Drivetrain losses
Discussion
Perfomance Bikes ran a series of tests many years back on a 750cc 4 cylinder 16 valve road bike engine.
In theory, with 100% efficient combustion it should have produced something like 360bhp but obviously there were losses due to heat, friction, pumping losses etc and IIRC the bike put down 90bhp at the rear wheel.
They then stripped the engine down bit by bit and measured how much horsepower was required to spin each individual part.
Most of the losses were due to heat with the pistons and valve train a close second, the gearbox cost just over 20% IIRC but it's been a while since I read the article.
When ever someone starts talking about fly wheel horse power I just quote my horsepower at the filler cap
In theory, with 100% efficient combustion it should have produced something like 360bhp but obviously there were losses due to heat, friction, pumping losses etc and IIRC the bike put down 90bhp at the rear wheel.
They then stripped the engine down bit by bit and measured how much horsepower was required to spin each individual part.
Most of the losses were due to heat with the pistons and valve train a close second, the gearbox cost just over 20% IIRC but it's been a while since I read the article.
When ever someone starts talking about fly wheel horse power I just quote my horsepower at the filler cap
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