Reverse Question

[morgie]

We now know that the 2.0l DOHC heads on our 2.2l engine (8:1 stock CR) will have a ~7.5:1 CR..

With all the parts left over by my frankeinstein project... I may rebuild an engine with a wrx 2.0l shortblock + ej22T SOHC heads.

My question .. if the Dohc heads on 2.2T block is a .5 Cr drop, is the opposite (sohc heads on 2.0T block) will be a .5 CR increase ? or maybe more ? with a thin gasket, could it get a 9:1 or 9.5:1 CR ?

thanx !

[ciper]

Where did 7.5CR come from though? Thats not what I have seen...

EJ22 combo
bore 96.9
stroke 75mm
head chamber 49cc
piston volume 28cc
gasket thickness 1.52mm
calculated 7.27:1 CR

But the 2.2 turbo heads are the worst flowing option available, why do you want those? Plus the hydrolic lash adjusters become a problem at higher boost if they are worn.

You'd end up with a partially closed deck block, smaller bore and old heads! The only benefit I could see is that it would be easy to use a 2.2t manifold and associated electronics.

Ej20 with ej22t heads and 1.52 gasket = 8.43 compression ratio using these specs:

92mm bore
75mm stroke
40cc head
17cc dish piston
1.52mm gasket

[morgie]

Oki, i was just curious...

7.5:1 comes from ejcalcs website.. was the first thing i remembered

I have 1 EJ22T engine, 1 EJ20T engine, 1 EJ20T shortblock, 1 EJ22 NA engine.

I take the ej22T shortblock + ej20T dohc heads for my main project. But i'll have plently of parts to build another engine with a ej20T shortblock + the ej22T heads, and maybe this way recover some money instead of letting all those parts catch dust in my shed (cabanon)

[ciper]

I wonder how EJCALCS got that number? Id like to double check what Im doing wrong.

[morgie]

absolutely no idea. I think it's also written 7.5:1 in the sticky "notes on ej22T" post

[morgie]

I think i've found why !

on EJCalcs, they uses the 2.5l DOHC heads in their calculs, wich has 46cc of head volume, a bit less than the 2.0l DOHC heads, wich are 49cc head volume.

That may explain why you get a lower CR.
7.21:1 on 49cc
7.40:1 on 46cc

That makes sense ?

[teaguespeed]

could you lower the CR with the ej20t heads by planing them or something?

p.s. i hardly understand CRs

[ciper]

I thought about this. Issue is that you have to worry about exhaust and intake spacing. If you plane them down you end up reducing the width of the engine X2 of the amount of planing!

[morgie]

then nothing fits, you bolts the intake, it forces out, then the gaskets gets loose, you have bubbles in your prestone, Sahara desert gets flooded, and we all die.

Planning heads + boxer engine = badddddddd move

Planning heads + any other engine = quite ok.

[Legacy777]

simply by cr.....putting EJ22 or EJ22T heads on an EJ25 and most likely EJ20T block will increase CR.