Split Pulse Gurus! Just Need An Answer.

[Daboss]

What housing and power do you currently have??

I haven't seen the combo on an RB25 myself but from what I have seen on other cars I'd go with a 1.06a/r T4 Twin scroll housing... I am guessing you have a .82a/r hot side from that spool level, so maybe shift that to around 3800-4200rpm range for a twin scroll setup with generally more torque as it builds boost and more midrange at full boost. Just a semi-educated guess...

I have a .63a/r hot side. Power level I can't really say. Just had it road tuned. So from what you are saying my spool is to laggy for a gt35r .63a/r?

[JonnoHR31]

go a .82 twin scroll, should spool the same if not a touch better than your current housing and make much better power/torque

[Daboss]

go a .82 twin scroll, should spool the same if not a touch better than your current housing and make much better power/torque

What flange type t3 or t4? Lithium said t4 1.06. I am looking for about the same spool maybe better if it can happen and about 350-380rwkw.

[JonnoHR31]

whatever suits the manifold you have. or if you can choose, go t4. .82 should do 350rwkw if everything else is up to the task

[Daboss]

whatever suits the manifold you have. or if you can choose, go t4. .82 should do 350rwkw if everything else is up to the task

Ohh ok I thought t4 would allow for more efficient exhaust gas flow. I would have to change the manifold so just wanted the best for my application.

[Daboss]

So the .82 a/r t4 flanged would be the best suited for my application?

[JonnoHR31]

it'd be my choice

[Lithium]

Twin and single scroll a/rs aren't comparable. .82 is a happy medium for open housing on a but I would personally not go anything other twin scroll 1.06 for that power level.

[GTScotT]

So gents, back to TS.

What is everyones thoughts on one gate vs two? I cant seem to make a logical decision on just how much benefit to expect from two gates.

Sure enough running two gates will eliminate the gas bleed between the two runners and will result in faster spool. However, just how much difference will it make in the real world? Well known companys like trust and HKS make single gate twin scroll manifolds.. So surely the single gate cant be THAT bad.

My logic tells me, that the passage for the gate would fill with gas and form its own pressure system allowing the mainstream of gas to flow past without bleeding between runners. Furthermore, I have the feeling this would happen fairly quickly, making the need for two gates fairly low.

An opinion or two or ten on the matter would be good... Im honestly at a loss with it and this sort of info (along with my other problem - 1JZ) is fairly hard to come by.

Look forward to seeing what is to be said.

[Lithium]

I honestly haven't seen enough first hand to be able to say for sure that there is a big difference. All the "big results" you see are twin wg, and its the way I'd go just because I like knowing its going to work - however one of my mates who swapped to twin scroll (from .95a/r single to 1a/r twin on a T04Z on a 300ZX) just changed the collector to suit the twin scroll, everything else including single wastegate remained. He made 300 or so rpm spool, more peak power, and HUGE midrange torque gains so it can't be too bad.

[DR 32R]

I have the split pulse manifold built by Kyle at 6 boost, and the split pulse turbo on order from USA, naturally i have to complete the project to find out the "real world" results in spool and response. I'm a split pulse believer, but will wait and see on my own car.

[Lithium]

So which turbo / turbine housing combo did you go?

[GTScotT]

I have the split pulse manifold built by Kyle at 6 boost, and the split pulse turbo on order from USA, naturally i have to complete the project to find out the "real world" results in spool and response. I'm a split pulse believer, but will wait and see on my own car.

I hate seen a 6boob with 1 gate on it before also. Does yours have 1 gate or 2?

[Lithium]

My logic tells me, that the passage for the gate would fill with gas and form its own pressure system allowing the mainstream of gas to flow past without bleeding between runners. Furthermore, I have the feeling this would happen fairly quickly, making the need for two gates fairly low

Because you said this much and obviously like to think about the whys of the different ways of doing things... don't forget that the gases at this point in the system are not as simple as a fluid flow. There are high pressure pulses and there are gaps between them, hell the reason people call race manifolds extractors is a reflection of the fact you are effectively playing with acoustic tuning.

I assume you have heard of the use of balance pipes on V8 exhaust systems...

[discopotato03]

I don't think too many people worry about acoustic tuning with turbos in exhaust systems , the drama is the turbine housing nozzle and turbine blades just about nullify and reverse pressure waves .

For a twin scroll system to give its very best you need two waste gates because its the only way to keep both halves of the system truly isolated . I think part of the issue is that you need a fair bit of waste gate area to get good boost control because you're trying to vent gas that's generally at a lower pressure than in a single scroll system .

Expensive to do and well worth comparing the costs to a larger engine with a simpler single scroll system .

A .

[Lithium]

I don't think too many people worry about acoustic tuning with turbos in exhaust systems , the drama is the turbine housing nozzle and turbine blades just about nullify and reverse pressure waves .

Sorry, I didn't mean getting into the full on tuning of it all - more the fact that because of the fact you have pressure waves bouncing around etc there is could be more likelyhood of contamination between the two sides than he was speculating. I wouldn't make a certain call on it, just stating that its one aspect to possibly consider... the fact that twin scroll makes a substantial difference over single scroll suggest that the science is certainly more than just a bunch of pipes pointing exhaust flow generally in the direction of a turbine wheel.

[DR 32R]

I hate seen a 6boob with 1 gate on it before also. Does yours have 1 gate or 2?

So far, as I understand it GT35 twin scroll turbo, split pulse manifold with twin 38mm gates.

[DR 32R]

So which turbo / turbine housing combo did you go?

GT35 twin scroll, don't actually know the housing, but thought I'd prefer twin scroll for any GT35. This is a real time (slow) real project, and I'll just wear the results.