coltboostin

Car is currently making 740whp with dual 3 inch down pipes only (Twin turbo). I am in the middle of making a full exhaust and would not mind hearing people's opinions. I want it to be able to support a max of 1200 WHP for the future. I am leaning towards merging them to a 3.5, but feel i may be better served by a single 4. The Math says dual 3's flow the best....

What to do?

Fat Jesus 808

iTrader: (5)

What can you realistically fit? Like you said, Dual 3's have the most cross sectional area of what you mentioned

oscs

iTrader: (19)

Dual 3" will be plenty

JoeNova

I've seen more power than you're making made on a single 3", and 1200 made on a single 4". I don't think you're going to have restriction issues with dual 3".

coltboostin

I agree-made 667 on a single 3 inch on a 4 banger-and then made 708 with a 4 inch at the same boost level! I guess I am more concerned with 3.5? see below


I have dual 3's already run through the tightest area of the car-but I am leaning towards merging into a single 4.

I have 3.5 laying around-so that's why I ask about 3.5 and if their is anyone's experience, or math that supports that being an issue at 1000+

oscs

iTrader: (19)

(1) 4" pipe has a circle area of about 12.5" (2) 3" pipes combined have about 14.12" (1) 5" pipe has about 19.6" and (2) 3.5" pipes are about 19.2

I've seen a lot of dual 3" cars make a lot more than 1200HP. Does this mean it is the most efficient? No. However if your going to merge duals into a single make sure you increase or at least match inside surface area. My .02 anyways

coltboostin

That's fair.

Looks like I am now leaning towards dual 3's or a 3' cut out @ an X pipe and a since 3 or 3.5 out the back. Have a few 4inch scraps and in "eyeballing" it it would be more trouble than its worth

Fat Jesus 808

iTrader: (5)

I just did single 3.5" out the bumper

Orr89rocz

iTrader: (13)

I ran dual 3 vs single 4 and had more backpressure with single 4". Single 4" is smaller than dual 3. My wastegate only boostpressure dropped 2 psi when going from 4" to dual 3"

If you were to do anything go dual 3.5". Sure 3" may support it but doesnt mean its right. Theres gonna be some pressure in those pipes

2000RATA

I have dual 3" out the rear bumper. I'm making 1025 rwhp with it on. With the exhaust off it picks up about 80 rwhp just running the down pipes open. Same boost. (Yes twins also)

oscs

iTrader: (19)

Are you running mufflers/cats?

2000RATA

Magnaflow mufflers 5" round think 15"-18" long you can look straight through them located at the bumper.

oscs

iTrader: (19)

Wow that's a huge number.. My exhaust is similar to yours so that's good to know.

Orr89rocz

iTrader: (13)

I moved from dual 3" to bumper making 1009 whp to 3" downs to 3.5" a short run then into single 5", but havent had the chance to redyno with it on.
I went under axle and have to remove it to strap car down. Butt dyno is useless at these power levels. 800-1000 all feels same. But area wise the single 5" is huge compared to dual 3

oscs

iTrader: (19)

You should see nice gains moving to a 5"

Johnv

According to Poiselle's Law (flow through a pipe)

2.5" pipe flows 0.0220 m3/sec
3.0" " " 0.0457 "
3.5" " " 0.0846 "
4.0" pipe flows 0.1444 m3/sec

so a single 4" pipe should flow more than twin 3" pipes.

Orr89rocz

iTrader: (13)

David Vizard exhaust science puts flow thru a pipe at 115 cfm per square inch. Dual 3 flows more than single 4 in that scenario

chevy69

sory to use this post but, what about 3.5 from turbo to a 3" duals to make 700 whp ?

oscs

iTrader: (19)

It's not that simple. Let me see if I can dig up a better explanation I read a few years ago.

69-chvl

iTrader: (11)

Probably best to get as big a pipe as you can in there for max hp. For quietness, err on the smaller side.