low compression on all cylinders

[silversr]

I've been having some issues with my sr20 running rich. So I did a compression check cold and it was 90psi across, warm 65psi across. I also did a leak down test and all the cylinders were below 10% loss which I thought was great. Obviously something is wrong now im leaning towards the rings but its barely leaking from that area. I have s3 cams not that it would make a difference...

[GuardianLlama]

Since when do cams not make a difference?

[silversr]

So would s3 cams make a difference since its built around the stock valvetrain? Before anyone asks it is mechanically timed right.

[GuardianLlama]

More valve overlap = lower active compression ratio. Although 65 paid is way too low. Running compression test at WOT?

[jacobs13]

check your cam timing

[silversr]

I am doing the compression test at WOT. I installed the cams just like I would with the stock ones heres a pic. The crank pulley is pointed at the 2nd mark from the left I didn't get the pic though.

http://i115.photobucket.com/albums/n290/blu24d/2011-09-12_18-05-23_380.jpg

[KiLLeR2001]

Are the cam lobes pointing outwards in the above pic?

[silversr]

Yes, they are pointed away from each other. Oh, I tried a cap full of oil and it didn't raise the compression either...should I pour more oil into the cylinders?

[jacobs13]

you should have the chain marks lines up as well with the sprocket marks. Do yo have a tune?

[silversr]

Why do I have to line up the silver marks? Couldn't I just count the rollers? I have a Enthalpy tune but I dont think it should affect it doing a compression test.

[KiLLeR2001]

You sure your compression tester is working properly?

At 90psi I would think your car would have a lot more problems than just running rich...

Do you have a tune?

[silversr]

As stated above I'm running a Enthalpy tune. My mods include GT2871R, Z32 mafs, 740cc etc. I checked the signal from the MAF and its sending 1.3VDC back to the ecu at idle and the TPS signal is sending .046VDC. I'm sure that falls into spec but I'll look into the electrical part tomorrow and take the readings right at the ECU.
I'm sure the compression tester is working like it should. As a reference at idle its running 10-11afr cruising too

[delado]

Your compression tester can be completely off. Happened to me.

[silversr]

I guess it could be off...but its still really low compression.

[delado]

I guess it could be off...but its still really low compression.

I recently bought my sr and decided to compression test it just for the hell of it even though I pulled it off a strong running car. It came out to 80psi all across. So I was like wtf... Then I borrowed a bro's tester, and came out to 150psi all across. Then a dude from the shop goes "oh, I forgot to tell you to add 70psi to whatever you get. haha".. :hahano:

[[email protected]]

well first of all, something is wrong with the compression numbers. hot numbers should be higher than a cold engine numbers. make sure the tester is on correctly

[silversr]

I will buy a new compression tester and go from there. Still doesn't explain why it's running rich if the compression is fine. The injectors aren't stuck open, mafs sending the cqorrect signal voltage, tps too and the cts resistance was within spec with the water temp. Seems like I got a lot of issues going on.

[usedgoldfish]

Happened to me mine read 80 all the way across after new tester it read good

[silversr]

So if the compression were good what would cause those rich conditions?

[fliprayzin240sx]

How rich are we talking about? Rom tunes will always be rich no matter what. Now if its rich like its flooding or you have black smoke coming out of the back, then you have something else going on.

[silversr]

10-11afr rich idle and cruising

[[email protected]]

could be a faulty/fucked harness?

[silversr]

So if I check at the ecu for all of the signals and it reads right then the harness should be fine, right?

[obsolete]

did u double check the timing with a timing gun?

[vas570sx]

Where did this ECU come from? did you purchase it 2nd hand? It is possible that the tune in the ecu is scaled for 550cc injectors and is running rich on your vehicle due to the larger injectors. Maybe someone needed to sell it and lied to you...

As for the compression, get a new tester and try again.

So if I check at the ecu for all of the signals and it reads right then the harness should be fine, right?

yes

[silversr]

The tune is for 740cc I know because thats what Chris at enthalpy told me. I had this ecu for over 4 years. Just recently I had enthalpy do something with the tune again and it did fine for like a week felt pretty good the maf plug was fucked so I replaced itand took the extra ground off the maf plug, took it to the track 11.5-11.8 afr in boost and cruising home 14.7afr. Parked it for a week started it and it ran really rich at idle. I should've checked the compression before but I wasn't thinking. I will double check the ignition timing again.

[ChinkyChris]

What are you pulling for Vacuum at idle? How do the plugs look?

[silversr]

The vacuum at idle is around 16-18 in hg. The plugs are black .

[iveexcaped3]

If their all low and your compression idn't go up wwith oil. It's mostly going to be your timing. How many miles are on this engine?

[silversr]

I have no idea on the miles not a whole lot. Okay, bought a new compression gauge on a cold test 150+-2psi. Thank god! Still having the richness issue though. Checking timing now.

[iveexcaped3]

from the fsm i got it says:
spec is 190psi and 170 min with a 14psi variance between cylinders <---- thats for a 1992 SR20DE
spec is 178psi and 149 min with a 14psi variance between cylinders<---- thats for a
1998 SR20DE

[KiLLeR2001]

SR20DET is different. 160psi across all 4 is perfect. 150psi is acceptable as well.

[iveexcaped3]

not trying to thread jack or any thing but why would it be lower for the turbo application if you dont change any of the internals?

[silversr]

Alright, I think I figured out the problem the ground in the firewall that was attached to the head was on the same bolt that the coilpack harness ground was on. Relocated it and its running fine for now.

[KiLLeR2001]

not trying to thread jack or any thing but why would it be lower for the turbo application if you dont change any of the internals?

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