4 Stroke performance Exhaust Header pipes

[XXX-747]

hey guys,
i have some queries to know the benefits of a performance expansion chamber?
my mates' dad build's race bikes for KTM, and all his bike have them but not really sure if there worth having on a four stroke ?
or are they a big performance gain or just pointless? :confused-smiley-013

 

[my67xr]

they will improve the bike if they are tuned/fabricated to suit the individual bike

 

[8r3nd0]

EXPANSION CHAMBER

It's not an expansion chamber as such on these bikes they are a resonator, it deadens the exhuast note before it hits the can.
Euro bikes have these as they have strict noise regulations that they have to adhere to at tracks and such.
To answer the question in terms of gain in power, no there's none to be had with these smaller 4 strokes if any it's very very small.

 

[my67xr]

this is FMFs' explanation-
http://www.fmfracing.com/Products/MX/44

 

[8r3nd0]

That picture shows a resonator and the arrow and doma pipes are both resonators also not designed for power gains.

 

[my67xr]

yeah, slightly different set up, that was a bad example

the Akropovic factory header pipe is said to give Perceptible increase in performance throughout the rev range
with extra torque, and noise reduction
http://shop.husaberg.com/au_en/pure-tech/exhaust/4-stroke-offroad/factory-header-1428.html