The Split Pulse Turbocharger Thread

[PSI Parts]

I have been discussing my set-up with Geoff and it looks like we are going to get their Manifold, T4 TS GT3582R 1.06AR and 2 x Tial 38mm MVS Wastegates. Although he is also having a fair bit of luck with the 1.15 a/r S200SX 75-70 Borgwarner (which is around the $900 mark compared to the $1350 of the Garrett), but I'm unsure of their upper power limits and leaning towards the Garrett.

Adrian - Do you have the test results of the RB25 at all? If not I'll ask Geoff.

[PSI Parts]

A reply I got from Geoff from Full Race. Thought it might be helpful for some.

-the borgwarner turbos are exceptional performers with unmatched durability and value. We have had great results, and not one turbo failure to date. not to say we wont have any go bad - but thus far out of all the BWs weve sold, there hasnt been a single failure. beyond this, the BW engineers are great to work with and will support us and our customers far more than any other turbo mfg

-the engine we saw excellent results with the S200SX was an evo9 with hks 272 cams, otherwise stock engine. I also have received an email from a 1JZ customer who used this turbo and was very happy. It seems that the important part being 1.15 a/r - not the 1.22 a/r we previously recommended. This turbo maxxes out around 500whp, maybe up to 520hp, i dont see 600hp being possible

-e85 is a wonderful fuel, and highly recommended. I use it in my personal cars with great results and the only negative being it is tough to get in consistent formulations. The big benefit of powerband and spool gains is without a doubt worthwhile

-i spent the better part of last week swapping turbos on my RB26, i will go to the dyno shop early next week and get a good overlay showing the different turbos response on my engine. The models i tested were S300SX 88-75 1.00 a/r (690whp at 24psi) and S300P 83-74 in .80 a/r and 1.00 a/r

if your goal is 500whp, i strongly suggest you consider the 83-75 1.00 a/r

[Dale FZ1]

So are you going with the GT3582, or BW S200SX?

And what engine capacity and spec is the system being applied to?

Definitely interested to follow this one.

I'd reviewed the Airwerks catalogue earlier, and concluded that BW offers a great product range and priced so you've just got to look at them. They've smartened up their act on the performance aftermarket turbo scene, but some of the technical specs aren't presented logically. Mix/matching metric and imperial measurements is annoying, and their maps aren't extensive. The broad range of housing options is just what is needed, and for anyone with the funds and performance goals requiring an EW setup, you should be able to get an unbeatable result.

Interestingly for virtually any nominal hp range, the BW product runs much larger turbine specs than Garrett.

Given the value of their OE supply contracts I'm not surprised that Full Race haven't experienced any failures with BW.

[juggernaut1]

If going for the 200sx split pulse I would go the T3 version.....the T4 version has a smaller turbine inducer and exducer for some (ill) logical reason yet the T4 is supposed to be rated for more hp?

[2lazy]

Bigger a/r?

[Dale FZ1]

If going for the 200sx split pulse I would go the T3 version.....the T4 version has a smaller turbine inducer and exducer for some (ill) logical reason yet the T4 is supposed to be rated for more hp?

My specs sheets say that the biggest version of the S200 and S200SX are both nominally rated at 580hp. The compressor map for the S200 says it can flow marginally more, but that is at PR >3.00 so you're looking at very high boost levels to achieve that.

For me the S200SX is possibly the better with smaller sizes in both compressor and turbine rotor, hopefully pointing towards quicker spool rates as the rotating assembly should have lower levels of inertia. Speculation of course, until you could see the units side by side with housings off.

The other things that make the T4 patterned S200SX more attractive are the 3 inch comp inlet = more room for inlet plumbing (is 4.25" piping easy to come by??), and the V band outlet on the turbine housing.

Either way it appears you'd be spoiled for choice.

[PSI Parts]

I've actually decided to go for the Garret.

I know this can be seen as the easy choice, however there still isn't enough data of the BW on RB's for me to throw some cash at it without seeing some figures first. I've already decided to run 9.5:1 (Custom CP pistons) and the Full Race Manifold/MVS gate set-up (first on a Aussie RB25?) so it should be interesting to compare these results to other standard compression (8.5:1) engines running a single pulse GT35. My bet is marginal spool differences on the dyno, however much better response on the track, which is where I want it to count. This engine should be pieced together in the next 2 months.

I'm not fussed about the inlet piping, as I will most likely reduce the intake pipe to 3" as that is what my GReddy air filter has.

[discopotato03]

PSI just to add to the mix apparently Garrett sells a hybrid GT35R being the 68mm GT35 turbine but with the compressor end of the GT3076R - 76.2mm GT37 comp in 56 trim .

It may pay to run that combination past Geoff because being an Australian XT6 Typhoon option they may not know about them in the US .

In the end I guess it comes down to how much crank power you're aiming for and what sort of power delivery you want it to have .

Cheers A .

[Lithium]

Awesome, will be interesting to see how it goes PSI Parts- what displacement are you going to be running again? I approve of all the options I have looked at, for what its worth on a 3litre I am completely sold on the Borg Warner S300SX 83-75. I'm not convinced it will be any better than a GT35R performance wise, but price and also having a turbo which sound like a fighter jet I have to confess to being big attractions.

I have no doubt that spool would be more than sufficient, and they clearly flow nice. If you're willing to spend the extra, the 1.06TS GT35R is an amazing piece of kit - have experienced one first hand in a "2.4litre" EVO and the thing is a complete animal from surprisingly low revs.

[juggernaut1]

For your reference .....twin scroll T4 GT35 1.06 rear on RB26 at 20psi.

Edited April 30, 2010 by juggernaut1

[Lithium]

Wow, that looks laggy

[Dale FZ1]

For your reference .....twin scroll T4 GT35 1.06 rear on RB26 at 20psi.

Ok so give us a bit more detail on the engine internals and manifolding please.

470rwhp @ 20psi is respectable, no doubt about it. But the shape of the curves makes me wonder, when split pulse is supposed to help yield better spool with the potential for freer breathing up top too.

Scaling on a dyno sheet can skew how the curves look, but to me that torque curve looks overly steep (concaved) as though the turbo is slow to spool, and then doesn't hold max torque long enough. I'd just have thought a RB26 would keep making torque at high revs, especially if the turbo doesn't appear super fast to come on.

Getting beyond my area of direct knowledge, over time I've seen several RB25s producing similar outcomes with single scroll GT3582 0.82 turbine. Whether they drive differently is the litmus test.

^^ All comments above are free to be rebutted, particularly if that machine outperforms a similar spec conventional single scroll setup on the road. My interest has always lay with the practical outcome, not the dyno sheet.

[juggernaut1]

Unfortunately I can't offer any more details on the setup as I plucked it from another forum and the details were scant. I only posted what details I knew.

Here's the original thread link.

http://www.nissanroadracing.com/showthread...1055&page=3

Edited April 30, 2010 by juggernaut1

[juggernaut1]

I think I found more of the details and pics on another forum....it appears as though he is using a Greddy exhaust manifold (refer post 1 & 6) So in summary it sounds like a twin scroll housing on a single scroll/single gate exhaust manifold....lol?

http://www.freshalloy.com/forums/showthrea...ght=twin+scroll

Edited April 30, 2010 by juggernaut1

[Dale FZ1]

Looking at the Nissanroadracing.com thread, that owner said this:

the shop tuned an rb26 z32 prior to mine with a T3 .82 35r, single scroll. i believe also a stock head with drop in cams, and also on pump gas 93 octane. the tuner said the t3 .82 was spooling faster and his psi overlay was shifted to the left of mine without any mid range overlap. it would have made sense for the TS and SS differences to show somewhere in the midrange, but they did not. the .82 SS looked to be a better choice. that was a bit of a surprise to me, but there are just too many factors to make a solid comparison

Looking a bit harder, he also appears to be running a split pulse manifold but with a single / undivided wastegate vent. Perhaps he doesn't have the Full Monty from a split pulse system perspective, but it's close enough to warrant a good viewing.

I'd really like to see Full Race post the back to back testing and establish what advantages the complete split pulse system offers over single scroll. Hopefully they were forthcoming in earlier communiques with Adrian?

[Rolls]

That dyno does look quite laggy for only 470hp. I would be expecting 600+ for that sort of lag especially when its loaded up on a dyno, on the street is going to be even worse.

[PSI Parts]

I'll be running the standard RB25 stroke.

If anyone is willing to supply a SS GT35R and manifold, I MAY look into doing some testing when this engine is dyno'd.

[discopotato03]

It may pay to do some searches on Geoff's "R14" which was a USDM S14 240SX converted to basically most of a GTRs drive train . I seem to remember him trying a few TS turbo combinations on his RB26 in that case , was a while back though .

A .

[PSI Parts]

Just got this from Geoff's latest testing on his RB26 with the BW turbos.

this compares the S300P 0.80 a/r to the S300SX w/ 88mm compressor 1.00 a/r

pink:S300SX 88-75 1.00 a/r 19psi

blue: S300SX 88-75 1.00 a/r 19psi (same as above) with slight cam gear adjustment (advanced to +3 intake from +2, and added a little fuel during spoolup)

orange: 0.80 a/r S300P, custom machined housing - 17.5psi tapering to 16psi

green: 0.80 a/r S300P, custom machined housing - 20.5psi tapering to 17.5psi

after is all done, the amount of work I went through for this, i think the 83-75 would have provided virtually the same powerband. FWIW here is a friends twinscroll STI with 83-75 1.00 a/r and 2.65L stroker:

[PSI Parts]

PSI just to add to the mix apparently Garrett sells a hybrid GT35R being the 68mm GT35 turbine but with the compressor end of the GT3076R - 76.2mm GT37 comp in 56 trim .

It may pay to run that combination past Geoff because being an Australian XT6 Typhoon option they may not know about them in the US .

In the end I guess it comes down to how much crank power you're aiming for and what sort of power delivery you want it to have .

Cheers A .

I will do that, however I'm not sure what my chances are of buying the rear housing alone if I was to use the typhoon spec compressor. As I understand it, there are no GT35 TS exhaust housings in the country. However I have seen a TS exhaust housing on GCG's website somewhere but unsure of the specs.