Can you mathematically estimate top speed?

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I am curious if a vehicle's top speed can be estimated mathematically.

For example, if a given vehicle is doing 64 mph in top gear at 2000 rpm, and 95 mph at 3000 rpm, is there a way to estimate what it's speed would be at 6500 rpm?

This would be assuming the vehicle had enough power to overcome drag and achieve 6500 rpm I know. I don't really understand gears well enough to know if this can be done with two points of reference, or if it could work that way at all.

Thanks!
 
Sure, it's just a ratio.

So 64/2000 = 0.032 mph/rpm. Multiply that 0.032 by whatever rpm to get speed.

So 0.032 x 6500 = 208 mph top speed (rpm limited).

Your actual top speed is probably electronically limited or drag limited.
 
Since this is just an approximation for fun lets assume that 64 mph at 2000 rpm is accurate. To find speeds or rpm for a different RPM or speed is a simple (cross multiply and divide calculation) So if we wanted to calculate the speed for 3000 rpm it would look like this.
64/2000 x/3000 64 X 3000/2000 = 96 mph To calculate the speed at 6500 rpm it would look like this:
64/2000 x/6500 64 X 6500/2000 = 208 mph
 
Originally Posted by KCJeep
For example, if a given vehicle is doing 64 mph in top gear at 2000 rpm, and 95 mph at 3000 rpm, is there a way to estimate what it's speed would be at 6500 rpm?
As others mentioned, this is a simple ratio.

There are also various calculators on the web as well as for your smartphone that let you estimate speed at various RPM based on vehicle's transmission gear ratios and tire size, for example, GearBuddy or Gear Speed Calculator.
 
This also assumes no slippage in an automatic transmission ( torque converter lock up ) or tires . Or the clutch with a manual transmission .

But pretty close .

As has been stated , it also depends on if the engine has enough torque , at that RPM , to overcome mechanical losses / friction and aerodynamic drag .

Also , the person in the vehicle with the red flashing lights ! :)

Such experiments can get expensive ! :-(
 
Yes, you can calculate top sped, or any speed.
Remember using the result assumes the car has enough torque/horsepower to achieve that speed.

For example, my old 1990 Corvette reached top speed in 5th gear because 6th was so overdriven.
The engine did now produce enough power to use 6th.
 
Originally Posted by andyd
Wind resistance (drag) isn't a constant and is a limiting factor. Not sure of the formula, but it is a factor
Sounds like the OP just wants to know what the theoretical speed would be at a given RPM level, not taking HP and drag into account.
 
sure, it's basic math. if i put my foot all the way down and keep it there i can get to a little over 100. 100=100, so my top speed is 100. see, that wasn't so hard!
 
My Jaguar will go 124 in 4th gear and 120 in 5th. It's drag limited in 5th, but 4th gets the engine up to the rev limiter.
 
You can do the math to come up with a top speed number but in reality don't presume the car can physically do it.
 
Thanks for all the input, the on line sources will be fun to play with. Clearly it is not a simple math problem there are way more variables than I even imagined.
 
Just because an engine can get up to redline at lower speeds and lower gears doesn't mean it will do redline in high gears and high speeds.

Figure your typical mid-sized car (ie: VW Jetta, for instance) takes about 35hp to go 65mph on flat land. We know that drag is related to velocity^3, so to go 130mph would take 8X as much power, or in excess of 200hp.
 
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