Quote:
Originally Posted by W_S
most (non-turbicharged) petrol engines generate maximum torque around 4000 rpm. So shouldn't they have best BSFC around 4000 rpm? If so, shouldn't the driver use revs around 4000 while accelerating to get the best economy?
I suppose a reason for the suggestion to shift at 2500 rpm is that maximum torque is achieved at (let's say) 4000 rpm at full load only, while at 75% load the peak may be at lower rpms. Is this correct?
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My guess (correct me please!) is that at 4000rpm there is a lot more internal friction to overcome than at 2500, so as engine speed crawls up towards max torque efficiency increases but so does friction (at a faster rate). At some point one starts to overcome the other and that's when you should shift.
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