99monguse

I just received my SLP Dual Dual from another member here and I am going to either my my y-pipe repaired(it broke right where the two pipes are welded to one another) and then have the flowmaster Merge installed into it OR I may jjust buy a Y-pipe from Mufflex since it already has the Merge incorporated into it. My question is this: I noticed that most people who use the Merge have the 4 inch version , does Flowmaster make a 3 inch version. If Flowmaster doesn't make it in 3 inch and I have to use a 4 inch, would it benefit me to have a 4 inch I-pipe then reduce down to the 3 inch over axle pipe or not? I was thinking about utilizing a 4 inch I-pipe and a 4 inch overaxle pipe then reduce done to the 3 inch going into the Dual Duals muffler.

CriminiSS

iTrader: (16)

I have been thinking about this setup. What I would do is use the two 3in into a single 4in merge with 4 inch I pipe with a 4 inch cutout and then reduce back into 3 inches over the axle.

ds98formula

iTrader: (3)

Flowmaster makes a 3inch in and 3.5 out merge pipe. Just got mine couple days ago from summit. http://www.summitracing.com/parts/FLO-Y300350/

Siciliano15

iTrader: (7)

it wouldnt pay to do the 3" in 3.5" out. the 3.5" out is simply not enough to handle the 3" in. if you measure for the surface area, a dual 2.5" input is optimized with a single 3.5" exit. a dual 3" inlet is optimized with a 4" or 4.5" single outlet.

just do the math its a simple equation

Area of a circle = πr²

using this method is how i realized when i got my mac mids that the y-pipe on it is simply a poor design. it was two 2½" pipes going into a single 2.75" pipe. The surface area of two 2½" pipes is 9.82. The surface area of the single 2.75" outlet was 5.98 which is way less. What is really needed is a 3.5" outlet which gives a surface area of 9.62 which is close enough to the 9.82. Since I already had an slp loudmouth exhaust which is a 3" system I havent yet wanted to spend the money to replace it so for now I went with a flowmaster merge which converts the dual 2½" pipes into a single 3" pipe. This gives me a surface area of 7.07 which is way better than the 5.98 from the mac y-merge but I am still giving up some surface area which means that until i go with a 3.5" catback, the gain from the mac mids will not be taken advantage of to the fullest. Hope this helped.

Intercooler2

iTrader: (24)

4" or go home. I have a couple of posts here with pics of mine if you search. It rocks!

taws6

iTrader: (2)

Good thing I read this, I was planning 3" in , with a 3.5" out and into a 3.5" I pipe with cutout.
Guess I'll aim for the 4" I pipe and a 4" cutout. Thanks for educating us.

Will I be okay then stepping down after the cutout to a 3" pipe to go into my GMMG??

Siciliano15

iTrader: (7)

as long as that 4" cutout is open at the drag strip it doesnt matter what the rest of your exhaust is. just know that when the cutout is closed u will be down about 10-15hp most likely.

Intercooler2

iTrader: (24)

On the dyno I saw a HP difference open but at the track it didn't show any improvement on the slip

taws6

iTrader: (2)

No ****, I thought the GMMG was 1 of the most free flowing catbacks out there. And it's still restricting that much??!
Only consilation I guess is at least the price of the cutout will be worth paying......

Sorry to the OP for

c0ncEpT

iTrader: (4)

You hit the nail right on the head.

TORCHD 02 TA

iTrader: (39)

Here is my exhaust set up..

QTP LTs + Custom Kooks OR Y + FLowmaster Merge (3"x3.5") + PowserStick Muffler + DMH E-CutOut + GMMG C/B

Siciliano15

iTrader: (7)

in the higher rpms yea no doubt