alright, i just got done working the inlet tract of my GTUs. the Throttle body is modded and the UIM and LIM are fully ported. the 6PI system is completely eliminated; the 6PI sleeves, rods and diaphragms are removed. the bronze 6PI actuator rod guides are punched out and blocked off w/ a pair of dimes. the 6PI rod guide bosses are ported and smoothed out flush w/ the walls of the runners. the dividers between the secondary ports and auxillary ports have been knife edged. my ACV is also removed and blocked off.

so my intake tract from the TB all the way to the rotor housings are set up for high volume and will probably sacrifice velocity... this is going to put my peak power up high in the RPM range, so i want to build a header and exhaust to maximize and compliment the intake flow rate and will work with the stock ports on the rotor housings.

from my searches, i understand that a TRUE dual system would be best for MY completely stock-port housings. soo, i think ive got an idea of what i want my exhaust system to be.

ive got the header flange and a pair of dual exhaust flanges to make a break-away from the header and the exhaust system. i ordered these from Mazdatrix along w/ the gaskets. now i just need to get some input from experienced people as to what i should set my header primary diameter and exhaust system diameter at.

i think the header flange port diameter was 2.5" and the exhaust flanges were 2.25".

let me know what you guys think about what ive got goin on so far; True dual for stock-port housings... but what diameter header primary and header-back? id like to get a power peak to maximize power delivery while shifting at STOCK 8000rpm redline..

thanks guys.
chris

 

this might not sound that inteligent,

but you could go onto Racing Beat website, and see what sizes they use on there headers, since they have put alot of reasearch and development into sizes and angles, im sure they pick one of the best sizes for max hp.

one thing to really look at when considering true duel vs not, is WEIGHT!
running 2 pipes to the back will basicly double your exhaust weight, so if you think duel will net you only a few more hp then it probably wouldnt be ideal if it adds alot of weight.

 

yeah... RB headers are teh lose anyways... they promote collected systems w/ short primaries for stock-port cars w/ no airflow upgrades. they are a good improvment over the thermal reactor, but definitly not something that will maximize the resonant pulse tuning of a 13B... which is what i want to do.

and im not TOO concerned w/ weight on my car... ive got the lightest S5 produced and have converted the Auto seatbelts to the S4 manuals... and once i toss the thermal reactor, ill offset the additional weight of 5' of piping between the engine and where the stock exhaust would normally split apart anyways

besides, it looks way better w/ twice-pipes than once pipe and an empty cut-out in my rear apron