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A comment on Porsche 919 – Racecar Engineering. Parent comment

Re:Porsche 919 – Racecar Engineering by msandford on Sunday September 27, 2015 @01:56PM (#10287282)
You actually don't waste any energy accelerating pistons as the system is balanced. If it wasn't you shake the engine apart due to huge amounts of vibration. The crankshaft has counter weights so that it is balanced and the individual pistons all balance each other out.

It's like a see-saw, yes the mass isn't evenly distributed but it is balanced. And it takes only a small amount of force to make it oscillate relative to the force required to support it.

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Re:Porsche 919 – Racecar Engineering by vegabook on Sunday September 27, 2015 @02:26PM (#10287382)
I stand corrected, and I think I've figured it out. Even without burning fuel, in a frictionless system, the decelerating piston would be putting its energy back into the crankshaft? So it draws energy then puts it back every 180 degrees? Takes energy on the acceleration, puts it back on the deceleration?

I suppose the friction is the main loss source then?

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Re:Porsche 919 – Racecar Engineering by aunty_helen on Sunday September 27, 2015 @06:18PM (#10288136)
Conversion of linear motion to rotational motion is the loss you're looking for.

To your point about effectively gas turbine/electric drive trains from your OP, the problem is efficency in burning the fuel. This comes from the lack of achievable compression ratio in a turbine system. 6:1 is good for a jet, 13:1 is good for a N/A piston engine (not sure what race engines run exactly). Higher compression ratio = better fuel efficency.

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