CVT Horsepower Loss

Coldfinger · Dec 16, 2007

I'm wondering how much horsepower is lost in the clutches.

It is common knowledge that with motorcycles, a non-O-ring chain transmits more power to the rear wheel than an O-ring chain because there is less friction.

It is also a fact that shaft drive systems are much more inefficient than O-ring chains.

Now, considering the amount of friction and heat generated by our snowmobile clutches it makes me wonder how much power is lost in this convenient setup.

Anyone ever seen any official figures on this?

Jim

fantom · Dec 16, 2007

The guys with the a track dyno are doing very well to get 50% of the engine HP to the track. This is why clutching is so important.

fantom

MARCUSO · Dec 16, 2007

You will see some losses, but so far there is no better way to get variable power to the track better.
As for the o-ring chain... I would bet that you can turn both an o-ring and non o-ring chain around a couple of sprockets with a finger and a thumb. so what are we talking about? 1/20th of a horsepower??

mattymac · Dec 16, 2007

I read on here where a sled dynoed around 200 HP at the crank, on the track dyno it made around 85 or 87 hp? 50% loss is typical IMO.

bogey · Dec 16, 2007

Read an article several years ago I believe it was originally published by gates. They did not indicate losses in percentage but did point out in the article that belt speed was a significant contributor to transmission efficiency, higher the belt speed the less effient the transmission efficiency. So when you change to twin pipes or triple pipes and your engine speed increases because the pipes make peak power at a higher rpm you may potentially not gain anything to the ground. This also would be a good item to consider in that we walk a fine line when gearing our mountain sleds as it will always be a compromise between belt speed (transmission efficiency) and belt life.

shortstop20 · Dec 16, 2007

AAEN has some good info on this in his clutching book as well. If I remember correctly he says when choosing a gearing combo you should aim for a ratio that you put you as close to a 1:1 ratio as possible for most of your riding/riding style.

Norway · Dec 17, 2007

track vs clutches

You should separate between power loss in the clutches and the track, since the track is the bigg hp robber. The CVT system is actually quite efficient (tho I confess I dont remember the numbers).

Aaen explains it verry well in his book and on a sled there are reasons why you dont want thos hp that demands terribly high rpm's, you loos to much in the clutches.

The tuning is important since it decides at what rpm you load the engine. Miss by 500 rpm with the clutching and you may start 10 to 40 hp below max power, and then take away the losses..

I might be mistaken but I seem to remember that FAST said something like 85% efficiency. Anyone else?

Rune

drmiller100 · Dec 17, 2007

how hot do your clutches get????

if they melt, you are losing 10 horsepower in your cluthes.

if they get too hot to touch, 1 to 4 horsepower lost.

much more inefficiencies in running the wrong rpm's. miss by 200rpm and you lost 25 horsepower pretty easy.

and a big 2.5 track eats half or more of what it gets, plus it takes a LOT of horsepower to spin it a little bit faster.

CVT Horsepower Loss

Coldfinger

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fantom

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MARCUSO

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mattymac

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bogey

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shortstop20

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Norway

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drmiller100

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