graphitegrey9

I recently just bought my evo 9 basically heres the run down its a built motor from turbo trix with manely internals. I just recently did a compression test on it and it had about 95 to 100 psi cold accross all the cylinders and about the same when it was warmed up +or- about 1 to 5 psi. i put about a teaspoon of oil in the cylinders with almost no change, but when adding more than normal oil to the cylinders they jumped up to about 140 or so. The engine was built probly about a year ago it seems a little soon for a rebuild but i am not ruling it out. i haven't done a leak down check yet but will do it this weekend and post the numbers I get any comments or ideas let me know. I know the min. psi is 92 per. the manual but that just to low for me. My other question is could the manely pistons cause the low compression?

Blue91lx

iTrader: (44)

You may need a valve job. Losing compression through the seats.

graphitegrey9

i thought that too but with putting extra oil in the cylinders the compression goes up. Also the head was rebuilt with the engine around the same time.

project_skyline

iTrader: (30)

40 psi isn't a big jump, its unlikely its the rings in all cylinders. Still pretty low, what cams do you have?

Do a leak down!

graphitegrey9

Well looking through my receipts I thought I had cosworths but the newest receipt says it has kelford 272's. I took the valve cover off and I could see where the numbers 272 were ground into the cams. This is how I bought it so I am still going through everything and learning. Also I will do a leak down tomorrow and post the numbers

1sxyrxy

iTrader: (10)

If it runs ok then it's probably fine. Your cams will bring down compression.

stackhouse

iTrader: (8)

This may sound crazy but have you tried a second compression gauge? A friend of mine recently bought a supposedly solid car. He did compression test all 4 cyls were ~90 and he was in full freak out mode.
He ended up borrowing a second and third gauge they both read 140 across the boards.
Could explain your low# if the car is running OK. Also I think built motors tend to have lower compression than stock, but I cant say for sure.
Good luck, regardless.

project_skyline

iTrader: (30)

That is a good point!

When I bought mine I thought why trust it to something cheap? So I bought a snap on.

siceclipse

iTrader: (7)

try another gauge.
How does the car run??? good or bad??
What is the CR on the pistons?

graphitegrey9

I tried the gauge on my wife's car and had 175 on all four cylinders so I think that the gauge is ok also it's a snap on. The car runs good it was dyno'd last summer or so at 367 hp and 398 tq. It still feels and runs like it has that kind of power. There are no idle issues only issue I have right now is that it is running rich. When it was tuned last it was at 35 ft. and where I live now it's around 900ft. It's tuned on speed density so that's why I am thinking its running rich I did see a couple of other post that said the cam over lap will cause a low comp. psi especially with mivec. I will do a leak down and post what I get thnx for everyone's help

mt057

iTrader: (6)

I find a leak down test is just as easy to do a compression test and tells you so much more. I would definitely do a leak down test next.

graphitegrey9

Ok i did a leak down test on my car and found it to have about 10% leak down in all for cylinders not to bad if you ask me. So i am guessing that the low compression check was from the vavle over lap from the cams. Who would have thought?

10isace

iTrader: (12)

I had a similar problem https://www.evolutionm.net/forums/ev...sion-help.html

I did compression test and freaked out! Car drives great and even better after fixing a boost leak. I'm sure it's the compression gauge. The main thing is that all the cylinders are at similar compression. I've talked to a few mechanics and they say the tool is used to compare the cylinders.

10isace

iTrader: (12)

10% is very good! I have S2's so I think we're in the same boat with a leak down test.

graphitegrey9

The compression gauge is working fine I was just thinking that the camshaft overlap was causing the low compression. I also found a boost leak at the TB after changing the shaft seals so I will put a new gasket on the TB hopefully that will help my running rich issue a little. Thnx for everyone's help!