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Old 04-26-2001, 09:08 PM   #1
jhuang76
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Question Difference between different STi motors

Okay, another question that could go into many different Topic - but like before, I like this crowd (too many WRX people in the turbo group ).

Anyways, calling ColinL, P.K. Motorsport, Joel, + lots of others!!!

I spend over one hour wading through old posts trying to find all the technical differences between the different STi version motors - still no clear picture. SO, if anybody knows any technical info related to the STi motors, please post for everyone's benefit (and mine ).

Thanks,

Joe
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Old 04-26-2001, 09:57 PM   #2
North Ursalia
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<FONT face="Comic Sans MS">Do you want specifics of how and what they were built with, even more specific like cam grinds, valve duration, bore/stroke/blah/blah or just things like torque and horsepower? Most of that I can dig up, just some of it ALOT easier than others...

Brian

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Old 04-26-2001, 10:02 PM   #3
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The more technical, the better. I'm thinking of a building up an STi motor (obviously with my friends help). He's an engine guy but obviously not familiar w/ Subaru history.

If it is really excessive, you can email it to me as an attachment if you want.

Thanks A LOT!!!
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Old 04-26-2001, 10:19 PM   #4
SubyRacer
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for starters the STi has a semi-closed deck while we have an open deck. its got a larger IHI turbo that runs 17.5psi. and its got a much larger intercooler. its also got the AVCS variable valve timing. and it redlines at 8000rpm, and has the 6 spd (yea you only asked for motor, but the 6spd does effect the car's quickness)........very basic differences there i know....
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Old 04-26-2001, 10:27 PM   #5
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<FONT face="Comic Sans MS">The quick and nasty:

V1/2/3: All closed deck blocks
V1/2: I've always been told, not the best engine for excessive tuning... ~240 HP
V3: The start of the good ones. Closed deck, 276HP, forged internals. This is the block I've been told to get to push to MASSIVE amounts of boost.
V4/5/6: Also 276HP, all open deck blocks. I believe all internals are forged minus the crank, which only the RA models get a forged crank.
SubyRacer took care of the Version 7. Keeping in mind I'm talking out of a very tired body and some of what I just said might be off a bit- I've got specs down to gear ratios in the tranny's and final drive ratios, lift/duration of the valving, compression figures, bore/stroke... I'm just far too tired to find it. I will locate it all (they're all links to webpages... the info is out there somewhere ) this weekend when I get a free moment to look (my "links" folder is approx. 4MB large, and considering your average link is about 100bytes, there's more than one or two to go through )

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Old 04-26-2001, 10:52 PM   #6
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SubyRacer, so that's the new Ver 7. Very nice, but I'm sure WAY out of my budget! But, I am thinking about the tranny - are they standard helical cut syncromesh gears?

Brian - hey, go to bed. Post whatever you can/want to get. I really appreciate it!

Okay, this is the reason I asked:

I am thinking about getting a STi block to work on (and learn from too). Maybe semi-close deck it if needed AND then bore it out to around 2.2L. The friend of mine is a JE dealer so he'll get me whatever forged piston I want at his price (cool friend!). Plus, he has contacts close by to him who are very top notch experienced machinist who can do some PnP, multi-angle valve job (from new blanks) ... etc flowbenched (limited time since it not going to be cheap).

I'm just deciding what would be a decent thing to start out with (and looks like the Ver 3 is better - since I assume it'll be cheaper too right?).

The thing is, http://www.adelaidejap.com.au has a WRX engine (didn't mention what ver, definately older though) for $2750 AUD with quoted $450 AUD shipping to the US ground which totals to around $1650 US! This is less than a EJ25 SOHC phase II engine.

BTW - What do you guys think about the cylinder head of the STi ver 3-7. I know Trey is not a big fan of the 98RS DOHC - is the STi DOHC much better than the crappy US Frankenstein-ish RS? Do they also require the use of shims?

Thanks,

Joe
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Old 04-27-2001, 08:10 AM   #7
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to add to brian's list:

ver3 = solid lifter
ver5 = revised thrust bearing location (same as our EJ25 phase II)

if you're using good pistons and rods, there is NO reason to use anything less than 2.5L, unless you have a hot 2.0L crank and want to spin major RPM (like 9k). I'm sure a built 2.5L is good for 7200-7500 rpm and that should be plenty plus you enjoy a lot of additional torque thanks to the displacement.
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Old 04-27-2001, 08:47 AM   #8
Matt Monson
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And there is no reason to worry about an EJ20's DOHC head. EJ25's and EJ20's are apples and oranges. One is a turbo head and the other is not.
Also, I agree with Colin's point, unless of course your intention is to build a full blown STi replica and the you want an EJ20 to be legit.
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Old 04-27-2001, 10:02 AM   #9
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i hears that ver 1-Ver 6 usues an SOHC engines while the Ver VII uses DOHC....anybody know if this is true
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Old 04-27-2001, 10:16 AM   #10
jhuang76
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ColinL, true an EJ25 should do just fine. But the SOHC would be slightly harder to regrind right (unless I have Trey do it) since you've only got on shot at it. And, there seems to be a few drawbacks to the DOHC versions. And, a SOHC long block isn't cheap right now (like $2000 best price - if I could only find just the heads, short block, and crank and save some money).

Anyways, I'm just collecting as much info as possible right now.

Thanks,

Joe
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Old 04-27-2001, 10:50 AM   #11
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Thumbs up

Absolutely nothing wrong with gathering info!

I also think that if you have the money AND a trustworthy exporter, a modern STi engine isn't a bad choice. I personally would upgrade it further, but it still comes with a much more robust than an EJ25. They need it to make power though...

I have a list of WRX models, power output and trim codes... sort of. It's a bad scan, which is a bummer because if you could actually read the trim code, you could compare that to what's on the fender of a donor car and know *EXACTLY* what you're getting. It's here .

Ask on the STi mlist, Simon Sirin also has a great deal of data. Obviously it's labor intensive to help someone though...

Oh, and I also have some data on transmissions if it's of any value... here and here . This all comes from the FIA homologation competition manual.
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Old 04-27-2001, 11:42 AM   #12
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You don't have to bore the EJ20 out to get to 2.2L, you just use a stroker kit (which usually involves the crank from EJ25).


Ben
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Old 04-27-2001, 11:43 AM   #13
jhuang76
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Thanks ColinL. I've seen the chart before and it doesn't seem to be helpful for me since they all say 280PS, which tells me nothing about the potential. And yes, I do plan to do a good deal of work on the engine afterwards (esp. the short block).

Just to double check, an EJ20 head will fit an EJ25 block right - I think I read that somewhere in an old post?

I just found out that a ver 5 long block is over $5000 shipped. Still, I don't know any exporters nor their rep SO ... I've contacted TRi - any other suggestions?

Heck, I'd rather get a plane old EJ25 block and buy a forged/balanced crank, forged rod and piston and get a much stronger bottom end for around the same price (almost)!

How about the heads? Do the STi heads (any ver) still need to use shims on the cams - shouldn't since they can rev to 9k)?

Thanks,
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Old 04-27-2001, 02:42 PM   #14
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I'm tired.. and I feel like poop...

Personally.. in your situation.. I would build a 2.5 bottom end... new rods.. pistons.. etc..

As for heads.. well... u can keep the 2.5 heads.. either SOHC or DOHC.. or fit STI 3 or IV heads... these will need some work (designed for 92mm pistons... not 100mm).

Fitting the 2.5 crank doesnt give 2.2... its 2.1something...

fundamently the 2.0 and 2.5 blocks are the same... same design of main bearings... same design of casting.. liner support... passageways...etc...

You can bore about 0.5mm oversize... same goes with 2.2, 2.0 and 2.5 bores... I wouldnt suggest anymore.

the STI III and IV heads use underbucket shims... which in my opinion are better than over bucket.. but are a pig to set up.

STI I-II are hydraulic... III-IV under bucket.. V- over bucket.

Cam specs vary from year to year.. with the newer spec STI's uses the same cams as Euro/UK cars.

So.. IMHO.. for ease.. and most power/torque build a 2.5 engine.

J.
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Old 04-28-2001, 12:17 AM   #15
jhuang76
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bsquare, that'll work to (and allow me to keep the current pistons). From what I just heard, you can't really bore the 2.0L engines safely anyways.

[This message has been edited by jhuang76 (edited April 27, 2001).]
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Old 04-29-2001, 12:04 AM   #16
jhuang76
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Thanks for the info Jay!

I'll relay this info to my friend and see what he has to say. BTW, to fit a head designed for 92 mm to a 100 mm bore, would you just use a custom head gasket?
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Old 04-29-2001, 02:42 AM   #17
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Howdy..

The heads will bolt up...

The issue is the squish area... the heads will be designed for a 92mm bore.... and the block will be 100mm... so you will have a 4mm step between the two....

The head gasket will need to be designed for 100mm bores.

You will need to reprofile the head... I wouldnt run with the 92mm squish... wouldnt do much for the combustion...

J.
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Old 04-29-2001, 10:36 AM   #18
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AM, PM.
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