piston resistance

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Jan 8, 2013 | 04:06 PM

3rdCoastPowerSports

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From: Loony Bin

piston resistance

throughout the stroke of the piston travel is the resistances (dont know if that is the right word or not) even? Or is there more resistance at the bottom of the stroke? kinda a theory question i guess

Jan 8, 2013 | 05:02 PM

RezinTexas

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From: Katy, TX

I have not studied this in detail, however I would think that piston-wall friction is greatest when the side loads from the connecting rod are the highest - the middle of the stroke.

Jan 8, 2013 | 10:59 PM

JPH

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From: Fort Wayne, IN

Quote:

Originally Posted by 3rdCoastPowerSports

How much Ft lbs of torque does it take for you to spin over your short block assembly with NO valvetrain hooked up?

Jan 9, 2013 | 03:44 AM

vettenuts

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From: Little Rhody

Here is an SAE paper on the subject. Rod length, oil, etc. will all play a role in the final frictional resistance.

Link

Jan 9, 2013 | 04:22 AM

chrisfrost

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From: phx the cactus patch

The most resistance to the spinning of the crank is going to be every piston from 1/8 atdc to 3/8(rod journal location)(intake stroke) and 5/8 to 7/8 rot (compression stroke) and again during the exhaust stroke from 5/8 to 7/8 ,,,,,so in a typical ice that is a 4 cycle design 3 of 4 strokes are resisting the spinning of the crank and that is the main reason We only get around 20-30% efficiency that and heat loss ,,,,,,etc