Lets take it in reverse order:

1. Yes, I think so.

2. 'Engine design' in terms of 'max rpm allowed' is not a binary output: Your metric is expressed as a probability... We are 95% confident that 99.9% of the motors produced will survive 6500rpm for 1% of their operating life over the course of 50k miles (actually it is probably specd in operating hours). Raise the revs, move further down the probability curve.

If all you do is generate type 1s with a bump against the rev limiter- and all the overrevs are due to that, it is still an indicator of how often the engine hit it, and perhaps how the engine was driven. Is this behavior within the design envelope?

3. If we knew WHAT ACTION creased a type 1 or type 2 we could ignore it. But the issue is they we don't know if the 2000 type 2s was a major blown shift, or if it was the accumulation of a few here and there due to whatever.

A

 

They aren't from when you hit the rev limit, they are from when you EXCEED the rev limiter. Thing is, lots of cars have aftermarket tunes that RAISE the rev limiter, but the computer still looks for ignitions above the old rev limit. Type 1 overrevs are revs above the rev limiter and type 2 overrevs are revs a specific number of RPM's above the rev limiter (maybe 500? I am not certain). So, if you have a raised 7200 rpm limit, you will get type 1's every time you get to that limit. If you shift late in 1st or second, you will most likely exceed the 7250 rpm limit for the type 2 limits and the computer will count them up as well. Like I said, i am not certain of the specific rpm, that is only an example and I hope someone else will come in with the specifics.

 

The concern here is missing a downshift, say you are downshifting from 5th to 4th, but accidentally put the car in 2nd, and overrev the engine. On a STOCK car this would be the typical way of generating a stage 2 overrev, and is the bigger of the 2 concerns.

If the car has aftermarket tuning (CHIPPED) with an extended rev limit, you can also generate stage 2 overrevs, in this scenario, I wouldn't be NEARLY as concerned about the overrevs as the other scenario above.

Question is, how can you tell the difference ? You really can't say for sure, that is why a PPI is important, get a compression test, if that doesn't check out, you can pass on the car or consider a leakdown test.

My car had some stage ii overrevs, previous owner was very open about it being chipped and didn't try to hide the fact that it was. He also didn't hide the fact that he didn't buy a Porsche to park it in the garage and granny shift it once a week.

Personally, if you like the car, and you KNOW it was chipped with extended rev limit, and the PPI checks out, I wouldn't let that stop you.

Just my .02, I've logged a few II's since buying my car, and I have not missed a downshift yet. With the extended rev limit, it's not hard to pile on some Stage 2's, especially in first, and sometimes second gear.

 

Range 1 is 6800-7000rpm while range 2 is from 7000rpm and over for 996TT...When range 1 or 2 occur during acceleration it is ok...(e.g. with a rev limiter set to 7200rpm)but when they occur from down shift there is a problem...This is the reason porsche developed 6 over rev ranges to 997 in order to have specific rpm ranges to determine whether there was a downshift...