I wanted to make you aware of some work I started a few weeks back which can maybe help some of the track guys on this forum.
I created a little simulation program that models straight line acceleration. It allows the engine, gearbox, tyres, aero, weight/inertia etc. to be changed.
In OEM spec the figures are not too far off real life data (). They would be pretty close accounting for shifting:
0 – 100 kph : 4.91s (4.9 – 5.0)
0 – 200 kph : 16.73s (17.0)
400 m : 13.06s (13.2)
1000 m : 23.51s
Vmax : 281.1 kph
Max g : 0.63
First look is at different final drive ratios, comparing the stock 3.62 (
Blue) to 3.91 (
Red) and 4.1 (
Green). A shorter final drive is a bit quicker across the board and helps top speed as well by being closer to max power.
0 – 100 kph :
4.91s ->
4.82s ->
4.81s
0 – 200 kph :
16.73s ->
16.46s ->
16.34s
Vmax : 2
81.1 kph ->
284.5 ->
285.4 redlining 6th gear
First gear acceleration is similar to stock as you are grip limited (dotted line). Acceleration after that is slightly better for the shorter final drive ratios when you are in the same gear and drops off where the gears are offset (i.e. 3rd gear on 4.1 and 2nd on 3.62 ratio). The time delta and the delta of longitudinal tyre force shows this behaviour and their relationship quite well.
The original gear and final drive ratios would theoretically allow a top speed of over 300 kph. The OEM 6th gear and final drive combination is mainly chosen to keep the cruising RPM and fuel consumption a bit lower. The RPM drop is defined by the gearbox ratios and therefore do not change.
I have posted this a little while back on the z4-forum if you want to see some additional effects on weight reduction and additional power.
https://z4-forum.com/forum/viewtopic.php?f=9&t=123260