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

drftsub · Post by **drftsub** » Thu Aug 31, 2006 5:18 pm

I am not saying it wont function, I personally think that c:r in the low 7's is too little ( for what I would do in my personal setup ) , unless you are building something that you are going to boost a ton, but off boost performance will suffer a bit.

Matt Monson · Post by **Matt Monson** » Thu Aug 31, 2006 9:16 pm

Yeah,
I hear that all the time, but have had the pleasure of driving and riding in some of the earliest Ej22T/Ej25 hybrid engines in the country. Off boost performance is not what everyone assumes it will be, and other than at stoplights, it's very rare to be at an RPM where the transition from part throttle vacuum cruising to boosted is an issue. I also like to remind people that early 911 turbos were 6.5:1 compression and many of their early NA engines, including my 1970 911, were between 7.5 and 8.6:1

I am not trying to make you wrong here. I am just pointing out that a CR around 8:1 is not as important on a turbo build as it is commonly made out to be on these boards. And if the $500 cost of forged pistons were cost prohibitive to someone doing something like this, I think if they threw it together with stock pistons they would be pleasantly surprised by the results...

drftsub · Post by **drftsub** » Thu Aug 31, 2006 9:27 pm

I agree, but as I will be in area's where off boost is of issue, and I want to have something with off boost grunt a little ( and it is my daily driver when the weather is not good enough to be on the bike ). I am concerned with moving the thing from a stop. Again , its just my preferance. Now I have ridden in some vehicles with very low comp ratio's myself, and am not a newb when it comes to this stuff. I do know its very workable, but I was unhappy with the off boost and transiant response if it were my own.

btw - Dont take this as me being argumentitive, I do agree with your point. But I personally still feel that a C:R of more than 8/1 will net a better Overall performing engine. Just because it can and has been done does not mean it is optimal.

BhamRoadrunner · Post by **BhamRoadrunner** » Thu Sep 07, 2006 5:41 pm

Has anyone, by chance, figured the compression ratio with stock HG and EJ205T heads?

I'm thinking I'm going to be replacing 2.2T heads with USDM WRX heads.

Post by **Legacy777** » Thu Sep 07, 2006 5:46 pm

BhamRoadrunner wrote:Has anyone, by chance, figured the compression ratio with stock HG and EJ205T heads?

I'm thinking I'm going to be replacing 2.2T heads with USDM WRX heads.

Just an FYI, the stock turbo legacy intake manifold will not bolt up to the newer WRX heads.

BhamRoadrunner · Post by **BhamRoadrunner** » Thu Sep 07, 2006 6:02 pm

Legacy777 wrote:
BhamRoadrunner wrote:Has anyone, by chance, figured the compression ratio with stock HG and EJ205T heads?

I'm thinking I'm going to be replacing 2.2T heads with USDM WRX heads.
Just an FYI, the stock turbo legacy intake manifold will not bolt up to the newer WRX heads.

I know. I was looking at only using the Intake so I could mount a TMIC easier, then I found the intake doesn't bolt to the EJ22T heads, so I figured I might as well go ahead and do a head swap.

Then my project has spiraled downhill into an all out rebuild

drftsub · Post by **drftsub** » Thu Sep 07, 2006 6:14 pm

those heads should be a 49cc chamber, I dont have time to do the math at this second but it would be in the mid 7's

douglas vincent · Post by **douglas vincent** » Thu Sep 07, 2006 7:18 pm

My "off" boost power is plenty good enough to keep me happy, and I am in the 7.5-1 to 7.2-1 range probably.

BhamRoadrunner · Post by **BhamRoadrunner** » Thu Sep 07, 2006 10:30 pm

douglas vincent wrote:My "off" boost power is plenty good enough to keep me happy, and I am in the 7.5-1 to 7.2-1 range probably.

This car will be strictly Rally-x. I need boost ASAP, preferably when the tires start spinning

douglas vincent · Post by **douglas vincent** » Fri Sep 08, 2006 5:36 am

SC it. I did.

220 plus torque at 3000 rpm. 11 psi at 2500 rpm.

Matt Monson · Post by **Matt Monson** » Fri Sep 08, 2006 4:21 pm

Legacy777 wrote:
BhamRoadrunner wrote:Has anyone, by chance, figured the compression ratio with stock HG and EJ205T heads?

I'm thinking I'm going to be replacing 2.2T heads with USDM WRX heads.
Just an FYI, the stock turbo legacy intake manifold will not bolt up to the newer WRX heads.

Furthermore there are some compatibility issues with the EJ205 sensors and cams gears. Unless you are running a standalone ECU, getting Ej205 heads to work on the stock ECU will be a real challenge. The issue is the trigger points on the cam gears and them not being the same as the Ej22T gears...

Subtle · Post by **Subtle** » Sat Sep 09, 2006 12:15 am

I believe that the earlier Porsche turbos had the low cr of 6.5 because of the quaint air-cooled cylinder heads.

Not the cooling capacity of liquid-cooled heads.

shipjumper · Post by **shipjumper** » Wed Sep 13, 2006 3:18 am

On the issue of cam gears, do the early EJ20x (90-00) do they all have the same amount of teeth for the trigger sensor?

Matt Monson · Post by **Matt Monson** » Wed Sep 13, 2006 5:02 pm

Subtle wrote:I believe that the earlier Porsche turbos had the low cr of 6.5 because of the quaint air-cooled cylinder heads.

Not the cooling capacity of liquid-cooled heads.

Actually that has very little to do with it. If you do a little digging, 935's, 956's and 962's all had variants with water cooled heads and they ran anywhere from 6.5:1 to 7.5:1. The first Porsche factory turbo car to hit 8:1 CR was the 959, which also ran water cooled heads. If it was such a "qauint" design feature to run air cooled, explain to me why Porsche used air cooled engines all the way up until 1998??? Porsche would very likely still be using air cooled heads if it weren't for noise regulations that made it very difficult to continue running air cooled engines in their cars...

ej22t kid · Post by **ej22t kid** » Tue Jan 29, 2008 10:58 pm

if im not mistaken the wiseco pistons have a 20cc dish wich will put the ratio of a a ej20g head at 56-57 also with a cometic hg will place compression around 7.9:1

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