<div class="FTQUOTE"><begin quote>Originally posted by: atvman29

Is it just a stamped piece of steel? Can you fit it under the plastic guard?</end quote></div>

I wonderif I have that under my plastic guard?

atvman29, when are you getting your new arms?

 

<div class="FTQUOTE"><begin quote>Originally posted by: atvman29

Is it just a stamped piece of steel? Can you fit it under the plastic guard?</end quote></div>

Its the stock oem piece. So if the plastic guard is stock oem, it will fit.

Its probably stamped, but I can't remember for sure.

 

Randy, you were talking exhaust. Have you looked at what www.fmfracing.com has done for the 400cc + motors? There calling them power bomb, and mega bomb headers. Supposedly increases speed of exhaust leaving the cylinder. Just got an '06 z400. Think I may try it. My son in-law got a new exhaust system for his '06 400ex and the power bomb and fmf muffler made a BIG difference all across the powerband.

 

My friend's warrior has that system. I think most of the power comes from the muffler, not the bomb. The bomb is just a spot in the pipe that allows the gas to expand, kinda similar to stepped headers. Stepped headers are specific lengths of increasingly larger diameter pipes. The bomb is also a kind of helmholtz resonator, which may quiet the exhaust some before entering the muffler.

 

Expansion chamber to help scavenge the exhaust leaving the cylinder like 2-stroke?

 

On a bit of a sidenote, taping your headers doesn't do jack. I got that straight from a formula 1 tech guy. The only time you want to tape your headers is if you need to keep heat out of the engine compartment, like in a car. But for bikes, its a waste of money and speeds corrosion by trapping water and mud. However, ceramic coating does help. Not because it keeps the gas hot like you'd first expect, but because it keeps the pipes stiff. The stiffer the pipes, the less energy goes into making the metal move. Therefore, more energy stays in the gas and can be used to scavenge during valve overlap. And scavenging is what the bomb is supposed to help out. But only at a certain rpm based on the speed of the gas in relation to the speed of the piston. If the piston outruns the wave, it does nothing to help. If the wave outruns the piston, it also does nothing. Only when the wave and the piston are in the right spots does it help scavenge.

Another bone I have to pick with the muffler manufacturers are these oval or square pipes. They let energy out by virtue of geometry. Who ever heard of a square or oval air compressor tank? They're always round! Round is the best shape for containing pressure... And when we're talking pressure differentials near absolute vacuum, we're talking some serious pressure! These goofy geometrical designs they come up with to sell more mufflers are invariably louder than a simple, cheap, round design.

I do believe FMF is on to something with the square perforated tube they use inside the glass-pack. "Slots" usually do flow better than round tubes. I don't know why, I just know that they do.

 

The back of my head is trying to remind me something I heard a long time ago from an old hot rod guy. Something about an airbox and a " Helmholtz " resonator. Or am I dreaming.

 

<div class="FTQUOTE"><begin quote>Originally posted by: MMZUKI

Expansion chamber to help scavenge the exhaust leaving the cylinder like 2-stroke?</end quote></div>

Not really. A 2-stroke counts on the wave to push the "exhaust" (which is actually gas that got sucked into the exhaust pipe) back into the combustion chamber at the right time. The bomb gives the expanding gases a place to expand in addition to expanding on down the pipe. If valve overlap happens at the precise moment the wave hits the bomb, it should suck more gas into the combustion chamber. Assuming the volume of the header up to the bomb is sufficient to hold the entire gas volume of the combustion chamber and then have room left to suck. Its sounds pretty complicated to me. Get it right and it should add hp over a narrow band of rpms. If the rpms are too low, it may do the same thing an expansion chamber does for a 2-stroke, but instead of pushing gas back into the combustion chamber, it would be pushing exhaust. Seems like it to me anyway.

 

Check out this animation: http://quadracerhq.com/tech_tips.htm

 

This is a good read. Was reading it last night hoping for a tip about tips.

"On your typical cat-back exhaust system, you'll see a couple of bulges in the piping that are apparently mini-mufflers out to help the big muffler that hangs out back. These are called Helmholtz Resonators and are very similar to glasspacks. The main difference is that firstly, there is no sound-absorbing fiberglass or steel wool in a Resonator. And secondly, their main method of silencing is the reflective principle, not absorption. An easy way to tell the difference between a glasspack and a true Helmholtz Resonator is to "ping" one with your finger. A glasspack will make a dull thud, and a true Resonator will make a clear "ping!" sound."
http://www.nsxprime.com/FAQ/Mi...eous/exhausttheory.htm