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Question Regarding Rev Limiter

S

Skyrider

PCGB Member
Member
Could someone please provide some information on how the rev limiter works on the 718 Cayman (PDK)? For example, does it cut-off fuel, ignition, or both? What are the characteristics when the rev limiter is in operation?
My reason for asking is that I may have experienced this recently, but can't be sure that it was the rev limiter: pedal to the floor, car accelerating nicely (uphill), when there was a sudden loss of 'sensation', accompanied by a slight jolt, which took me by surprise. There was no 'pop, pop, pop, that I was aware of it. Want to be sure that the car is okay...
 
In my experience the rev-limiter on a PDK 718 only cuts-in when the car is being driven in Manual mode, that is when you are determining the gear change points. In Auto mode the ECU determines the rev limit for up-changes which in the case of Sport Plus is at the 7400 red line before the rev-limiter cuts in.

I have never hit the rev-limiter in Auto mode in either of my 718's. In my current GTS I have hit the rev-limiter once in Manual mode, 2nd gear, when accelerating out of a hairpin bend in damp track conditions with the PSM off. The engine instantaneously cuts out, both fuel and ignition, for a split second only, up-shifting to the next gear resumes power delivery as normal. No drama, no problem.

The rev-limiter settings are controlled by the ECU and are there to protect the engine from over-rev damage. In the case of the 718 GTS this limit is set at 7600 rpm. No damage will result from activating the rev-limiter occasionally. Just don't make a habit of it.

Going by your description I would guess you lost traction momentarily and spiked the rev-limiter on full throttle. Nothing to worry about.

Brian

 
Hi Brian,

Thank you for your reply. The bit about the engine cutting out for a split-second, then resuming power, seems to describe what I experienced.

It's actually happened three times recently, twice on the same piece of road. On each occasion, the gearbox was in Auto mode, with Sport engaged.

Will try to be more careful...

Doug

 
Doug,

Mmm.... The rev-limiter doesn't usually activate in Auto mode, as the ECU upshifts before the rev-limit is reached. It could be PSM activating to cut engine power momentarily, although in Sport mode the threshold is backed-off slightly.

If this happens a lot, I would have your error codes checked at your OPC.

Brian

 
Doug,

Just to point out that rev over-ranges are logged as 1-4, where 1 and 2 are rated acceptable. Your Porsche centre will be able to run diagnostics to tell you whether or not you've experienced a rev-limiter over-range. As Brian has pointed out, it would be unusual for a car equipped with the PDK transmission to hit the rev-limiter, but the diagnostic check should also throw-up any error codes.

Jeff

 
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