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Old 12-02-2010, 07:56 PM   #69 (permalink)
some_other_dave
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Quote:
Originally Posted by todayican View Post
Seems like I read somewhere about people "sharpening" their crankshafts, persumably so they would "slice" through the oil as it came down into it?
"Knife-edged crank". Helps cut friction losses from oil (usually a mist, not a slug of liquid) that the swinging crankshaft hits. Also, to some extent, air. "Boat-tailed mains" also are for helping air flow inside the engine.

Some gains can be had from pulling a vacuum on the crankcase, because there is less air for the moving parts to push around. It allows more power to be made in large engines; my guess is that it would cost more power to drive the vacuum pump than could be saved in small-displacement low-RPM engines.

There are small gains (reduction in friction and other parasitic losses) to be had from paying lots of attention to everything that flows in the engine, from air that moves in the crankcase, to oil flowing through the oil passages, to coolant being pushed through the coolant passages. I have heard of noticeable gains in power (again, high-RPM moderate- to large-displacement engines) being made from careful match-porting of the oil pump inlet and outlets and the oil passages to and from the pump in the crankcase. And friction and other parasitic losses tend to be less in "worn-in" engines than in fresh "tight" ones.

Some gains may also be made with specialized coatings on some parts; I have heard that even something like coating the inside of the sump with Teflon (obviously not just dumped in there with the oil, but professionally coated/baked on) can produce more power by getting the oil out of the way of everything faster.

Pretty much all of the above is taken from the context of improving power in high-powered engines that are of large or at least moderate displacement, and run at high RPMs. That said, reductions in friction (and other losses) are still reductions. They may be too small to notice at the sorts of RPMs that economy-minded folks run at, but they would still probably be there.

I would think the break-even period for money saved on fuel versus money spent on the coatings and machine work and such would be longer than the engine would last, but that is a total guess.

-soD
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