Compression Test Results.

[OneFastEclipse]

I just did a compression test on my car and came up with 190,190,180,180. Aren't those numbers a little high? What you guys think?

 

[awd4g63]

It should be somewhere around 160 if I remember correctly. I don't think it should be that high

 

[kpt4321]

1g's should be around 165.

180-190 is normal for 2g turbos.

They have different compression ratios.

 

[96boosted]

are you sure 190psi on 2gis normal? The service manual says 178psi is normal and 133 is the service limit. I did mine, and mine's about 160~155 in all 4.

-96boosted

 

[95blackGsTurbo]

I thought the 2g turbos had LESS compression then the 1g's. Maybe just my misunderstanding.

 

[billdo_83]

Originally posted by 95bLaCkGsTuRbO
I thought the 2g turbos had LESS compression then the 1g's. Maybe just my misunderstanding.

Thats your misunderstanding.
The compression of a 1g is 7.8 while 2g is 8.5

 

[KPWSerpiente]

Numbers are good, but your spread is a little wide. I have 180-185 in my four as of last time I checked which was about two weeks ago.

Be happy your numbers came up good.

-T

 

[96boosted]

the lower the number means the less power the engine can make? Assuming the numbers are even and within service limit? If engine A gets 180 across all cylinder and engine B gets 140, engine B would be making less power? Given every else being equal.

sory for hijacking the thread, but it's sort of relevent and I don't think anyone would want a new thread on this.

-96boosted

 

[tsunari]

POSSIBLE reasons for the high readings might be carbon build up. If you're anal about your car like I am about mine . . . might want to buy a can or 2 of MCCC and try that.

 

[1gfromND]

Hey if it runs good why even wonder u know do fix what aint broke.

 

[Kakoriat]

My compression check came out about the same, 190-185-190-188.

The car has 95k miles.

 

[whitegst97]

Seems normal, maybe a little high but when i checked my compression after i installed the Mitsu metal headgasket and it came out to 195-210 in all 4 pistons, the car ran good for about maybe a month or two then i sold it, the buyer told me that one of the piston's had lost compression all the way down to 60, don't know if there's any correlation between the high compression and the sudden drop. Just my experience.

 

[crankbender]

Originally posted by 96boosted
the lower the number means the less power the engine can make? Assuming the numbers are even and within service limit? If engine A gets 180 across all cylinder and engine B gets 140, engine B would be making less power? Given every else being equal.

sory for hijacking the thread, but it's sort of relevent and I don't think anyone would want a new thread on this.

-96boosted

Assuming the 2 engines have the same CR the one with the lower compression numbers isn't sealing as well. This usually equates to less power.

If the 2 cars have different CRs like the 1g and 2g then how much power they can make is really not related to their readings comparison.

 

[TTKarl]

If your worried about carbon build-up the best thing i've found to do is go to a GM dealership and get GM Top Engine Cleaner in the spray can not the pour in type. Start the car and run it about 1.5k-2k rpms. Spray it into a vacuum hose with that car running until it starts to smoke a good amount. Immediatly shut the car off and let it sit (overnight preferable). Go back of course re-attatch the hose and take it down the road. It will smoke and load up a little but a couple of hard pulls will burn it all out.

GM has been using this on their northstars for quite a while now that have problems with spark knock due to carbon build-up. I've been told by other company's that make nothing but automotive cleaners *cough* BG products *cough* that there is nothing better on the market to break up carbon than the top engine cleaner.

 

[1fast97gsx]

manual says 178 is stock on 2gs ... you must have a lot of carbon buildup.

 

[u2slow]

I just had my head ported, rebuilt, and added 272 cams. Something ain`t right!! The engine runs rough, but smooths out a little around 4000rpm. Timing marks all line up: crankshaft pulley @ 0 degrees, cam pulley marks are aligned with the dowel pins @ 12 o`clock. A compression test shows 110 lbs on all four. I`ve been a DSMer for 7 years, I`ve done the T.B. before with no problems. I would like suggestions before I tear back into this thing.

 

[kpt4321]

Originally posted by 1fast97gsx
manual says 178 is stock on 2gs ... you must have a lot of carbon buildup.

He got 180 in two cylinders. That's 2 psi more, nothing at all.

Hell, considering most gauges tend to to read a little high, he's probably almost right on.

I'm betting on a little bit of carbon buildup.

 

[tsunari]

Originally posted by u2slow
I just had my head ported, rebuilt, and added 272 cams. Something ain`t right!! The engine runs rough, but smooths out a little around 4000rpm. Timing marks all line up: crankshaft pulley @ 0 degrees, cam pulley marks are aligned with the dowel pins @ 12 o`clock. A compression test shows 110 lbs on all four. I`ve been a DSMer for 7 years, I`ve done the T.B. before with no problems. I would like suggestions before I tear back into this thing.

Do a leakdown test . . . might find out it's just heat-worn rings. Can't really speculate though . . .

 

[1fast97gsx]

Originally posted by kpt4321
He got 180 in two cylinders. That's 2 psi more, nothing at all.

Hell, considering most gauges tend to to read a little high, he's probably almost right on.

I'm betting on a little bit of carbon buildup.

yea ... but he got 190 on the other 2. That's 12 psi over stock!!

 

[spoolinawddsm]

Originally posted by 1fast97gsx
yea ... but he got 190 on the other 2. That's 12 psi over stock!!

like he said the gauge prob. isnt the most accurate. When i did a compression test on my 90 there was water sitting in the spark plug hole, which caused my higher compression.

 

[slowAWDTSi]

Originally posted by 1fast97gsx
yea ... but he got 190 on the other 2. That's 12 psi over stock!!

Before I melted a piston on my 130k stock motor this was my readout, starting withthe number 4 cly: 175, 160, 155, 138

When I pulled the head after the meltdown I found about and inch of carbon had built up on the underside of all the valves in the number 4 cyl

Dru