Quote:
Originally Posted by stefanv
The difference is in the speed delta. To get the car moving, you're starting with an 800 or so RPM/difference (engine speed 800 RPM, driveline speed 0). To restart the engine at speed, the difference is around 2000 RPM (engine speed 0, driveline speed 2000). So that 1/10th of a second is probably about equivalent to 1/2 a second of getting a car moving.
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The RPM delta doesn't matter. You only need to transfer X newtons to get an engine cranking. During a bump start, the greater the speed differential, the shorter the required contact. Same energy transfer= same amount of wear.
You can try this (in someone else's car of course). Sit on a hill, hold the car on the clutch at idle. Increase RPM. The car doesn't move because regardless of RPM, you're only transferring the same number of newtons.
Slip time is what wears out your clutch, not RPM.
The reason people think it's RPM is because from a standing start engine and road speed will take longer to match if you release the clutch at higher revs.
Besides which, I can bump start my car from around walking speed in 3rd. That's about a 200rpm delta.