I went to Shadowdawn's house yesterday for a valve adjustment and compression test to diagnose my "slow car problem." (I should be getting near 400hp, when I can barely beat stock ITR's).

The test numbers for cylinders 1 thru 4 are as follows:
145
135
125
155

Now, this is a BRAND NEW rebuilt motor. Right away, I called my friend who built it (he's very good, honest!) and he said that with JE's (as opposed to SRP's), they are a much "hotter" piston and you'll get lots of blowby when it's cold. That's why JE's are considered more of a race pison, and SRP's more of a street piston. He claims that JE's won't yield high compression numbers at all.

What do you guys think?

Both Shadowdawn and I think that my compression numbers are the problem of my slow car.

 

Get the engine to running temp and then perform the test.

 

I did....I drove about 75 miles to get to Eric's house, then did it on a hot motor.

BUT!! The method I used was to simply take out the ECU fuse and crank the motor for several seconds. When he did that test, he never got over 100psi, while I was getting around 130-150psi. When he did it his way of unplugging the injector clips, he got around 175 or so (see his post).

Could this be the reason my numbers are so low?

Cliff notes:
Shamoo - Took out ECU fuse and cranked motor to get numbers of 130-150psi
Shadowdawn - Took out ECU fuse and cranked motor to get numbers NEVER over 100psi.
Shadowdawn - Unplugged injector clips to get numbers around 175psi or so.

Am I doing it the right way? Plus my plugs are like white as hell.

 

its easy man. pull the fuel pump fuse under your dash. there are 2 fuses off on the side by themselves, raised up a little higher than the rest on a little square block. one is the SRS fuse i think, the other is the fuel pump.(you will know when you turn the key and dont hear the pump start. ) then unplug the big connector at the distributor. do the test, crank at least 7 times(i crank until it stops moving) i have JE 9.5:1, and i had 180 across the head.

 

Did you have the throttle wide open?

Those numbers are Extremely low...

With cracked sleeves, I had 120

 

oh yea, forgot about that, stand on the gas or wedge the throttle linkage wide open.

 

Why does everyone say this? I never did this anytime I did comp test on my car, before turbo I got 185-190 across the board just cranking with injectors clips off, and now did it the same way and got basicall 175 across the board

 

Don't you remember how I showed you to do a comp test?

Hot car, pull ecu fuse, WOT, crank 5-7 times, write down #, repeat.

If your car was hot then your comp #'s should be higher than that I think. 9:1 compression right? If so, then your #'s should look a lot like stock ls #'s. Also, the disparity between #'s shows that something isn't quite right.

In any case, stop boosting now till you get things sorted out...and turn the boost down too.

Tom


[Modified by Tomakit, 3:48 PM 9/25/2002]

 

Because when you leave the throttle closed you pressurize the intake manifold which makes it harder to reach full pressure in the cylinder.


[Modified by filetofit, 10:28 PM 9/25/2002]

 

Hey Tom, when you did the comp test in front of your apartment that time, who was cranking the motor? Were you? Because if I was, I didn't hit the gas when I cranked it.

All I remember you doing was taking out the ECU fuse.

I guess I'll have to try that then.

In that case, how come Shadowdawn got numbers close to 100psi while I got numbers close to 140psi? Weird...

 

Yeah, WOT. Re-try that way. Hopefully you'll turn up some better #'s.

Tom