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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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equations to calculate power and torque?
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Tue, 17 June 2003 12:58
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Heya Ppl,
was just musing over some numbers and thought i'd share.
thinking of a way of guesstimating what power and torque an engine _can_ produce (any engine) and how to tell when ppls numbers are over the top...
i was thinking that a good estimate the max torque of an engine is to take a figure 100Nm/L (since bikes get around that and are damn efficient, close to 100%volumetric efficiency) then multiply by your capacity, multiply by 1+ number of atmospheres above boost (ie 1atm boost is x2, 1.5bar boost is x2.5), or by the expected efficiency like 0.9 for 90%, and since power is calculated from torque, then plug ya rpm numbers into
Nm = (9402 x kw) / rpm
or
kw = (Nm x rpm) / 9402
so then
kw = (engine size x 100 x (1+ boost) x rpm) / 9402
where engine size is in litres, boost is in Bar or atm)
and Nm = engine size x 100 x (1+ boost)
or Nm = engine size x 100 x efficiency (in %)
you can then divide by your expected losses to get expected RWkw
note that this assumes 100% efficiency unless you factor in lower than 100%VE.
thoughts?
Cya, Stewart
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