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In the never ending quest to distract myself from revising for various ecology and survey methodology exams, I've decided to take up aerodynamics. The thing is, it's years since I did any proper maths. So how the f*ck do I calculate maximum speed from frontal area, Cd and power? I can't even rearrange mildly complicated equations any more...

Reply to
Doki
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"Doki" wrote in news:f1umuv$si3$ snipped-for-privacy@registered.motzarella.org:

Google it. :-)

Reply to
Tunku

Try rec.auto.sports.f1 - there are a couple of aerodynamicists on there. You might even find the equations have been posted before if you Google the group.

Reply to
Krusty

P is power, F is force, V is speed, S is area, rho is density:

P = FV, (1)

and force is equal to drag:

F = Cd 0.5 rho V^2. (2)

So, insert (2) in (1):

P = Cd 0.5 rho V^3, (3)

and

V = (2P/Cd/rho)^(1/3).

Reply to
M J Carley

Strangely enough, one of the pedal-power groups appears to have come up trumps:

formatting link

Reply to
CT

All SI units? Where's frontal area in that lot?

Reply to
Doki

Paging TOG

Reply to
MikeH

Bugger. It should read:

P is power, F is force, V is speed, S is area, rho is density:

P = FV, (1)

and force is equal to drag:

F = S Cd 0.5 rho V^2. (2)

So, insert (2) in (1):

P = S Cd 0.5 rho V^3, (3)

and

V = (2P/S/Cd/rho)^(1/3).

Reply to
M J Carley

S = CG ^ ---------------- STEEP HILL

Reply to
Krusty

Ta for that. I'm using a 15% fudge factor for transmission losses & rolling resistance (looking at various versions of the Golf) and I get rather high top speed figures for MK2s and 3s and 4s, but pretty much bang on for the later MK5s. I suspect this could be down to gearing mind, as the MK2s are geared to get to the red line pretty sharpish in fifth rather than to reach all out top speed, and it's also perfectly possible that VW didn't want the MK2 G60 to do 155mph given that it's probably generating considerable lift at that speed.

Reply to
Doki

In article , Doki writes

It is the same as what you should all ready know for fluid dynamics except the fluid isn't quite as much of a fluid but is still very dynamic. Easy really.

Reply to
steve auvache

messagenews: snipped-for-privacy@bath.ac.uk...

Don't forget that if the drag is higher than the power output lower in the rev range the car may never get to the top of it's powerband in top gear.

You can cheat with:

It has the 1991 16v in there already and there is nothing to stop you adding any more you like if you have the right information.

Reply to
Depresion

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