PPI Compression/Leakdown Results
 

Hi all,

My brother just received the results from a PPI done on a 82 SC here in Oz.

Results as follows

175 - 4%
185 - 14%
50 - 2%
180 - 8%
175 - 6%
175 - 6%

With the exception of #3 cylinder, the figures look OK to us. Are they good results?

My other question is....
What could be causing the problem with the #3 cylinder. To me the figures contradict somewhat since leakdown is only 2%.

Any help would be greatly appreciated.

Cheers
X...

No expet but may be a bit of carbon under the valve.

Would water injection clean the valve?

It is almost like something happened between tests on #3. The compression # is low, so there could have been something holding a valve open. The leak down looks good, so whatever it was that affected the compression # had disappeared at that point. I would run the tests again, perhaps with a different shop, if you are interested in the car.

My guess on #3 would be misadjusted valve or a piece of carbon got stuck under the valve. Hard to believe only one cylinder would be reading that low without problems in the other cylinders.

Is this car a garage queen? If so, best to perform these tests after a week or so of good hard driving.

A valve adjustment may be in order. Carbon under the valve may be the case - if so a retest is needed.

Stuck ring(s)? Regardless, it is a negotiating point.

John

If the car has been sitting up for months - years, then carbon falling loose from intake valve or combustion chamber is the most likely problem.

Do a search on "chemtool carbon procedure" to get one method to clear the carbon and restore compression ...

Thanks for the help guys.

Info has been passed onto the current owner who is willing to fix it regardless of cost.

Should be in our driveway within a fortnight.

Being the first Porsche in the family, we're both walking around with smiles from ear to ear!

Cheers
:)

Good luck - please pass along the results of the repairs.

I don't understand all the posts that suggest the low compression may be caused by carbon under a valve. This would also result in high leakdown.

I agree with Tom Owen. I don't see how you can have such poor compression and such good leakdown. Something's odd.

Doesn't #2 look a little odd also, with the highest compression, and the highest leakdown?

...Bruce

Just an update gents.

The car has gone on a spirited drive. Upon return, it was re-tested at the current owners workshop where the resultss came back good.

We confirmed the results with our workshop.

We pick the car up this coming Tuesday. Sweeeet!!!

Thanks for all the help everyone. We'll post some piccies next week.

Cheers
SmileWavy

Congrats! ( and welcome to the SC kingdom).
You'll come to realize that there isn't any other site that can compare to this one. It's chock full of great guys, gals, cars and info.

Regards,
Gary

What's the compression you'd want to see on an 84 Carrera with 180,000 miles? I think my 3's read between 155-135. Good? bad?

xblode, whereabouts in Australia are you?

Sunny Melbourne!

Glad to hear this worked out for you.
Good luck,