Split Dump Pipe- Opinions Wanted

[Dorifta]

My dump gasket has gone and 4 of the bolts have vibrated off, so I thought Id put a split dump pipe on

The turbine outlet is quite smaller as it is split,   This will obviously bring boost on faster but sacrificing top end flow

I believe they split them to stop the pulsing of the gases out of wastegate interrupting the flow of the turbine outlet

Are they a worthwile upgrade, or only for response and midrange

[paulr33]

i dont believe there is any response gain by using a split dump

when the gate is closed, it is closed and nothing comes out, so the size is irrelevant

its only relevant when the gate is open

the split dump reduces the turbulance by ensuring they each have their own seperate paths

having the turbocharger outlet hole going into the size of the split dump dump (if that makes sense) or runnign to a 3" bell mouth, i dont believe there would be any different in response

they both must travel through the smallest common denominator, which is the exhaust wheel outlet first

[Dorifta]

  paulr33 said:

i dont believe there is any response gain by using a split dump

Whenever u change the size of a pipe,  

bigger pipe=more flow at top end and reduced flow(air speed) down low.

smaller pipe= increased flow at low rpm  while being restrictive in the top end.

3 inch pipe will flow say 500hp.

Where two 1.5 inch pipes will flow 500hp will alot faster air speed and alot better response

[R31Nismoid]

^ I don't know where you get your advice from mate, but it's horribly incorrect.

Bigger pipe down NOT reduce down low torque. Infact it increases it by allowing the gases/air to move around more freely - so long as the motor is tuned accordinly of course.

[Dorifta]

  R31Nismoid said:

^ I don't know where you get your advice from mate, but it's horribly incorrect.

Bigger pipe down NOT reduce down low torque. Infact it increases it by allowing the gases/air to move around more freely - so long as the motor is tuned accordinly of course.

So putting a bigger exhaust on ur car will have the same response as stock,    Not a chance

So ur saying a bigger pipes air speed velocity at low rpm is the same as a smaller sized pipe.   Not a chance

The smaller the pipe, the greater the air speed velocity will be, until it gets restrictive, where it robs u of top end

Edited February 4, 2010 by Dorifta

[R31Nismoid]

You're first post is wrong, as Paul has stated.

Have a look @ the turbine inlet housing, then perhaps you might appreciate what happens after the turbine wheels doesn't mean a whole lot in the situation you are talking about here.

The sheer fact of the matter is, you are not right. My own car is a testament to this.

Having gone from large, 2.5" twin aftermarket dumps, BACK to factory, with exact same results. It was if i never changed parts.

Not only is my own car a great example, but the 1,000's of other cars on this forum as well.

If you think you need backpressure in the exhaust to make low end power/torque... then i'm throwing in the towel before this goes any further.

So whatever you reckon mate - i'm not going to argue with you if you think you are right as i have proof, you have a theory.

[bozodos]

also bearing in mind that turbo cars don't need backpressure for a scavenging effect on the exhaust manifold like an N/A car does

[R31Nismoid]

N/A cars don't need it either. Issue is the same there as i said earlier.

People put exhausts on, and don't have the car retuned.

So the N/A feels sluggish all of a sudden as the car is setup/tuned for emissions and straw sized exhausts.

[Harey]

One thing is for sure the bigger the dump pipe and exhaust on a turbo car the better. Less restriction means turbo spools up quicker increasing response, decreasing lag and also increases top end. Its better in every way.

I have heard of people putting larger exhausts on an N/A car and saying they lost a bit of down low torque but gained mid range and top end. Although I am no expert on that so will leave it there.

As said by paulr33, the split dump will not help with response but will help top end flow. How much I do not know. Surely someone has done a back to back dyno.

Edited February 4, 2010 by Harey

[MrStabby]

1. To present the greatest difference in pressure across the turbos' turbine (to make it work the best), you want to have zero backpressure after the turbine. Bigger is usually better, but you also want to limit changes in cross sectional area.

2. Split dumps should help when the wastegate is closed as well, due to their ability to limit turbulence just downstream of the turbo. Turbulence = backpressure.

3. Split dumps are much more sensitive to sizing than bellmouths. With Bellmouths you can pretty much bolt any dump to any turbo and it should work fine. With splits you need to take some care.

^^ that's all theory. Reality may be different.

[Dorifta]

Thanks for the input everyone, Back to the books for me