Double exhaust

[Ugluk]

Wouldn't a double set of mufflers be easier to get that thundering ducati-termigioni like sound character out of without fitting a oval muffler as big as the bike itself?
I've just hammered out a rather ratty slip on muffler, and it's a bit sharp and farty sounding.. But bigger is not good either.. Perhaps dual is the way after all.

Please up a vid of the resulting sound signature Olivieeeer. Awesome looking bike btw. Makes me wanna attack my bike with grinder and welder, in spite of the original plan to keep it just that and using it as a boring everyday hack to save my turbo ninja some wear..
Cheers

[Olivieeeer]

  You want more pics ? I have !






  I will take time to make a vid. The sound is .... vintage, and LOUD ! 

[johnny ro]

if engines needed back pressure, we could all get more HP with potatos or doughnuts stuffed into exhaust tip. I wonder why some people think back pressure is good? Back pressure is evil.

Two mufflers is better than one if it lowers back pressure without being too loud and you rejet appropriately. Except they are heavier than one with piping. And they look good if set up nice.

Anyway, the bike is awesome.

My 1975 Commando 850 (bought 1976) had dual exhaust. It had balance pipe, clumsily and ugly-ily connecting the two sides, towards the front. An upgrade I did not buy was two into one into two. The two into one gives more scavenging power, the one into two gives sound muffling with less back pressure. One larger low back pressure muffler would work best (most economical with the metal) but this approach is not part of the current motorcycle world.

I think mufflers are the same as airboxes in this regard. You cant have too big an airbox, as long as it fits.

[tt_four]

The bike looks awesome with those new exhausts, they definitely fit it well!

if engines needed back pressure, we could all get more HP with potatos or doughnuts stuffed into exhaust tip. I wonder why some people think back pressure is good? Back pressure is evil.

Unfortunately it's a bit more complicated than that. There's too much and too little back pressure, and you need to get in the right spot. Aside from the exhaust there's other random things you don't think of like valve overlap, some higher hp bikes use more to suck some of the old air back in with the fresh air before blowing it back into the engine, as opposed to having less valve overlap on the same motor to give you better low end by blowing less air back. Having certain amounts of back pressure in exhausts can also help to mix and suck the air/fuel mixture into the motor more efficiently. There's definitely a good chance there's some errors in how I worded that, because I don't know a ton about engines, but I definitely know there's a few things going on more complicated than air/gas in and air/gas out.

[Olivieeeer]

  Actually my exhaust is a direct 2 into 2. Works good, and particularly loud. My choice is to remove the pipe front of the cylinders, and put it under the engine and have a more common 2 into 1 into 2, like a EX500.

 For sound, I will make some reducers.

[smaeda]

wow that looks fantastic!!

[tt_four]

You do have that connecting pipe right by where the header bolts to the engine, so even though it's not really 2-1-2, the pipes at least get somewhat of a chance to equalize.

I'm really liking the TRX too, it's a great looking bike. For some reason I always thought those were v-twins, but obviously they're not.

[aaronjosephward]

theres a ton of information on that http://gs500e.free.fr site, if only i could read french
sweet site

[valvesprung]

I had those seemless peashooters on my KZ400 and they have an AWESOME sound, I bet the GS sounds amazing with them. Can't wait for a vid clip!

[Olivieeeer]

  Aaron, try this : http://translate.google.com/translate?hl=fr&sl=fr&tl=en&u=http%3A%2F%2Fgs500e.free.fr%2F

 ttfour : TRX is a 270° parallel twin. Ignition is like a 90° V twin. Sound is same, big torque and low power, like 900SS Ducati. Mine is upgraded with 900TDM cylinders, pistons, crank and rods. Cylinders are aluminium with nickel/silicium treatment. These engines doesn't exist in US. Mine deliver about 89hp at the rear wheel, 106hp at the crank. It is 82hp stock at the crank. I have a lot of modifications. It's really a nice bike ! If one of you come into France, I would be happy to accomodate you and try my bikes !  

 I also have a XTZ750 Super Ténéré, the engine is the basis of the TRX, but it is a 360° engine. It is not as fun as TRX.

[Chanse]

If back pressure is needed so badly why aren't race cars built with mufflers instead of open headers or straight through exhaust?

[black and silver twin]

If back pressure is needed so badly why aren't race cars built with mufflers instead of open headers or straight through exhaust?

Because race cars/bikes run at high rpm constantly so they are willing to sacrifice the lower rpm drivabilty that a traditional exhaust would provide to get more high rpm power. And just to clarify its not necessarily back pressure thats needed, its exhaust velocity. a small amount of back pressure can increase low rpm velocity giving more low rpm torque. but in a perfect engine there would never be any restriction in the exhaust, the pipes would be the correct shape/size/length to provide velocity without restriction. changing the pipe diameter, length, shape, and/or restriction will change the rpm that a particular exhaust will be the most efficient on a particular engine.