expansion chambers

[BlueZ31]

im sure youve all seen/heard or even used expansion chamber exhausts on 2-strokes (200+hp from a 650cc snowmobile is insane!) but ive always thought that these only worked due to no valves (except on reed-valve motors) which poses no restriction to the sound wave supercharging effect..BUT i got to thinking that with a set of well p/p heads and low restriction intake manifold,along with good smooth-stemmed valves and a cam with a good amount of overlap might allow for a similar exhaust system and the benefits that come with the expansion chamber

 

after looking around i found that a company called "fmf" sells powerbomb pipes for motorcycles that use a expansion chamber (also called a reverse cone system) in the middle of the header pipe to increase low-midrange power (10% increase in power output on a otherwise stock 450cc 4-stroke 1 cyl) considering the vg30e i have displaces about 500cc per cylinder (im guessing) 3 of these on each side in a 3-1 style header system might show some potential.

 

i know equal pulse headers develope the same results but are difficult to make, so has anyone ever thought of using expansion chambers or seen them used on 4-strokes? i know many porsches of the 60's-mid 80's used megaphone exhuasts that use a varying diameter cone with reverse insert to achieve a similar positive pressurizing effect in the combustion chambers, as do many formula 1 motors, but a search on google yielded little results on this subject.

 

i hope someone can shed some light on this subject for me as this might be an awesome upgrade for N/A motors period and might be something alot of the forum might be interested in if it proves worthwhile

[MONZTER]

check this http://burnsstainless.com/BTEC/btec.html

[HowlerMonkey]

Overlap in valve timing would have to be significant to get any gains.

 

Might work better in a rotary since they have a ton of overlap and also use ports like most two strokes.