heres the graph:

www.custom-concepts.co.uk/untitledgraph.JPG

could y'all compare your bhp to your top speed an tell me whether or not my graph is anything like reality,

the graph assumes a weight of 600kg, with windscreen

cheers

Matt

bhp at engine or wheels?

wheels

if ya know your flywheel bhp take roughly 18% for drive train losses

cheers

Matt

I would say that it is reasonably accurate.

I think it maybe a touch optimistic in practice, but it certainly looks to be in the right ball park.
Cheers
Richard

I don,t think it will be accurate at the higher speeds.
The aerodynamic brick that is a seven will lose out over 60 to wind resistance. I would expect your graph to climb more steeply over 60mph.

I will add a link to Cartest later. A little program which allows plotting of COD, gearing, weight, BHP etc and predicts your vehicles performance.

It tends to give pretty accurate results and is nice as it allows comparison against known vehicles and around different tracks.

I guess some will say it is inaccurate though is it will deflate the expectations of some.

oh yea that is (hopefuly, if my maths is good ) be the absolute maximum your car can achive, it would need to be geared to suit the speed and rpm taken into account

It looks too much like a simple mathematical curve than a true MPH vs BHP curve. I would suggest that you need more power than that for the higher speeds, perhaps 10% or 20% more at 100 MPH.

My graph is lumpy as the power loss changes according to RPM. Each section of the line is a different gear.

I have 170 bhp (flywheel) car with an aeroscreen, a 3.89 diff and 13" wheels. At the end of the hangar straight I managed 125mph, but it was really losing the battle against air resistance. (The mph was worked out from the rpm, as the speedo is useless.) I think I might be able to squeeze another 5mph out of it if I had a very long straight, but I doubt it would do more than that. Not sure if that helps.

[Edited on 4/1/07 by Phil. S]

Get someone to take you out for a run in a seven. Bike engined and on a track preferably. It will soon become apparent these cars are about acceleration, nimbleness, handling.

Top speed is slightly more relevant than boot space.

I managed 110 out of my old xflow powered westy pre-lit, but that was as far as it would go (138bhp)

CarTest Program

I have managed to upload the program now. Give it a try. Open the zip file and double click CT.exe.
I used the Drag Coeffs from the Caterham for mine.

Lets see some results them!! I will be happy if mine goes as well as this suggests it will.

Mine are

0-30 1.6
0-40 2.2
0-50 4.0
0-60 5.0
0-70 6.1
0-80 8.5
0-90 10.6
0-100 13.2

Top speed 115
1/4 mile 13.7 @ 101.3.

It shows that it would be slightly quicker with a higher diff.

Car Settings
2000cc
HP 175@6800
Torque 145 @4000
Compression 10:1
RedLine 7100
Weight 1430lb
Coeff 0.7
Height 48in
Width 56 in
Ground Clear 4 in
Weight on Fr wheels 55%
Tyres 205/55 15
Diff 3.44:1

[Edited on 5/1/07 by TangoMan]

quote:

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Originally posted by alister667
these cars are about acceleration, nimbleness, handling.

Top speed is slightly more relevant than boot space.

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Can't get the CarTest program to work..

It says it's not a valid win32 application...

[Edited on 5/1/07 by akumabito]