What gear do you dyno in?
Drifting
Joined: Jul 2003
Posts: 1,796
Likes: 1
From: Annandale VA
Originally Posted by AU N EGL
Now my questions is Do A6s have to recaculate the HP & TQ. A6s 4th gear is 1:1.1
As to which gear to dyno in, I did both. The results were interesting. Fourth gear results were 14 HP and 16 TQ higher at peak, but average TQ was 28 higher. The parasitic losses of the shorter 3rd gear really do affect the numbers across the power band, moreso at lower RPMs. That surprised me a bit. I think we commony assume that a shorter gear acts as a TQ multiplier. Not necessarily so. A shorter gear makes the engine rev more quickly, but does not necessarily make the car accelerate more quickly. (You need to think this through before you rush to your keyboard to dispute this. The numbers do not lie).
Why dyno in both gears? I can think of a couple of reasons. If all you're looking for is bragging rights, then a 4th gear pull will yield the highest number. But how many times do you actually accelerate from 2K RPMs to redline in 4th gear? At the track, you will spend most of your time in 3rd gear, starting at whatever RPM you are at when you shift, and continuing through the RPM you are at when you cross the finish line. The average TQ in this RPM range, in that gear, will directly affect your ET and trap speed. So if you're trying to pick out a cam for track use, the available power in that RPM range should be your focus. And if you're trying to predict actual performance, the most accurate power numbers will be found in the actual gear that you will be in at the track.
For a true quarter-mile simulation, it would be helpful to have separate dyno pulls for each gear. With the right simulation software, you could then not only predict the differences between different rear end gear ratios, but also between tranny gear ratios (such as the difference between the Z51 M6 ratios and the standard M6).
Interesting stuff.
Team Owner
Joined: Sep 2003
Posts: 43,084
Likes: 33
From: Raleigh / Rolesville NC
Originally Posted by HITMAN99
So if you're trying to pick out a cam for track use, the available power in that RPM range should be your focus. And if you're trying to predict actual performance, the most accurate power numbers will be found in the actual gear that you will be in at the track.
.
.
3rd gear, 2,000 to Redline
4th gear, 4,000 to redline
the time it takes to downshift to 2nd and back upshift to 3rd is lost with any performance beneffit. Better to stay in 3rd and use low end torque.
Very Interesting indeed.
