Lets talk pipes and mufflers

[stknrdr]

Question:

Why is it that we are still using loud glasspack mufflers when the automotive industry discarded them decades ago because they really dont flow all that well anyway? Surely, there has got to be a better way!

I love my 450 but im almost embarrassed to ride it anywhere near people because it is so offensively loud, my neighbors must hate my guts but are too nice to say anything. We have a little neighborhood track here that a bunch of us ride, but mine is the only bike that is really painful to listen to. Im worried about it but I still havent found a solution. Any ideas?

FWIW im running the stock exhaust with a PMB quiet insert that kills power and isnt that quiet, I had high hopes for it but the 450 is just too much for it.

[450_rider]

Yeah that would be pretty cool to have an exhaust like a flowmaster, with baffels and no glass pack.

[stknrdr]

Yeah i know, can you think of any performance car that runs glasspacks anymore? I can't. I know they are dirt simple and light and all, but surely...

I think it has to be possible to get the DB down and still have decent flow. Id buy a quiet muffler for this bike in a hearbeat, if one existed...if the the FMF Q is still too noisy. No, i dont want to give up 5 horsepower but we NEED something.

[grayracer513]

The ultimate is electronic acoustic mufflers.

[stknrdr]

The ultimate is electronic acoustic mufflers.

Just the guy I wanted to hear from... have you ever seen anybody try a baffle type muffler? Im thinking of building one just to see how it sounds...but the research is pretty intense trying to figure out baffle placement, flow rates...and so forth.

Wonder if Bose will build me an active noise cancelling one hehe. Maybe I should just go out and buy all my neighbors of Bose QC2's hehe.

[e30M3]

I read somewhere a baffle type muffler would have to be so large to be efficient (both noise and performance) that you wouldn't want it on the bike.

I will say I do like my FMF Q2 (they say it has internal baffles). I didn't notice any drastic difference when I switched from my stock pipe but I think FMF says it is suppose to provide more power than the stock unit. I know it isn't as powerfull as other aftermarket systems but since I am not a pro and can't handle all the power the bike has anyway, well I decided to go the quite route.

[JSanfilippo]

The WB E2 and the FMF Q2 are the quietest pipes I've heard on Yamahas...try to go that route

[grayracer513]

... have you ever seen anybody try a baffle type muffler? Im thinking of building one just to see how it sounds...but the research is pretty intense trying to figure out baffle placement, flow rates...and so forth.

Not a really well thought out one, no. Taking Flow Master's, or Chevrolet's Camaro or Corvette exhausts as an example (sidebar: a customer brought me a near new 1998 Z28 once, He was pissed off because he just paid out the big bucks for a Flow Master and lost 3 HP compared with stock. Chevrolet does their homework on their high perf stuff), neither is very large relative to the engine size they run on, yet they flow and dampen sound very well. This is done by constructing internal chambers that reduce resonance and produce their own noise canceling pressure pulses. To do so on your own would require a lot of experimentation, unless you could do some computer modeling. The results could well be worth the effort in the end, though.

Acoustic noise cancellation works on the fact that sound is a modulated pressure wave. The trick, in concept, is to create a mirror image of that wave, with negative pressure peaks to match the wave's positive peaks, and vice-versa. The net effect when the two meet is that the mirror wave pressure balances the sound wave, resulting in no wave, and so, no sound.

[e30M3]

I could be completely off base since since the little I know is from an article or two I have read over the years. I don't think the muffler gets to shrink proportionately with engine size. Sure the inside diameter of the pipe will get larger, but not too large or else you lose some back pressure and bottom end power. I think to get the sound waves to cancel themselves out effectively you need a certain size chamber.

I think an an airplanes wings. A bigger wing provides more lift but doubling the size does not produce twice the lift. Same thing in reverse, if you halve a wing you get less than half the lift.

I believe that is why FMF uses chambers plus packing material. I think we have a better chance of seeing electronic devices down the road than a full baffle type muffler.

[grayracer513]

You're correct in that the relationship of the required muffler size to the size of the engine is not proportionally linear. There is a relationship based on the volume of gas passed through the muffler, but there is also a minimum size imposed by the behavior of air. Nevertheless, many Flowmasters are relatively small, and in some cases, almost small enough to be practical on a bike. I feel pretty certain that something effective could be built that was around half that size, but maybe not. Remember that the volume of the internal chambers is important, but not the shape, so the dimensions can be pushed and pulled to make the whole thing more workable.

Electronics probably will supplant baffled mufflers, but I think that's a ways off at this point.

[stknrdr]

Well, I dont know much at this point but im reading and looking at everything I can get my hands on....I'm a pilot by trade so I have definately spent a lot of time studying airflow - however not much of my knowledge translates...but I can learn. Just a few DB reduction would be a good start.

I know that when I use my PMB insert Im a lot more comfortable with the noise - I just need to get rid of a little bit more. I dont really miss the power at all...Im a realist and realize that while im reasonably fast for an old guy, there is plenty O' power for me...I just about wheelied over today trying to compensate for the power loss my grabbing more throttle through a little rutted up triple whoop section that I normally wheelie through - theres still plenty of torque there ?

[stknrdr]

ye gods is there an engineer in the house?

http://rclsgi.eng.ohio-state.edu/~selamet/docs/1999_JASA_105(3)_1548-1562_three_pass_muffler.pdf

[grayracer513]

Well, that certainly delves into it, doesn't it?

But Flowmasters are not three pass mufflers. In the illustrations on the page, the near end appears to be the inlet.

[stknrdr]

Well, that certainly delves into it, doesn't it?

But Flowmasters are not three pass mufflers. In the illustrations on the page, the near end appears to be the inlet.

Yeah, ive been looking at everything trying to figure out what frequencies need to be cancelled, and so forth, i found a few more at NACA but they are tough stuff hehe. Just kind of trying to gain knowledge....

[stknrdr]

ya know...the case on the hushpower II is only about 18" long...with 2" pipes......hrmmmm.

http://www.flowmastermufflers.com/hp2.html

ours measure 17" or so... wonder what one would sound like hehe.

[SurvivorMan]

the PMB endcap with silent insert and spark arrestor annoyed me! the Q2 also annoyed me. my 06 450 is so responsive down low with lots of torque. This makes riding the bike easy, especially in technical woods sections. Any type of flow restrictions (pmb sa screen and Q2) create a momentary drag in throttle response...this drives me nuts. The low end torque/response is the reason I switched from a smoker to this heavy thumper. My 450 makes a lot of racket at the top but is producing next to nothing....just sounds powerful. my bike is all bottom and mid, just the way I like it.

06 yz 450 stock exhaust and air filter

[grayracer513]

Remember that the cute little Mustang in the picture has a catalytic converter which will presumably still be in place when the Hushpowers are installed, and which does a fair amount of muffling on its own. The difference in the sound output of the converter equipped, but otherwise mufflerless V8 and your bike with only an open mid pipe is, um, considerable, and that's what the muffler would have to work with. Besides, you were trying to step away from the glasspack design, weren't you?

[JSanfilippo]

Any type of flow restrictions (pmb sa screen and Q2) create a momentary drag in throttle response...this drives me nuts.

Jetting...you have to jet for baffles/inserts/quiet pipes.

[Baron Von Beard]

My brain hurts!

[stknrdr]

Remember that the cute little Mustang in the picture has a catalytic converter which will presumably still be in place when the Hushpowers are installed, and which does a fair amount of muffling on its own. The difference in the sound output of the converter equipped, but otherwise mufflerless V8 and your bike with only an open mid pipe is, um, considerable, and that's what the muffler would have to work with. Besides, you were trying to step away from the glasspack design, weren't you?

Well, it looks to me like that muffler is a combination of glasspack and chambers...hell, I dont know. The more I look into it the harder it looks, but ill keep looking ?