Strange compression readings

[telnut]

Newly aquired 91 awd turbo.

I have some strange compression and leakdown results. Any ideas?
Test done with engine warm @ at normal OT
130 static compression all across
6% leak down, pressurized at 100psi reads 95 @TDC. At BDC 1pt less reads 94.

Leakdown readings are not that bad, only 6% rechecked on another leakdown tester got same readings.
Recheck with another compression gauge tester and got 125 straight accross, difference of 5 psi. engine had cooled slightly but still warm.

No oil in water, no water in oil, no smoke @ idle or cruise except under boost. car runs smoothly, Turbo leaking slight amount of oil in IC and appears in exhaust DP. Smokes between gear shifts @ high boost then clears, Turbo is 16g large with about 40k miles. engine is JDM pull out with same amount of mileage 40k miles since replaced and had probably 15k to 20k on it when put in. Cylinder walls look good, no signs of scoring, cross hatch honing pattern still visable. No cylinder ridge. Pistons are stock dish 4 valve reliefs

Low static compression readings would indicate a problem, however leak down test indicates okay. Head is stock, no warpage, cams are stock and timing belts are correct. Headgasket measured .050 thick when removed, this seems a little high, I would think I should see around .030.

Question are:
Why is static compression so low and leakdown numbers are good for turbo motor?
Is the headgasket compression at .050 to thick?
If the compression of headgasket was down to say .030 or changed to MLS type gasket would that bring the compression numbers up to normal? Say, 145 to 150 which is what I would expect to see with this mileage and this engine.

These readings are preplexing. Thankyou for responses.

Telnut
"Motor oil in my veins, nuts and bolts in my brain."

 

[Quasimondo]

Did you test with the throttle closed or open?

My personal opinion is that if the compression numbers are consistent and are not close to what the service limits are (114 psi, and it should be noted that the FSM doesn't give a standard value), then you have a healthy engine. With a leakdown value of 6%, it sounds to me like your cylinders are holding pressure and you have a healthy engine, despite your suspicions about the compression numbers. I'd worry more about the turbo that's spitting oil into your exhaust.

If you still have lingering suspicions about your static compression, take a look at your camshaft timing to make sure they're properly set. Note the location of the dowel pins and timing marks on the camshaft gears and crankshaft sprocket.

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[Z32]

Was there a difference between each cylinder? Ie 3 were 130 psi and 1 was like 110? How does the car drive?

 

[telnut]

Throttle was at WOT
Cam gears and all marks line up
130psi in all cylinders

It occured to me last night that I live at 5000 feet, air is less dense and humidity is generally low (10 to 20%). Could this account for why I generally see lower compression readings on cars that seem to run just fine?

Telnut

 

[Rob10_99]

exactly!
if you use the barometric pressure to figure out what your compression should be,

14.7 sea level

and whats the drop, I dont remember but I know the difference between 1500 ft and 5000ft is quite a bit, and a lot when it comes to performace in a car.

Im sure you can get a good calc from google,
I did a quick search but only found some harley thing which wasnt helpful.

 

[telnut]

What about headgasket thickness? I noticed the one that came off seemed to be a little thicker than ones I have pulled off in the past. I measured it for the heck of it and found out that in measured .050! I thought most of these HG should measure around .030 compressed but I never really measured them to find out.

Any ideas

Telnut