20% Driveline Loss?

HellFire

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Joined
Aug 16, 2008
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I was poking around on the web and was a bit taken aback when I read that there could be as much as 20% Hp and Torque lost through the transmission and driveshaft. So I thought I'd put it out here and see if it was true. The Roadster is boasting 163 ft.lbs. and the 20% loss would put it at about 130 on a dyno at the rear wheel. Sound right?
I realize the transmission on the R3 is a beast and not all that efficient, but 20%?

And on the other side of the coin, those of us with the typical mods that put the bike just shy of 160 ft.lbs. on the dyno means it's real close to 200 at the crank. Really? My math has to be off somewhere. I'm rounding up just a little to make it easier and still I'm thinking it's got to be off somewhere, that just sounds too high. Are we really tooling around on bikes with nearly 200Hp and 200 Ft. Lbs. of torque? Cant' be right.
Someone show me where I screwed up the math here. I'm not THAT kind of Engineer.
 
I doubt it's 20%

From what I've read on cars, 2 wheel drive loses 10% and 4 wheel drive loses 20%.
Maybe 1-wheel drive loses only 5%
;-)

Not facts, just heresay.
One way to prove it is to put the motor directly on a dyno,
and then put the bike with the same motor on a chassis dyno
 
...

Even with chain drive you can calculate with 6% loss so 10-15% is more true for saft...
 
If we could bet Wayne "Power-Tripp" Tripp to chime in.... He has explained it to me in depth but I wouldn't want to attempt relaying the info. He also says there is significant difference in "real" hp/torque readings depending on the type of dyno used.
 
Guys that use a dyno to determine their HP/Torque is wasting their money. The correct use for a dyno is to insure your bike is running its best. IOWs, you should be looking for a nice linear curve, smooth fuel delivery, etc... You should never think the HP/Torque numbers from a dyno transfer to the road. It ain't gonna happen. Also, the numbers will even vary from dyno to dyno. My Thunderbird Dyno'd at around 90 or so to the rear wheel after a pipe and re-map. My Tiger dyno'd at just over 120 hp. I MIGHT halfway believe the Tiger number. I don't the TBird for a minute. It has good power, but I'd be shocked if I'm really getting over 90 to the rear wheel. Triumph only claim 85 to the CRANK. I find it hard to believe I'd pick up enough to get to 90 to the rear wheel.
 
I'm not attempting to stir the pot or debate what is often is perceived as a sore subject, but the same thing can be said for rear wheel power losses when one employs a car tire on this, and pretty much any other, motorcycle. The larger, often heavier, car tires will eat up h.p. and torque, too.
 
Stock is 'supposed' to be 140 at the crank
most show 118-123 at rear wheel
Around 15% seems about right.
So my 350rwhp is, at the crank
a bit more.
 
1234567890


Someone show me where I screwed up the math here. I'm not THAT kind of Engineer.[/QUOTE]
 
15% DT losses is about right for a stock engine IMO
But obviously I do not have 15% on mine as that would be 52hp loss
I believe 20hp is a better figure to go with, higher rpm would create more
heat/friction therefore incur slightly more loss.
 
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