High Compression Frankenstein

[t3hWIT]

Maybe I'm onto something. Maybe I'm stupid. But i was looking over a chart of specs of all the subaru engines built, 91 and up. I was looking at the different sizes of things and their compression. I also remember somebody comparing these cars to lego blocks. So i was thinking maybe I(or someone else) could build a high compression motor with stock parts or aftermarket parts made to fit the stock vehicles. I personally think that it would be cool to build a powerful NA motor over a period of time, and someday swap it into my Prezza. Or like I said, maybe I'm just stupid. But hey, at least I dod something constructive during study hall.

the list of parts and reasons are as follows:

My stock engine is the NA EJ22, just for reference. If I would ever do this, it would be a second engine, but i want to keep to the 2.2 block.

Because of the above, the first part is:
MY91-94 EJ22T block. its built sturdier than the NA, or so im told.

The following is a choice of the 2, but i dunno which would be better:
MY98 EJ25 DOHC cylinder head (cuz its dohc)
OR
MY00-04 EJ25 SOHC cylinder head (boasts higher compression)

I also dont know about the following. I dont know if they will fit(prob not), of it they'll help me with power or anything but...:
MY98-04 connecting rods and crankshaft. If they dont work, id go with the EJ22 or EJ22T rods and shaft.

MY97-98 EJ22 pistons (higher compression, and they'll fit)

finally...
MY97-98 SOHC EJ22 head gasket. (higher compression than the dohc gasket)

I'd like to stick to better than OEM parts on stuff, including the other stuff, such as clevite bearings and arp bolts/studs

my questions are:

Will it all fit?

What kind of compression would be expected?

What about engine magement?

Sohc head or dohc head?

Would it start?

Any other suggestions?

One more thing... am I freakin nuts?

-shaun

* Registered users of the site do not see these ads.

[Tim Sanderson]

I think the best thing you could do is get all the stats of all the parts you are considering using and take it to an engine builder. Have a little chat with them and see what they think.

[t3hWIT]

Originally Posted by Tim Sanderson

I think the best thing you could do is get all the stats of all the parts you are considering using and take it to an engine builder. Have a little chat with them and see what they think.

ah no man. that takes all the fun outta it.

not being an ass here but if i was gonna spend that much money, id just turbo the thing. theres a twin turbo kit out there. and this HC thing is junkyard parts.

[t3hWIT]

and i live in central Pa, aka Penntucky. the closest thing to an engine builder we have is the neighborhood mechanic, or some guy at AAP who'll gather the parts together. The biggest thing in tuning around here is slapping a big ol aluminum wing, stick on hood scoops, chrome exhaust tips, and APC spinner wheel covers. I'm interested in performance and teaching these tuner wannabes a lesson in real cars. But since I'm one of the few and proud, i dont have access to this stuff. just junkyards. ugh... i hate this region...

[Tim Sanderson]

Maybe you misunderstood, If you get the copies of the service manuals you can have a nice reference for all the parts you are considering using. I did'nt suggest that you go get all the parts and mickey mouse around with them.

Have at it and good luck. Like to see what you come up with.

[Kevin Thomas]

Originally Posted by mi_cistemz_loudr

Any other suggestions?
-shaun

Paeco Industries!

[redwagon]

Originally Posted by mi_cistemz_loudr

Any other suggestions?

Get the toughest block and pistons on the list, combine that with the best flowing heads, and then let the machine shop deck the block to give you the compression ratio you desire. Either that or go the custom piston route.

[BoostdScubaru]

get as close to 13:1 compression as possible..

[bugeyes]

Whilst your on the point of mixing and matchingI"ve often wondered about this combination.
EJ25 block for maximum bore capacity
EJ20 crank , shorter stroke better rpm capacity
custom long rods - improve rod ratio by having the taller ej25 block and the short stroke ej20 crank. The long rod combination improves rpm capacity.
Overall capacity will still be close to 2.5L (about 2.4L I think).
I really dont think the strength of the block is an issue after all turbo motors are putting out much higher hp's than n/a would ever be capable of and whens the last time you heard of a block failing?

[Tim Sanderson]

Originally Posted by redwagon

Get the toughest block and pistons on the list, combine that with the best flowing heads, and then let the machine shop deck the block to give you the compression ratio you desire. Either that or go the custom piston route.

Decking the block too much will cause problems with the crank and cam sensors. It would be better to have pistons made.

[Tim Sanderson]

Originally Posted by bugeyes

Whilst your on the point of mixing and matchingI"ve often wondered about this combination.
EJ25 block for maximum bore capacity
EJ20 crank , shorter stroke better rpm capacity
custom long rods - improve rod ratio by having the taller ej25 block and the short stroke ej20 crank. The long rod combination improves rpm capacity.
Overall capacity will still be close to 2.5L (about 2.4L I think).
I really dont think the strength of the block is an issue after all turbo motors are putting out much higher hp's than n/a would ever be capable of and whens the last time you heard of a block failing?

I don't think they fail so much as flex and cause head gasket failure. I like your ideas though, A rod ratio of 1.8 or more would be nice. Not sure on the crank though, I think the n/a 2.2 are'nt forged.

[greg donovan]

do what i amp planning:

phase II ej25 shortblock with the older dual port ej22 heads and the thick ej25 gasket. should get you right around 11.5:1. any higher and you would need to possibly add a piggyback to retard the ignition timing or add water injection or find a way to increase the fuel or all of the above.

[jamesfacts]

You could use your 2.2 ecu. It would run, but it wouldn't be ideal. ECUs can run cars pretty different from the cars they were designed for. I believe Supermoose is running his 5mt ej25 off a 4eat 1.8 ECU.

[Kevin Thomas]

Originally Posted by americanyouth

You could use your 2.2 ecu. It would run, but it wouldn't be ideal.

In what way wouldn't it be ideal?

[jamesfacts]

Originally Posted by Kevin Thomas

In what way wouldn't it be ideal?

Obviously, some type of engine management would be ideal. E-manage or maybe the hydra if cost was no object, right?

[greg donovan]

Originally Posted by Kevin Thomas

In what way wouldn't it be ideal?

might have too much advance and is a little too slow to react to knock perhaps and may not provide the ideal amount of fuel. is what im guessing. im going to try anyway though.

[Kevin Thomas]

Originally Posted by greg donovan

might have too much advance and is a little too slow to react to knock perhaps and may not provide the ideal amount of fuel. is what im guessing. im going to try anyway though.

This is what I wanted to know. Actually, from my experience from switching from a 1999 Legacy 2.5ltr ECU (AD61A) and my stock ECU (AC831), my stock ECU ran richer throughout the rpm range and I believe it ran with less timing advance (I lost my pocketlogger logs on this). Perhaps WAC can help out with the timing info since I sent him a 2.5ltr ECU a while back for testing/keeping (My memory escapes me). I do know my stock ECU is much more conservative and it dumps more fuel.

http://mywebpages.comcast.net/thomas...un-3rdGear.jpg

[Handsdown]

that font color is killing my eyes.

but yeah, the dohc heads really aren't that great, they've had a lot of problems iirc.

why not just use the strongest block and some cobb heads that are made for high hp engines? you're going to be using some crazy pistons and internals anyway, right?

[jamesfacts]

Originally Posted by Kevin Thomas

This is what I wanted to know. Actually, from my experience from switching from a 1999 Legacy 2.5ltr ECU (AD61A) and my stock ECU (AC831), my stock ECU ran richer throughout the rpm range and I believe it ran with less timing advance (I lost my pocketlogger logs on this). Perhaps WAC can help out with the timing info since I sent him a 2.5ltr ECU a while back for testing/keeping (My memory escapes me). I do know my stock ECU is much more conservative and it dumps more fuel.

http://mywebpages.comcast.net/thomas...un-3rdGear.jpg

Interesting... Kevin, you really are the dyno whore.

Originally Posted by Handsdown

that font color is killing my eyes.

but yeah, the dohc heads really aren't that great, they've had a lot of problems iirc.

I think you're talking about the headgaket problems that were so common on 97-98 ej25s. The new 4-layer hgs seem to have fixed that problem now, and I love the way my DOHC ej25 revs...

[Matt Monson]

Ok,
A couple of corrections to the opening post that I don't see adressed in what is some very good discussion.
1. Putting either DOHC or SOHC EJ25 heads onto an EJ22 or EJ22T will lower, not raise the CR.
2. '98-04 rods and crankshaft are a downgrade in quality. All phase I EJ22's NA and Turbo have a forged crank and rods.
3. There are very very few parts out there that are "better" than OEM. stick to Subaru parts for most everything except maybe some custom high CR pistons

As for the other discussion about the 1.8l ECU. I know that Xphyr has a project car that is running an '04 EJ25 block w/ '98 DOHC EJ25 heads that he has fitted with HKS STI v3 cams, and he uses the 1.8l ECU to run the thing. It recently put 140hp to the wheels at 5000 on the dyno with Borla headers and no CAI...

[greg donovan]

Originally Posted by Matt Monson

2. '98-04 rods and crankshaft are a downgrade in quality. All phase I EJ22's NA and Turbo have a forged crank and rods.

are you sure about this? had never heard that before. that would be really cool.

[JonofScio]

I don't know what I would suggest an EJ25 block.

All n/a ej25 blocks are open deck. remember the EA63? subaru was almost sued over the fact that they all blew head gaskets big time. The FIRST engine after the EA63 (EA65, EA71, EA81, EA82) to be open deck was the EJ series... and the only reasons that the EJ18 and EJ22s DON'T blow headgaskets as much as the EJ25 is because the EJ25 is not only a bigger stroke, but is a bigger bore. so much so, that, it's really cutting the line on the space between the cylinders. The EJ25 crank has a 4mm longer throw (distance between TDC and BDC) which means 4mm more volume space (raises a 2.2 to 2.3L displacement) and increases the compression by 2mm (half of the stroke is going back 2mm more increasing displacement, and 2mm more forwards increasing compression.)

I say, an EJ22T block and rods, EJ20T heads, a phase I EJ25E crank, and EJ22E pistons. And then O-ring the heads. O ringing means no gasket, so there is no loss in compression from the space of the gasket between the block and heads.

The EJ22E/T block has the same main bearing and rod bearing locations as the Phase I EJ25. Until you get to the EJ22B engine, which has different internals. but that's off topic. All E designated engines (1, 5, 7, E, G, B, ect.) as far as what I know, have forged internals. forged internals are better because they are much stronger... but they are heavier... so...

anyhow, this combination of stuff (EJ25 crank, EJ22 bore, EJ20 heads) would be upwards of 14:1 CR. This is a rough estimate. You'd need a stand alone management... you'd need... this and that and this and that... blah blah. You'd want massive cams, a turbo water pump, the turbo oil pump, an intercooler, probably polished water jackets... lots of things. Plus you'd need like 115+ octane. The highest n/a I've ever read up on was 290hp, but it was a 2.0L and had dual throttle bodies, and massive work done to it.

I''ve seen and heard of 5.7L engines making 670+hp and 4.5L engines making 600+ and even a 4.4L making 900hp. (how about a 32v northstar in the back of a fiero!) But that's serious money.... the more n/a power you make an engine achieve, the less likely it is to be reliable.

All in all, it's easier to turbo, and get away with, and get power gains from it, than to make a high hp n/a motor. you have to be determined.

[Tim Sanderson]

That's crazzzy!!!

I'm Brian Fellows.

Thanks for all the great info Jonofscio.

[Warp3]

Originally Posted by mi_cistemz_loudr

The following is a choice of the 2, but i dunno which would be better:
MY98 EJ25 DOHC cylinder head (cuz its dohc)
OR
MY00-04 EJ25 SOHC cylinder head (boasts higher compression)

The bump to a 10:1 CR in the 2000+ EJ25 comes from the piston design, not the heads. In fact, the 1999 2.5RS has the same SOHC heads as the 2000+ models, but still has the same 9.7:1 CR as the 98 DOHC model.

Shane

[JonofScio]

Brain fellows rocks. That's just CRAAAZZZY!

I'm surprised nobody flamed me for having the opinion that I'm not a fan of the EJ25.