Insane speed in german cars... slightly OT, had to share...

[jason@scirocco.org (Jason)]

At 02:57 PM 11/6/2002, Someone wrote:
>I know you have that badass program that you wrote handy.  just how much Hp
>would it take with say a 2Y tranny and .80 5th, 205/50/15 to get to 140Mph?
>My guess => about 250HP. Am i close?


Yeah, very much so, actually!

I plugged in a Rabbit (A=1.80, Cd=0.42) with 205/50-15s on it and 2Y 
gearing replaced with an 0.80 5th.
I massaged a 2.0 16V torque curve until it gave me a top speed of 140 
even.  Rather than add cams or anything (i.e. increasing power at the high 
end with a sacrifice down low), I was lazy and just used a multiple of 
stock output all over.... the result is the same exact curve, just 
higher.  The multiple was 1.7, meaning 70% more power at every point than 
my 2.0 16V put to the ground.  The peaks are 205hp @ 5500rpm and 213 lb-ft 
@ 4250... at the wheels.  Using the same 16% loss that 16Vs seem to 
consistently measure (106hp to the ground, 123 at the motor), that gives us 
around 237hp at the motor... only 13 away from your guess.  Nice shot!

The 0.80 gear isn't really ideal for that much power.  140mph occurs at 
6110rpm, well past the hp peak.  Dropping it to an 0.75 drops revs to 5732 
and increases top speed to 144.  Even better is an 0.71, which gives you 
147mph at 5426.

Using the 0.71 5th gear, you can actually get to 140 using a multiple of 
1.48:1, so 179hp / 186lb-ft at the wheels, or around 208hp at the motor... 
So you'd save yourself the expensive of squeezing 30 more hp out of the 
motor, get better gas mileage, cruise more quietly, and still get to the 
top speed. :)


Jason