Exhaust Fabrication

[alex_nzl]

Hey guys

I\'ve been trying to source a split/divorced type downpipe for my V7 STI for a while now, been a mission to find one.

I\'m thinking I might just buy a bell mouth type pipe and get a splitter welded on. Has anyone had this done before? If so, would be great if I could get some recommendations on some exhaust fabricators in Auckland and a rough estimate as to how much it would cost.

Cheers

[boon]

Just get a Rage bellmouth one. I dare say the difference with a splitter is slim to bugger all.

[NomadGonad]

Research I\'ve done indicates the opposite bell mouth with splitter performs better.Prodrive started putting splitters in down pipes years ago.Keeping the wastegate gases out of the path of the gases coming off the turbo is a better option.

[rex-leggy]

something about when the wastegate opens turbulence effects the flow ... read it a while ago have no idea if it true.

in my mind it would be sfa

[Koom]

As general rule of thumb, you need a length of pipe to be 4x its diameter for the flow inside to settle from turbulent to laminar. So it\'d just be allowing the wastegated flow to settle itself out before mixing back in with the main exhaust flow.

But in my mind also, it may be worthwhile for Prodrive to chase these things as thats what they\'re paid to do, but for a roadcar, how much are you willing to pay for what could be zero gain at roadcar power levels? In saying that, I separated the two exhaust paths when I had a bellmouth downpipe. But it cost me my time and that was all.

[alex_nzl]

 Koom said:

As general rule of thumb, you need a length of pipe to be 4x its diameter for the flow inside to settle from turbulent to laminar. So it\'d just be allowing the wastegated flow to settle itself out before mixing back in with the main exhaust flow.

But in my mind also, it may be worthwhile for Prodrive to chase these things as thats what they\'re paid to do, but for a roadcar, how much are you willing to pay for what could be zero gain at roadcar power levels? In saying that, I separated the two exhaust paths when I had a bellmouth downpipe. But it cost me my time and that was all.

That\'s a good point. I\'m not really looking at doing extensive mods, just a few done well. For a road car/daily would a bell mouth do?

[Guest]

I run a bellmouth with internal on VF22 and it netted me good results. Splitter is diff length between TD and VF turbos also so can be a c*nt if you change turb later. I dont know which housing is deeper.

[boon]

 alex_nzl']

[quote name='Koom said:

As general rule of thumb, you need a length of pipe to be 4x its diameter for the flow inside to settle from turbulent to laminar. So it\'d just be allowing the wastegated flow to settle itself out before mixing back in with the main exhaust flow.

But in my mind also, it may be worthwhile for Prodrive to chase these things as thats what they\'re paid to do, but for a roadcar, how much are you willing to pay for what could be zero gain at roadcar power levels? In saying that, I separated the two exhaust paths when I had a bellmouth downpipe. But it cost me my time and that was all.

/quote]

That\'s a good point. I\'m not really looking at doing extensive mods, just a few done well. For a road car/daily would a bell mouth do?

Yes. I run a bellmouth with a VF34 and I am limited on power by the turbo and spool-wise it will already furiously compressor-surge under a variety of conditions. Hence it is fair to say that the downpipe is not the limiting factor, and I have pretty much every single mod you would want to do with a VF turbo, apart from running a twisted setup.

[Pappu1]

Mrt do a split downpipe for v7

Get that if u wana get a quality unit

I have run both split and open bellmouth and couldn\'t feel any difference

If u already have a downpipe don\'t spend to doing mods that may net nothing

Spend that money on a nice intake or even a nice ebc if u wanted

Get a tune done as that will result in the best gains

What mods have u got on the car at the moment

[Guest]

Spend money on a tune or for exhaust 1.75" up pipe w/o factory flexi restriction and 3" TB.

[alex_nzl]

 SP00N said:

Mrt do a split downpipe for v7

Get that if u wana get a quality unit

I have run both split and open bellmouth and couldn\'t feel any difference

If u already have a downpipe don\'t spend to doing mods that may net nothing

Spend that money on a nice intake or even a nice ebc if u wanted

Get a tune done as that will result in the best gains

What mods have u got on the car at the moment

I\'ve seen the MRT one on youtube, I was after something like that but considering I\'m not looking at doing extensive work on my car maybe a bell mouth will be okay.

Looking at putting in a boost controller after the down pipe and then getting a tune. Just have a cat-back exhaust at the moment.