PRO Exhaust trick?

Can anyone tell me what the deal is with the canister that is attached to the head pipe on alot of the PRO's bikes? I am thinking it has more to do with sound reduction than a power adder but i dont know.

Are you talking about the muffler or the smaller device such as the one that FMF manufactures? It mounts between the header and the midpipe and does in fact increase performance (so they claim) and has nothing to do with reducing the exhaust noise. Also a well designed canister (muffler) can reduce the exhaust noise while increasing the performance of the vehicle.

IMO, that FMF "bomb" exhaust is a marketing gimmick and doesn't do anything, but that is just my opinion. If it did improve power, everyone would have it.

On a 4 stroke engine, the best exhaust is one with clean, smooth bends and little restriction.

in a recent issue of dirt wheels, it showed joe byrds and a few other pro bikes that had what appeared to be a soda can sized canister welded to the head pipe. it wasnt part of the headpipe like the powerbomb, it was attached to the pipe on top of the headpipe. i will see if i can find the pics online and post one.

IMO, that FMF "bomb" exhaust is a marketing gimmick and doesn't do anything, but that is just my opinion. If it did improve power, everyone would have it.

On a 4 stroke engine, the best exhaust is one with clean, smooth bends and little restriction.

If it is just a "gimmick", why is everybody copying it....and risking getting sued by FMF because they own the patent on the technology?????

in a recent issue of dirt wheels, it showed joe byrds and a few other pro bikes that had what appeared to be a soda can sized canister welded to the head pipe. it wasnt part of the headpipe like the powerbomb, it was attached to the pipe on top of the headpipe. i will see if i can find the pics online and post one.

I have been running bombs since the first day they came out!!!

These "cans" are just a way to attempt to get around FMF's patents. While FMF could sue them, they consider it a form of flattery to have their technology coppied by all the wanna bees.....

It is common knowledge that a longer header increases low end power, for a varienty of reasons. The purpose of the "bomb" is to give you the effect of a longer header (without any actual extra length), without losing any top end. It also has the added effect of cooling the exhaust and decreasing noise.

If it is just a "gimmick", why is everybody copying it....and risking getting sued by FMF because they own the patent on the technology?????

IDK, but greed comes to mind. If something is selling more than the rest because of a gimmick, then why wouldn't anyone want to copy it and join in on the increased sales?

I'd love to see a dyno sheet prove that it offers any substancial performance gains. I could be wrong and it won't be the first or last time, but if proven wrong, I still benefit because I learned something new. :bonk:

The expansion chamber helps to quiet the system down to meet dB requirements.

All it allegedly does is affect the reversion waves that affect back flow into the cylinder through the open exhaust valve and out the open intake valve during overlap. This only occurs in a narrow rpm range on a four stroke. There is little to no sound attenuation by this device. Look at the massive expansion chambers on two strokes. If the expansion chamber reduced the exhaust noise, two strokes wouldn't be any louder than a "weed eater".

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