Outer Limits 4x4 Board

What do you fellas recon about a twin exhaust on a turbo diesel? The maximum dia pipe I can come out of the manifold is 2 1/2 inches and there needs to be a 90deg bend straight out of the manifold. To save on space and money I can do two 2" mandrel exhausts effectivly getting 4" outlet and have them coming out each side of the truck at the rear.

why?

I dont think 2x 2" equals a 4" pipe.
The cross sectional area of a 2" pipe is 3.142sq"
The cross sectional area of a 4" pipe is 12.56sq"
J Top

Daisy wrote:why?

Why not? Better Gas flow!!

J Top wrote:I dont think 2x 2" equals a 4" pipe.
The cross sectional area of a 2" pipe is 3.142sq"
The cross sectional area of a 4" pipe is 12.56sq"
J Top

Thanks thats constructive input.

I would think that the two pipes will be more restrictive as you will have one bigger pipe trying to split into two smaller ones

But its your truck if you want it do it forget about what we say





Steve

DR Frankenstine wrote:

Daisy wrote:why?

Why not? Better Gas flow!!

of course.. and lose all down torque and get heaps of gain at the top end.



like above said.. its your car

Hey Dr Frank - soprry I didn't get down to see you in december... runnin late on way home or I would of popped in.

Sure there are people out there that know more than me but wouldn't there be too big a drop in back pressure with twins?

Don't know much but its just my thoughts - feel free to advise otherwise.

Mk

Hey Dr Frank - soprry I didn't get down to see you in december... runnin late on way home or I would of popped in.

Sure there are people out there that know more than me but wouldn't there be too big a drop in back pressure with twins?

Don't know much but its just my thoughts - feel free to advise otherwise.

Mk

Can't you fit a 3" pipe? it's cross sectional area would be 7.065 sqaure inches, better than 2, 2 inch pipes, and probably cheaper too..
Also i don't think you'd lose bottom end by having too large a pipe after the turbo as the turbo is the restriction, and after the turbo the less restriction the better!!
If not i'd just go a mandrel 2.5" with resonator... i.e. if you were restricted to 2.5"s from the manifold would there be a big gain from having more flow after that? - as the exh gas cools it condenses and takes up less space, therefore the biggest pipe is required closest to the turbo.
only my drunken thoughts though...

DR Frankenstine wrote:

Daisy wrote:why?

Why not? Better Gas flow!!

And would look shit hot to , if you want to do it go for it man

i've got 3 inch from my turbo on gu, you can buy a new 3 inch outlet for turbo, there a gq that does the ute shows with twin stacks on it and it sounds like a wet fart.

the diameter vs flow is also affected by surface currents (eddy currents) so there is a dead space of the same depth for every pipe so in effect a smaller pipe has even less flow due to greater surface area effected around the diameter vs the total surface area. 2x 2" flows around the same as a 2 1/2"

but in reality the flow is more restricted by pipe length than diameter for a restricted tube.

eg a twin 2" would prob be worse than a single four with a 2" restricted inlet out of the turbo as the resistance in so small in a 4".

why a diesel other than a 600hp cummins needs a 4" exhaust is strange to me. 3" is big enough for any 4lt odd turbo currently running the comp scene

bru21 wrote:the diameter vs flow is also affected by surface currents (eddy currents) so there is a dead space of the same depth for every pipe so in effect a smaller pipe has even less flow due to greater surface area effected around the diameter vs the total surface area. 2x 2" flows around the same as a 2 1/2"

You are like that exhaust gansta. Man you know heaps!

Good input, what's your thought's on the reduction in back-pressure by installing high flow systems?? Would the twin system counter this?

jav wrote:there a gq that does the ute shows with twin stacks on it and it sounds like a wet fart.

GOLD!

just cut it and do this. lol

Must have two dicks!!

phippsey wrote:Good input, what's your thought's on the reduction in back-pressure by installing high flow systems?? Would the twin system counter this?

i was of the understanding that a turbo didnt have any back pressure in the exhaust system

Yea you deffinately don't want any back preasure in a turbo diesel.

Go for a 3" system. Anything else is pretty much reducing potential power. My truck peaks at 20psi, is intercooled etc etc and I have a 3" system with very small resonator. Any back pressure or a small exhuast will reduce low down torque. The more flow you can get the faster the turbo will spool and so develop power. Also don't forget inlet, as it will make the same amout of difference.