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Old 10-10-2013, 12:08 AM   #17 (permalink)
RedDevil
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Quote:
Originally Posted by HypermilerAX View Post
If he's at 10% higher load with 12% less revs, it means that the conditions were not the same.
Power = torque*rpm so if you lower rpm by 12% you will necessarily increase torque by 12% to have the same power. With a higher gearing, you only gain with the second thing you mentioned: efficiency.
Ah, no. One effect of lowering the revs is reducing the power needed to spin the engine. If the load goes up by just as much as the revs go down there is no gain.
It is obvious that you need less power to rotate the engine at a lower rpm. There should be a lesser load increase.
The better efficiency at higher loads makes up the rest.

Btw. the discrepancy between rev reduction and load increase is not 2% (as it might seem to be) as one cannot subtract addition and subtraction percentages from each other (I am at fault here for bringing them up).
Instead, multiply total values so 88% times 110% makes 96.8%.
Reducing the rpm means you need 3.2% less power to maintain the same speed.
Again, better FE at higher load means the total gain is bigger than that.
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Last edited by RedDevil; 10-10-2013 at 12:21 AM..
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