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Peak HP @ 8250; power curve starts to fall off above.
So....?
Let's look at a 2nd to 3rd gear shift. Gear ratios are:
2nd: 2.38
3rd: 1.72
If you shift at 8600 RPM in 2nd, you will drop to 8600*1.72/2.38 = 6215 RPM in 3rd.
How does your power at 8600 RPM compare to your power at 6215 RPM?
Now imagine you could keep accelerating from 8600 RPM to 8800 RPM while that other poor sucker had to shift and was stuck accelerating from 6215 RPM to 6360 RPM over that same speed range.
Who's going to be in front of who in that drag race? That's easy...
Trust me, on nice high-revving naturally aspirated engines, you want the highest redline possible if you want to put the most average power to the ground!
Assuming the RPMs take the same amount of time to increase through the rev band - aren't you hurting yourself using your example and looking at the power curve?
About a 50 hp drop going from 8250 to 9000 RPM (call it 750 units of time). Torque is dropping at this point as well. The negative slope of the curve at the high rev range is much more steep than the positive slope difference between 6215 and 6360.
You're looking at a 145 units of time with call it a 10 hp difference and more torque, seems you're better off to shift early using your figures + the curve.
Thanks ToyGuyAZ. That seems to settle it--8800 it is (at least in 1st)! I'm a little surprised Porsche hasn't formally acknowledged the variable red line anywhere.
Assuming the RPMs take the same amount of time to increase through the rev band - aren't you hurting yourself using your example and looking at the power curve?
About a 50 hp drop going from 8250 to 9000 RPM (call it 750 units of time). Torque is dropping at this point as well. The negative slope of the curve at the high rev range is much more steep than the positive slope difference between 6215 and 6360.
You're looking at a 145 units of time with call it a 10 hp difference and more torque, seems you're better off to shift early using your figures + the curve.
Forget the torque, it's midleading until you multiply it times the transmission ratios to get wheel torque. Just look at power, which is the actual rate of energy accumulating into the kinetic energy of the vehicle.
So just look at the power at 8600 RPM vs the power at 6215 RPM and that will tell you which one accelerates the car faster at that instant.
For a power curve like the GT3, the shift point is redline in every gear, thus you want the highest redline possible. Physics!
Rev limit is 8800 in first, 8700 in second, 8600 in third. I posted a video showing this several weeks ago linked here again. I took screen shots at one point showing it hitting 88, 87, 86 but you can see it in the video: Video Link: https://www.youtube.com/watch?v=SurUse_wsMQ
Sorry ToyGuyAZ. I recall you mentioning this before. So it looks like it is a staggered rpm limit in manual dependant on gear as I thought.
So SportAuto = 8600
manual = 8800/1, 8700/2, 8600/3 (as reported by OP)
What is the peak rpm on #4,#5, #6 & 7? I assume 8600 rpm?
Forget the torque, it's midleading until you multiply it times the transmission ratios to get wheel torque. Just look at power, which is the actual rate of energy accumulating into the kinetic energy of the vehicle.
So just look at the power at 8600 RPM vs the power at 6215 RPM and that will tell you which one accelerates the car faster at that instant.
For a power curve like the GT3, the shift point is redline in every gear, thus you want the highest redline possible. Physics!
Simplified calcs, ignoring torque as you suggest and assuming the engine build revs at the same speed through out the RPM range, I ended up with a 1 hp advantage (using a time-weighted hp calc of 1 rpm = 1 unit of time) shifting from 2nd to 3rd at 9000 vs 8600 RPM.
Add torque in, add slower building revs above 8000 RPM and the data to me would say shift earlier.
I wouldn't be surprised if this is part of the reason that Sports Auto is faster than manual shifting - it's probably setup to optimize the higher gear shifts more, clearly the RS was taken one step further in the PDK-R with the rev limiter being adjusted.
You would need to test it in the real world to be certain, but the problem here is the horrible shape of the 9A1 power curve. For example, 458 is pretty much the same slope all the way to redline - so rev the hell out of the thing. I shift my track car at red line every single shift, but it doesn't have the same downward slopping power curve, only torque starts to drop around 7000 RPM and I shift at 8000...
Power making range aside,I believe the guys that are getting the RS will be missing the race car sound made from 8500 to 9K RPM. That's the whole point of waking up at 4 am with the chickens and blast those mountains early morning. Is the RS a " feast for the senses " ?
Rev limit is 8800 in first, 8700 in second, 8600 in third. I posted a video showing this several weeks ago linked here again. I took screen shots at one point showing it hitting 88, 87, 86 but you can see it in the video:
09-01-2015, 10:07 PM
