chevy1500z71

is there any information out there on what an ideal exhaust setup would be with forced induction. from what i understand, generally you want your exhaust tubing to be 1.75 times your primary size, so around 2.75, id go 2.5 for more torque. but does all this hold true with forced induction? i mean, im putting alot of air and fuel through my motor, meaning alot more exhaust is being pushed out, wouldn't a 3" exhaust seem more appropriate? im just afraid of loosing all my torque. a smaller tube will pull more velocity, giving more torque, but what if it becomes a restriction at higher rpms and higher boost levels? i also read that you need about 2.2 cfm per hp, a 2.5" strait pipe only flows around 450cfm i would need about 600cfm per side to be safe. i dont know what to think about this whole deal, what your guys thoughts on this?

right now, if i run with my cutouts open, i loose alot of torque vs themk being closed, and they are set about 30" behind the collector on 2.25" pipe.


i have to redo the exhaust either way. heres my current plans 2.5-3" pipe strait back form the collectors even on both sides, not a single bend in the entire exhaust, have the h pipe by about past the driver seat, cutout, and then reducer cone directly to a 5" inlet flowmaster 40 race muffler (the smaller flowmasters dont flow enough cfm and i dont like the glasspack sound) and then directly to a big turn down tip. it would all be said and done before the gas tank, this way there are no bends in the system, very simple. the tips will be as far back as they can go without the driver side getting into the gas tan, so theyd be dumped just infront of the bed. i dont think it will be too load with such a huge 2 chamber muffler, and resonance wont kill me.
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chevy1500z71

nobody? shoot, i got more responses on the retarded truck forum. was expecting you guys to know your stuff! lol

myvmax1

Your on the right rack with your thoughts on velocity/tubing size/back pressure. From what I have been told though, the loss of torque with more open exhaust becomes less of a concern with forced induction.

Maybe if you listed your engine combo, along with your target performance and predicted driving habits the members of this forum could better instruct you on what decisions to make in regards to exhaust choice.

chevy1500z71

i always seem to forget that my sig has no specs on my motor nor do alot of members really know me well.

its a 355 with forged slugs, got a lunati voodo cam(flat tappet) and it ends up about 500 intke lift and 520 exhaust(taking into account my 1.6 rockers) with a duration of 219/227,dart iron eagles, big valves, fairly small runners, bout 9:1 compression with flat tops and a .40 quench w/76cc heads. got the whipple supercharger on top making roughy 9psi with methanol injection. still tbi with 80# injectors cranked to 33psi under boost with the boost referenced regulator. my expectaions of the motor are a little better then 500hp, maybe a little less but big torque. i only spin it to 5300rpms, cast lunati crank.

EDIT: the reason you have been told the torque isnt a concern with f/i is because once you light up the blower, there is so much velocity in the ports you are going to have tons of torque. but what im talking about is casualy leaving a red light, i dont want to have to dig deep into the pedel. the excessively small exhaust gives me alot of really really low rpm response. at the sake of hp tho.

chevy1500z71

so far i think iv decided on 3" pipe and im the high bidder on these huge flowmasters right now
http://cgi.ebay.com/ebaymotors/ws/eB...K%3AMEWAX%3AIT