PDK Over-Revs
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Jwgilmore (10-03-2019)
11-04-2009, 03:13 PM
#17
Race Director
Either pdk or 6speed will not over rev by simply pressing
the accellerator pedal and rev it up to redline. The rev limit will cut
fuel and save you. The way you over rev a car is by downshifting
to a lower gear and mechanically cause the engine to turn past redline.
Pdk will not allow this to happen.
the accellerator pedal and rev it up to redline. The rev limit will cut
fuel and save you. The way you over rev a car is by downshifting
to a lower gear and mechanically cause the engine to turn past redline.
Pdk will not allow this to happen.
11-04-2009, 05:14 PM
#18
Three Wheelin'
11-04-2009, 07:19 PM
#19
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Either pdk or 6speed will not over rev by simply pressing
the accellerator pedal and rev it up to redline. The rev limit will cut
fuel and save you. The way you over rev a car is by downshifting
to a lower gear and mechanically cause the engine to turn past redline.
Pdk will not allow this to happen.
the accellerator pedal and rev it up to redline. The rev limit will cut
fuel and save you. The way you over rev a car is by downshifting
to a lower gear and mechanically cause the engine to turn past redline.
Pdk will not allow this to happen.
Driver's should not believe for a moment that the rev limiter will keep you entirely out of trouble with upshifts. The Sports Chronometer option also somewhat exacerbates this, with it's much more aggressive rev cutout.
11-04-2009, 07:58 PM
#20
Race Director
Edgy, from my experiance with a Tip and PDK the fuel is cut at redline and the engine will not over rev. I instruct for DE's and students always forget to shift and redline the car and the 6 speeds I've been in do the same. With a manual you can over rev with the "money shift" and danage the engine. There are different over rev's counted in the ECU some maybe the mildest over rev is when you hit redline and fuel is cut?
11-04-2009, 08:24 PM
#21
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Either pdk or 6speed will not over rev by simply pressing
the accellerator pedal and rev it up to redline. The rev limit will cut
fuel and save you. The way you over rev a car is by downshifting
to a lower gear and mechanically cause the engine to turn past redline.
Pdk will not allow this to happen.
the accellerator pedal and rev it up to redline. The rev limit will cut
fuel and save you. The way you over rev a car is by downshifting
to a lower gear and mechanically cause the engine to turn past redline.
Pdk will not allow this to happen.
Mike, here are the 6 over rev ranges for a 997.1 (6 speed):
A 997-1 DME records the following rev ranges:
Range 1: 7300-7500 RPM
Range 2: 7500-7700 RPM
Range 3: 7700-7900 RPM
Range 4: 7900-8400 RPM
Range 5: 8400-9500 RPM
Range 6: 9500-11000 RPM
You can exceed the rev-limiter by at lest the 3 different ways:
1) Hitting the rev-limiter, and not shifting soon enough (usually range 1 or 2)
2) Missed down shift (no protection from the rev-limiter downshifting)
3) Spinning the car, and not getting the clutch in fast enough (engine gets spun backwards)
11-04-2009, 10:37 PM
#22
Race Director
No HTwo O, thanks for the info...so Porsche says hitting the rev limitier is an over rev. I understood your 1) but now I understand Porsche says that is an over Rev. I understood your 2) and 3).
THANKS!
THANKS!
11-04-2009, 11:46 PM
#23
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Just remember that these high reving engines can well exceed the 7300 rpm redline simply on engine inertia. Fuel cutoff at 7300 isn't sufficient to spare you from that. I have many "over revs" from my aggressive driving and have never made a "money shift." It's just the momentum of all that mass.
09-19-2014, 05:26 PM
#24
Nordschleife Master
Either pdk or 6speed will not over rev by simply pressing
the accellerator pedal and rev it up to redline. The rev limit will cut
fuel and save you. The way you over rev a car is by downshifting
to a lower gear and mechanically cause the engine to turn past redline.
Pdk will not allow this to happen.
the accellerator pedal and rev it up to redline. The rev limit will cut
fuel and save you. The way you over rev a car is by downshifting
to a lower gear and mechanically cause the engine to turn past redline.
Pdk will not allow this to happen.
09-19-2014, 10:09 PM
#25
Rennlist Member
My understanding is that if you are in "auto" w PDK you can not over rev. But if you are in manual mode (shifter selected to left) and manual shift (down) you can over rev! Sport chrono makes no difference. It in fact saves you even better as it shifts sooner/quicker!
09-19-2014, 10:53 PM
#26
The programming will not allow a downshift if rpms will exceed the limiter in manual mode or otherwise.
09-20-2014, 03:19 AM
#27
Just remember that these high reving engines can well exceed the 7300 rpm redline simply on engine inertia. Fuel cutoff at 7300 isn't sufficient to spare you from that. I have many "over revs" from my aggressive driving and have never made a "money shift." It's just the momentum of all that mass.
09-20-2014, 07:57 AM
#28
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Yes, it is possible to over rev a car with PDK when you are accelerating and hit the rev limiter. See the link below:
2011-gts-pdk-dme-rev-ranges-observed
Alan C. states "Recently I bounced off the rev limiter in manual mode. The count this time is higher than the one I had around 2000 miles so the counter is cumulative." So even though the rev limiter was activated, some ignitions in rev range 1 were recorded. This is true with both PDK and manual equipped cars.
Here are the Rev Ranges for the 997.2 models:
However, when talking about a "money shift" over revs, apparently the PDK software will not allow you to downshift to a gear that would cause a mechanical over rev or "money shift."
2011-gts-pdk-dme-rev-ranges-observed
Alan C. states "Recently I bounced off the rev limiter in manual mode. The count this time is higher than the one I had around 2000 miles so the counter is cumulative." So even though the rev limiter was activated, some ignitions in rev range 1 were recorded. This is true with both PDK and manual equipped cars.
Here are the Rev Ranges for the 997.2 models:
Rev range 1: 7,500 to 7,699 = Maximum permitted engine speed exceeded; engine damage possible.
Rev range 2: 7,700 to 7,899 = Maximum permitted engine speed exceeded; engine damage possible.
Rev range 3: 7,900 to 8,099 = Maximum permitted engine speed exceeded; engine damage possible.
Rev range 4: 8,100 to 8,399 = Maximum permitted engine speed clearly exceeded; engine damage probable.
Rev range 5: 8,400 to 8,899 = Maximum permitted engine speed very clearly exceeded; engine damage very probable.
Rev range 6: over 8,900 = Engine damage has generally occurred.
Exactly when does the "rev limiter" activate and stop or diminish the fuel supply? I don't know the answer to that question. If Rev range 1 starts at 7,500 RPM and "if" the rev limiter activates at 7,500 RPM, you have already entered range 1 and will have x number of ignitions recorded by the DME in range 1. The rev limiter is there to keep you from accelerating into a rev range that could damage the engine. If Porsche absolutely wanted to avoid acceleration revs at or above 7,500 RPM, they would set the rev limiter to activate well before the 7,500 RPM number. Rev range 2: 7,700 to 7,899 = Maximum permitted engine speed exceeded; engine damage possible.
Rev range 3: 7,900 to 8,099 = Maximum permitted engine speed exceeded; engine damage possible.
Rev range 4: 8,100 to 8,399 = Maximum permitted engine speed clearly exceeded; engine damage probable.
Rev range 5: 8,400 to 8,899 = Maximum permitted engine speed very clearly exceeded; engine damage very probable.
Rev range 6: over 8,900 = Engine damage has generally occurred.
However, when talking about a "money shift" over revs, apparently the PDK software will not allow you to downshift to a gear that would cause a mechanical over rev or "money shift."
09-20-2014, 01:34 PM
#29
Race Director
Just my two cents. I was told it is possible to over rev a Tip and even a PDK.
The scenario involves a substantial downgrade and having the tranny set to hold a gear rather than upshift at redline.
Momentum/inertia can have the vehicle obtain a speed that over revs the engine even though the DME would kick in and cut fuel.
Anyone who has driven in the mountains (and not just the big old Rockies but smaller mountain ranges) can attest to a car picking up speed on a down grade even with no pressure on the gas pedal and the transmission in (probably top) gear.
Another possible way is to in neutral raise RPMs to their redline.
I know of one guy who for some reason did this to his car's engine (in a Ford car) and the engine overreved to the point valves floated and some got bent.
Me not knowing he did this this guy came to me some months back with a persistent misfire. We discussed various things and he did the whole coils, plugs thing and still the misfire persisted.
I told him that about all I could think of is a valve had burned. As an aside, another guy I know experienced this with his car (a Subaru). A persistent misfire and plugs and coils didn't help. I told him the same thing, that about all I could think of was a valve had burned. (The engine was factory turbo-charged.) Finally he took the car in for a head job on the side of the engine that had the misfiring cylinder and sure enough an exhaust valve had small groove burned in the edge of the head where it seals in the valve seat looking like someone had taken a small cutting torch to the valve.
Anyhow, I left it at that with the first guy but recently heard he had his misfiring car in the shop and was having the head redone and the reason was the valves were bent. It was then I learned of what he had done, though I never could ask him why he had done that, given the engine WOT in neutral at a standstill.
The scenario involves a substantial downgrade and having the tranny set to hold a gear rather than upshift at redline.
Momentum/inertia can have the vehicle obtain a speed that over revs the engine even though the DME would kick in and cut fuel.
Anyone who has driven in the mountains (and not just the big old Rockies but smaller mountain ranges) can attest to a car picking up speed on a down grade even with no pressure on the gas pedal and the transmission in (probably top) gear.
Another possible way is to in neutral raise RPMs to their redline.
I know of one guy who for some reason did this to his car's engine (in a Ford car) and the engine overreved to the point valves floated and some got bent.
Me not knowing he did this this guy came to me some months back with a persistent misfire. We discussed various things and he did the whole coils, plugs thing and still the misfire persisted.
I told him that about all I could think of is a valve had burned. As an aside, another guy I know experienced this with his car (a Subaru). A persistent misfire and plugs and coils didn't help. I told him the same thing, that about all I could think of was a valve had burned. (The engine was factory turbo-charged.) Finally he took the car in for a head job on the side of the engine that had the misfiring cylinder and sure enough an exhaust valve had small groove burned in the edge of the head where it seals in the valve seat looking like someone had taken a small cutting torch to the valve.
Anyhow, I left it at that with the first guy but recently heard he had his misfiring car in the shop and was having the head redone and the reason was the valves were bent. It was then I learned of what he had done, though I never could ask him why he had done that, given the engine WOT in neutral at a standstill.
