That (from what I hear) is the main benefit of the TS. I am interested in seeing a TRUE A/B comparison of the two turbine housings run. I honestly dont know how you would go about doing a fair test seeing as the headers would be different (one open outlet and one divided outlet).

IMO, its hard for me to see how a turbine housing that improves spool will not hurt top end performance. It seems to me it would be a lot like putting a smaller A/R conventional turbine housing on. Then add the turbulence created by TWO WG feed holes in the side of the collector. You also have twice the wall surface in the turbine to slow the exhaust down.

I am pretty sure a lot of the benefits seen in a TS setup is due to better headers being installed. I also believe that a divided outlet header is a band-aid for a poorly designed unequal length header. Basically you now have half the chance that exhaust pulses will interfere with each other.

In the end, the main thing I have been trying to point out is that it is far more important to improve power in the RPM range you will be USING.

 

I was directed in the other thread to look for threads on 240sx forums where people were touting great advantages of the TS.

The one thread I found showed a dyno chart with later spool with the TS but a significant increase in mid range (40whp) and the same power up top on an SR powered 240sx.

The funny thing about this thread was that the comparisons were done 1 year apart. The header was changed from an SS Autochrome to a custom built divided outlet header. The turbo was changed completely (not just the turbine housing) and I believe the turbo was different (3071 to a 3074 or something like that) The ROM tune chip in the ECU was changed because the car would not idle on the chip that they used in the original dyno session. The drive shaft was changed to an aluminum one from a steel one. Race gas was in the tank for the twin scroll. Basically, there was just no possible way to compare the two equally. Nearly everybody in the thread commented on how awesome it was that 40 whp was gained JUST by swapping to a TS...... Am I wrong for being a little skeptical?

 

Droopy - Why do you think OEMs use twin scroll? Why is every large Garrett TS? Surely companies that spend millions of dollars on R&D wouldn't also waste money building something that added complexity and cost without benefit.

It amazes me that anyone could doubt the benefit of TS considering there are probably 6 different OEMs using TS turbo systems. But hey, what do a group of guys spending billions of dollars on research know.

 

Once again. OEM designs for how they want the car to preform STOCK! We are NOT keeping these cars stock. We do NOT want a stock style power band. Stock the cars have cast manifolds.. why do we put tubular manifolds on??? Stock turbos have internal WGs. why do we change to external? Your argument doesnt work here. What OEM does for OEM applications does not necessarily work for the performance industry.

My guess is that the stock TS setup separates poor timed exhaust pulses from an unequal length cast manifold. This is the most likely benefit IMO.

Why did Precision Turbo take the time and spend the money to cast an open turbine housing for the large GT series turbos?

Why did Tial spend the time and money to cast an open turbine housing for the large GT series turbos?

 

You know why the OEMs do it. They do it to improve throttle response and spool up. You also know why Tial and PT built the housings. When making 800 plus whp, an open volute is preferred. However, that isn't the power level most of us are shooting for.

I noticed you didn't make any comments on the 240 guy cutting 2 seconds off his track time. IIRC, it was a good a/b test that showed some pretty impressive benefits.

I think it's time to just let this thread die. You've made your opinion clear and there's nothing further to be gained with this discussion. The results will be out there for us all to see soon enough.

 

I could not find that thread anywhere. A link would really help.

 

We are not talking about OEM parts here. If Mitsubishi designed their cast manifold so well then just bolt up a green and call it a day. Until someone can HONESTLY prove that twin scroll is so much better I'm still going to stick with what has worked awesome thusfar!