I'm builiding a P-port soon and have a guy to build the header....for a decent sized p-port, how far back should I collect the pipes?

I'm thinking just to the end of the trans with a 3" collector.

2 Bolra XR-1's, and my Rotaflo at the end will try to shut it up enough to be street-driven.

 

85 views and no one has any imput on ideas for P-port headers? Primary lengths (and yes, I do know what RB recommends...) Tube size?

 

16-24 inches

 

All the way back to the diff, joining into the muffler

 

large pipe short length and nice collector.

 

I use an uncollected ISC stainless header. I have my collector at 89" from the engine. The throat of the collector is pretty important - it merges to about 2-3/8", then gradually expands to 3" diameter pipe running to Borla stainless steel straight thru muffler.

 

To all of you...thank you. I want to collect early enough to have room for plenty of mufflers. Are the Borla's sufficient to cork it for street driving? Since I'm aiming for a 9500 limit, I can muffle it a bit more than a full-song 11,000rpm race version.

So what Im hearing is....gradually collect the pipes, near mid car, smooth transition to a 3" pipe, trying to fit a 16" (or 14") and a 12" Borla before the diff.

 

"Are the Borla's sufficient to cork it for street driving? "

No.

A peripheral port engine is extremely sensitive to exhaust back pressure. If you try and quiet one down for street driving, you will loose at least 50 horsepower.

I have been racing PP motors since 1997. I have tried driving them on the street, and they are not streetable. I do not want to be stuck with a peripheral port motor in city street driving, stop and go, redlight to redlight driving. Street driving is what street porting is for - that's why they call it a street port.

 

2 borla's are not enough. I use 3 Borla's on high output streetport n/a engines with very good results. This was up to 9200 rpms. More than streetable on the noise, and non-restrictive. However a full p-port as stated will not like backpressure, but the triple borla may be a good compromise for street use and race use.

 

You could always put v-bands on the mufflers so they could be quickly replaced with straight pipes on race days if you really want it quiet for the street. It would be more expensive than simple flanges and gaskets, but much less of a pain and less time consuming in the end.

 

Thanks for the responses guys. I may end up building my own mufflers (via Ausrotary forum)using stainless mesh blanket and high-temp rockwool, making a long and short mid muff. If I can get it to 100-110db, I won't have a problem where I live, there are open-piped, slicked down badboys all over Burbank! The headers will be custom 2" merging to 2.25 with a 3" collector to the middle of the trans...a long muff, a short and the Rota.