Engine Compression Tests

[martiy2006]

Had a compression test done on a 2000 Esprit and it came back with 6 of the 8 cylinders around 120psi, but 2 cylinders came in at 115psi. Is this an acceptable range & level of compression (The car has 14,000 miles on it).

Any advise is appreciated!!!

[Autocross7]

I would say it is not bad. My car is a 4 pot, but the last time I did a comp test I think (from memory it was 120, 120, 119, 121... good for almost 50 thousand miles. You would be within "okay range" in my humble opinion - but other more knowledgable folks may have more to offer.


Drive topless!!!
Cameron

[GreenV8S]

Ideally they should be within 10% of each other. You're well within this and I'd say that's a very good result.

[lotusse89]

martiy2006 said:

Had a compression test done on a 2000 Esprit and it came back with 6 of the 8 cylinders around 120psi, but 2 cylinders came in at 115psi. Is this an acceptable range & level of compression (The car has 14,000 miles on it).

Any advise is appreciated!!!

Minimum compression for the V8 is 155psi +/- 15psi at sea level. Thats with the engine warm of course.

If you are at 120-115, you are too low, and could rationalize a rebuild... Unless you're at a high altitude, or the engine was cold. It is good that they are all about the same reading though, within 5% is good.

[martiy2006]

The car is in absolutely mint condition, noleaks, rattles etc etc.

It came with a full history right down to the original window sticker & looks like the factory tires.

I agree that the variances in the cylinder compression levels are v/good, but was a little concerned with overall compression of 120psi / cylinder, but the more i read about compression testing, I have learned that it is very difficult to compare one car to the next, due to test equipment variantion, warm & cold engines, and it is the relationship between the cylinders that is most important. Is this a logical rationale?

Overall the car is in virtually perfect shape, other than it needed a bolt on the from spoiler, an exhaust heat sheild bolt and one winshield washer jet nozzle.

The compression test numbers were (it is a higher altitude as its in Calgary 40min from Rocky Mountains)

Left Right
Rear to front

120 120
115 120
120 115
120 120

Any more thoughts guys (and thanks for the advice so far)

Edited by martiy2006 on Thursday 12th October 23:56

[martiy2006]

The test was performed at 3600 feet above sea level....Is there any way to normalize the test or for this altitude so I can compare against the "sea level" testing???

[lotusse89]

martiy2006 said:

The test was performed at 3600 feet above sea level....Is there any way to normalize the test or for this altitude so I can compare against the "sea level" testing???

For example I live at 5300ft (colorado) my normal atmospheric pressure is roughly 12.5psi, rather than 14.7psi at sea level. So my location has roughly 15% less density. So my compression test results could be 15% lower and still be in spec. Though the density also varies with temperature and humidity.

Heres some info
www.csgnetwork.com/pralttodensalttable.html

an if you'd like to do a calculation
www.csgnetwork.com/densaltcalc.html

But at your altitude, your probably a little low. But if the variation is small, and the car runs well without a loss of power or oil burning, then you're probably ok for many miles.

[Autocross7]

You could always get another guage as well. I have two, and while they look the same, one tends to read a little higher than the other. but only a pound or so... so if you are "supposed to be" 155ish...dunno. If you do not burn oil and your plugs are fine... I'd tend to think you are okay.


Drive topless!!!
Cameron

[anonymous-user]

Autocross7 said:

If you do not burn oil and your plugs are fine... I'd tend to think you are okay.

Agreed. If it ain't broke....

[martiy2006]

Thats just it, the car is perfect, lots of power, no smoke & made it through the PPI perfectly.

I'm thinking that the dealership must have performed the test on a cold motor.