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If you were aiming for 300mph then what would need to change and would it be possible. There is less heat so less drag which must be a huge advantage.

What kWh battery pack would be needed?

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  • $\begingroup$ I'm very confused by this question, what do you mean "there's less heat so less drag?" kWh isn't a measure of battery strength, it's a measure of battery capacity. We can't even answer the question in terms of a kWh battery pack. $\endgroup$
    – JMac
    Mar 7 '17 at 21:32
  • $\begingroup$ With increased battery pack size comes better performance and also drag is increased by the heat going out the back. @JMac $\endgroup$
    – SRawes
    Mar 7 '17 at 21:53
  • $\begingroup$ How does heat going out the back increase drag? A bigger pack size does not mean better performance. kWh is strictly a measure of capacity. Changing the kWh doesn't require anything else to change, so you can't measure battery performance by the kWh. $\endgroup$
    – JMac
    Mar 7 '17 at 22:03
  • $\begingroup$ @JMac increased pack size increases total current available I think. An example of this is p100d being faster. I am not sure about drag but watched a YouTube video on why no car has been over 300mph and it was a huge reason for drag it said. $\endgroup$
    – SRawes
    Mar 7 '17 at 22:06
  • $\begingroup$ Increasing pack size doesn't necessarily increase the available current. To increase the current you would have to change other things in the car and the battery itself potentially to accept these new currents. Once again though, the kWh doesn't measure current, current measures current. As far as drag goes, I think you misunderstood something. Drag is a big limiting factor on car speed, and drag produces heat. Drag increases with $v^2$ so more speed requires way more power to overcome, which means your car weighs more... which means you need more power, on and on. $\endgroup$
    – JMac
    Mar 7 '17 at 22:11
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Maximum speed in a straight line is largely determined by the vehicles maximum power output compared to its drag although once you get past about 200 mph dynamic stability can start to become a serious issue as well.

The current Land speed Record is held by Thrust SSC which was powered by two jet engines, reached supersonic speeds and has as much in common with a plane as a conventional car.

A crucial point is that aerodynamic drag is proportional to the square of speed so all else being equal to double the maximum speed you need to quadruple the thrust/torque available and 8x the power.

In any car, even a high performance one there is a trade off between maximum speed and handling and even very high end performance car manufacturers have pretty much given up chasing headline top speed as if becomes a bit meaningless once you get cars which can top 200mph and acceleration, braking and handling become more meaningful measures of performance. Even current F1 cars don't get anywhere near 300 mph simply because adding aerodynamic down-force increased overall average speeds around a track at the expense of increased drag.

I suppose it is possible that you could use the electric drive train from a Tesla to attempt to get to 300mph but it would for all practical purposed be a completely different vehicle as you would need totally different chassis, body shape and gear ratios.

As a point of reference the current Land Speed Record for an electric car is 341 mph. As you can see from the article this is a very different vehicle from a Tesla.

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  • $\begingroup$ actually, drag force goes with v^2, but power is force times velocity, so power required goes as v^3. $\endgroup$
    – agentp
    Mar 7 '17 at 18:57
  • $\begingroup$ Quite right, talking about jet engines got me thinking in terms of thrust, edited to correct. $\endgroup$ Mar 7 '17 at 22:41

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