Hello to all! I am new member and need your help. I am in a bind in trying to purchase my first Porsche!! I recently located a 2001 Porsche 996TT that I am interested in buying. The car has about 23000 miles and is in excellent condition. The current owner takes care of all his cars and is very meticulous about them. He also seems like a very unlikely person to abuse his cars. Aside from suspension work and rims the vehicle has the AWE 700R Kit which is huge! The price is reasonable for what I would be getting. NOW I went for my PPI today and everything was running smooth. I got a full compression and leak down test done. The compression test came back with 190PSI in all cylinder and the leak down test came back with 2-3%, which from what I understand is pretty good. HOWEVER when the ECU log was downloaded the "number of ignitions range 1" showed 12307 and the "number of Ignitions range 2" showed 1560. From what was explained to me this is bad but it contradicts the good results from the leak down test. The last recorded log for the Ignitions range 1 and 2 show the car was likely at AWE getting its upgrades done. I contacted Mike at AWE who confirmed the owners personality and unlikeliest to abuse cars. He stated that when the kit was installed they ran it on the dyno to tune it and ensure all parts were working properly without any excessive abuse. He did mention that the redline on the car moves up from 7000 RPM to 7200 RPM with the upgrade. SOOOOOOOOO what do I do. Buy or not to Buy? Please help!

 

Overrevs don't affect the engine until they do.

I do not like mod'd cars. The mod's and the usage the mod's suggest brings into the car purchase too many more unknowns.

Leak down test results rather meaningless. These engines have oil jets that spray a considerable amount of oil into the cylinders and this oil at the cranking speeds that are used to test compression works to really seal the pistons/rings in the cylinder. Then a leak down test with is done afterwards with the cylinders still quite oily...

Regarding the range 2 overrevs... with the upgrade which raises the redline from 7K to 7.2K (and btw I think the Turbo's stock/factory redline is 6750 rpms) perhaps the new higher redline has muddied the overrevs counts? I'm always leery of how well these aftermarket chip/flash mods work how well they maintain critical engine in use performance data such as overrevs and what have you. My opinion is that once the car's been so mod'd you can't trust the counts and other in use performance data.

Anyhow, how does the engine sound upon cold start and as it idles and gains heat?

Let the engine idle to nearly fully up to operating temperature then go for a test ride and have the driver demo the car's behavior to you. The test route wants to subject the car to all sorts of everyday driving, from city and stop/go driving, to steady state medium to high way speed cruising. The engine should be run up from near idle to redline then shifted to the next higher gear and the throttle continued to be held down to ensure the engine pulls strongly, smoothly from idle to redline and then pulls again once the next higher gear is selected.

If all is well when you return to the starting point take the car out on a test drive this time and drive the same route and drive the car the same way to get a feel for the car.

Route should cover 15 miles or so and thus the car covers around 30 miles first as you as a passenger and then you as a driver.

This 30 miles gives the engine controller some time to detect any problems and set a check engine light. Assuming of course that whatever firmware is in the engine controller is still performing the usual checks for engine problems like misfires and so on.

Of course, when you first start the engine from dead cold you verify the check engine light (all dash warning lights) come on then go off after engine start.

But regardless, I don't like a mod'd car.

Sincerely,

Macster.

 

sounds like a good car with alot of money invested to increase the performance. But if you are scared of boosting the performance because it might hurt the car, then buy one thats stock.

 

We "WANT" to run LEAKDOWN tests on turbocharged engines. The leakdown test will show us IF the valves have been crashed by a forced type 2 overRev.

The #2 piston RING is pinned. These means that we have a roll pin keeping it from rotating around the piston. However, with a few 996TT engines that torn apart, I have see the oil control rings STACKED similar to the #2 ring. We have a ring gaps for #2 and lower oil control ring lined up. A compression test will NOT show any leakage.

A leakdown test requires TIME between pulling the plugs out and aligning top Dead center. When you pump in 100 PSI of air into the combustion chamber, you really see where the loss is going. On a turbo engine where there is detonation, NO oily ring is going to hide broken rings or broken ring lands. A bent valve will quickly be apparent.

A leakdown test after a compression test does not "twist" the results.. The results that we are looking for is major damage. Valves that aren't sealing and ring/ring-land issues.

If it was me, I would datalog some of the engine functions to see what the engine is doing. You can ask the owner to put the car on the dyno and use a datalogger to log fueling and AFR's and boost.

 

car is tight and runs perfectly. I think ill take your advise and do a more extensive test drive though to help me decide. The car has all the mods that I would already do. Maybe not as much HP but im not complaining. I'm looking at a moded car instead of stock to save money on the mods..... hopefully! Thanks for the replies guys! BTW mods were just done approx 1300 miles ago!

 

That's odd, why would someone invest $15K on mods and sell the car shortly after? I would be looking really hard at how the engine and tranny perform.. These engines are VERY expensive to repair.

 

"HOWEVER when the ECU log was downloaded the "number of ignitions range 1" showed 12307 and the "number of Ignitions range 2" showed 1560. From what was explained to me this is bad but it contradicts the good results from the leak down test. "

The thing to consider about checking over revs is that it is showing how the engine was treated. It is not a guarantee of engine's longevity. With this engine if it is running good and doesn't have bent leaking valves, overrevs can be the difference between throwing or bending a rod at 600hp or not. When an engine is overrevved three common overrev failures/damage can happen. The first is valve damage due to floating lifters. Hydraulic lifters are meant to operate at a certain designed RPM and can experience float if that designed RPM is exceded. This can result in valve/piston contact. This is a variable effected by the oil pressure the heads are designed to provide to the lifters and the weight/mass of the lifters. The other common possible failure is excessive stress on the rods causing a bent, crack or a break. The third failure is oil supply. The engine's oil system was designed to move enough oil through the engine to operate at the designed RPM. That means that in some engines when overrevved the oil pump is not equiped to keep everything oiled at the speed everything is spinning. Other variables to this oiling design is if the crank or rod journals are double or single drilled. Simply put can the oil system can't deliver enough oil at the required pressure to keep every part floating on a film of oil. This can cause spun bearings and other random wear. Kevin knows these engines way more than me and can tell you more accurately what fails on them in these scenarios.

To make a long story short, the engine may run fine now but may grenade further down the road if the overevs are excessive. I would not waste any time on this car personally. It isn't wrth a 30k maintenance bill to find out the weak parts IMHO.

 

Does anyone know if there are only 1 and 2 output readings on teh 996 ecu vs the 1-5 overrev readings you could see on a 997?

 

Im pretty confident in saying the car was babied by the owner and the high rev readings were from getting several dyno tests at AWE

 

The ECU logs type 1 and type 2 overrevs only. As far as I know the ECU doesn't log to what extent the overrev was though other than the type catagory. So it may have been slight or a all the way to 8500 for all I know. But I know I would not buy it with those mods and overrev history. But that is just me. Everyone has their own idea of what babying a car means and nobody buys one of these cars with the intent of destroying it. As a buyer the overrevs are an imprtant detail to pay attention to. Especially when the repair bill could be 90% of the purchase price of the vehicle.

 

+ 1. Seems a little suspicious.

Remember, generally speaking, mods do not add substantial value to a used car. I hope you're not paying a premium for these mods.

Edit:

There's an X50 for sale on this forum right now - https://rennlist.com/forums/index.php

 

I was told that if you raise the rev limiter, the ECU will still record anything over the stock redline number as an over-rev, which would mean that the time on the dyno would be counted as over-revs. The type 2 over-revs concern me more since those usually come from a missed downshift where the rev-limiter would not come into play to protect the engine. That being said, these ignitions happen so fast that "1560" is a very small amount of time. I defer to Kevin in all these matters as he is the expert. Good luck whatever you decide.

 

All it takes is one overrev to compromise a valve should there be valve to piston contact. Not all valve springs exert the same pressure closed or open and not all valve hardware assemblies weigh the same.

Porsche felt it important enough to count/note range 2 overrevs. How these are produced -- missed shift or a spoofed rev limiter via an aftermarket flash chip -- makes no difference to the engine.

Sincerely,

Macster.

 

Some months ago when I asked a Porsche tech gave me a copy of the overrev ranges documentation from some source he had access to. My recolletion is there are 2 ranges for the 996 and more (6?) for the 997. However, I can't find the copy of this info here at the office to confirm. The copy is probably at home in my files.

Sincerely,

Macster.

 

The 996TT has a Type 1 and a Type 2.. No more.