Dump Pipes

[R34P3R]

Hey guy i'm wondering what the difference between a split dump and bellmouth one is. Which style would be better aswell?

I've tried searching but keep getting an error 3312 and this is over the course of an hour.

Thanks for you time

Sunny

[The Dan]

Error 3312

[The Dan]

But seriously, each to their own. Some people will tell you there is no difference, some will say it makes a massive difference, 99% of them probably haven't gone from one to the other on the exact same car so aren't really fit to comment.

Personally, I don't think there is a difference as with an internal gate you are fairly restricted in the power you can make anyway so flow at that point is not really a concern. Get whatever is cheapest and/or the most shiney.

[MrStabby]

Theoretically split dumps should work better, but that hasnt been confirmed in the real world and there doesnt even seem to be anecdotal evidence to support it either. Also you need to take more care with split dumps to verify everything fits well, in particular that the wastegate flapper doesnt catch.

[Birds]

Theoretically split dumps should work better, but that hasnt been confirmed in the real world and there doesnt even seem to be anecdotal evidence to support it either. Also you need to take more care with split dumps to verify everything fits well, in particular that the wastegate flapper doesnt catch.

I agree...

I recently bought a cheap split dump and the wastegate flapper was catching like a bitch. Plus it's travel has been severely affected too, giving me other problems. I think with the more expensive split dumps you shouldn't have any trouble, it's just the cheaper ones that have poor weld jobs and pipe allignment. Gonna try a JJR system next and hopefully that bolts up no hassles.

I think all the split dump will do is alter the sound of the exhaust a bit...

[Beer Baron]

bell mouth is superior. simple.

split dumps on small internal gate turbos are a big compromise as you end up with 2 very small pipes. and they then merge almost straight away anyway.

also the claim of improved spool up is bullshit. how can they possibly improve spool up? while the turbo is spooling up the wastegate is CLOSED so the split is doing nothing. split or not split there is no wastegate gass mixing with turbine gass until the gate is open by which point the turbo is at or very near target boost. the bell mouth (well a good one) gives you greater overall area, gives greater flow, will make more power, and response (allows the gas to expand quickly) and you have no risk of any of the stupid problems people get with the cheap split dumps with wastegate flaps fouling etc.

[R31Nismoid]

Personally, I don't think there is a difference as with an internal gate you are fairly restricted in the power you can make anyway so flow at that point is not really a concern. Get whatever is cheapest and/or the most shiney.

Agreed

Although i would have said go with the one that is best made (which doesn't necessarily mean the most expensive)...

Having to change out a dump because it was a cheap ebay special and the welds have split is definitely not cool

[Brandon]

Dont mean to hijack the thread but what would the HKS dumps for GTR be? Will it be logical to change the stock one for them (not changing turbos at the same time)?

The reason for asking is if there' no real/significant gain, I wouldnt be putting them on (only after around 300awkw and no more).

[MrStabby]

also the claim of improved spool up is bullshit. how can they possibly improve spool up? while the turbo is spooling up the wastegate is CLOSED so the split is doing nothing. split or not split there is no wastegate gass mixing with turbine gass until the gate is open by which point the turbo is at or very near target boost. the bell mouth (well a good one) gives you greater overall area, gives greater flow, will make more power, and response (allows the gas to expand quickly) and you have no risk of any of the stupid problems people get with the cheap split dumps with wastegate flaps fouling etc.

Big call to say the theory is bullshit if you havent studied fluid dynamics....(my guess is you havent :-)

Consider the flow path from the turbine - its actually better in a split dump, especially when the wastegate is closed, so theoretically will present higher pressure difference across the turbine, and therefore it will spool better. The fact that the bellmouth is "big" is not beneficial, it causes more turbulence, which is more restrictive than a less turbulent path. When the wastegage opens the difference is less pronounced. Of course everything i'm saying is a massive oversimplification as well. Back to back dyno (or CFD) is the only way to KNOW.

[R34P3R]

ok thanks for clearing it up