Redmist

I've homed in on an '08 Turbo in Dallas. In need to do a PPI before I close the deal. The car is being sold by Park Place Porsche. I can use another local Porshe dealer to do the PPI or I can use an independent shop. I can think of pros and cons on both sides but would like some input from those with maybe more knowledge and/or experience.

ltc

Some dealers will not allow/provide for a PPI outside of their service department for a vehicle that is still covered under warranty (OEM or CPO). Have you asked Park Place?

Also, make sure your selected independent shop has experience with Turbos and access to a PIWIS. Also keep in mind that doing a compression/leakdown check (i.e. removing plugs) may involve removing body trim (i.e. rear bumper), so there is some potential liability and cost involved.

TT Surgeon

i would have PP do it in their svc dept. They should have nothing to hide, you'll get printouts on everything.

TT Gasman

Ask Ruf Auto Centre for a ppi. best independent shop in Texas.

Macster

If shop has access to PIWIS its operator can command each cylinder's fuel injector and spark plug off while engine at operating temperature and idling.

The engine's rpm is noted before the cylinder is deactivated then after it is deactivated. If any one cylinder's deactivation does *not* result in a rpm drop the other cylinders when deactivated did then the cylinder is weak and one doesn't case what a compression or leak down test shows.

Let the owner worry about the reason why the weak cylinders are weak.

Obviously too a thorough check of the car wants to be done including a road test in which the shopper is a passenger first then a driver to get a feel for the engine's level of performance and its behavior at cold/warm/hot start and idle.

Only if the test turns up no reason to suspect the engine may have a subpar cylinder or cylinders then should a PPI be done at which time the cylinder deactivation test can be done.

Bottom line is with the proper equipment and experienced tech using it there is a way to check an engine for a weak cylinder or cylinders without having to resort to the considerable expense of a compression/leak down test. (Leak down test unreliable anyway. Compression test the better of the two tests for the purpose of determining an engine's health.)

Sincerely,

Macster.

gota911

+1 on Ruf. Call and ask for Hans.

Redmist

So,
Macster, if the shop has a PIWIS I may avoid a compression test? Both the other dealer and the shop are asking $500+ for the PPI. How far is Ruf from Dallas?

TT Gasman

Ruf is in Dallas.
Ruf Auto Centre 3219 Commander, Dallas TX 75006

Michael-Dallas

RUF and if you're seriously OCD, go to Boardwalk for a second PPI.

Trust but verify.

///Michael

Redmist

I appreciate the help everybody. Forwarned is forearmed.

Macster

You can ask for a compression test if you want. Nothing wrong with seeking more knowledge about the car's condition.

However, a PPI and compression test are expensive and a bit of a bother. You should do everything in your power though to only have one car PPI'd and possibly compression tested and this is the car you end up buying.

A compression test, in fact a PPI, is the last thing you do before you buy and the thing you should do only once. If you find you are having to eliminate cars that fail to pass PPI or fail a compression test you need to improve your used car evaluation skills.

One way around a compression test is to have the PPI tech -- who should have access to a PIWIS system and know how to use it -- systematically disable each cylinder in turn and note the drop in engine rpms. If the engine rpms drop the same or nearly the same upon each cylinders's "deactivation" then you know all cylinders about the same, and presumably good. A weak cylinder when deactivated will result in less engine rpm drop off cause a weak cylinder is contributing less to the engine's total output in the first place.

(Another "test" is if you have access to a good temperature probe with the engine idling and on a lift take each exhaust pipe's temperature close to the head. Any that is lower than the rest or higher brings the engine's health into question.)

Now the aforementioned cylinder deactiviation test with equal or nearly equal drop off in engine rpm for each cylinder is not conclusive evidence the engine is in good health. A worn out engine would deliver the same behavior.

If at this point you want even more confidence, a compression test of each cylinder could be done. This adds a bit to the cost of the vehicle but can be worth the extra peace of mind. The compression test should only confirm what your up to now research and other tests have led you to believe: The car is in fine fettle and worthy of you making an offer to buy the car.

Your evaluation of the car *before* the PPI and its cylinder deactivation test would have eliminated, should have eliminated a car with a worn or tired engine already.

If the car is in otherwise good condition and the cylinder deactivation tests turns up a weak cylinder -- the engine's rpm drops less maybe not at all when this one cylinder deactivated -- you should probably walk away and think about how you can avoid getting this far into the buying process with a car with a weak cylinder in the future.

Or if you are interested in the car and have the means to deal with a weak cylinder, perhaps you are looking for a car and its engine for rebuild project or something similiar, then you can have a compression test and even a leak down test done to help you and your mechanic determine the cause of the cylinder's weakness.

Of course what you find can only result in you substantially lowering what you're going to offer for the car and you have to have a pretty good idea what it is going to cost to put the engine right so you can adjust your offer to suit.

Also, before you do this deep into a car that has a questionable engine, consider the seller will probably reject your rightfully so lower offer and hope for a less discerning buyer to come and take the car off his hands.

But except for the few buyers prepared to deal with this situation the best course of action is just walk away and vow to do better in one's evaluation *before* the PPI.

Sincerely,

Macster.

Redmist

Macster

The car I'm looking at is an '08 with 6,000+ miles. I doubt if the condition of the engine is "worn and tired". The car is for sale by a Porsche dealer but carfax shows that it was purchased by them at auction. I agree that the PPI is a hassle, especially since I'm buying a car in another city far from where I live. Assuming that the car is as represented by the dealer, it's the one I want and this IS the last step before purchase.

Macster

I too doubt the engine is worn and tired. But the dealer bought car at auction. Worst case is dealer can claim "it didn't know" if something bad turns up after you buy the car. Is car being offered with CPO warranty?

If not that's not necessarily a bad sign but should put you on hightened alert mode. Added: Be sure to have dealer tech pull all the rev counter values and give you a printout. Post results here and you'll get good input as to what the numbers mean.

Not trying to scare you away from the car. If the car checks out otherwise and you want a PPI to include a compression test then so be it. A leak down test is less reliable though so go with a compression test.

Just as an aside: Given these engines have oil piston jets which spray oil at the bottom of each piston this puts a lot of oil in the cylinder. Great for engine longevity. (No doubt my 02 Boxster's 2.7l engine has benefited from this oil jet feature in covering its 225K miles with no signs of any deterioration in its performance. And I look to my 03 Turbo's engine benefitting from the oil jet feature as I drive it towards whatever miles I put on it before moving on to another car.)

But my point is that with all this oil the oil helps improve the sealing of the piston in the cylinder so a worn cylinder/piston/ring interface may not show up as a cylinder low on compression. The test is still valid for finding a weak valve and valve seat seal or a cracked head or a leaking head gasket though.

By disabling each cylinder in turn one removes the power the cylinder generates towards the total engine's output. The presence of oil is the same for all cylinders (and represents some hydraulic drag, friction) but you are looking for a cylinder that because it is weak (for whatever reason) and because it contributes less to the engine's output results in less drop in the engine's rpm at idle. This is more reliable than a compression test. However, opt for both tests. Idle cylinder deactivation test first then if every thing looks ok then a compression test. All are more data points and for the good towards you making the right decision.

Regardless, I'm sure you'll do what's best for you.

Best of luck and if you do decide to get the car I'd like to see some pictures. I fancy a 997 Turbo at some point -- unless I hang on to my fantastic 03 Turbo until I take my last breath which I might very well do -- and I'll gladly view any and all pictures you post.

Happy shopping!

Sincerely,

Macster.

Redmist

I'll print out your posts and show them to the whoever I choose to do the PPI, hopefully Ruf. 1Thanks again Macster! If I get it, I will post pics.

Redmist

OK, I had it taken to Ruf. There were 13 overrevs in "stage 2" (I'm told this is nothing to worry about, bumps against the limiter), no mechanical overrevs. Car is otherwise "essentially flawless." It should be mine by the end of the week!