zracer323

iTrader: (12)

So I''m getting ready to tackle my header install this weekend and I have a quick question. I'm getting a custom ORY fabbed up with a flowmaster 3" in - 3.5" out merge. Will a 3.5" cutout right after the merge be too big for my setup? Or should I just transition to 3" and put a cutout there? The cutout will be primarily used at the track.

The car is mostly stock with:
SLP Lid
Magnaflow Catback

To be installed:
LTs & ORY
Cutout
SSRA

Intercooler2

iTrader: (24)

Why not do the 4" merge? That's what I bought and getting the pieces/piping is easier. I think a single 4" is good to 600 HP so if you put a cut-out before the muffler (I'm using the stocker) you are good to go.


We are putting mine on this weekend so I will post pics.

zracer323

iTrader: (12)

I'm just afraid I will have backpressure issues if it is too big. It seems to me 3.5" will be fine, but just wanted to see if anyone had any experience with a similar setup.

teke184

iTrader: (5)

you realize the "backpressure issue" is a myth right?

Mr.MartyStone

iTrader: (12)

What are you referring to? You don't need backpressure in an exhaust system. Scavenging creates torque, not backpressure. Run 4" and be happy.

Nate

LS1-450

iTrader: (33)

Do yourself a favor & review the exhaust write up in the stickies. You'll find better information there that is provided by the professionals whom have studied the issue for years. My interpretation of the information in the stickies is that your 3.5" single is at the high end for your set-up, certainly not bigger. The more important issue is the runner size of your new headers. I'd pay very close attention to the sticky regarding your header runner size. This area is more critical. Good-luck

zracer323

iTrader: (12)

Maybe I wasn't exactly clear with what I am asking. I'm really just looking if anyone else has experience with a similar setup and some results. Anyone switch from 3" to 3.5" and lose horsepower? If not, how big of a gain. I already have a 3" cutout and am trying to see if it is worth getting a 3.5" or just keeping the one I have.

JBIRD02

iTrader: (4)

+1
I doubt you will see any gain from a larger cutout. You already have a 3" cutout behind the merge collector thats what, like 10" long? So the only place that flow will change is within that short 10" space because everything in front of the merge will remain the same. So for that last 10" the exhaust will be a 1/2" bigger. Like was mentioned earlier, your mods dont require it, so it shouldn't help or hurt power.
I look at it like swapping out 2.5" exhaust tips for some 3" tips. Everything remains the same except for those last 10". Just save your money for more mods