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Discussion Starter #1
Okay, the question is about the negative and positive affects of using a Turbo with a divided twin scroll exhaust housing with a regular undivided flange turbo manifold.


I would like to try out the new GT4276R or the GT4580R. However, they come with a divided turbine housing. The GT4580R doesn't have an undivided housing.


I am curious as how the performance would be affect if I mounted one of these to my undivided T4 manifold. I love my manifold and don't want to get rid of it but I want to see more power than what my 76GTS can deliver without nitrous.

I would think that the benefit of spool would not be there but I would also think that a downfall would be that the center of the dvided housing on the turbine would create more backpressure in the manifold reducing boost efficiency.

Any thoughts on this?
 

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There should be no positive or negative effects of running the divided housing on a non-divided manifold. The center divided should not cause any major issues or degradation in turbine efficiency.
 

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I have found the exact opposite. I build turbo manifolds for a living, and have seen as much as 76rwhp and 1000rpm faster spool from a turbo 6 cylinder running mid 9's(i'm in australia, not US) and the car picked up 7mph and 6/10's at the track by changing nothing on the car ther than a split housing on an open manifold to a open housing.

I have also just finished building a manifold for a local drag car(RB30-3litre nissan single cam) that picked yp 6-800rpm of spool, and they have a turbo tach(sensor to measure shaft RPM) and with there open manifold and split housing they were seeing turbo shaft speed of 2000-2500rpm at 1200rpm idle, which has now increased to 5500-6000rpm at 1200rpm idle. I'd stay right the hell away from a split turbine on an open manifold!!!


Cheers..................................6BOOST
 

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Discussion Starter #5
I have found the exact opposite. I build turbo manifolds for a living, and have seen as much as 76rwhp and 1000rpm faster spool from a turbo 6 cylinder running mid 9's(i'm in australia, not US) and the car picked up 7mph and 6/10's at the track by changing nothing on the car ther than a split housing on an open manifold to a open housing.

I have also just finished building a manifold for a local drag car(RB30-3litre nissan single cam) that picked yp 6-800rpm of spool, and they have a turbo tach(sensor to measure shaft RPM) and with there open manifold and split housing they were seeing turbo shaft speed of 2000-2500rpm at 1200rpm idle, which has now increased to 5500-6000rpm at 1200rpm idle. I'd stay right the hell away from a split turbine on an open manifold!!!


Cheers..................................6BOOST
6boost. Well, I ask this as I cannot find a open housing for a GT4276R turbo on the 1.01 A/R.
 

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I'd like to see proof of 6-800rpm better spool and big power gains from switching to divided mani's and turbos....
 

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This is a test Full-Race did. It was on an SR20DET



The solid line is with the twinscroll 3071R, the dotted line is with the singlescroll 3076R. There is about a 20whp/wtq gain by 2000rpm, a 30whp/wtq gain by 3000rpm, and a 100whp/wtq gain by 4000rpm. It makes 200 ft lbs @ 3600 rpm, 200hp at 4100 rpm, 400ftlbs at 4600 rpm and 400hp at 5400rpm
Even with the Honda's. With a good design divided collector exhaust manifold (Full-Race, Neukin) they're making full boost quicker than similar open collector exhaust manifold setups. GT42R's making full boost by 5800RPM when other's are making it at 6500RPM. I personally have no back to back data :(
 

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Discussion Starter #10
That looks like more of a power band shift instead of gains. I wonder how a divided manifold would perform with larger turbos with larger turbine housings and how it affects the top end.
 

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19in 795R HRE's FTW....
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We've all seen the FR stuff and 4 cylinder claims. I'd like to see something on a 6 cylinder car mainly a SUPRA since this discussion pertains to Toyota Supras.
 

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We've all seen the FR stuff and 4 cylinder claims. I'd like to see something on a 6 cylinder car mainly a SUPRA since this discussion pertains to Toyota Supras.
I agree. I was just posting the only public comparison I have seen
 

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imo, they are the most beautiful and best designed single scroll turbine housings most anyone has ever seen (including competing turbo mfgers). Unfortunatley, they are single scroll so other than the convenience of a vband, eliminating the possibility of nuts/bolts loosening and providing slight performance increases, they still wont be able to touch the potential of a twinscroll single turbo (unless you go twins with 2 tial turbos..)
 

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That looks like more of a power band shift instead of gains. I wonder how a divided manifold would perform with larger turbos with larger turbine housings and how it affects the top end.
when you pair a properly designed twinscroll manifold with an optimized twinscroll turbo, you can run huge turbine housings and still have great spool. If you ran an A/R that was this big on a undivided setup it would laggggg.

Sertan gets 30 psi by 5000 rpm on an 80mm turbo and he is using a 1.28 A/R.

If you are planning on using that 1.01 on your turbo, it wont allow you to get the spool you want (becuase the housing is too big for low rpm) and it is too small of a turbine housing to get the top end power you want (because the housing is too small for high rpm).
 

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I will add to my previous comment and clarify that I have no problems with wither split or single entry manifolds as such, or turbochargers for that matter. The simple fact is that you should not run a split turbine on an open manifold. You can run open/open, split/split, or even a split manifold with an open housing is fine. When you run a split turbine on an open collector, gas flow, especially when hot and turbulent doesn't divide evenly, or calmly into the split housing when its swirling around in an open collector, and we have done some testing with a fog machine on the flow bench and perspex on the side of the collector to watch through, put simply, your loosing power, and spool.


For the whole split V single manifold debate, I personally have found little difference on anything up to a GT42R turbocharger. Wehave a few customers with stock internal 2J's that make full boost at 4800-4900rpm with a GT4276 and are using the T6 footprint 1.01 rear housing. With the smaller T4 footprint housing this would probably drop another 100rpm. I haven't done any back to back testing with an open manifold on this big a turbocharger, but with smaller T66 style turbo's and my 6 into 1 merge collector, we have seen the same spool rpm and more top end power from using a single entry design over a split pulse setup.

I will say however that Geoff at full race builds both types of manifolds, single and split, and has nothing to gain it telling you that one works better than the other, so if his testing has led to those findings, rather than question it, possibly ask yourself why he would make that statement when he could easily suppy you with either.........

Cheers..............................6BOOST
 

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As far as I am aware, and judging by looking at their website, they make single entry and divided yeah?? So where is the question as to why they use divided?? They use both???

6BOOST
 
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