djmisio85

Ok, Ive heard that these are meant to improve performance, but how?

Also, do these make the boxer rumble louder, or quieter?

I have a mate with a blobeye STi RA here in Japan, and his car sounds like a normal straight 4.....

chrisdicko

iTrader: (21)

Yeah, they are suppose to give a small performance increase.

But you loose the boxer rumble..

psigeek

iTrader: (17)

It's got to be something to do with the fact that an unequal length manifold gives irregular pulses of gas from the pistons. Well the pistons are regular just that some of the pulses have to travel further than others to reach the up-pipe and then turbo. So you get an offbeat, staccato series of pulses hitting the turbo (and exiting the exhaust giving the burble).

An equal set means that the pulses are equally spaced reaching the turbo (providing the revs stay constant, but you know what I mean), giving a regular series of noises and no burble. I suspect the extra oomf comes from the turbo receiving a regular series of hits pushing it round rather than a hit to push it, a gap letting the propellors slow a little, a couple of hits making it spin harder, a gap letting the propellors slow a little, etc, etc.

This is all my own thought. Will accept corrections or adult debate about it.

midloscooby

iTrader: (2)

all the jap varaints have these manifolds as standard with twin scroll turbos, you get better tourque and a lot quicker spool up of the turbo, but not sure of the improvement of fitting a equal lengh manifold to a uk spec turbo???

Juice

^^^^ i know its off topic but Midloscooby im lookingg at your avatar pic, and damn your lights are nice, got any more pics?

psigeek

iTrader: (17)

All special Jap variants and Jap blob STI onwards had equal length. The bugeye JDM still had unequal. The UK got unequal ones partly because of the huge Market appeal of the boxer burble (that and the high level spoiler). I shouldn't think there is a huge difference between the stock equal and stock unequal manifolds. The difference is when you fit far less restrictive aftermarket versions which should improve over both stock ones.