has not been any substantial claims as to the effectiveness of the older NA 2.5 heads/cam and this bottom end. I'm not very familar with the older Subaru heads and cams, so I really can't comment on what would work well. Generally Cams for NA cars don't work that great on low compression turbo motors.

You might want to look around for some flow numbers. I thought someone had tested the SOHC 2.5 heads as well as the WRX heads.

Just knowing that the compression and interference doesn't have problems does not equate to the heads 'working well'

Jeff

Jeff,

I don't much about quelch distances and what not... thanks for the explanation.

As for the block, I picked it up off Ebay for about $1600.

Scott

Originally posted by Stime187
I just purchased an STi short block... so basically the RS heads will bolt up to it an work well? Will the RS heads work with forced induction? I've always heard "no", but this thread is making me think otherwise...

By the way, this is some great information... keep up the good work guys.

Scott

The 2.5L n/a heads and cams work fantastic with forced induction.

At least that is what my dyno and 200+ customers have told me.

Quirt Crawford
Crawford Performance

Originally posted by Quirt


The 2.5L n/a heads and cams work fantastic with forced induction.

At least that is what my dyno and 200+ customers have told me.

Quirt Crawford
Crawford Performance

Quirt,
That's great news... do you possibly have a dyno or something you could show me? I really appreciate it.

Thanks!
Scott

does anyone know if the 2.5 sti shortblock will work on a 2.5rs?

Does anyone know the torque and sequence when installing the heads?

Mahalos!

Originally posted by custus
does anyone know if the 2.5 sti shortblock will work on a 2.5rs?

This has been answered at least 2-3 times in this thread.

Originally posted by chibby goku
Does anyone know the torque and sequence when installing the heads?


I'm sure this has been covered elsewhere...

Front-----------------------Rear
-----------------------------------
-----3----------1----------6-----
-----------------------------------
-----------------------------------
-----5----------2----------4-----
-----------------------------------

Apply coat of oil to threads and washers. Torque to 22 ft-lbs in sequence. Retorque to 51 ft-lbs in sequence. Back off bolts 180 degrees in reverse order. Back off another 180 degrees in reverse order. Torque to 29 ft-lbs in sequence. Tighten bolts 80-90 degrees in sequence. Tighten bolts another 40-45 degrees in sequence.

-Jon

Originally posted by stimpy


I'm sure this has been covered elsewhere...

Front-----------------------Rear
-----------------------------------
-----3----------1----------6-----
-----------------------------------
-----------------------------------
-----5----------2----------4-----
-----------------------------------

Apply coat of oil to threads and washers. Torque to 22 ft-lbs in sequence. Retorque to 51 ft-lbs in sequence. Back off bolts 180 degrees in reverse order. Back off another 180 degrees in reverse order. Torque to 29 ft-lbs in sequence. Tighten bolts 80-90 degrees in sequence. Tighten bolts another 40-45 degrees in sequence.

-Jon

Jon,

Thank you! Now I can start the swap. Wish me luck.

Much Mahalos!
-chris

Originally posted by chibby goku


Jon,

Thank you! Now I can start the swap. Wish me luck.

Much Mahalos!
-chris

Same here

wow, a lot of people are buying these shortblocks. does anyone have info on the 03 jdm wrx heads? i'm getting that motor swapped into my car and maybe i should drop in this block while the engine is out rather than doing it twice.

I have just re read this thread for the 5th time. Wow, what an impressive bit of information. I do have one question that was brought up early in the thread. Has it been determined if there would be valve interference from the US WRX heads if mounted to the US STI shortblock?

Yes, I do realize that STI heads would work better, but I was not planning on using bone stock US WRX heads. I was thinking more along the lines of ported and flowmatched WRX heads with JUN cams and an upgraded valvetrain. I do not want to install a JDM ECU to control the AVCS, nor do I want to do yet another wiring harness. The two that we have going at the moment will be enough to keep me away from harness swaps for a LONG time.

Templar,

You will have no interferance problems with the valves in your heads. Or any other heads that you might choose to use on the STI short block with the stock pistons.

And as a side note, Do not believe everything you read.

Quirt Crawford
Crawford Performance

Originally posted by Quirt

And as a side note, Do not believe everything you read.

Quirt Crawford
Crawford Performance


WORD

On open deck EJ20 blocks, do the sleeves fail often? If the pistons, rods, rings can handle more boost, any idea if the sleeves would?

Originally posted by Quirt


The 2.5L n/a heads and cams work fantastic with forced induction.

At least that is what my dyno and 200+ customers have told me.

Quirt Crawford
Crawford Performance It was my impression (please correct, if wrong) that you've never done head work for Subarus (besides, perhaps, supplying head studs). Are we to believe that you've supplied pistons/rods that have gone into 200+ conversions of normally aspirated EJ251 10:1 compression engines into turbocharged engines and there's never been a problem? Nothing but testimonials?

Where have I been? I thought I'd been keeping an eye on the Aftermarket Forced Induction forum (albeit the lazy one).
Originally posted by Quirt

And as a side note, Do not believe everything you read.

Quirt Crawford
Crawford Performance You can absolutely count on that.

bark?

Originally posted by Jon [in CT]
It was my impression (please correct, if wrong) that you've never done head work for Subarus (besides, perhaps, supplying head studs). Are we to believe that you've supplied pistons/rods that have gone into 200+ conversions of normally aspirated EJ251 10:1 compression engines into turbocharged engines and there's never been a problem? Nothing but testimonials?

Where have I been? I thought I'd been keeping an eye on the Aftermarket Forced Induction forum (albeit the lazy one).
You can absolutely count on that.

Indeed. Everything that's been said here for the last few yrs (including comments From Trey Cobb; People who have a LOT of EJ building and dyno experience; more so than Crawford Performance in this thread) says that stock EJ25 don't flow that well. The EJ205 heads are supposedly a lot better, and we know those aren't great heads. Then, Crawford Performance comes on here and tell everyone otherwise? What kind of flow bench did you use and where are your results?

Why don't you show us dynos of some stock (cams, CR, valves, etc) EJ25 making good power in same boost. With 200+ dynos, you should have plenty.

And 240awhp@18psi doesn't show us anything.

Originally posted by hatchy
On open deck EJ20 blocks, do the sleeves fail often? If the pistons, rods, rings can handle more boost, any idea if the sleeves would?

Methinks to break the cylinders of a USDM EJ205 you would either have to:

a) Make a ton of power or

b) Be a really bad tuner

then there is always:

c) Make a ton of power, be a good tuner, and break a part.

There are numerous threads of persons running >20 psi of boost on these engines (and making alot of power). The pistons and rods can handle it, IMO. What they can't handle is prolonged detonation. I'm currently running 24 psi; I've never heard of a cylinder failure due to anything other than a rod or piston damaging it. :)

Originally posted by TypeC

Then, Crawford Performance comes on here and tell everyone otherwise? What kind of flow bench did you use and where are your results?

Why don't you show us dynos of some stock (cams, CR, valves, etc) EJ25 making good power in same boost. With 200+ dynos, you should have plenty.

And 240awhp@18psi doesn't show us anything.

Ya know... It's one thing to ask for proof from a tuner about power claims. It's another to acuse the tuner of lieing and then proceeding to rip on said tuner. There are well over 37,000 members on this board. 200 cars that you have not heard of posting anything is .0054% of the total members. Gee, think it's possible that you have missed them?

Learn some manners guys, or there will be no reputable companies giving free advice here.

Kevin

You guys pissy much? I certainly have my fits of it.

Is it worth driving someone away who is contributing good information just to get your rocks off and attack his poor choice of words?

He didn't say "Subaru 2.5L N/A heads work great with FI."

He *should* have said, much more clearly, "Other marque 2.5L N/A heads that I have worked on have worked very well for FI."

He didn't. Fine. Tell him to be more specific, but do we need all of the attitude?

I'm as guilty as the next person sometimes in this regard... just taking notice this time.

Originally posted by Enigma76
where'd you get it and for how much? im very curious to kno...

Several people have emailed me about where to get the new 2.5STI blocks from. I got mine from Joe at Mikeshawauto. I believe he still has 6 blocks left, so I would give him a shout. I got my block in about a week, perfect condtion, still in the original Subaru sealed bag. Very good to deal with.

Contact info:
Joseph Cox
josephc@mikeshawauto.net

Jeff Sponaugle

first of all, subafastr, there are not 37000 2.5RS owners so your percentage is way off, but the reality is that the N/A heads in their factory state are not good for high horsepower FI setups. this has already been proven by Hayscoob when he didn't make any power going from 14psi -> 18psi.

and by any chance, does he have EJ257 shortblocks ?

Ok. Intelligent conversations that give way to all out flame wars aren't going to be accepted.

If you have a legitimate concern with a vendor, being nice about asking them for more information is a better way to go than jumping on them. Calling them out in a rude manner such as the one Joe has used is only going to drive vendors away.

I don't know anyone that wants to be treated so rudely. So, I'm giving you two options; 1) Play nice and be more considerate, or 2) go away.

I'm going to be watching this thread. The second it gets [i]any closer to becoming a flame fest I'm locking it down, cleaning it out and handing out warning points. I hope we all understand whats going on.

Sorry to sound so hard, but it's Monday.

Originally posted by EJ20K
and by any chance, does he have EJ257 shortblocks ?

Yes, that is what I was refering to in the first post. 2.5LSTI blocks.. aka EJ257s.
Jeff

There were some flow bench results posted here many years ago (most of you probably didn't even own subarus at the time) that showed the flow characteristics of the Phase II 2.5 SOHC heads vs. other Subaru Heads. The SOHC head outflowed everything including the Legacy turbo heads. It outflowed the DOHC 2.5 heads as well, by a relatively large amount. It will not outflow the DOHC heads from any form of EJ20 turbo. This test was done before you could get an EJ20 in the states.

So, yes, the EJ25 heads do respond well to forced induction. No, they are not a fantastic head for high boost, however the pistons on MY00 and newer EJ25s aren't going to handle more than 7 psi at the most anyway. I have seen WAY to many of them cracked and most of those was without FI. But this is not the point, the point is that the heads are fine to run up to around 14 or 15 psi on.

Originally posted by spiralsmurf
first of all, subafastr, there are not 37000 2.5RS owners so your percentage is way off, but the reality is that the N/A heads in their factory state are not good for high horsepower FI setups. this has already been proven by Hayscoob when he didn't make any power going from 14psi -> 18psi.

I don't recall specifying RS owners... Anyways, any idea how much the STi heads cost each?

well considering that you are talking about 2.5 N/A motors than you kind of need to single out legacy gt and 2.5rs owners.

I thank all of those that have posted worthwhile information. This thread has been very informative.
For those that continue to lose the topic at hand for other such puposes, I am sorry that you do so.
I hope that I can help to get it back on track. I still have some questions that still remained unanswered for me, and I believe for others as well. I hope that the "big guns" can help summarize and clarify their findings:

1a) Will the ej257 block "work" with the WRX heads? (I say "work" because to each person, there might be different opionions as far as what that means.) Can the STi block handle the higer compression (8.66:1)? What would be the estimated maxiumum horsepower limits from this setup?

1b.) What would be some disadvantages? What would make this setup undesirable?

2) Given the concept of the Sti block and the WRX heads, what are other factors that should be considered?

3) There are some sides that are changing the stock piston to a different aftermarket psiton. Is this necessary? Or is it only recommended?

4) What, if any, other parts of the short bloack should be changed for aftermarket parts, and why?

I hope that we can keep this a spirited, yet technical discussion as new information is released and discussed.

Thanks.

Originally posted by johnnytran
I thank all of those that have posted worthwhile information. This thread has been very informative.
For those that continue to lose the topic at hand for other such puposes, I am sorry that you do so.
I hope that I can help to get it back on track. I still have some questions that still remained unanswered for me, and I believe for others as well. I hope that the "big guns" can help summarize and clarify their findings:

1a) Will the ej257 block "work" with the WRX heads? (I say "work" because to each person, there might be different opionions as far as what that means.) Can the STi block handle the higer compression (8.66:1)? What would be the estimated maxiumum horsepower limits from this setup?

1b.) What would be some disadvantages? What would make this setup undesirable?

2) Given the concept of the Sti block and the WRX heads, what are other factors that should be considered?

3) There are some sides that are changing the stock piston to a different aftermarket psiton. Is this necessary? Or is it only recommended?

4) What, if any, other parts of the short bloack should be changed for aftermarket parts, and why?

I hope that we can keep this a spirited, yet technical discussion as new information is released and discussed.

Thanks.

Read the freakin thread.

You will have no interferance problems with the valves in your heads. Or any other heads that you might choose to use on the STI short block with the stock pistons.


You wont be doing the block justice without headwork to the ej205 heads though....thats earlier in the thread.

santofontana:

I appreciate your response, and also you candor. I have read the thread, and did not feel that the questions I asked were concretely explained. I think that your response answers some of the questions at hand.

I was pretty sure about some of the answers to the questions, but I wanted to get absoulte answers if possible. I feel other issues have not really been addressed. I hope that you can help to get answers to the rest of the questions, as they would be helpful in evaluating this setup.

Thanks.

You guys can chew on each other's boo-tox all you want. I want to know more about this stuff. And finally, I want a built 2.5 with the best heads, the best CR, the best cams with the valves re-worked for more rpms, all flowed and ready to go for a street motor (don't wanna race) for 5k .. and it aint ever gonna happen....

Johnnytran,

This is my opinion on your questions.

1a) Yes, it can handle the higher compression of 8.74 to 1, and the maximum HP is unknown at this point. (Not enough testing)

1b) Possible detonation from 91 octain.

2) The propper head gasket which would be .019 thick or the STI gasket.

3) Changing the pistons would only be recomended to avoid 1)b and to increase the life span of the motor.

4) I would recomend using head studs.

Thanks,:)

Quirt Crawford
Crawford Performance

Quirt

Thanks for your responses. I really do appreciate you comments. I think that I would definitely follow all of your suggestions.

As far as you comments on 1b) about detonation on 91 octane...do you think that engine management and/or larger injectors could solve this problem? Or is it an inherit flaw with the dynamics of the setup, and cannot be resolved?

Thanks.

Johnnytran,

Yes, If you went in and removed some timing it would help.

Adding fuel would just kill the power.:)

Quirt,

That makes sense. It's too bad, but that makes sense.

That is what I will do.

Thanks.

Contact info:
Joseph Cox
josephc@mikeshawauto.net

this isn't who i think it is, is it ... joe cox ala jcsports?

yup

Well...

If you go to http://www.mikeshawauto.net/ , then follow the link to Mike Shaw Subaru (http://www.mikeshawsubaru.com/en_US/) , you'll see they're located in Thorton, CO...

Yeah, Joe's a good guy. I know he's got a few of these left, but one's mine.

Subaru of Schaumburg in Schaumburg, IL is also a good place to get them, they have gotten at least 5 of them thus far, I have one of them. Craig is the parts guy there and he's the one to talk to.

BUMP

Good news. I spent my whole holiday weekend with Crawford Performance and a little known head shop....DPR. I know I didn't get any vacation, or sleep, but I think you will all appreciate the outcome of our endless nights and countless hours of labor.
Needless to say we will be dynoing some interesting things/set-ups in the next week or so.
I will keep you all posted:)

Chris
I-Speed USA
cescamilla@i-speedusa.com

Sounds great Chris thanks for the good conversation and letting me speak to quirt. I will give ya a call tomorrow- I like the path i speed is taking here guys

Ok, I have a busted STi motor (EJ20K) and an EJ251 block from my MY2000 RS. In the STi motor a piston bent, presumably from mild detonation and the cylinders are mildly scuffed. The EJ20K heads will be fine after some valve replacements.

I can have the STi block cleaned up and close decked with new bearings, pistons, balanced, blueprinted etc etc etc for about $5kCAD. Same deal with the EJ251.

With all this work going on with the USDM STi block is it a viable competitor dollar-wise for the built and close decked EJ20K or EJ251 blocks I have at my disposal? Would you care to comment on what would be strongest?

Also, with an STi block and EJ20K heads which intake manifold would fit? Would the old EJ25, or the EJ20K or none of the above? I wouldn't want to lose the 50hp red paint.

-Michael

Feer not, your intake manifold is safe.... I have some yellow stickers you can buy. :lol:

Actually if you look at the STi manifold you will see the inside is significantly larger than the 2.5RS one.

-Michael

d00f

You can over bore a new block twice, and then it is scrap.
If you spend $5k on your damaged block having it closed decked and over bored, you will have a large investment in a block that can be over bored one more time before it becomes scrap!

As for wich will be the strongest, The as cast closed deck block is the strongest. There is some R/D to be done on the STI block before an opinion can be offered.

Your manifold is a match to the type heads that it came on. Also the 2.5 STI block is the same width as all of the EJ blocks.

In my testing the red paint is good for 58HP :)

Quirt Crawford
Crawford Performance

Quirt,

As I'm sure you're aware if you offer closed decking services to your customers that the block must be rebored because of heat distortion from the close decking process. Closing the deck also alters the distortion from torquing the heads down so normally one would close the deck, install the studs torque it down with a torque plate and re-bore.

This means that the minute scuffing that could probably be cleaned with a cylinder hone will not have an effect on a block that has to be rebored anyway.

From your photos the STI sleeves look much thicker than the EJ251 sleeves. I just took the calipers and measured the EJ251 sleeves at 8.2mm with a fairly signifcant reduction for one of the bolts so the sleeve has a minimal thickness of 6.61mm and that goes the length of the sleeve. On the EJ20K block I measure a thickness of 9.3mm with one very minor machining that reduces it to 8.76mm in one spot that is about 30mm deep.

The earlier EJ20G blocks were fully closed deck from the factory but these were mostly bought and modified by the japanese performance market. Thus a factory closed deck block is nearly impossible to get. Closing the deck is really the only option available to me.

-Michael

Michael,

I have "brand new" as cast closed deck blocks with piston squirters, in stock.
With matching 75mm,79mm or 83mm cranks, also new.
Forged pistons, and 4340 Forged rods that are made in the USA.

Pick the stroke/displacement you want, they all fit in the closed deck block.:)

Quirt Crawford
Crawford Performance

Ok, if these are subaru parts cast in closed deck form then can I ask where you got them? If they are custom cast units then that's fine too so long as everything is compatible with the stock accessories and they are going to wear and hold at least as well as a subaru block.

How are the cast blocks available? Can I just buy one bare since I have an STi crank, rods and all the goodies? Do you have a pricelist that you can refer me to?

-Michael

Originally posted by d00f
The earlier EJ20G blocks were fully closed deck from the factory but these were mostly bought and modified by the japanese performance market. Thus a factory closed deck block is nearly impossible to get. Closing the deck is really the only option available to me.

-Michael

um no
they are easy to get and quite cheep
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=46098&item=2430258914

i only paid 650 for mine
http://home.velocitus.net/jaredw/images/MVC01909a.JPG

Michael,

The blocks were made by Subaru.

My intent in this forum is to offer fact based information.

If you are interested in prices, you should contact me.

Thanks,
Quirt Crawford
Crawford Performance

Originally posted by Jaxx


um no
they are easy to get and quite cheep
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=46098&item=2430258914

i only paid 650 for mine
http://home.velocitus.net/jaredw/images/MVC01909a.JPG

Jaxx,

I have dismantled many of the motors that you have pictured.

Have you removed one of your head's to see that your deck is closed?

Quirt

word. Even STi blocks from the early years are cheap to buy.

Originally posted by Jaxx


um no
they are easy to get and quite cheep
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=46098&item=2430258914

i only paid 650 for mine
http://home.velocitus.net/jaredw/images/MVC01909a.JPG

The link you quoted is for an EJ20DET. A review of some shop manuals I have do not even list such a motor. I remember years ago (before i-club existed) there was a discussion about this and the conclusion we arrived at was there is no such thing as a EJ20DET. Rather some importers are calling this a DET as per the coding nissan uses, ie SR20DETT or whatever.

In any event the info I've seen over the years indicated that this JDM EJ20 is open deck. Hell it's not even an STi motor. The only block I've been able to find that's cast factory closed deck was the EJ20G (STi version 2-3 I think) and of course the 2.2l.

I've talked to several subaru people so far and each of them has called BS on the idea of a fully closed deck cast 2.5l block from Subaru. Everyone is quick to point out that the ej257 STi block is semi-closed. Best explaination someone was able to come up with is that it may be an old legacy turbo block that's been bored / stroked.

-Michael

To my knowledge Subaru has never made a 2.5L fully closed deck block.

For what it is worth.

Quirt Crawford
Crawford Performance

http://forums.nasioc.com/forums/showthread.php?s=&threadid=364542&highlight=closed+deck

Most engine importers like that have no understanding for proper engine codes. As such, they label them as EJ20DET since the common ricehead would pick up on that as being a turbo engine.

There has never been a factory closed deck 2.5L. Some people have closed their EJ251s and some have bored out the EJ22-T blocks.

-Jon

Quirt,

I pmed you with a few questions.

Thank You,
Matt

Originally posted by Jaxx


um no
they are easy to get and quite cheep
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=46098&item=2430258914

i only paid 650 for mine
http://home.velocitus.net/jaredw/images/MVC01909a.JPG


Ah.. tolnep is dumb.. you put these in 911s? Are these things better than a porsche motor and how hard is it to replace the porcshe motor with these things (and do people really do that??).

Heck.. how bout some reverse stuff. How bout we put a 911 porsche motor in a subie.. Whats good for the goose and good for the glockinspiel..........

This thread has be very educational (until the toads attacked) I am interested in a future cost effective shortblock replacement for my WRX block.

The 2.5STI block with USDM heads will give me a 8.4 or 8.6 CR(forget which to many numbers for my little head).

Would this combination with say some minor head work and proper tuning work well. It seem slike a very cost effective way fot people to upgrade/replace a stock/broken block.

Also on a side note, would an 18g flow enough for the extra displacment?

Thanks to all those who have shared so much information, keep it comming, I thank you.

Again, unless you are doing a tractor pull, you are going to want to seriously open up the heads.

-Jon

Originally posted by stimpy
Again, unless you are doing a tractor pull, you are going to want to seriously open up the heads.

-Jon

Well Id like to hear some comments on this as some swear youd have a motorhome and some laugh at that as so stupid.

The only thing bad with the WRX head is the cam profile with basically a 200-300 later spool difference between the STi and WRX (similar turbos)thats with the help of AVCS. With a similar boost profile and possibly a 7.5K redline (ecutek) just force more air in there

The WRX casting is from recent Ver 6 STis so while not the latest and greatest surely competent besides how many of us with like stage 4 1820s big turbos ect hated life with the wrx heads??

The difference is all top end with bigger cams, take a look at some of the stroker buildup dyno sheets that utilize stock cams and youll see it. I agree with Stimpy (who agreed with me).

Bolting on v7 STi ra heads onto our 2.0 EJ20 even makes a huge difference.

Mike is correct. Once you have a real EJ207 engine in your car and you have fingered the ports yourself you will not fully understand. Is there anything wrong with v6 heads? Not really. But V7's are WAY better. Will upgraded cams make the V6 heads work better? Sure. Would I use them? Not if I had an option for V7's.

The discussion was about increased displacement from the 2.5 STI block and simply using the WRX heads (V6). If you do that what you will do is drop your power peak down to the left at least 500 rpm. Power will peak 5000-6000 rpm even with a larger turbo. The amount of power you will be giving up (had you gone with cams and heads or the V7's) will be outright painfull to watch on your first dyno pull.


Clark

Yes,

Take a look at the stroker dyno sheets. See how the power band is increased. The motor starts pulling sooner and continues to Pull!
I love my tractor :D

Remember: Horse Power=MPH and Torque= acceleration.

Chose your weapon:)

Quirt Crawford
Crawford Performance

Originally posted by Quirt
Yes,

Take a look at the stroker dyno sheets. See how the power band is increased. The motor starts pulling sooner and continues to Pull!
I love my tractor :D

Remember: Horse Power=MPH and Torque= acceleration.

Chose your weapon:)

Quirt Crawford
Crawford Performance


Yep. My weapon of choice is HP. Its a small displacement engine and I need RPM to move the Airflow for 600hp. Midrange trq and a short power peak does not help me and only hurts driveline parts.

Q. Your tag says Vista. Are you in Vista CA? If so I grew up there. I might be back in town soon and would like to stop by to check out your shop.

Clark

Clark,

Yes, I shift sooner. And that puts me in the next gear,...... watching my pray disappear,........ in my rear view mirror.

Thats my poor attempt at humor.

Come on by any time, I am in your old stomping ground:)

Quirt

this is an EJ20G
all of the first gen ej20s were closed deck w/oil squiters
this engine is from a 91-94 legacy RS (pre impreza)
when they revised the engine in 95 it went to open deck

and yes the ebay seller is misnaming the engine

but no i have not opened it..

So are the V7 heads completely new in design, or are they refined V6 heads which our WRX heads are based on, how many cfms I/E is needed to take advantage of the 2.5 block? Is this cost effective, or whould the cost of buying V7 heads be more worth while. I have seen some people getting mid 300 CFM's intake mid 200's Exhaust, I don't think that the STi's slow near that, do they?

I would think that to reach 400ish CHP you shouldn't need to so to much. I should get well over 300CHP with the stock block and an 18G, I just want to plan ahead for a cost effective solution.


Thanks guys!!!

Here is the US WRX head which is the V6 STI casting. It has the short depth ports with high rise splitter.

http://www.wishbone.audi0.com/~clark/images/RAswap/pic00026.jpg
http://www.wishbone.audi0.com/~clark/images/RAswap/pic00027.jpg




Here is the EJ207 head. Notice the deeper, larger ports. According to the FIA rule book for the impreza the ports are 5mm wider on the V7.



http://www.wishbone.audi0.com/~clark/images/RAswap/pic00030.jpg

http://www.wishbone.audi0.com/~clark/images/RAswap/pic00029.jpg


V7 heads have AVCS but contrary to most people V6 heads had or can have AVCS as well.


It apears that the V7 heads are a new casting and are not Modified V6 heads. When speaking about flow numbers and HP even the V6 heads flow well compared to some other Japanese 4cyl heads. The V7's are just superior and come with 256 or 258 duration cams with over 10mm of lift. Redline on V7's is 8000-8300 depending on the cam.

If all you are after is 400hp then leave the EJ205 stock as it can do 400 easy. Most of us are talking about 500+ hp like my car is making now with the EJ207.

I can tell you that I was told from a Japan tuner that the EJ207 is worth 30whp over the EJ205(Japan version 9-1 comp) at the same boost level. What I found by running my car with the same setup with each motor is that its worth 40whp over my US EJ205. For example, At 15 psi on 91 octane fuel my car dyno tests 40-45whp more then a STG4 Turbo XS car at 17 psi. Both cars on 100 octane I a further the gap to 60whp. I have dynotested and tuned so many stg4 cars my vision is blurry.

That said... I think some of the extra power is from the piston design and the tight quench area of the EJ207 shortblock but the rest of the power must come from those heads.



HTH

Clark

P.S. Quirt. I grew up in Vista and san marcos. My mom was dragging her el camino in the 60's at Carlsbad. Good friends are Scott and his sons from VW paradise. I was a VW nut. Probably know some of the same people.

Still waiting patiently for an i-speed dyno plot of the 2.5STI + WRX heads + Crawford piston setup.

It's a mild bummer, often, to see so many of the hardcore guys are all 1/4-mile heads. I couldn't care less about goofball 4200RPM-spooling triple-your-HP-in-1500RPM turbos and the like :D

Just saying... not complaining. I love reading about it all ultimately.

Clark,

Then you must know that Scott's dragster is the fastest 4 Cyl in the world, running a 6.71 at 204 MPH!

Yes I know Scott well, I built the exhaust, Intake system, Turbo, and Fuel system. I also supplyed the MoTec system and did all of the tunning of the motor.

Thanks for the pictures.

Quirt Crawford
Crawford Performance

Originally posted by Quirt
Clark,

Then you must know that Scott's dragster is the fastest 4 Cyl in the world, running a 6.71 at 204 MPH!

Yes I know Scott well, I built the exhaust, Intake system, Turbo, and Fuel system. I also supplyed the MoTec system and did all of the tunning of the motor.

Thanks for the pictures.

Quirt Crawford
Crawford Performance

Skewing off topic.. Sorry guys.

Yes. I know Scott and his Sons well. Scott buil my motor for my 56 oval that put me in the mid 13's back in 1990. I have seen the dragster many times in person... I watched as they almost broke 200mph at Firebird in PHX.

Jblaine. While you could care less about top end power (I guess thats what you are sa