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Old 06-05-2001, 06:25 PM   #1
Naturally Aspirated
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Post Compression ratio?

Does anyone know what the compression ratio would be if I were to put 2.2L heads onto a 2.5 block with dohc pistons?


-Mike
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Old 06-05-2001, 07:12 PM   #2
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Just a guess, 11-12..too high..... but why? 2.2 heads have much smaller valves and ports than 2.5 heads..
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Old 06-05-2001, 07:24 PM   #3
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Ok, you're talking about the EJ25 from a DOHC right? The EJ22's heads are all SOHC (in north america that is). You'd be taking a step back in "evolution"
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Old 06-05-2001, 07:56 PM   #4
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Naturally Aspirated - you are on to something here. There are a lot of Subaru Dealer Techs who have done this very thing - it rocks. I don't know if anyone has taken the time to figure the compression ratio but it is significantly higher, to the point of requiring high octane fuel for heavy load driving (mountainous roads, high temps). EJ25 block, EJ22 heads (phase I), with EJ25 Phase II head gaskets.

Yes, there is a significant sacrifice in valve size - 36mm Int. to 31mm Int., but everyone I know who has done this did it because the parts were free or cheap.

Of course, if you can use EJ22 Phase II heads then there is no sacrifice. The valves are the same size.
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Old 06-05-2001, 08:04 PM   #5
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hmmm, gtbguy, you know the 00-01 RS EJ25 motors are sohc as compared to the 98-99 EJ25(phase 2? dont know about "phases") motors which are DOHC, subaru took a step back too, i guess (sorry im being argumentative, but i love it so much)
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Old 06-05-2001, 08:48 PM   #6
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Someone I know was talking about doing this, and I'm somewhat interested, since I plan on staying N/A, and this is an easy way to boost the compression. If anyone has more info on this, it would be greatly appreciated (since the search function doesn't work now). I have a MY00, which is SOHC, so that would make things easier...
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Old 06-06-2001, 01:56 AM   #7
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Yeah I am getting the block for a good price, I may be "stepping back" in time but we will see what turns out. Hopefully a pretty fast n/a car. I am doing this cause heads are to expensive for my taste, so I figure why not just use the heads from my existing 2.2 engine. I need to figure the compression ratio first, I dont just want a guess.


-Mike



[This message has been edited by Naturally Aspirated (edited June 06, 2001).]
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Old 06-06-2001, 04:06 AM   #8
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Well then, buy a burette, a piece of plexi glass and measure it. Use ATF for the liquid and measure the size of the two chambers. Then easure the thickness of the head gasket use height x Pi x radius squared to find the volume of the head gasket. Measure how far down the piston is at TDC, use the same formula to find this volume(I'm assuming flat top piston). Then find the volume of the cylinder by putting the bore and stroke dimensions into the equation. Divide the volume of the cylinder by the combined total of the combustion chamber (chamber, headgasket and area above the piston) and that is your compression ratio.
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Old 06-06-2001, 06:59 AM   #9
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How much of a gain are you taking about?
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Old 06-08-2001, 05:14 AM   #10
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Bumping this one up... I'm going to talk to a Subaru tech on Saturday who knows people who have done this, and I'll try to find out more definite answers (i.e. what the new effective CR will be, and how big of a gain should we expect).
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Old 06-08-2001, 05:41 AM   #11
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Thanks fellfrosch7, much appreciated!


-Mike
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Old 06-08-2001, 07:22 AM   #12
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But how much of an advantage is higher compression if you're flowing less air? I'd use a 97-up 2.2L head and it would be better to port the heck out of it.

SubyTechMaster-- please tell me these guys are using modified stock EFI or aftermarket programmable EFI and not cutting the top off the intake manifold and using a carburetor.
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Old 06-08-2001, 01:09 PM   #13
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The Phase I head has a single cam contained in the head, 31mm Intake Valves, 27mm Exhaust Valves, valves angled at 15deg from center. Early years (90-96) have hydraulic lash adjusters and they didn't get roller rocker arms until '93 (Impreza) or '95 (Legacy). '93 Impreza and later, '95 Legacy and later, have EGR which makes the heads either right or left side. These heads usually have dual exhaust ports but may have a single exhaust port if it's a CA spec, TLEV motor.

The Phase II head has a single camshaft sandwiched between the head and a camcase, 36mm Intake, 32mm Exhaust. Intake valves are 23deg off center, Exhaust valves are 20deg off center, contributing to a swirl effect in the combustion chamber. They do not have EGR and so the heads can be used left or right. The only differance between 2.5L and 2.2L heads is the 2.5L has dual exhaust ports and the 2.2L is a single.

Yes, the people I know who have done this are using the stock Fuel Injection. Hence the pinging under certain conditions.

The head gaskets on all the Phase I motors were a heavy composite type until '97 when they went to adjustable valves/interferance motors. At that time they switched to a 3-piece metal head gasket which may appear thinner but is very durable. This is the head gasket you would get today, they superceded the #s.
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Old 06-09-2001, 12:17 AM   #14
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Question

SubyTechMaster-
What is the difference between the Phase I & II 2.2L? Did Subaru change from DOHC to SOHC on this block as well?

Also, I've heard that the head gasket from the DOHC EJ25 (Phase I) is beefier than the SOHC one (Phase II). Is this not true?

Thanks,
-Chris
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Old 06-09-2001, 02:13 AM   #15
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Subaru didn't take a step back by going from DOHC to single.. less rotating mass, quicker revs, and less drag. Also makes for simpler engine design, and repair.


RD
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Old 12-31-2002, 05:37 AM   #16
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To answer the question asked: 11.0:1, a bump of <1.5
P2 SOHC 2.2L heads on P2 SOHC 2.5L motor. High octane is a must. ECU reprogram helps too.
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Old 01-29-2003, 01:28 AM   #17
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Default Phase I & II. Engine? or Heads?

I need someone to straighten me out about terms "Phase I" and "Phase II". Oh, first of all, I would appreciate if we can stick to 2.2L (on Impreza) to make things simple.

Before I started reading this threads, the only knowledge I had about "Phase I" or "Phase II" is that the terms appliy to Engine. Subaru had modification on their EJ22 starting MY99, which they call "Phase II motor" that bumped Impreza's EJ22 engine from 137hp to 142hp.

Then I got confused when I started reading about Phase-I-Head and Phase-II-Head. When I checked into the history of EJ22 on Impreza, seems like there have been at least twice of modification. I am not sure this is correct or not, but one website (SubaruParts.com) specify them as EJ22E, EJ22EZ and EJ22#, and 135hp, 137hp and 142hp respectively.

So, from all these information, my conclusion is... (which is my first question if I am right or not)

1. When first 2.2L was introduced for Impreza OBS, it was Phase I engine with Phase I head.

2. In 1997 (?), head on EJ22 was changed to Phase II head, which my MY98 has.

3. From MY99, EJ22 is Phase II engine and has Phase II head.

I hope I am right... but this would be the only conclusion I could draw...

I have general idea about the difference between Phase-I-Head and Phase-II-Head, but when SubyTechMaster talked about bigger valves and Swirl-effect because of off-set valve, I got confused. Is this info applying Phase-II-head or Phase II-motor?

Subaru Homepage

http://www.subaru.co.jp/spirits/mechanism/1/index.html

talks about their major modification about their piston, which they call LF (Low Fuel) Piston that has shorter, thinner piston-skirt. According to them, this was done in 1997 (in Japan), but when did they do this to US model? Does this apply to when Phase-II-motor was brought (1999) or Phase-II-head was brought (1997?)?

Sorry for the lengthy post, but last quick question. If I am talking things straight, my MY98 OBS should have Phase I motor and Phase II head (Single port). I've read some post about switching the head to older head (Phase I. Dual port) in order to get more flow, which might bring another benefit to use more available Exhaust header.

1. Is this going to be better than using Exhaust-header for single port (like Borla has)?
2. If the head were changed to Phase I 2.2L, can I use those Exhaust headers for 2.5RS?

Again, sorry for digging up the old thread, but I would appreciate if you guys could help...

"T"

Last edited by Cefiro26; 01-29-2003 at 01:47 AM.
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Old 01-29-2003, 09:11 AM   #18
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Only problem that I see which sorta botches things up in your research is that you're limiting yourself to the impreza. The Legacy was introduced about 2-3 years before the impreza, or something like that.

The original EJ22 found in the 1990 legacy had 132 hp & I think 135 or 137 ft/lbs of torque.

To my knowledge that motor design didn't change drastically until 95 or 96.....which brought the single exhaust port heads, larger valves, roller rockers, and other goodies.

Any modifications again past 99 I'm not too familiar with....I'm pretty sure Subaru stopped making the EJ22 a year or so later.

As for your specific questions. Leave your heads alone. Like I mentioned, the heads currently on your engine have larger valves, the swirl effect, and roller rockers. Those things alone will give you more power then having dual exhaust ports.....and don't forget, you have smaller valves & no swirl effect with the older heads.

I'd say just use the single exhaust port header from borla.

If you "were" to swap heads to the dual exhaust port heads, yes the headers from the 2.5 will bolt up to the 2.2 heads.

Josh
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Old 01-29-2003, 05:06 PM   #19
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I got a reply Yay!

Thanks Josh. So glad to see another 2.2L owner. Well, I love legacy, too, but I have Impreza... so...

But FYI

<Legacy 2.2L>
1990-1994 2198cc 130hp 137lb/ft
1995-1996 2212cc 135hp 140lb/ft
1997-1998 2212cc 137hp 145lb/ft
1999-? 2212cc 142hp 149lb/ft

So, Legacy had 3 modification on their 2.2L engines...

The first 2.2L appeared for Impreza in 1995, from what I can see from the spec, it seems lidentical to what 1995-1996 Legacy had (2nd listed above). Then that brought some conflict to what I predicted about Impreza. I said...

First Impreza's 2.2L (1995-1996) had Phase-I-motor and Phase-I-Header.

Josh says, in 1995 or 1996, Legacy got Phase II head, which has single port instead of previous dual port. That makes sense if you look at the change in displacement (well, I am not a mechanic... but kindda makes sense?).

So wouldn't that be more plausible if I say...

"Impreza's 2.2L never had Phase I head" <-- ???

When people talked about Phase I head or Phase II head for Impreza (beside 2.5L), wouldn't that be posiible they were talking about 1.8L instead? Then, what brought 2hp up in 1997 on both Impreza and Legacy?

-OR-

"1995-1996 Impreza and Legacy had Phase-I-head and Phase II head wasn't used until 1997 for either model. Thus 2hp up was brought by the use of Phase II head" <---???

If the second prediction is right, then 5hp up in 1995 compare to 1st generation Legacy was because of EGR and the use of Roller Rocker arms?

Someone mentioned how to identify Phase-I-Head in earlier thread, and he mentioned that valve cover has "Subaru" logo if it's phase I. Well, my MY 98 says "Subaru" on it's valve cover, but single port. And I know that this isn't TLEV. Josh? Can you help me clarifying this?

hmm... I need someone to post definitive answers to these questions...please?

"T"
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Old 01-29-2003, 09:29 PM   #20
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Ok......here's a question.....if the 90-94 heads/motors are not the phase 1 heads/motors.......what comes before 1? zero.....what do you call them......phase 0......or do they just not have a name.

I had been calling my engine a phase 1......because it was the first one......hence being number 1. If subaru in their ultimate wisdom just didn't give the 90-94 engines a name, and then started off with phase 1 with the 95 models......which is sorta what some have implied.......it seems just stupid IMO.....but that's subaru's fault.

I'll try and take a look at my heads and see if I see any emblem or anything.....where abouts was this emblem located?

Josh
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Old 01-30-2003, 01:49 AM   #21
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Mysterious, ain't it?

I'm sure EJ22 on 1990-1994 Legacy is Phase I (or not much different from Impreza's Phase I).

Well, this is my diemma, which is the reason why I started asking about this in first place. When people say "Phase I" or "Phase II", which one (Motor or just Head) are we talking about? Or first of all, is that definitively true that "Phase I motor" and "Phase I head" are completely different terms?

I am too new here. I would appreciate if someone could provide a good definition.

When I look at Valve-cover on my engine, it says "Subaru". It's not like Emblem (or any separate part) but being carved. Thank you for checking Josh Hey, if I remember correct, you transplant head from later Legacy to your Legacy, right? Do you happen to be able to compare them side by side? <--- or am I thinking of someone else?

"T"

Last edited by Cefiro26; 01-30-2003 at 01:59 AM.
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Old 01-30-2003, 01:54 AM   #22
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Abyways, nice homepage, Josh!

"T"
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Old 01-30-2003, 08:41 AM   #23
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I'll tell ya what I'll do.....I'll give the guy I bought my FSM's from an email. He's a former subaru tech. So he may know.

Not sure if SubyTechmaster is still around or not, but he is a wealth of information. I think he teaches the techs.....so if you can some how contact him, I'm sure he would know.

My valve covers just say Subaru across them, raised letters.

You're thinkin of someone else.....I haven't really touched the heads/internals of this motor.

and thanks for the compliments on the site. It's in dire need of an overhaul, but I'm waiting for some things to get done on the car first.

Josh
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Old 02-01-2003, 01:42 AM   #24
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Thanks again for the reply, Josh

Yeah, I was thinking about contacting SubyTechMaster, but then I realized that he hasn't appeared to this forum these days... I hope he is still around...

Don't we have "Tech" who knows old stuff around here? or They just don't care about 2.2L anymore...? Well, my question itself might be meaningless... but I am just too curious to know

I will try to contact SubyTechMaster (somehow). If you find anything new, please let me know

"T"
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Old 02-13-2003, 09:26 AM   #25
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Just got a reply back on the naming convention stuff. Here is what Dave had to say.

"Hi Josh,

The EJ22 1.8 was available in Lagacy and Impreza. Port change was in 1996 and called phase II, In 1997 they went to solid lifters still called phase II. From 1999-2001 It was only available in the L model and Impreza.

Dave"
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