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Hobot · Dec 27, 2014

My drag loss quesitmates from scope of dyno reports implies about 5-6 hp but certainly less than 10. Its not good to think of our drive drag as percentage of power, which it is per each engine, but as its the same drag at same rpm no matter the engine its more accurate realistic to just subtract a set hp/watt amount rather than fudge a sliding percent scale. Mystery remains on what that set amount realistically is.

comnoz · Dec 27, 2014

hobot said:
My drag loss quesitmates from scope of dyno reports implies about 5-6 hp but certainly less than 10. Its not good to think of our drive drag as percentage of power, which it is per each engine, but as its the same drag at same rpm no matter the engine its more accurate realistic to just subtract a set hp/watt amount rather than fudge a sliding percent scale. Mystery remains on what that set amount realistically is.

The testing I have done in the past has shown a speed dependent curve that averages somewhere around 5%.
A little less with belt drives and a little more with chain drives.
Tire deflection has a larger effect. Just setting on my bike during a dyno run takes an extra 2 horse. Jim

Hobot · Dec 27, 2014

Er-a, still confusing me with non dimensional unit percentage numbers, so 5% drag from a 40 hp or 80 hp engine?

comnoz · Dec 27, 2014

hobot said:
Er-a, still confusing me with non dimensional unit percentage numbers, so 5% drag from a 40 hp or 80 hp engine?

I really don't know if Superflow uses a percentage or a set figure/rpm for drivetrain loss. You create a curve that is used in the calculations but all you see is the result -not the math.

As I recall the 5% figure I quoted was the difference in the result when I had a 62 peak horsepower engine. So that would be just over 3 horse at 7000 rpm. Jim

Hobot · Dec 27, 2014

Cool finally narrowing down this nebulous drive train drag that agree with my napkin figures. 62 hp is well above average so 4 hp is realistic value we can mentally add to rwhp for crank shaft out put, more or less. Glad to learn the belt are a tad more efficient than chain beside lighter. Oh yeah is there a rpm limiter on your scoot? Cosmic rays at your elevation may give glitches out the blue.

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