At what point is 3" exhaust needed?

[auto_x5.0]

As Im building my 393w, I will also be picking accessories as well, exhaust, gauges, etc. I currently have a set of new SLP loudmouths that are 2.5" resonators. My questions is will 2.5" exhaust choke the motor or will I need 3" for it to flow freely?

 

[Teal94]

Are you gonna run 3'' header collectors? Dual 2.5 is good for up to around 460 hp or so according to the calculators online. 3'' is good to up and around 700hp and 3.5 is good to around 1000hp. Just a quik search cant say if they are dead right.

 

[93blucoupe]

I read in an issue of 5.0 a couple years ago that 3" exhaust wasn't needed unless 500 hp was exceeded. That being said I ran a 393 in a 91 GT and had long tubes into 2.5" to tailpipes tuned on e85 and didn't have an issue. The car pulled like a team of horses that never ran out of power.

 

[mikey94gt]

Im making about 500rwhp boosted thru stock style 2.5" duals with an x pipe and flowmaster mufflers. Granted, I have dumps, but that shouldn't make too much difference.

 

[auto_x5.0]

Well right now it's just a motor, no headers yet, so that was my decision. I didnt want to have to buy new mufflers unless it was needed. I will be doing custom sidepipes so I guess you can consider those dump-ish exhaust.

 

[forcefedhatch]

3" single or true 2 1/2" dual are good to around the 450-500 hp.. I chose 3 1/8" single to dual 2.5" free flowing ( gutted mufflers)for my combos max potential of about 500 rwhp.. But it just works well I could have went larger because my turbo creates enough back pressure, but to make sure I still kept the basic guidelines for my combos maximum potential..
There's a formula, but I'm a lil too tipsy for that as of now..


Sent from my iPhone

 

[justinschmidt1]

I dont think its ever "needed"....but at a certain point you probably could gain from it....might not be till 500-600 hp until its worth your time.

 

[Venom351R]

My long tubes have 3" collectors so I bought a 3" Mac Prochamber to match up with it. I was going to run a 3" cat back but the options are limited so I'm just going to get a 2.5" system. Just not sure what I'm going to get yet. I really want a borla system but its $$$$