930 PPI test results, imput requested

[aigel]

The absolute dynamic compression numbers (in psi) are not really important. They depend on a lot of parameters. How well the starter works, ambient temperature and air pressure etc. The imporant thingis that they are close to one another. And that's the case here. The leak down numbers, I am not experienced with but in any case, I would NOT buy this car without having that engine checked again elsewhere. Make sure the second PPI shop talks to you ahead of time, so you can give them the heads up regarding the ping.

25k may be reasonable, but if something is wrong with the engine, it is a 35k car very quickly, even if you do most the work yourself.

Cheers,

George (who also wants to be a 930 owner one day!)

[aigel]

Oh, yes, one more thing. Why are the compression numbers all even with 10s of PSI? Most gauges I have seen read more accurate than that. I would almost be worried that they stuck the gauge in one cylinder per bank and made up the rest.

This is why I would NEVER buy long distance, unless I had the time to show up in person. Sorry that this is such a painful process for you!

George

[William930t]

Thanks for the help so far, I was also wondering at what percent leakdown can air be heard in intake or exhaust, pinpointing potential problems?

[jrl]

One thing I've yet to understand is the amount of time specified for leakdown to occur. If a cylinder leaks, it'll eventually leak all the way down to ambient pressure. That is, leakdown would seem to be tied to a standard time interval. Is it taken at 15sec, 1 min, etc?

[javadog]

William,

I would think you should be able to hear leaks at those leakdown percentages. Did they listen for ring leakage at the oil filler pipe?

On the last PPI I had done for a turbo (1980 Euro car, 40k miles shown, real miles probably higher) the leakdown numbers for all cylinders were 4-5%.

For the amount of money you spent, they should have done a lot more work. The rest of the car needs to be appraised as well; there are a lot of things to look at. My local shop charged me $350 and that included looking at essentially everything on the car that you could inspect, without dissaembling parts. The list of needs was a page long. You need to get some of your money back.

I'd get another PPI done, by a well-respected Porsche-only shop. Make sure they do it by the book. At that mileage, I'd spend the extra bucks and check the valve guide wear. Drain the tank and put fresh gas in it. 91 octane should be fine for a stock engine. If it pings on that, it has problems. Detonation will kill a 930 engine quickly.

You may be better off spending a little more money for a car with less miles, good records and more regular use.

Good luck,

JR

[slow&rusty]

I did a full PPI on a 930 last May (2005), this is a car that I eventually bought and the leakdown numbers were all between 4-6% and this was on a warm engine.

The car had just over 56K miles on the clock.

I paid $250 for this PPI at a Independent Porsche Specialist in San Diego. And they went through the entire car bumper to bumper incl. the electricals, brakes, tires and checks to ensure that the car was never in a crash.

Regards - Yasin

[aigel]

THE COMPRESSION TEST WAS DONE WITH A COLD ENGINE. So, those leak down numbers are pretty worthless IMHO.

jrl, a leak down tester is constantly "fed" with compressed air from a hose. The leak rate is read on a gauge.

George