Originally Posted by Earlierapex

..... I certainly know a lot of really fast drivers who don't downshift to second at oak tree because they lose time and momentum trying to get both the 3-2 downshift and turn-in point perfect in tight spaces like oak-tree at VIR.

Originally Posted by MaxLTV

I assure you it's correct - the HP (power) is the same through that entire RPM range, because torque falls down at the same rate as revs go up. Here is an illustration (the blue dashed line). You can see that the turbo practically emulates CVT effect.



Acceleration is determined by average power to the wheels through the used rev range, and if the power to the wheels is not changing much through the used range, the average will be very close or equal to peak power. Once that point is reached, adding more gears will not increase average power to the wheels and thus will not help acceleration.

Originally Posted by wanna911

I agree with the OP for the most part, but still believe the overall affect is quite negligible for a talented driver. I think the biggest benefit is a lesser dependency on gear ratios being right, shifting mid sweeper where in a manual you would probably be better off just staying in one of the gears as the time/balance lost shifting while turning increases dramatically. I know I skip some shifting opportunities because it's just plain faster not to, and because I can't use the additional torque from the lower gear at the edge of traction anyways.

I think the affect depends on how much torque the car is actually putting down. In a straight line, it's pretty much identical, but mid corner, an increase in torque will not help unless you have more grip than power. Which is quite hard to do in a street car on street tires with no big DF.




I have been amazed how it's not in the right gear and downshifting mid corner while watching the Cayman Interseries guys drive around in auto mode. Pretty much every one of them going through turn 1 at Road Atlanta, you could hear the car kick down a gear likely from 4th to 3rd.

Sometimes it's beneficial to be in a higher gear because you can't put down more power in the lower gear anyways so you aren't feathering the throttle in 3rd vs planting it in 4th.

Originally Posted by jumper5836

There was a thread about this in the Racing & Drivers Education Forum. There where a few guys saying to just leave it in auto and telling students to leave it in auto. It's easier on the car and it does a better job.

Originally Posted by Earlierapex

Good point, but I certainly know a lot of really fast drivers who don't downshift to second at oak tree because they lose time and momentum trying to get both the 3-2 downshift and turn-in point perfect in tight spaces like oak-tree at VIR.

Originally Posted by Earlierapex

Most of you true gearheads know that torque peak is where the engine makes the most torque, but horsepower peak is where the engine/gearing combination can deliver the most "gear multiplied torque" to the wheels. The balance between these two occurs because the mechanical advantage of increased gear-based torque amplification with increased RPMs adds more "multiplied torque" than is lost as the "engine torque" curve decreases with increasing RPMs. Horsepower is a mathematical calculation of the point at which these two independent variables (engine torque and theoretical gearing) are maximized.

In a perfect world, the maximum mathematical acceleration would occur with an engine spinning at the horsepower peak with an infinitely variable frictionless transmission.

On one hand, current variable transmissions are inefficient. On the other hand, the rate limiting step in adding more gear ratios to a manual is the ham-fisted human being shifting gears with big feet and a hairy chest.

While the journalists have touted the obvious advantages of PDK (keep both hands on the wheel, quicker shift times), perhaps the real advantage is the ability to manage more gear ratios in less time to maximize the mechanical gearing advantage available when one keeps RPMs as close to the horsepower peak as possible?

Most of us use gears 3 and 4 on most tracks on most manuals most of the time. What if you could add another gear by keeping 3rd the same and making 5th the same ratio as 4th without any loss of function by having to wave your arms and feet around like a madman between southbend and oaktree at VIR? What if you could add 2 gears?

I've never bought the argument that a manumatic gives a huge advantage in acceleration because shift times are faster - you don't lose half a second of velocity, just half a second of acceleration time. While better, the argument that the computer can heel-toe more consistently than humans is equivalently marginal in my mind (and less fun).

But what if PDK moves the game on by doing something human beings literally don't have the physical prowess to do? Human beings don't have 4 feet and can't replicate ABS. In the same manner, we don't have quick enough, non-chassis-disturbing enough shift capability to manage 50% to 100% more meaningful gear ratios.

I'm sure someone will point out that the 991 Carrera pdk has basically the same ratios as the 7spd manual, and all Porsche has told us is that the GT3 has "shorter ratios and reaches top speed in 7th rather than 6th." The increased RPMs available with the GT3 create the perfect environment for gear ratio optimization.


What if PDK really gives us access to 10% to 20% more usable torque via increased and optimized gearing over 30% to 40% of the track?

But what if PDK-S doesn't just do what we do better, but does what we can't?

Originally Posted by Mike in CA

Based on my experience, I think you would be amazed at how well even the first generation PDK is at anticipating and being in the right gear at any given time. Sport + auto mode is incredibly "intuitive" in track and fast road driving situations. A very skilled human driver might be able to match it, but would be unlikely to beat it. PDK-S is at least two generations on from the original and should be that much better.

Originally Posted by Horstair

Does Macca have a PhD...I'm wondering...

Originally Posted by Macca

LOL Hostair. I wish! Im still struggling to make any sense of the paragraph under section 2 next to the graph!