PDK and Overrevs

I'd appreciate it if the brain trust here could weigh in on the whole " PDK and overrevs" question. I know it's not a new subject, but I'm new here, and after reading a bunch of threads, I want to see if I understand this correctly, especially since I have a PDK in my 2009 Cayman . So, as I understand it, overrevs (exceeding the maximum engine rpm -- "redline") happen either by accelerating beyond the limits or by downshifting improperly, usually by mistake and to a low gear that wasn't intended for the downshift. The ECUs in our Porsches remember these things, and under certain conditions, warranties can be voided because of overrevs. In our cars, accelerating past the redline isn't possible because the ECUs take over and cut off the fuel first. This is what's known as "the limiter," right? Downshifting improperly is more possible and problematic, and is the source of many (most?) of the overrevs that show up on DME reports of the five stages reported for our 987s. Those driving manual transmissions are much more susceptible to this because there are no "built in" ways to prevent this from happening. With PDKs, though, when in automatic mode, the ECU will take care of the engine regarding rpms when accelerating or downshifting. When operated in manual mode with the stick shift or paddles, the ECU will not allow the PDK to accelerate past redline OR downshift into a gear that would result in an overrev. Is that correct? I don't want to learn the hard way that I had this wrong! Finally, when I go to my indy shop that does my work, would asking for a DME for my car make me look like an idiot? Is there even such a thing as a DME for a PDK -equipped car? Thanks in advance!

Correct. You can't truly over-rev a PDK . The DME /transmission control unit won't let you downshift to a gear that would run the car past redline. BTW - The DME is the ECU . Stands for Digital Motor Electronics or Digitale Maschine Elektronik in German. There are different zones where the revs will fall. See this post for more info: Tech Q&A - Can You Explain Over Rev Reports And What The Numbers Mean? | Porsche Club of America You can get an over-rev report on a PDK, but it's probably not necessary. An over-rev report was done on mine when I had the pre-purchase inspection on my 981 w/PDK. The person I was buying it from took it to the dealership where he had originally purchased it and they ran the full CPO-level inspection on it for me. I had a number of over-revs in zone 1, but none in 2 or higher.

Thanks very much, Ledbette. I know zones 1 to 3 aren't considered significant, and I understand that overrevs in zone 1 are the least problematic since they include the redline value. Just wondering how they occur in the first place, with the design of the PDK transmissions and the ECU ( DME ). I've read that, for instance, going downhill when downshifting can actually push the rpms past the limit momentarily. Do you, or does anyone else, know other ways a PDK transmission could overrev the engine?

I've tracked my car extensively. If you run in Sport+, it'll run it all the way up to the redline. So at the redline, you get into zone 1. I've hit that downshift button milliseconds after the car downshifted and can confirm it won't let you downshift past the redline.

That's great to know, ledbette. And a ballsy move too, I might add! I don't track my Cayman , but if I ever buy the 987.2 Cayman S with PDK that I keep a watchful eye out for, I'll know what to ask about regarding the transmission's history. Thanks again!

I believe zone 1 & 2 are not considered "over-revs" - they're simply instances where you may have gotten close to maximum revs, and instances where you reached maximum revs and the ECU/TCU prevented a true over-rev condition from occurring (zone 3..) Porsche rev range activity | engine over revs explained by 911virgin Understanding Porsche rev range activity. A detailed guide from Porsche specialist dealer 911virgin based in Uxbridge, West London 911virgin.com I may consider combining this thread with one of the already existing threads on this exact topic. Unlike Facebook, we can search for this sort of discussion on Planet-9..

Don, it's your call. When I tried searching PDK and overrevs, I didn't find any threads about the topic, only articles mentioning one or the other. I felt sure they were out there. Thanks for the link.

That's because the internal search engine of xen-fora isn't all that great (no forum actually is) - the trick if you REALLY want to find something is to use Google: It came back with 420 results - this thread being the first...

I like being first. Thanks for what you do here, Don!

Wasn't intentional. PDK and I were thinking the same thing and it was just a bit faster than I was. Sometimes you need to give the PDK a little nudge because it doesn't know you're heading into an mid-speed uphill turn that'll need a downshift. I'd rather give it an early nudge in the braking zone rather than have it try to downshift mid-turn.

Gotcha. I've started trying to get used to using the steering-wheel mounted buttons a little more than the gear shift, and also shifting while in automatic transmission mode. It's a work in progress, and mainly I'm trying to develop some muscle memory for these things, especially keeping in mind not to be accelerating at all when downshifting and vice-versa, since it's a good way to confuse the PDK . I appreciate all your posts and observations, and Dan's. I think the PDK is one of the most incredible engineering feats ever, and I'm so glad I found a 987.2 that had one.

When I purchased my 987.2 CS w/ PDK back in 2013, I requested the DME report to add to the car's documentation history. Keeping good records is important.

I re-wired my steering wheel so that the LH pull downshifts and the RH pull up shifts. I disabled both push buttons. You know, just the like every other paddle shift car out there. BEST. FREE. MOD. EVER. Here's a guide on how to do it: Rewire Steering Wheel PDK Buttons? - 2010 Cayman

When I bought my'09 w/ PDK I had a PPI done to check it all out. While discussing the report with the mechanic at Porsche about over revs he chuckled and said I had nothing to worry about as it's impossible with the PDK . Good peace of mind on that info.

I once read that the Rev 1 range is actually 200 rpm below the redline. And that the Rev 2 range is also below. When I was accelerating on the track one time, I got high enough with RPM’s that I felt the fuel cut back in my manual Cayman . I later checked the DME and had not added any revs at any levels. I suspect the computer is sophisticated enough to anticipate the need for fuel cut off ahead of time based on the throttle position and rate of acceleration. It’s not just a matter of saying that the engine has reached a certain rpm. The computer anticipates that you will reach redline and cuts off fuel preemptively so you don’t even get to the 200 rpm’s below redline limit that gets recorded. Based on this experience, I’m going to hypothesize that all rev range recordings in the DME are originated via a downshift.

Mine had the exact same response when doing the PPI...😅 I can imagine him in a meme.. saying....."over revs? we dont need no *#&@^% over rev reports...."