is this exhaust enough?
 

i currently have a set of lpp longtubes with 3 inch ORY into a 3 inch single exhaust and out through a borla xr1... is this enough flow to support a maggie supercharger, cam, and overall goal of about 500+ horse? or do i need to go true dual? or upgrade to 4 inch?

You will begin to benefit from a more free flowing exhaust around that kind of power. The headers are fine as is, but a single 3.5"-4" or true dual 2 3/4" depending on your muffler would be a good choice. Single 3" is good to about 400 from my understanding beyond that it starts to restrict some.

Im wondering the same thing. ive read about 3in-400hp before too. im wondering how much just adding a cutout helps with flow?

ok if i have to go true dual then ill be done with it and go true dual 3 inch with 2 borla proxs and an x pipe before them... so i ask... is there anywhere i can just pick up the rear tailpipes? everyone around here wants to rake my body over hot coals and sell my daughter to do a true dual setup in stainless... so i figure im a welder and fabricator... this is cake... however i cant bend pipes and dont feel like dickin around with u bends for 45 million weld joints... so can i just pick up some prebent tails from anywhere? its for an 05 avalanche.

Is that 400 at the flywheel or rear wheels?

I'm wondering the same thing, as my exhaust is pretty much perfect for my current setup (mild 5.3, StainlessWorks LT's w/ 1 3/4" primaries, 2.5" collectors, and 2.5" to 3" y-pipe, with a 3" cutout after the y, and 3" I/O 18" Magnaflow, dumped after the axle), but I fear that it will choke my LQ9 which I'm planning to have about 475-500 crank hp (if I can ever afford to build it). I'm kinda crossing my fingers that the cutout will be helpful in this situation...

you can buy some pre-bent pipes from jegs....i bought a kit and handed it over to my welder.

I've got dual 3" single DI/DO magnaflow, and it was still holding me back 1mph & tenth or so. Not really sure cuz it wouldn't hook after that.

I think cam design plays a big role in exhaust setups

yeah im sure cam design def plays a big role. i guess if swapping in a bigger motor the best route is to get a custom spec'd cam heavier on the exhaust side of course

Yes, your exhaust will support over 500.

I dynoed with ebay stainless headers/ORY , 3'' into a shitty SI DO summit 3'' muffler and made 562 rwhp on a 90* day.

On the way home from the dyno i blew the back out of the muffler, so i put a maganaflow 3'' SI DO muffler on and i could feel the difference, wish i had it on the dyno pulls.

Was my setup optimal ? prob not, but it did support over 500 like you want to do.

ya im wondering this to witht he 383 im building have lots of cr and a custom cam etc and didnt know if i should still with my 3in si/do or just do dual 3in and whatever mufflers but ya tim if u put the down i mit stay with the 3in si/do

As Tim mentioned, the single 3" will still perform, although something a little more would probably be optimal. If you do decide to go true dual, I think that dual 3" would probably be overkill, as dual 2.5's should more than support 500+ hp.

I'd like for Tom fastnblu to get off of his butt and put his Maggie on his 5.3, as he's running Dynatech LT's and !catted! y-pipe, into a 3" Corsa cat-back. The Dynatech's have 2.5" collectors and y-pipe like my SW's, so if his setup will work out well for him, something similar should also perform well for your boosted 5.3, as well as my planned NA 6.0.

I'm pretty sure that for my projected setup, 3" collectors into 2.5" pipes, to a 3.5" cat-back would probably be just right, but as I constantly mention, I can't even afford to build my LQ9 that I've had sitting for over 6 years, let alone re-doing the exhaust.

I second that Billy!!!

Hey Tom get off your rear and get goin!phump

thanks guys i think ill do a tru dual 2.5 with a x pipe and some race mufflers

Before you consider the possible need to "open up" your exhaust side, have you already opened up the intake side? Or is the intake side still stock?

I found this....
How To Calculate Muffler Size and Exhaust Pipe Diameter | Exhaust Videos

I have a 2.5" true dual setup into flowmaster 10 series race mufflers ran out in front of rear tire. That being said I picked up a noticeable gain and had to add fuel and tweak timing in my tune after I replaced the single 3" Dynomax Bullet dumped before the axle setup I had. I dynoed a tad more then 400hp at the crank n/a with the mods in my sig with the 3" dumped setup.... No after dyno with the dual exhaust setup just Seat of the pants and the need to tweak the tune.

BTW: I have the Ebay headers with 2.5" ORY

According to the chart listed there, my current exhaust will be considerably too small for my projected setup :(

According to the chart listed there, my current exhaust IS considerably too small for my setup :bang: