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Transmission Losses %?


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#1 neal

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Posted 16 August 2017 - 12:52 PM

Assuming an A+ standard transmission is in good order, as well as the rest of the running gear including correct tyre pressures and no binding brakes etc, what would be the power loss as a percentage. I have been looking and the figure seems to be quite varied depending on the individual.



#2 ACDodd

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Posted 16 August 2017 - 01:24 PM

Power losses are not a percentage. They are dependent on a number of issues the iggest of which is the speed of rotation. This figure also increases at a higher rate the faster you go. Typically transmission losses are between 8-12hp for helical gearboxes with roadbtyres. 10 inch wheels tend to be 8-10hp, 12 to 13 wheels tens to be 10 to 12bhp.

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#3 neal

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Posted 16 August 2017 - 01:29 PM

Interesting....I have been trawling the net and the general figure was 20% loss, but as said the figure varied below and above but your info makes sense, cheers.



#4 mini13

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Posted 16 August 2017 - 02:50 PM

I think the 20% figurecomes from a lot of cars around 100hp being tested and giving 20hp losses.



#5 pdaykin

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Posted 16 August 2017 - 06:43 PM

IIRC years ago Miniworld used to quote transmission losses on their group tests at around 25-30%

#6 Moke Spider

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Posted 16 August 2017 - 06:50 PM

. They are dependent on a number of issues the iggest of which is the speed of rotation.

Ac

 

I think it also fair to add that load also comes in to it and the losses increase roughly in a logarithmic scale in proportion to speed.



#7 Moke Spider

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Posted 16 August 2017 - 06:51 PM

IIRC years ago Miniworld used to quote transmission losses on their group tests at around 25-30%

 

Yiks!!   I think there's a decimal point missing from that.



#8 jt19

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Posted 17 August 2017 - 09:23 AM

What about straight cut gearboxes? I assume they loose a bit less than helical?

#9 ACDodd

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Posted 17 August 2017 - 12:40 PM

Straight cuts would be 7-8bhp depending on what tyres are used. Slicks would see this rise.

Ac




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