Hi all, as the title says,

I am looking for a compression gain for a major power increase.

My car runs LPG and they love high compression.

Ant help would be greatly appreciated.

Cheers,

Matt

Hi all, as the title says,

I am looking for a compression gain for a major power increase.

My car runs LPG and they love high compression.

Ant help would be greatly appreciated.

Cheers,

Matt

 

I've been asking SAME question for long time, no one seems to know as far I know, I don't wanna gamble if it doesn't work.

 

I wanted to get EJ18 SOHC and fit it on EJ22 for increase of compression, won't be much but noticeable in theory.

Cheers

AP

I don't know why they wouldn't, they are basically the same engine. I know people who have installed EJ22s into a car that had an EJ18 in it, they had to use the EJ18 intake manifold, so I know there is no difference there.

 

Why do you feel that the EJ18 heads will give you high compression? Does it have fewer cc's (in the compustion camber area of the head) then the EJ22 heads? Or is it the pistions that are giving teh EJ18 higher compression?

 

EJ-18

BORE 87.9mm

STROKE 75mm

 

EJ-22

BORE 96.9mm

STROKE 75mm

 

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I can't seem to dig up any combustion chamber volume specs, but both engines are running the same block with the same stroke, only the bore dimension is different. I'll make that leap to rump roast-u-me that the EJ-18's chamber would have a slightly smaller diameter to match the smaller bore of the EJ-18 piston.

Math isn't my strong point, but since the 2.2 piston is pushing 1.215 greater displacement upward the same distance means that it would increase the CR by 1.215?

If so, that would bump a 9.7:1 CR up to 11.8:1

Unless I missed something, that doesn't seem too shabby.

check out www.bbs.legacycentral.org

 

Matt Monson should be able to answer your question. I believe the ej18 heads will increase your compression ratio, by how much I don't know.

 

Another thing to note is the EJ18 has slightly smaller valves too. I don't recall if it was just the intake or exhaust, or both.

Thanks for the help guys, yes its posssible, yes the valves are smaller, yes I am giving it a go.

 

From what my Gas Guru has been telling me, a 20% increase in compression will get me a 40% increase in HP.

Its to do with the specific burn rate of LPG.

 

I will post results as soon as its running.

 

Cheers all,

Matt

Thanks for the help guys, yes its posssible, yes the valves are smaller, yes I am giving it a go.

 

From what my Gas Guru has been telling me, a 20% increase in compression will get me a 40% increase in HP.

Its to do with the specific burn rate of LPG.

 

I will post results as soon as its running.

 

Cheers all,

Matt

 

Yeah that sounds about right, let us know how you went and see if you do save on fuel etc... see if you came any problems etc, could you keep us informed.

Cheers

AP

Matt Monson should be able to answer your question. I believe the ej18 heads will increase your compression ratio, by how much I don't know.

 

Another thing to note is the EJ18 has slightly smaller valves too. I don't recall if it was just the intake or exhaust, or both.

 

I read a bunch of his posts, Matt Monson is vehemently against using the EJ18 heads on an EJ22 because he says they "flow like crap."

 

But... he's never done it I don't think, and as far as I know no one else has, either. At least no one who has posted the results to a forum.

 

I've been debating the same issues you have, but I'm leaning toward doing the head swap anyway. For me, the power increase over the full RPM range from a boosted CR should outway the downfalls of limited flow, since it's going into an offroader and not a street screamer.

You might get higher compression, but, as hatchmonster says, they don't flow as well. Wouldn't that make the increase negligible? As far as I understand, the heads on the EJ22 are an improvment over the EJ18 ones, so wouldn't reversing them be going backwards in terms of performance?

 

Brian

just do a port and polish, and a valve job, replace the old valves with newer ones from a 2.2 im sure you could do it...... it would just take money...

just do a port and polish, and a valve job, replace the old valves with newer ones from a 2.2 im sure you could do it...... it would just take money...

 

PnP + valve job = way more money than I want to spend. I may PnP myself but I the valves are still going to be a bottleneck.

 

My point is that lugging around at lower RPM I'll still have a power increase even if the engine gets choked up at higher RPM/More throttle. So the swap might work for me in my offroad hatch, whereas I would not want to run it in my impreza...

Along with the smaller valves choking the top-end HP, you'll be condending with the EJ-18 cam.

 

As you say, the combo of tall compression and small ports will will give you tractor torque between 2000-3000 RPM.

is there a difference in cams between the 2.2 and the 1.8? I'm interested in this swap down the road in my imp.

I have run LPG in trucks and we used to raise the compression. I suspect the smaller valves will easily be offset by the extra power in LPG use.

This is not something I would do on a US street car because gas is getting worse and high compression can be a problem without reprogrammed electronics. The other reason is that reducing the size of the valves reduces potential top end power with gas.

Would the 2.5 head work? that might raise compression too, and flow better than the 1.8

Would the 2.5 head work? that might raise compression too, and flow better than the 1.8

 

2.5 heads on a 2.2 block will result in lower compression.

 

The mod that I guess really works great is 2.2 heads on the 2.5 block. Good flow, higher compression, beastly motor.

is there a difference in cams between the 2.2 and the 1.8? I'm interested in this swap down the road in my imp.

I'll admit my cam comment was conjecture, based on the smaller displacement motor having different (lesser) airflow requirements.

 

I could be completely wrong.