Split Dump + Front Pipe Or Split Dump All In One Front Pipe

[KrazyKong]

Is there a difference between a split dump pipe + front flex pipe vs a split dump and front pipe all in one?

I have a split dump pipe + front flex pipe, but due to another dodgy install, I need to have it modified to remove the horrid car virbration. Cost wise it's going to be not that much more to have a new dump and front pipe installed, thus was wondering what might be better for my car.

Other than a return flow FMIC, pod, boosted ground wire, and 3" turbo back exhaust my car is stock. However I do plan on putting in a highflow and nistune at some point. Thus I want to ask the right questions or hope I do at least about the dump and front pipes.

Is it a given to go the split dump pipe route? or are folks using non split dumps at still getting the same performance?

[GTSBoy]

Can of worms.gif

My opinion is that split dumps make sense. The good, well fabricated ones that don't have puny flanges, don't trap the wastegate flap, etc etc are a good thing. It is totally sensible to separate the nasty nasty flow from the wastegate exit away from the turbine exit flow, so that you get a better and more symmetric flow field downstream of the turbine. From a flow point of view, highly desirable.

My testing is limited to stock dump vs a split. The split improved boost threshold and reduced overall exhaust pressure drop (as evidenced by making more power). Did not compare with equivalent open dump.

Some people on here are massively against split dumps. They pray to the god of bellmouth dumps. It may be that with the bellmouths, the horrible flow conditions of the wastegate flow bashing into the turbine flow are offset by the fact the the volume of the top of the dump is simply larger. I dunno. Most of their arguments against split dumps have more to do with mechanical issues (like the wastegate flap jamming) than how fast they come on boost or max power levels.

One word of warning though. Never, ever contemplate the short split dumps that are intended to simply replace the original dump and connect to the original engine pipe. They drop the wastegate flow into the main pipe too close to the turbine exit to be of any benefit. The only split dumps that make any sense are the ones that replace the whole dump and front pipe all the way to the cat. That way the wastegate flow is dropped back in a long way down the pipe.

And why are you talking about a flex joint? I take it you're not talking about a Skyline. Some FWD shitbox? No need for a flex joint on a Skyline. Solid all the way through is fine. Flex joints are expensive and cost flow.

[KrazyKong]

I mentioned a flex joint because that's what's in my front pipe currently. I ordered it from a company selling out some stock in VIC and all they had left for the sale prices were ones with flex joints in them.

As for the dump pipe, eeek, I think mine is one of the short ones you are talking about that feeds back into the pipe right as it connects to the front pipe. I got it from the 999 Auto mob in Brisbane. Hmm sounds like I got the wrong setup then. Good thing I asked eh.

So then I need a split dump that isn't one of the short nasty ones. As for it being 2 pieces dump + front or combined, that's all I figure out now.

[wolverine]

+1 bellmouth.

Cheaper, no chance of fouling the wastegate, leaves a nice low pressure area just outside the turbine and my experience is they make a whisker more power vs name brand split dump (tested back to back with a 450hp turbo)

If you are looking down the barrel of spending more money a reasonable bellmouth will do the job.

[KrazyKong]

That's interesting wolverine, will keep that in mind.

Right now I have a horrid vibration in the car due to a mounting bracket that was welded onto the front pipe. There's no slack at all and is so tight, it's causing all kinds of rattles and noises. So I need to get that bracket taken off and mounted correctly. The system I have may be ok for what I'm going to do with the car, I was just leery of spending and paying for more time on a system that might end up being the same costs if I have it ripped out and put in a new bellmouth/split dump. Then at least I'm not throwing good money after bad, and could even recoup some costs by selling my original setup.

I'm not chasing +1hp or interested in those small kinds of margins. Rather just want a good footing so that when I go highflow and nistune, I dont have to ever come back and deal with the exhaust.

[Mitcho_7]

I has a jjr split dump/front on my r33 and the fit was not that great. Swapped it over to a bellmouth and have had no dramas. Performance wise I don't think there's much in it really.

[scotty nm35]

That's interesting wolverine, will keep that in mind.

Right now I have a horrid vibration in the car due to a mounting bracket that was welded onto the front pipe. There's no slack at all and is so tight, it's causing all kinds of rattles and noises. So I need to get that bracket taken off and mounted correctly. The system I have may be ok for what I'm going to do with the car, I was just leery of spending and paying for more time on a system that might end up being the same costs if I have it ripped out and put in a new bellmouth/split dump. Then at least I'm not throwing good money after bad, and could even recoup some costs by selling my original setup.

I'm not chasing +1hp or interested in those small kinds of margins. Rather just want a good footing so that when I go highflow and nistune, I dont have to ever come back and deal with the exhaust.

Are you in Melbourne?

Drop around, I can just cut the bracket off if you like and have a look at the quality and any issues you have.

I have found a supplier of smooth internal flex joints, they don't restrict power at all and will help save your manifold. Imagine the force your exhaust transfers through the turbo when you go through a corner hard, that's a lot of leverage.

[gotRICE?]

Mines got a GT30 hanging off it and hasnt broken anything yet Has been for over a year and many track days.

If were talking stock turbo, i think the bellmouth is just a more sensible option for simplicity. But when your talking a larger turbo (internal gate of course) when you have to have something custom made anyway, you might as well go for that extra "1hp" and get something nice made up to suit the application. Do it once..

Forgot to ask, Mounting bracket? Are you saying that the exhaust is mounted to the chassy somewhere? Just cut that off now lol. The only place it should be mounted, IF you do it at all is the block isnt it? None of mine have ever had any brackets mounted on them. Although if i was doing it again with the larger turbo id probly go the extra leg and get something mounted just to give the turbo a bit of extra support.

Edited May 23, 2012 by gotRICE?

[scotty nm35]

Mines got a GT30 hanging off it and hasnt broken anything yet Has been for over a year and many track days.

If were talking stock turbo, i think the bellmouth is just a more sensible option for simplicity. But when your talking a larger turbo (internal gate of course) when you have to have something custom made anyway, you might as well go for that extra "1hp" and get something nice made up to suit the application. Do it once..

Forgot to ask, Mounting bracket? Are you saying that the exhaust is mounted to the chassy somewhere? Just cut that off now lol. The only place it should be mounted, IF you do it at all is the block isnt it? None of mine have ever had any brackets mounted on them. Although if i was doing it again with the larger turbo id probly go the extra leg and get something mounted just to give the turbo a bit of extra support.

How many manifold studs have you broken though?

I agree, the bellmouth is easier for me to make and will flow much better until the wastegate opens, then it would depend on the internal design. They would be fairly comparable at wot if they were designed well.

[wolverine]

Scotty are you moving up to Sydney soon?

[gotRICE?]

I have broken zero manifold suds . Touch wood

[HYPED6]

Split pipe for sure. it is heavily documented that they always make more power, less lag and better fuel ecconemy.

If they were not the best then external gates would come out in exhaust housings.

End of story.

Lock thread.

[gotRICE?]

Because were all worried about fuel economy at full boost aren't we lol.

[scotty nm35]

Scotty are you moving up to Sydney soon?

No, lol. Too many crazy drivers up there.

[scotty nm35]

Split pipe for sure. it is heavily documented that they always make more power, less lag and better fuel ecconemy.

If they were not the best then external gates would come out in exhaust housings.

End of story.

Lock thread.

They do, Garrett have made quite a few external gate housings.

Split pipes are generally small in piping size, I have never seen one with 3 inch or bigger off the turbo, although I'm sure they exist.

[driftae76]

This looks like a pretty decent split dump - 3" all the way

[XKLABA]

I swear by the CES split dumps, I have the factory replacement type with matching front pipes on my 32 GTR and with 293rwkw the car has run 11.13 with stock turbos, that speaks for itself.

I am putting the comp series ones on the GT-RS powered 26/30 I'm building for my 34 GTR

[AngryRB]

i have extra brackets made up for my dump, 3 1/2inch with external gate, it was swinging and moving around, so extra brackets to the bellhousing, and to the gearbox mount and i had to hit the tunnel in to make more clearance so it wasnt hitting the body.

I dont think those split dumps are any good, the wastegate gas just goes straight into that flange separator and it ends up overboosting.