How accurate are the Durametric Ignition Ranges?

I finally got around to plugging my Durametric up to the 996 and looked at it's ignition ranges, but the values don't seem right at all. It lists 1770.4 operating hours, 8156/1725 range 1, and 315/1464.9 for range 2. We don't have a good feel for hitting the rev limiter (range 1) other than the value seems really high. The over rev, on the other hand, we can think of maybe a handful of times each that we've had a bad downshift that could have caused an over rev (but most probably didn't). So maybe at worst accounting for not realizing we did it we should only be talking about 25. This is a 1 owner car, the cluster is still original, the ECU hasn't been changed, one AutoX event, and no DEs yet. What else could explain these numbers since we know this car has not been subjected to the abuse these numbers imply?

Quotes source post: 11254800

Assuming the numbers are bogus then an explanation, rather just a theory, is the Durametric system does not read the over rev counters correctly. As I have mentioned before these counters represent an avoidance of risk to Porsche. The data must be (or should be) reliable, accurate, and tamper proof. Thus a simple "read" of these values may not deliver the real values. Worse, the read may change the values to let Porsche know the values have been accessed via an unauthorized tool. The approved method to read these is with a Porsche diagnostics computer. This computer is in contact with the factory. There can be some interaction between the reading of the data and some data at the factory that is used to derive the actual readings for public consumption. This gives Porsche a way to keep tabs on when the numbers were read, that they were read via an approved way, and have not been "tampered" with in the meantime. It also provides a way to detect if say the numbers were reduced or the higher numbers in the higher rev ranges were erased/zeroed. Just a theory mind you. However, without say having the ability to read the numbers via an official Porsche diagnostics computer, then read them with a Durametric tool, then re-read them with a Porsche diagnostics computer to see if the before and after readings are ok and consistent, this is just a theory.

You realized those numbers are number of ignitions and not number of times, right?

Quotes source post: 11254925

Yes I understand that there can be multiple hits within a single ignition cycle, but that is irrelevant in this case as even at 1:1 these numbers are way too high given that we intimately know the history of the car.

315 range 2 ignitions at let say 7400 rpm = 0.85 second, no?

With that many ignitions in range 2 thats not an anomaly. If I see less than 20-30 ignitions I overlook it, but when its 10X that, its real. Usually one zing thats really quick will count for 150 ignitions in range 2, one heavy over rev is usually around 300. This one was zinged once pretty good, or twice really quickly. Durametric only reads the data, in this scenario its just as effective as any other diagnostic tool. To achieve a range 2 in an earlier car (that only has two ranges, not six) requires the engine to be mechanically over revved to 7,800 RPM+. This will only occur if a shift is missed and the vehicle speed and momentum is multiplied through the gearbox, "zinging" the engine to an RPM well beyond that the ECU rev limiter will allow. Today on the track one of my engines was sent to a range 6 for 326 ignitions and lived through it. Its down a little on power as I am sure they bent all the valves, but it stayed together and running fine. It will have to come apart for good measure.

Quotes source post: 11255034

OK, I think I am misunderstanding the term "ignition" in this context. I thought it referred to a start/stop cycle, but your description leads me to believe I'm wrong. Can you (or anyone) please clarify?

It's the number of ignition events that is cut by the rev limiter.

It takes two revolutions of the engine for all six cylinders to fire, so there are three ignition events during every engine revolution. If my math is correct, there are 370 ignition events every second at 7,400RPM.

Exactly.

Ok, I think I get it now thanks. Less than a second over 1700 hours seems much more in line with what we believe the car has seen in its life. Thanks for all the info. Its much appreciated.