Total Motorcycle Community Forums

iwannadie wrote:ok, if you took say an r1 threw some straights on it and had it jetted/dyno tuned and all that could you maintain the engines performance?

not that i would ever do it. just curious how it would work out.

Yeah, if you knew what you were doing, you probably could. Might even get better performance without the muffler restriction. Sounds like MotoGP does. But it has a lot to do with length, diameter, and shape and the interactions with the intake system.

BuzZz wrote:If straight pipes were the answer for sportbikes, Moto GP grids would be pretty dam loud (yeah, I know the niose regs and all, you get my piont).

Dragbikes prove that you can tune a sportbike engine to work with them.... at exactly one certain RPM and no others. Not the answer for rideablilty.

BuzZz, I though Moto GP bikes were two strokes - ? Have they changed? If not we're talking about two very different engines here. Two strokes like expansion chambers, try that on an R1!

iwannadie wrote:i posted this before(pre hack) and didnt ever get the answers, so how come you cant put straights on a crotch rocket?

The exhaust flow of a lower RPM engine is less important to the tuning of the bike than high RPM engines. At low RPMs, it's easier to just 'get it out of the way' with a wide pipe, instead of using a narrow pipe/muffler to build backpressure to maintain engine stability at ultra-high RPM.

That's also why you hear those nice Big Block muscle car engines with large exhaust pipes- Because they're designed to run at low(er) RPMs. I owned a 427ci (7,000cc!) engine that redlined around 4-5,000 RPMs. Some sport bikes go as high as 14,000 RPMs, don't they?

A Yamaha R6 redlines at 15,500. That's at the upper end for sportbikes though.

Moto-Gp is 4 strokes, Grand Prix bikes used to be 2 strokes untill a few years ago, the smaller classes still are. I thought the F.I.M. had decibel restrictions like the AMA, but guess not. Either way, you can bet them pipes is tuned for whatever RPM range they want the bike to be strongest in. Like the top-end.... top-class drag bikes use what amounts to drain pipes to direct the gases away from the bike and little else. The engine only runs right at full throttle, cause that's all they need. Road race bikes need some throttle modulation control, streetbikes need even more.

BuzZz wrote:Moto-Gp is 4 strokes, Grand Prix bikes used to be 2 strokes untill a few years ago, the smaller classes still are. I thought the F.I.M. had decibel restrictions like the AMA, but guess not. Either way, you can bet them pipes is tuned for whatever RPM range they want the bike to be strongest in. Like the top-end.... top-class drag bikes use what amounts to drain pipes to direct the gases away from the bike and little else. The engine only runs right at full throttle, cause that's all they need. Road race bikes need some throttle modulation control, streetbikes need even more.

Thanks BuzZz! You're giving me a bit of Moto-GP Edumacation before I get there for the big show.

Anytime, but Bruce is the resident expert-guy on that stuff. I watch it when I can, but don't follow it very closely. It's like watching popcorn.... I'd rather be doing it than watching it . But when either one is on, I can't help but watch.....

BuzZz, If you keep watching THEM movies, you'll go Blind.

*cough* that explains the hairy palms *cough*

My glasses ARE about 2 inches thick..........