Hans

I am looking to bridgeport my 12a. I figured a webber 50DCO on the mazdaracing intake, but as for exhaust, I am unsure, I was thinking of the racingbeat header, but would like to have an uncollected header all the way to the end, with some metal presilencers and i head of using motocylce mufflers at end. would this be too restrictive? Im looking for a road race/track vehicle so quiteness isnt terribly important.

Is 250rwhp too much to ask for on a bridge or would i need to goto a J-bridge, or maybe even a mega bridge from pineaple.

thanks,
Hans

1st7heaven

Hans, I just saw a 13b peripheral port with fuel injection on it, on a chassis dyno and it hit 260hp, I thought was pretty good. You may have a tough time seeing that on a bridge 12a. The exhaust lenght is very critical on a bridge and peripheral port motor. I am truthfully not sure what the magic number is on a 12a. I know on a 13b bridge you need to collect 24" from the flange that meets the motor on the header to the "crotch" of the collector. I would recommend calling Roger Mandeville in Spartenburg, SC. This guy has road raced for Mazda since 1973! The name of his buisness is Mandeville Autotech......probably the most knowledgable on road racing. I am in Dallas, I have visited his shop and this guy is very impressive....not cheap! 1-864-582-0038

mperformance

**** I was born in '73!!!

Hans

as i stated I will go with uncollected, but would like to hear your input of primary diameters, and how detremental(sp?) changing exhaust diameter along the route afftects flow. for example if i run a 2" pipes per rotor to like a 3" chamber and then back to a 2" how will this affect velocity and performance. I figured a place at least one or more of these chambers with a bike muffler per exhaust pipe would provide enough flow but yeild a "softer" sound

mperformance

Hans I'm no expert but collecting at 3" then exiting at 2" is not going to cut it. Run at least a 2.5" exit

1st7heaven

I seriously would call Mandeville, I am not sure on those questions? I do know it is very critical on the exhaust! His wife Nacy is very knowledgable on these things also, she will probably answer the phone. I do know you need 2" primary tubes. I also know it is not as critical on collecting the exhuast on a street port but on a bridge or peripheral port it is very important!

Hans

sounds like a plan, i'll reply back so if someone looks this post up its not a waste =P

mperformance

thanks Hans I also want to know!