RCU Forums - View Single Post - Direction of Piston Engine Rotation - Which Direction is More Efficient?
Old 01-03-2012, 07:32 PM
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cutaway
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Default RE: Direction of Piston Engine Rotation - Which Direction is More Efficient?

Rotational direction efficiency is dependent on many other factors. Induction port design/orientation, front/rear/sleeve induction, etc.

With a front induction engine, the connecting rod can kind of mask the hole in the crankshaft with some timings. On some racing engines you'll see the counterweight scalloped out to mitigate this masking. I believe Nelson, Jett, and many of the eastern european engines do this to some of their engines.

With a sleeve induction engine (like some of the older ignition and diesel engines, ex. the GHQ), rotation wouldn't matter at all since the flailing crank and rod aren't in the incoming fuel charge's path. These type engines are can be happy running in either direction.

On some engines, like the Cox reed valve .049's where the cylinder port alignment is variable and dependent on minor machining variances, rotation direction might help in one example, and hurt in another.

I don't think the rotational direction impacts are much more than a few hundred RPM one way or another even in the extreme case of racing engines turning 30K. For sport type engines, its going to be almost negligible. Proper breakin and blueprinting would be worth more.