Muffler location/placement - pros/cons

[tltb26]

I have been doing much motorcycle research since I am considering the purchase of a larger motorcycle in the near future (more than likely something in the 600cc category).

My question is: are there advantages/disadvantages to muffler location? I've seen various motorcycles with either mufflers on the side of the swingarm, under the belly or under the seat. Initially, I thought that the larger CC'd (1000+) motorcycles always had them under the seat, but the 2009 Suzuki GSX-R1000 has it on the side (2010 Kawasaki Z1000 has it on both sides). The Yamaha FZ6R has it under the belly & the 2010 YZF-R1 has it under the seat.

So far, without finding consistent details, I have read that muffler placement may have to do with power, type of exhaust system (amount of tailpipe or location of catalytic converter) & the center of gravity.

Based strictly on looks, I like the mufflers under the seat or under the belly. But wouldn't a muffler under the seat create large amounts of heat for the rider's behind?

Thanks in advance.

[CRXTrek]

I have no heat issues from my undertail exhaust .
I haven't bumped into it and burnt myself like i have when i had a bike with a sidemount

[Samer]

I'm not really an expert on this, but as a casual observer, I've noticed that fewer and fewer production bikes have a muffler under the seat, which is my preference, mainly due to styling. On the technical side it may help balance the weight a bit more and maybe help with leaning clearance, but that probably isn't much.

If you look at the history of the Japanese supersports, only the honda 600 still has the under tail exhaust, from what I have seen. In the past, the Kawi 600 and 636 had an undertail exhaust, but no longer.

Ducati and Triumph Daytona 675 have them. My next bike will most likely be the Daytona, partly due to looks, performance, and the sound of the engine.

[CZroe]

Buell's "Trilogy of Tech" involved something they called "Mass Centralization." NO side-mounted exhausts on their bikes! They also discouraged undertail exhausts for heating up the passenger seat. They called their under-slung exhaust "the only 'right' place for an exhaust."

[ithaca00]

Side pipes are classic and were prone to dragging but the newer bikes have reshaped pipes (triangular instead of cylindrical) and are less prone to this.

The undertail exhausts came about for ground clearance. The side effects of this is a warm butt and a higher center of gravity.

Under bike exhausts were brought about by Buell for the performance advantage gained by the lower center of gravity.

[Apex]

The underseat fad went away due to, like Ryan said, a higher center of gravity. The higher the center of gravity, the more you "feel" the weight when it a turn and flicking it back and fourth. It will actually slow your transitions some.

I always wanted GP style exhaust on my ninjette to reduce the weight and lower my CG. I'm not worried about it because I am close to getting a new bike in the stable to replace my 250.

[Hadyn]

I love the under-seat exhaust, it gives bikes that 'rocket ship' kinda look. Unfortunately, as others have said, there are some drawbacks that make it kinda impractical.

[ScraitT]

I personally like the underbike exhaust like the Buells had and the Ninja 650 has. It's just out of the way period, you'd really have to try hard to burn yourself....or any admiring kids or passengers, etc...
The thing I hate most about side exhaust is when you have a passenger and they melt their shoe on your exhaust. (A lot of aftermarket exhausts are much cooler though)

[c-dog]

I had an FZ6 with the undertail exhaust. The stock exhaust made the seat get very warm for me. But when I switched the stock exhaust for an aftermarket Scorpion exhaust it didn't heat up anymore. I think the aftermarket was less restrictive so it didn't heat up as much.

I like all the types of exhausts. They all look cool in their own way to me.

[CZroe]

Originally Posted by c-dog

I had an FZ6 with the undertail exhaust. The stock exhaust made the seat get very warm for me. But when I switched the stock exhaust for an aftermarket Scorpion exhaust it didn't heat up anymore. I think the aftermarket was less restrictive so it didn't heat up as much.

No, it's missing the cat inside the exhaust to burn unburnt fuel. That's why.

[c-dog]

Originally Posted by CZroe

No, it's missing the cat inside the exhaust to burn unburnt fuel. That's why.

That makes a lot of sense. Never thought about it.

[backinthesaddleagain]

Ducati is still big into under tail exhaust except on the classics they have it from monster up to desmosedici. I think one cool thing (pardon the pun) is no shiny pipe on the side for a child to get near and touch.

[Apex]

Originally Posted by CZroe

No, it's missing the cat inside the exhaust to burn unburnt fuel. That's why.

Therefore it is less restrictive.

[CZroe]

Originally Posted by backinthesaddleagain

Ducati is still big into under tail exhaust except on the classics they have it from monster up to desmosedici. I think one cool thing (pardon the pun) is no shiny pipe on the side for a child to get near and touch.

Happened the very first time I showed my bike to my friend in 2008... his 2 year old ran out and threw his hands on the shiny and hot exhaust.

[Apex]

Ouch!! Poor little kid. I've been wondering why they don't offer optional heat shields to go near the passenger footpegs.

On a side note, the exhaust may be routed under the seat, but there is still the disc brakes that you'd have to worry about. Those things get pretty hot too.

[gogoKawi]

Sound is another issue. I can not hear the exhaust on my ZX6 while on the bike. But, walk around to the rear, and it sings a beautiful note. I have no problems hearing the exhaust note with the side-mounted ones. Maybe it's just me...

Like everyone said, the seat does get warm after a while. It's not terribly hot. But, you do notice an increase in temperature.

And the high center of gravity does affect riding. When I took off the stock exhaust, dynamics of the bike changed, totally. I had to adjust the way I turn and lean on the bike. Not to mention, pinging the throttle in 3rd makes it feel like the front-end is coming up.

[tltb26]

Thanks everyone for your insight & opinions. Yes, I have a childhood leg scar to prove the disadvantages of a side mounted muffler. I have warned all the kids around my house to stay away from mine.

I don't mind a bit of growling from mufflers (I love the sound of V8's) but since I do more commuting over joyriding and no track racing, I decided I don't want an aftermarket (non-EPA) or obnoxious sounding muffler. (I grew up though dreaming of my first Harley).

I like the idea of a lower center of gravity; especially when I think of riding against crosswinds & being pushed ever so slightly from side to side. But that rocketship look is way cool. It is way hot & humid where I'm from so my behind definitely doesn't need the extra warming.

The impression I'm getting is overall there may be handling differences but not necessarily power differences; and looks are always preference anyway.

I am now eyeing the Kawasaki Ninja 650R. (I just wish the ebony didn't have that greyish lower fairing).

[mcteague]

Originally Posted by c-dog

I had an FZ6 with the undertail exhaust. The stock exhaust made the seat get very warm for me. But when I switched the stock exhaust for an aftermarket Scorpion exhaust it didn't heat up anymore. I think the aftermarket was less restrictive so it didn't heat up as much.

I like all the types of exhausts. They all look cool in their own way to me.

I love the underseat exhaust on my FZ6. I certainly feel the heat from the engine but never from the underseat pipes. Many mfgrs have moved away from this design for the reasons mentioned. Unfortunately, the look of lots of these,out in the open systems, is appalling.

Tim

[Apex]

Originally Posted by tltb26

I am now eyeing the Kawasaki Ninja 650R. (I just wish the ebony didn't have that greyish lower fairing).

Then just get it painted. It shouldn't cost much to do, and if it "seals the deal" then I'd go for it.

[Rayme]

I don't think having the exhaust either on the side or underseat will have that much more effect on the street. Actually having more weight up high will increase stability in windy situation, not the other way. Stability and flickability are two oposite things.
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[revstriker]

I remember reading about the new 2009 zx6r. They were addressing how they were able to get more HP, and one of the things they mentioned was that they accomplished this in part by moving the exhaust from under the seat to the side. Better airflow perhaps (less bends in the pipe)?

[Apex]

Less pipe bends equal less turbulence. Less turbulence means higher velocity of air flow which means more power.

[sofo]

Higher is better for styling, getting the pipe off the side for cornering clearance and in some cases neccessity (old 2-stroke GP bikes with 4 pipes / mufflers), but at a cost of high center of gravity. Low-side mount is better for shorter pipe length and lower COG at the expense of cornering clearance. Today the trends seem to be mounting the bulk of the exhaust under the bike with a small silencer mounted on the side like the BMW S1000RR and Yamaha YZ-R6, or putting everything under the bike like the Kawasaki ER-6n / Ninja 650 and KTM RC8.

I think the latter of the two new trends is the most logical and may become the new "standard" for some time, especially as new tech. makes the overall exhaust size smaller and lighter. Plus aesthetically it really looks nice to me and gives the bike a much cleaner look.

[backinthesaddleagain]

Like the undertail exhaust on my 600RR looks like fighter jet afterburner. IMHO some aftermarket undertails stick out too far, while the stock is nice and flush with the cowl.

[TrueFader]

it's give and take, undertail gives you good lean angle clearance but manufacturers have gone against it because of passenger heat problems, small trunk space, and higher center of gravity. under engine gives you lowest center of gravity but may reduce ground clearance, and doesn't leave room for catalytic converters (california). if you've seen a buell they rep that, or like a 06/07 gsxr is close too. most common is the side mount, not really any ground clearance issues at lean or upright if the piping is designed to go with the flow of the stock pipe., and a mix of the center of gravity issue. not too high not too low.

[shavelieva]

In consideration to placement of exhaust pipes and mufflers..

Why in the world does exhaust come out the front and not out the back of the engine? Wouldn't the exhaust benefit better from being in the back and intake in the front? I could imagine even simple ram air for the air intake and for cooling of the exhaust.

Or is there something inherently obvious I'm missing out on that everyone else knows?..

[karlosdajackal]

I like the under the body styles and under the tail style, but i can tell you that if you find a buell with an underbody exhaust its usually rusted to hell, basically its right in the firing line of any stones that come of the front tire and it gets all the water that comes of the front wheel too. I know some KTM's had similar issues. Having said that, i'd happily have an RC8 even with our climate.

Ducati stick with undertails because they stick with L-twins to keep the bike narrow, so it makes sense to keep the exhuast in a line also and trade some of the potential power loss of a twin for a more aerodynamically efficient shape, also it helps them to look great

hmmm RC8 or Duke 848, glad I can't have either at the moment because I don't know which i'd choose

[Apex]

Originally Posted by shavelieva

In consideration to placement of exhaust pipes and mufflers..

Why in the world does exhaust come out the front and not out the back of the engine? Wouldn't the exhaust benefit better from being in the back and intake in the front? I could imagine even simple ram air for the air intake and for cooling of the exhaust.

Or is there something inherently obvious I'm missing out on that everyone else knows?..

If it came off the back of the bike, then it would interfere with the suspension system, electronics, rear brake system, etc. Coming off the front (for traditional I4's) is clean and easy. The heat is dissipated by the wind, thus keeping the entire system cooler. Not to mention that the pipes can actually help protect the crankcase in the event of a mishap.

Lets not forget that every engine needs some kind of back pressure. Back pressure helps the engine develop power. A total reduction in back pressure means low power. I do recall hearing that there also has to be heat around the valves, or else they can warp? I can't remember if that is true, but it makes sense. So you always need some kind of length of pipe. Route it right under the gas tank and seat, towards the back, though maybe efficient, would not be wise. That would be an insanely hot zone due to lack of airflow. Hot pipes right next to gas tank isn't good either. Best way is to separate the gas and electronics from the heat, so routing the exhaust from the front, down below the crankcase is the best method.

[ithaca00]

The new YZF-450 has rear facing exhaust ports.