single exhaust vs. duals

[paul bunyan]

I have a 2005 Dodge ram. Hemi, 3.92 gear,LSD (posi) No options, regular cab short bed. It weighs 4900 lbs w/ (fat) driver. Best e.t. is 14.115@93.38 mph.
Mods are:k&n CAI, transgo shiftkit, superchips, home-brew/muffler shop cat-back exhaust. The exhaust is replacing the factory y-pipe w/ 2 pipes back to a Walker Dynomax 2 into 1 race series muffler, then into the stock 3" mandrel bent tailpipe and factory resonator.
My question is: At what point do I need to go to dual tailpipes?

I also would like to know if an x-pipe is a good idea.
The exhaust pipes both have to run on the passenger side, due to the location of the fuel tank.

If the pipes are that different in length, would the exhaust pulses "collide" and hurt flow? What about the "acoustic" effects?

If I changed the exhaust to duals, would it be worth it to have the driver's side (engine) exit the passenger side, and the passenger side (engine) cross over around the spare tire to "equalize" the pipe lengths.

The goal of these(and future)mods is to improve both efficiency and power.

I would like to add long tube headers, a 6.1 liter cam, and a 5.7 car intake manifold.
The goal being no loss in gas mileage, and a 13.50-ish et.
Thanks.

[Devious]

A good place to start:
Auto Exhaust Science

[1989GTA]

I don't think it matters as long as both are sized properly.

[paul bunyan]

That is an outstanding article. I did read that before my post. (brownnose alert) It is the type of article I have come to expect from that 'WIZARD" of technology. The reason I would buy any magazine with an article by him. On any subject. OK, maybe not Hillman Imp hop-ups. lol.
What I am looking for is a mathematical formula correlating pipe size vs. hp. And an answer to part 2 re:
Dissimilar secondary pipe lengths and the possible ramifications of x-pipes.
The efficacy of trying to even out overall pipe lengths by crossing pipe from one side to another, strictly for acoustic benefits.
thx,
pb
ps, gotta go, damn ox got loose again....... lol

[MilesTugoh]

DV, in the above cited article, provides a rule of thumb correlating pipe size to hp.

He said that each sq. in. of pipe area will flow 115 cfm of exhaust gas, and, 2.2 cfm of pipe flow will support 1 hp. Therefore ..

a 2.25" pipe flows 457 cfm and will support 207 hp ..
a 2.50"............... 564............................. 256 hp ..
a 3.00"............... 813............................. 369 hp
a 4.00"............... 1445............................ 656 hp

Please note his caution regarding the flow through the muffler must match the flow of the pipe dia. used before and after the muffler(s).

My cam guru says the X pipe and the H pipe do the same thing .. the important thing is to place them in the correct location (header design/cam spec consideration) and size them no smaller than 85% of the pipe diameter. Mine needed to be 19" downstream of the end of the primary tubes.

[BlackCat13]

Originally Posted by MilesTugoh

DV, in the above cited article, provides a rule of thumb correlating pipe size to hp.

He said that each sq. in. of pipe area will flow 115 cfm of exhaust gas, and, each cfm of pipe flow will support 2.2hp. Therefore ..

a 2.25" pipe flows 457 cfm and will support 207 hp ..
a 2.50"............... 564............................. 256 hp ..
a 3.00"............... 813............................. 369 hp
a 4.00"............... 1445............................ 656 hp

Please note his caution regarding the flow through the muffler must match the flow of the pipe dia. used before and after the muffler(s).

I think you goofed the math.

As you said it is 2.2 times the cfm, not divided-by as you illustrated.

[MilesTugoh]

Thanks for pointing out my error, BlackCat13, however, DV said 2.2cfm/hp, my error is in my written description, not my math. See paragraph five on the second page of the cited article.

I will correct my original post.

[BlackCat13]

Originally Posted by MilesTugoh

Thanks for pointing out my error, BlackCat13, however, DV said 2.2cfm/hp, my error is in my written description, not my math. See paragraph five on the second page of the cited article.

I will correct my original post.

DV's quote
"Just make a reasonable estimate of its open exhaust power potential and multiply by 2.2. For instance, a V-8 making 500 horsepower on open exhaust will require 500 x 2.2 = 1100 cfm. Two 550-cfm mufflers will get the job done...."

Thanks for pointing out that I read too fast sometimes.

I was looking at a 2.25 pipe and seeing 207 hp.......

PER EACH CYLINDER BANK, and the normal dual exhaust supports TWICE the stated horsepower.

Thanks

(First mistake I ever made)

[paul bunyan]

By the formula stated, I am right up against it w the 3" single.
So time for 2.5" duals with the mods I plan to make. thx again
pb

[MilesTugoh]

I know of a fellow using two 2.25" into a Y into a single 4" pipe into a single 4" muffler and tailpipe. Muffler case length chosen to fill the space available . It is quiet and very low loss system.

If you used two 2.5" into the Y the 4" would still be adequate.