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      02-06-2008, 06:54 PM   #149
swamp2
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Drives: E92 M3
Join Date: Sep 2006
Location: San Diego, CA USA

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Quote:
Originally Posted by jaiman View Post
i read somewhere that the gearing is very short, which is why the acceleration is so fast.
Gearing has been known for some time and that is not what is producing the spectacular times. Footie: M6 is an interesting comparison for sure.

Gear/GT-R/M6/Overall % Advantage GT-R
1/4.056/3.99/4%
2/2.301/2.65/-11%
3/1.595/1.81/-10%
4.1.248/1.39/-8%
5/1.001/1.16/-12%
6/.796/1.0/-19%
7/-/.83
FD:3.7/3.62

What this means is that in all gears except 1st the torque multiplication is well in favor of the M6, the higher hp and higher redline should be in its favor as well. However, the actual torque produced by the GT-R is a large advantage for it. To really fully account for gearing you need to consider engine torque vs. rpm, gear ratios, final drive, losses and even tire size. When you do this you can compute accelerating torque and force at the rear wheels. At the end of the day this is the sole thing that accelerates a car. I updated the loss figures for the M6 and GT-R to be as follows (partly based on advice from Bruce A.)

Item/M6/GT-R
Trans/4%/4%
Diff/2%/1%
Axles/6%/3%

Tire and aerodynamics losses remain per CarTest defaults.

The force at the drive wheel then looks like this (1st figure below), again advantage is for the M6. For the acceleration simulations I have used shift times for SMG III at 150 ms (recent G-tech findings at m5board.com) and for the GT-R at 100 ms. I simply do not buy their quoted times of 200 ms for a dual clutch system. The updated performance simulations are shown below.

The numbers for the M6 are too good, again meaning that the loss figures are probably a bit too low for both cars. Adding loss for the GT-R will slow it down and the figures below are close to stated values for 0-60 but still a bit slow for the 1/4 mi. More losses will bring the 1/4 mi figure into the 12's and move the trap even further away from test results. The conclusion still remains that the car is performing better than its power, weight, gearing, etc. dictate.
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