R6_Don

Hi

Just received my second hand down pipe and realised it is not the bell mouth type, the type I have is similar to this.



What difference will it make performance wise having this fitted instead of the bell mouth type.

Thanks Don

jimnco

the waste gate may not open or open fully it will also restrict the flow of gasses comming threw the waste gate

R6_Don

Will this be worse than the standard cat then? Not sure if I should re sell and buy a bell mouth type.

wrx9181

iTrader: (2)

You want one large or two holes that will be restrictive
I'd not fit that personally

adz556

iTrader: (5)

That is the same as the factory pipe but decat so fractionally better than factory but really not ideal! I'd sell on and get a bell mouth mate

R6_Don

I've just done a bit of research and found out that it is a HKS downpipe (correct me if I'm wrong) there are also a few mixed reviews on it with some people saying its poorly designed and others saying that they have one and its good. Found this comment on another forum
" Re: Why does no one like the HKS downpipe?
I've tuned many STIs, and the HKS downpipe isn't junk. They perform just as well as most bellmouth pipes.

The wastegate flapper only opens a small amount. This forces the gases exiting the wastegate orifice to be directed into the main part of the tube anyway. the only design that provides less turbulence is a divorced outlet design.

In my experience, from actually viewing datalogs and dyno plots of identical stage 2 STIs, that I tuned equally at the same boost levels, the HKS does not show any indications of inferiority."

YoungY25

iTrader: (5)

Yeah its the same design as the standard downpipe mouth. It'll still work fine, just some people prefer the bellmouth or the twin exit type. The wastegate only opens a small amount anyways.

adz556

iTrader: (5)

It may force air over towards the orifice but it'll never be as good as a bell mouth...... Might only be a tiny bit worse, but it'll still never be quiteeee as good IMHO

craigwrx277

iTrader: (1)

I've ran bellmouth and a japspeed decat like the above and didn't make a blind bit of difference in my opinion. Maybe if you was running serious horsepower.

blackvenom

I have a decat with two holes fitted to mine currently, Two pipes go into one about 4" down from the flange, I have a bellmouth in the garage but was told it wouldn't be restrictive enough causing issues? And then I saw this?