Ok homies... This is just from another thread where we tried to establish how much power would be needed to get a Saxo to certain speeds...
I'm kind of hoping the thread will throw up a discussion where we can make the equation a bit more accurate and include more factors...so feel free to add inputs, criticisms etc
NOTE: These are fly hp figures. The wheels used are VTS standard 195/45/R15 and assuming that the tyres are capable of doing these speeds.
The Equation
Power required = 1.0505x10**(-3) x Cd x A x V**3
Cd = drag coefficient (no units)
A = front area of vehicle in m**2 (metres squared)
V = Velocity in m/s (metres per second)
1.0502x10**(-3) is a correction factor. Thats 1.0505(to the power '-3')
NOTE: It doesnt fully take into account rolling resistance although I've tried to factor it in.
This can be reversed so you can work out the top speed of a Saxo if you know the hp... obviously it wont be totally accurate as you could get peak hp at low rpm i.e well before you get near your top speed, but its a good indication of what is possible if you had the correct gearing.
Standard VTS
Power Output: 120hp @ 6600rpm
Top Speed: 127mph @ 6485rpm
Miles Per Hour to Metres Per Second
127mph to m/s is calculated by:
127*0.4444
which equals:
56.44m/s
Saxo Coefficient of Drag
the Cd (Drag Coefficient) of a saxo is:
0.34
Saxo Frontal Area
and the frontal area is:
1.82m**2
Therefore Power is calculated by:
Power = 1.0502x10**(-3)*0.34*1.82*(56.44**3)
Power:
116.9hp - which is about right as top speed does not occur at peak power for the VTS, although the calculated value is probably a bit low as the power curve tends to plateau as peak power it met. However it'll do for the sake of this text.
so thats cool.
HP requirement to reach 164mph
Using readily available parts the VTS engine in standard tune is capable of
164mph @ 7250rpm running a VTR box
Power required = 1.0505x10**(-3) x Cd x A x V**3
We want
164mph
which is
72.88m/s
so the power equals 1.0502x10**(-3)*0.34*1.82*(72.88**3)
which gives around
252hp required.
HP requirement to reach 176mph
Using the same parts as above but with the limiter raised to 7800rpm a theoretical top speed of 176mph can be achieved.
We want
176mph
which is
78.22m/s
so the power equals 1.0502x10**(-3)*0.34*1.82*(78.22**3)
which gives around
311hp required.
HP requirement to reach 200mph
Ok, there isnt a box in the saxo range that'll provide the correct ratio's to achieve this speed but just for a laugh lets see...
Power required = 1.0505x10**(-3) x Cd x A x V**3
We want
200mph
which is
88.88m/s
so the power equals 1.0502x10**(-3)*0.34*1.82*(88.88**3)
which gives around
456hp required.
HP requirement to reach 300mph
Right, now I'm taking the biscuit here but lets say you wanted a saxo(standard shell) top fuel car for trips to McRags.
Power required = 1.0505x10**(-3) x Cd x A x V**3
We want
300mph
which is
133.332m/s
so the power equals 1.0502x10**(-3)*0.34*1.82*(133.332**3)
which gives around
1540hp required.
As you can see there is a considerable rise in the required horsepower to achieve even relatively small leaps in top speed.
Hope you find this helpful/interesting
Any questions or abuse then post away
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