UMMMM what? Am I reading that right? Your saying 4" is a waste with a blower?

 

somehow I knew that comment wasn't just going to blow over

 

Yes. Blowers are slow and make no power.

 

 

You read correctly but let me clarify.
Was thinking stock manifolds and stock y pipe.
Anything with cats and small crossover.
It Is already choked down.

 

That I can agree with, but with decent long tubes and 3" mid pipes then 4" is absolutely beneficial.

I've done some playing around with exhaust sizes on mine and others, comparing back pressure and effects of exhaust size and mid pipe size.

 

Agreed. Seen what your talking about first hand.

 

On my setup with 1 7/8, 3" collector, 3" mid pipes but only a single 3" exhaust I seen roughly 12psi back pressure. With 4" I have none.

Another members truck had a similar engine setup but only 2.5" mid pipes and back pressure was over 15psi even though he had a larger 3.5" exhaust, with his cutout open the pressure didn't drop. At that point his restriction was his collectors and mid pipes. It's all relative. You only flow what your smallest point does.

I know on mine once I went to the larger exhaust my topend was completely different.

 

At 540 rwhp i had stock 3" exhaust with magnaflow muffler in place of stock, i swapped to a 4" exhaust from the Y pipe merge back using a straight thru muffler

I gained nothing at this power level, was expecting a gain but saw none

Dyno' d days apart on similar conditions

Procharged 5.3 on 12 psi


One thing i did see was a drop in boost

 

George, what did the rest of your exhaust look like before the exhaust system? Interesting that you saw a loss of boost, but not an increase in power.

I assume you re tuned it with the exhaust as well? Were you able to get any more timing out of it?