Did a compression test today...

[froggie3kb93cx]

Well i got a compression tester for christmas, and figured i would try it out... well the car is a bone stock 98 gst, i bought the car in september with 126,000 miles on it. I was kind of worried that a rebuild might be needed soon in the future but the car pulled good so i wasnt to worried. well now the car has 132k and i figured i should test it before i start ordering some mods... well i hooked it up to #1 cylinder and bumped it over about 5 times and it read 180, i was happy as hell and hoping the rest would be as high and sure enough they were, all read 180. As far as i know the engine has never been rebuilt, from what i've searched and read i think it is in pretty good shape as far as compression #'s, what do you guys think? thanks

 

[99gst_racer]

Excellent numbers. I dont think they can get any better.....
I did mine about 2 months ago. I got about 171 on all of the cylinders, so I was happy too. I think the service limit is around 145, but dont quote me.

 

[Strm Trpr]

Paul, you are correct on the 145psi, but that's for a 1g turbo.
The 2g Turbos have a max of 178psi, and a service limit of 133psi....
Not baggin', just helpin'.....

 

[froggie3kb93cx]

Alright i have a dumb question... What do you mean by max 178psi? does that mean my compression testers gauge is off if it read 180 and you say max is 178? thanks

 

[Strm Trpr]

Here's where I got that info.
I guess I was wrong about a max psi... in that case I stand corrected.
You're motor is in excellent shape with that many miles.
Here are some links of interest....
<a href = http://members.shaw.ca/costall/1000Q/>1000 Already Answered Q's</a>
This link is priceless....
<a href = http://www.vfaq.com/FAQlocator-index.html>VFAQ</a>
Browse both of them and you can find plenty of info.

 

[CanadianTSi]

With 215,000 kms my car has 180 acroos the board

 

[froggie3kb93cx]

Thanks for the links and the pic Strm Trpr, and all of the help/comments guys.

 

[2gGSX]

And I was happy with my 165's Just kidding, 134k and no problems

 

[diambo4life]

Quit complaining... my car trapped 110mph with only 1 cylinder reading above the service limit (121psi.) It should be interesting when it reads 180psi across next year.


Your compression was higher than spec. due to carbon on the piston tops as per the milage on the motor indicates. Your compression tester is just fine and I wouldn't worry about it if the car runs just fine.

 

[NeoStreamGSX]

juss did comp. test. results were 115, 116, 111, 111 ??? low #'s?

 

[froggie3kb93cx]

juss did comp. test. results were 115, 116, 111, 111 ??? low #'s?

That doesnt sound to healthy

 

[vteg]

juss did comp. test. results were 115, 116, 111, 111 ??? low #'s?

You can add more boost

My car has what sounds like rod knock now I want to do a compression test, but it has been raining for the last 2 weeks in socal. My engine had issues anyway. So needless to say it is parked again.

 

[tt281gt]

You can add more boost

My car has what sounds like rod knock now I want to do a compression test, but it has been raining for the last 2 weeks in socal. My engine had issues anyway. So needless to say it is parked again.

Yeah rain in socal sucks lately. You have a PM sir.

Guys, I just wanted to remind you that when you do a compression test do it at WOT. Before I had done it and got 165 across the board. But then I remembered I didnt do it @ WOT so I did it again last night 180 across the board!!!

And if you get low numbers do a wet test.

 

[99gst_racer]

juss did comp. test. results were 115, 116, 111, 111 ??? low #'s?

Are those numbers from your 99 GSX?? If so, then you are in dire need of service......

 

[Georg51]

juss did comp. test. results were 115, 116, 111, 111 ??? low #'s?

And what color is the smoke pouring out of your exhuast about now?

You need some service, seafoam cleaning and injector cleaner may not be enough

You may need new valve stem seals, hopefully that's it.

 

[NeoStreamGSX]

no smoke out of exhaust...valves and injectors are still pretty new...head gasket is a lil thicker than stock...

 

[Georg51]

no smoke out of exhaust...valves and injectors are still pretty new...head gasket is a lil thicker than stock...

No way a thick headgasket would lower your compression that low. You have to be experiencing some kind of power loss, I'd be amazed if you couldn't tell. Either you have 4 bad cylinders or your compression tester is flawed.

 

[99gst_racer]

or your compression tester is flawed.

^^^ Yeah, that's my guess. ^^^

 

[yugotdonkey]

i just tested my compression yesterday on my 92. My engine has 173k on the clock, i got 170, 165, 162, 157. High numbers but I don't like that they fall each cylinder.

 

[Strm Trpr]

NeoStreamGSX
So I bet, you got that motor hot once or twice, and blew the head gasket.
So the head was rebuilt, and that's why you say the valves and such are still
pretty new, plus you said that you have a thicker than stock head gasket.
Well, if you got water in your cylinders, you washed the walls and now all of your pistion rings
have lost their seat and this is why your comp numbers are so low.
First do a wet comp test, then a leak down to find out if it's the head or the block.
Pull the engine and give her some love....