3 inch piping for supercharged G8s

[NickelnDime]

All right all you exhaust and forced induction experts...

I have a question about the 2.5 inch piping used on most axleback mufflers and how it affects performance especially with a forced induction application.
My Situation:
I have a full kooks catted long tube header setup that uses 3 inch piping which includes the 3 inch kooks catted x pipe.
Would it be beneficial to fab up 3 inch piping for the axle back also? It made sense to me.
Several folks swear by it and say the 2.5 inch piping from the axle back is a real negative.
I'm looking into getting the solo axlebacks but they use 2.5 inch piping on their axlebacks.
The funny thing is that Kooks uses 2.5 inch piping on their axlebacks too.
Someone please clarify to me WHY?
I know Steve at SOLO is already looking into a custom made 3 inch j bend axleback system.

Thanks,
RJ

[VegasNate]

Subscribed for info on this too...

[-Ray-]

I see you posted this in 2 places. Which one do you want to keep?

[m1tankr]

Best bet to see how much restriction would be just head to the track, make a few passes w/the axleback bolted up & unbolted. Our cars have a nice advantage w/the exhaust set-up. I'd guess that the 3" system would depend on the mufflers used. Same muflers using 3" & 2.5" would guess maybe 10hp. My experience on my Magnacharged GTO (full 3" system w/headers) was no noticeable difference being getting louder.

[NickelnDime]

I see you posted this in 2 places. Which one do you want to keep?

Let's keep this one and delete the one in the exhaust section. Thanks G8 Ray. I sent out one and another as a feeler to see which would gain greater attention and interest.

[ulakovic22]

The farther away from the engine the least amount of restriction it will be. In some cases there are clearance issues as well, like Vette's for instance. If you put a muffler after the cat it will be more of a restriction than if you put it at the bumper. I could probably make up some stuff about thermal expansion and exhaust efficiency, but the short answer is, it's not needed. The same can be said for the bending of the exhaust as well. A 90* bend close to the engine is going to have a greater negative impact on flow than if you put one back by the bumper.

[NickelnDime]

This is actually a good post.
Thanks for sharing your thoughts.

[1stGXPmaggie2.3]

When I made my 3inch axleback exhaust, I was able to add more timing to my setup.

[Boss Hogg]

Rather than spending money on a entire catback exhaust, I bought dual electric cutouts.

[RJG8]

I will be getting a 3 inch axle back done.