930 PPI test results, imput requested
 

Just got the compression/teakdown test numbers back on a 1987 all stock 930 in Florida with 75,000 miles. Unfortunately the test was done on a cold engine, 65 degree room temperature. Plugs a bit black but not extreme. What are your impressions?

Cyl 1: 120lbs comp, 10% leakdown
Cyl 2: 120lbs comp, 12% leakdown
Cyl 3: 140lbs comp, 12% leakdown
Cyl 4: 130lbs comp 02% leakdown!!
Cyl 5: 130lbs comp 12% leakdown
Cyl 6: 130lbs comp 10% leakdown

Tester said he could not hear any air seepage in intake or exhaust. Car drives well except for cold start smoke and high RPM pinging supposedly from "old/poor quality gas".

William,
Seems to me that the compression/teakdown test was performed in all the conditions of how NOT TO perform compression/teakdown.
Vehicle should have fresh fuel, up to normal operating temp, driven briskly prior to performing the test to help blow out any carbon deposits and assuring best valve seating.
As stated, these #'s seem low on the compression, and high on the leakdown. I believe that leakdown should be <10%, with variance between cylinders around 3-4.
IMHO, based upon the stated conditions, I think this test was a waste of time and money.

I asked the tech if they could do it with a warmed up engine, and the excuse was the amount of time it took to remove accessories to reach the plugs, especially the left side. I was surprised since they have a SCCA ITC/ITB racing pedigree

possible waste of money: $421.67

** Better to find out **
 

(WOW) Thats for the PPI????? Holly C$#@.... Some times its better to spend that, and not have bought it... Then to buy it and need and engine later.......

FYI... A shop that complains on amount of time it took, well, i do those alot, and leak down and Comp test in 2 hours.... looks like they billed you for 4+ ..??????
Is it a Porsche only shop, or do they have every list of european car there......

Good luck on the hunt for a turbo... Pray to the PorscheGodshttp://forums.pelicanparts.com/uploa...1137264586.jpg

I find alot of shops in Fl shoud not be working on turbo cars far less trying to do PPI. But if you are out of town what are ya going to do.
Good luck with car hunt

With a lower nominal compression ratio, shouldn't 930 numbers be lower than the 150-160 psi I hear about for NA 911s? Taking 130 as the average of your results, looks like the variance was about +/-7%.

I bought an 86 all-stock 930 that showed ~12% fairly evenly across all cylinders and even compression, smoke puff on start-up. A few experienced Porsche specialists have told me that they worry when leakdown gets to 20%. Less is better, but for me 12% wasn't a killer on an unmodded car. A future rebuild will come quicker at 12% no doubt, but here the condition and the price of the car offset this.

If the car's a good deal and you like it, it'd be well worth a second PPI from the best, most conservative shop you can find that'll test it right, especially re purported gas-related pinging--worst that can happen is you find a good shop to care for an eventual purchase. If the PO gets uptight, keep shopping.

jrl, how many miles on your 930 engine when you had the engine tests?

William,
Was the $421 just for compression and leakdown, or did the tech inspect the whole car, and give you a written analysis of his findings?
P.S. Doing a search on this board has saved me more $ than I care to think about.

MobileWrks, the shop I used caters to imports, with good VW & Porsche experience. They charged for four hours of service to the 930. I felt that was too much time, but it was an out of town inspection near the purchaser...convienent, costly with mixed results

How much is this car?

The compression test looks okay to me. The leakdown numbers are high and potentially suspect - not ideal in my mind, although the test wasn't done when warm (which is also common too).

What is more worrisome is the pinging - as that can easily destroy an engine very quickly. If the car has be detonating (pinging) for a long time, you can have engine damage...

-Wayne

Nine9six, the cost covered compression test, leakdown test, plug evaluation, road test and written report

I would get anothe ppi!

Wayne, the car is $25,000

William,
Now I am confused...Are you the seller, or the prospective buyer?

From reading around this board, Wayne's awesome books, and 911turbo.com, a hot engine test is not that difficult. If I purchase this vehicle, I will do it myself at home! i am expecting more uniform numbers.

Nine9six, I am a potential buyer, sorry for the confusion

William930t,

My car had 57 kmiles. If the car is in excellent shape, $25K sounds like a very good price. I paid much more than that for mine, but this included $4300 of documented work the selling dealer put into it (and of course he was a dealer). Presume the first PPI covered the many other items (body damage, paintwork, transmission, electricals) that are costly.

The pinging could be a significant issue and is well worth a few hundred dollars more due diligence. $25K might be a great deal or you-get-what-you-pay-for.

I guess the proverbial 'asbestos octopus' is extinct these days ... or some technicians in Florida are just lazy ... and have no shame, to boot! $421.67 is highway robbery for an incompetent job! I think a talk with the shop owner is in order ... the lame excuse calls for some 'public relations' cutting of the final bill!

$421: way too much to pay for an inadequate test. Especially when their excuse is lack of time to do it properly. I also purchased a car out of town. The local shop gave me ridiculous numbers for compression (in the 70's-90's). I told the PO they were WAY off. He agreed, as did the shop when it was brought back to their attention. They did the second run gratis, and my numbers were also in the same range as yours (both compression and leakdown). No pinging on my car, though. My bill came out to about $250. In the end, FWIW, I paid a few thousand more than your asking price.

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!)

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

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?

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?

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

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

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