20g head/22t block combo, actual comp ratio

[drftsub]

did anyone ever figure out what exactly the comp ratio was for these? I need to CC my heads still but was wondering if someone else has already done it.

this is of course assuming stock 22t bottom end/pistons

thx

[Imprezive]

pish posh

[drftsub]

again with the pish posh....

go get that GTI ready!!

[drftsub]

ok,

I cc'd the heads 4 times tonite, consistantly got 56cc's , although that does not sound like a volume size I have heard of , that appears to be what these heads are.

anyone seen specs of 56cc's? ( or thereabouts )

[drftsub]

duh,

newer liberty heads....

anywho.. lets see what I can hodge podge together with these parts that wont sell

[drftsub]

ok.

sti block
arias forged pistons @ 22 cc volume
sti stock gasket @ .21 compressed
deck clearance of -.254mm
20g heads @ 57cc volume
std stroke/bore for 2.5
nets :

compression ratio of 8.06/1 <- acceptable
however
if I chose to run the ej22t block unmodified I would end up with somewhere around 7.2 / 1

nico must have found some of the 49cc heads for his to work, as this seems way too low to be functional.

anyway, figured I would post what I figured out. and it seems that ( barring anyone buying my stuff) I am going to build my 2.5l w ej20 heads.

[douglas vincent]

I have the ej22t turbo pistons in an NA block with the twin turbo heads which are much much much bigger combustion chamber than the stock ej22t heads. I am betting 7.5-1 or less. Pretty doggy NA.

[drftsub]

ack! that would suck NA , I assume that was a "need to get a motor running out of this pile of spare parts " project?

[Matt Monson]

57cc is the published number that I have seen for those heads.

[drftsub]

Yea, I figure that my 1 cc vairiance could have been from a little carbon on the valves etc. considering I got that close consistantly I say 57's it is.

[Threshld1]

anyone know if putting 95 leggy twinscroll 20g heads on the 22t block w/ stock internals is worth doing? any work required beyond moding turbo feed lines, new dohc t-belt, and 22t headgaskets (assuming it is paired with a proper intake mani)?

[drftsub]

would depend on the chamber volume, it could work if they are the smaller norm ( around 49cc ) and I still think that your comp ratio with stock gaskets will be too low. If you ran the thin gaskets it makes it better, but there isnt a good thin option for the 2.2 either.

[NICO]

i dont no about you guys but dont do anything, just stick the heads on the ej22t-block.

i heard from so many pepole that its going to be slow your nuts, you will have no low end power. well they where all wrong, not only do i have foot pound stopping 1st 2nd gear mid and high is just the same.

at 7psi i had a tunner tell me that this car is insane, when i boost it to a easy 19psi i will leave any car bike plane trian 0-100kms looking like there is no life in there motor.

1st an 2nd gear want to rip my tires tranny apart, plus tryin to steer the crazy ness in a stright line is impossible.

[drftsub]

but do you know what heads you have? if you have a small combustion chamber head it will be much better than if you had the ones I had. I seriously doubt you have 57cc chambers.

also,

what gasket did you use?

[Threshld1]

Blast, this is what i feared, so unless im planning on using new pistons the new heads are not a good idea?

[drftsub]

best bet would be to CC the heads and find an accurate chamber size, seems there were quite a few. Once you have that you can do the calcs to figure out what it is you need to do .

But yes, most likely you would end up with a very low comp ratio, while it would work, it would definitly be sub-optimal.

[Threshld1]

Anyone have the displacment specs on the stock 22t pistons and heads?

[drftsub]

there is that ejspecs page, although I dont know how much to trust it,
I saw 28cc for the pistons and 40cc for the chamber.

I think the head gasket compressed is ~1.5 mm for the 2.2 gasket

I have sohc 22T heads on my shelf at home, if I get a chance tonite I will cc them.

[All_talk]

Here’s what I got…

First stock:
Displaced volume = 554cc (97mm bore x 75mm stroke)
Piston volume = 28cc (published value, I have not confirmed)
Gasket volume = 11.1cc (1.5mm thick, stock EJ22T)
Head volume = 40cc (back calculated from published CR)
[554 + (28 + 11.1 + 40)]/(79.1) = 8.00:1 CR

I cc’d my EJ20G heads at 56cc, so 56-57 looks to be a good number:
[554 + (28 + 11.1 + 56)]/(95.1) = 6.83:1 CR

Now if you go with the “thin” 0.5mm head gasket you get:
[554 + (28 + 3.7 + 56)]/(87.7) = 7.32:1 CR
But I believe the EJ22T pistons come above deck height by about 0.25mm (0.010”), so that leaves only 0.25mm of deck clearance… to close for me.

I have heard there is a 1mm HG (from the phase II 2.5 DOHC?), which would give .039” deck clearance (.040 is considered optimal by many performance engine builders). Which yields: [554 + (28 + 7.4 + 56)]/(91.4) = 7.06:1 CR

You could use N/A pistons, 14.5cc?, but you get narrower (weaker) ring lands and the rings are closer to the piston crown and subject to more heat:
[554 + (14.5 + 11.1 + 56)]/(81.6) = 7.79:1 CR w/1.5mm HG
Or [554 + (14.5 + 7.4 + 56)]/(77.9) = 8.11:1 w/1mm HG
Might be an option for lower boost levels… but who wants that.

Best option is still custom piston, which means you can go forged… yeah, big boost here I come. But adds about $500 to the build, plus maybe the cost of a bore job… Booo, Hisss.

It all makes fitting the later, smaller chamber, DOHC heads & manifold look better… until you have try and fit up the EJ22T sensors so you can use the stock ECU & wiring. Then you could transfer a later ECU and wiring harness, or port the stock heads or go with the RS SOHC heads, and on, and on, and on… its all just time & money. But remember… if it was easy, every one would do it.

For now my EJ20G heads sit on my bench... decisions, decisions.
Gary

[drftsub]

bah,,

just go standalone and call it good.


I wish hydra would make a damn wire in.....


oh well, looks like I will haltech it.

[NICO]

the heads i used are from a ej20k 2.0l turbo vf22 480cc injectors motor. the heads come stock ported the same size as the gaskets, even the intakemanifold is the same size match as the heads ports.

i am useing stock ej22t head gaskets, there is a little meat from the heads not being a 2.2l.

[drftsub]

did you cc the heads ever? were they shim/bucket lifters or hydro w rockers?

[NICO]

dont no what the cc could be on these heads, it must say it on the internet some where. they where shim/bucket lifters.

im going to try a search.

[drftsub]

problem is without actually cc THOSE heads, you dont really know what they are ( from my experiance so far , looking at the available charts havent been so accurate ) . I would be interested to see exactly what you have, and see what your car is really running for a compression ratio.

[Matt Monson]

Nico's heads are virtually identical to USDM DOHC Ej25 heads, with the exception of his cam profiles. They will be right around 49cc. '97-98 WRX or Ej25 heads really would be optimum for this kind of build, but I personally don't see an issue with the lower CR numbers that the 89-96 Ej20G heads give you. But that's just me...