I have noticed that there seems to be two types od sports cat down pipes used on newage Sti PPPs.

The earlier type has a seperate wastegate pipe while the newer type appears to have a open mouth design.

Apart from the above, what is the difference and why did prodrive change the design?

Many thanks
Steve

 

Anyone?

 

I don't know why but can verify cats upto 2005 have seperate pipe and external heat cloth around the cat and later are bellmouthed with built in heat shielding, much better in my opinion, Only issue I had with the bellmouth was the amount of trimming required to the turbo heatshield so that it fitted correctly

 

Thanks Daz

I noticed that the later type appeared to never have a fabric heat blanket fitted.

Any idea if there is any advantage of the later type over the earlier type and why did Prodrive change it?

Cheers
Steve

 

I fitted an earlier example, and found the heat blanket was a little withered from mall the heat, and had to fit another metal cable tie to keep it on. I read somewhere that the twin dump design kept the gases from the wastegate away from the turbine, thus stopping any stalling and aiding the flow. I may be wrong..........

 

the twin dump down pipes are not always regarded as the best route to go down, as when the waste gate opens it can partially close close the hole for the exhaust gasses.

on a side not what power are ppp catted downpipes good for on a 03sti? thanks.