Bill Gregory

Just had a PPI done on a C2, compression came back 150-155 lbs. Not being familiar with C2 engines, is that within range? (My manuals get here next week...)

John K

I also had a PPI done recently and the cyclinders came back at 200. I was told this was "fine".
Hope this helps.

Richard H

Bill,
My C2 has a compression between 175 & 185. If you actually calculate it out it should be about 200 with ref to the compression ratio. As far as I'm aware the figures gained from a compression test should all read within about 10% of each other. The actual figures gained will depend on the accuracy of the gauge used, so a direct comparison between two peoples results from diferent gauges can not really be taken as gospel. If the test is done when the engine is hot or cold, not driven for some time e.t.c. can also effect the figures.
Is the range of yours within 10% ?
I have read a bit about this subject and quite a few people recommend that the the car is put on a dyno and the BHP figure gained. This will show if the engine is performing. Mine gave 249bhp which I thought was okay for 90k miles. If your reading is accurate at 150 and it should be 200 you would definately see a reduction in HP. Obviously the dyno result could also show signs of other problems if the HP is not where it should be and not directly relate to low compression.
Again I have read a bit about leakage tests and it seems to me that there are so many factors that can effect these I am cautious about the results gained on these.
Just my opinion, but note I'm not a expert.

Richard.

P.S. The manual does not give compression figures (just ratio) or I haven't found it!
I believe this is due to the above.

Bill Gregory

John and Richard,

Thank you for your numbers. Yes, the compression test was withing 10% of each other. Unfortunately, the leak down was either bungled or there's a severe problem. So I'll probably have a leakdown done by someone else.

GK

Hi Bill,

I've just found the compression test the previous owner did when my C4 had 55K mls, and 6 years of age:

CYL BAR PSI

-1- 12.0 175
-2- 12.1 176
-3- 12.1 176
-4- 12.5 182
-5- 12.0 175
-6- 12.1 176

I am using a conversion factor of 14.6 to get from bars to psi (from top of my head). The numbers seem to be OK to me. I will re-do this test next year to see the evolution (hope not to see any revolution )

Bye now,

Giorgio.