Whats everyone compression on stock motors?

[Chad Giffen]

I know the the 1G AWD comes with 164psi compression from the factory and 121psi is the recommended service limit. But after all these years, I'm curious what everyone averages at. I know 2G's are a bit higher.

Everyone post there compression numbers....

130-128-133-131

[Matt Demick]

164 164 164 164  Perfect score. just did it 30min ago lol not bad for a 1990 

[Chad Giffen]

does it make a big difference if you dont put the pedal to the floor?

[Shane Sawatzki]

:|:|:|:| looks like mine needs a rebuild...altho i dunno if i did the test 100% correct... i got 110-105-110-115

[Chad Giffen]

I wonder what the minimum compression these engines will run on?

[Shane Sawatzki]

gotta be lower than what i have...my car runs great , no smoke good boost and good power... hmmm :| unless its a no warning problem and my car is just going to explode one day. the only thing my car needs is valve seals...but i picked up a head and just finished rebuilding it with a fresh valve grind and a whole new head gasket set with everything including valve seals. maybe im hoping i just have bad valve seats and that why my compression is low and hoping this new head will fix it:D because my 16g turbo is going in this weekend with the new head:D

[Marke Bailey]

lower limit in the book is around 130-135. make sure you hold the throttle body plate wide open. also when you check it, let the cylinder turn around 7 times until the pressure starts to level out. do it twice on each cylinder to make sure it was right. if you still get low readings, add a tablespoon of oil and see if the reading goes up. if it does it could mean your rings are going.

PS. remember to disconnect the fuel before performing the test. you just pull the MPI fuse next to the positive battery cable.

[John Hartman]

disconnect the injector resistor pack, no fuel sprayin then 

And prop open the throttle plate somehow.

Factory service manual states 114psi as a low service limit with 14 psi difference between any 2 cylinders.

Matt, those are damn nice numbers.  I wish.

I have 155, 155, 115, 90.  yea.

And it still runs 114mph traps 

for reference, 1g turbo is a 7.8:1 engine and 2g is 8.5:1

[Shane Sawatzki]

okay so it turns out the gauge i was using isnt accurate...dad brought a newer/modern one from his work at landrover and jag, i got 130-130-135-135 and we are replacing the head as of 6 hours ago...just finished getting the head off and there is still cross hatching in the cylinders and no lip on the cylinders either...dad the mechanic says it has been re-ringed not long ago. so im happy:D means I dont gotta re ring it while im at it:D

[John Hartman]

most likely fine, but if your rings have gotten soft from overheating you will still have low compression.  I will be doing this same thing soon, and I am just gonna re ring it for shits and giggles.  head has to come off to pull the slugs out anyways, so might as well do it once right?

Just de glaze the cylinder walls with a ball hone(just a bit), clean the piston ring lands and do one at a time.

[Zach Holt]

mine is:

Cyl1, 141
Cyl2, 159
Cyl3, 164
Cyl4, 138 <--- I have a consitant air pressure coming out of my head over Cyl #4 the little line usually runs in to the stock intake. mine gose poof, poof, poof, poof, with the 4th Cyl ahah shity eh?

[John Hartman]

how did you determine that the pressure is produced by number 4?  Pull a plug so it doesn't make any pressure in number 4, then see if the poof, poof, poof stops.

138 isn't too bad really, but both 1 and 4 are below the difference limit to the higher ones.  Car should still be capable of being fast tho.

[Zach Holt]

I dont know The 4th Cyl plug has white film on it. the lowest compression and my valve cover coffs out Exhoust. Just guessing

Yea it will do untill I have a basterd block4g64 crank4g63 step up. rev to the moon they do

[John Hartman]

mmmm, needs a Jedi master to build it it does, and a grant from Queen Amidala herself to pay for it, yeeees...  mmmmm...

[Brett Haviland]

hahahha  my 3 4g63's have a combined reading of 1776 PSI.

i win