So Ted what exactly did you gain spool wise when making this switch?

What about peak torque and hp?

And why no graphs posted?

I always thought that moving to twin scroll sacrificed some top end... is that not true?

 

If i remember correctly my setups spooled as follows... (Flashed Stock ECU)

35r stock 2.0 - 4900 Full Boost
35r 2.3 - 4500 Full Boost
37r 2.3 - 5100 Full Boost

FYI - I just added Buschur 272 Cams which seem to have increased lag a bit....

Good Luck...

 

1000 rpm sooner jesus, looks like i will need a new turbo and manifold !!! damn you Ted, oh and i will get my dyno graph on here when i have access to it, it is in SD, and i'm in phx. oh and i doo hit full boost mid five but it takes astplit second from when it starts to spool and when it is spooled, some people are so worried about lag it is way over rated, ever been in a 1000 whp supra that is lag, 37r is smooth sailing.

 

Can we all agree if you say "full boost" for a GT30 turbo or larger you should be meaning about 34 PSI?

If less than that, then I think you should note what mild boost target you are referring to when you say "full".

 

That is dead on to all the results I have had with those turbos. Except I had full boost on the 35r on my 2.4 100rpm sooner!

 

The car is so much more responsive that it doesn't even feel like the same car, much less the same car with a larger turbo. This isn't something that comes across on the dyno. The difference is enough to convince me to never again use anything but a divided hotside, period. I've driven Drifto's divided GT3076R, and the result is the same.


Something amiss in the motor and clutch gone. No point.


I used to wonder the same thing, but it appears not to be the case. In fact, just the opposite seems to be true.

 

HEY "Ted" One question, does making the 67 spool faster limit its peak hp capabilities, I think it would. So lets say the 67mm makes 40-60 more peak hp than a 35r tuned by an excellent tuner. Does making the 67mm spool faster close that gap to something closer to say 20-30 mor hp. If so I think I will just continue to wait for the HTA 35R from Buschur.

Thanks for all the info everyone, this has been a very imformative thread for all!

 

Did you read what he wrote? He said that, if anything, the divided setup seems to make MORE top-end.

 

Geoff from full-race also believes that a good twin scroll will make more top-end.

If you don't believe Geoff or TedB, you don't believe ****.

Scorke

 

I would say 600RPM - 800RPM with an open inlet on the turbine housing. The average good tuner. You're starting to sound like someone ...

You were making 10.17lbs by 4234RPM. 14.20lbs by 4492RPM. 17.13lbs by 4738. That was with an 11.5:1 a:f

I can get twin scroll turbine housings for the P trim turbine wheel. We're going to see where we get full boost on X's car with the divided top mount exhaust manifold and twin scroll turbine housing

He not only believes but has proved it on a couple applications

Where you see boost is dependant upon a lot of things. To each their own. Everyone is different as far as what they think is better

 

More boost earlier is better, regardless of who you are, as long as less boost later isn't caused by it.

Scorke

 

say mate, if u don't mind, i'd pay to get a ride in ur Evo...shoot me a PM if you're cool about it

/off topic.

 

Ted, there are some things about your experience that should be noted. Twin scroll exhaust housings act different than open housings. They are indeed more restrictive than a single scroll housing. Splitting the exhaust into channels in a spot were it is being squeezed down already is definitely a restriction. Thats why you have to choose a larger A/R when switching to twin scroll. A 70 open will make more power that a 84 divided. This is common knowledge that has been around for 20 years. Also on the same point since the A/R has to be larger when switching to twin scroll its impossible to know if your turbo response improvement was from landing a more suitable A/R for the setup. You could switch from a laggy 82 to a better suited 63 and get the same back to back feel you are describing. "I will never use an 82 again, The 63 is so much more responsive" I have a friend here locally that switched the hotside on his 10 second 140mph VW bug 20 years ago. He switched from open t4 70 to a divided t4 84. The engined spooled 700 rpm faster. The header was a 4 into 1 with no divider. So the advantage of twin scroll housing in this case has nothing to do with keeping pulses divided but simply landing the correct A/R for the setup.

Twin scroll housings should be left out of this discussion anyway. They have nothing to do with how the 35r spools compared to a 37r.

 

To quote a Garrett engineer - "Twin scrolls often flow a hair less at equivalent a/r as boundary layer effects come into play.

Efficiency-wise, twin scrolls take a small hit due to increased 'wetted' surface area imposed by the divider wall. However, this is way more than offset by the vastly superior pulse conversion you get.

Edit: I should probably clarify that last bit. Twin scroll turbines, as mapped on a gas stand (steady state conditions) will exhibit a slight drop in efficiency compared to an otherwise equivalent non-divided housing. On-engine, however, is much different. The flow conditions are highly unsteady. The ability of a twin scroll to utilize the pulsing, unsteady flow of the exhaust exiting the engine gives it a huge bump in "apparent" efficiency, and ultimately spools up the turbine that much sooner.

Twinscrolls also isolate the cylinders' blowdown events much better than a non-divided housing, preventing the exhausting cylinder's very high PEAK exhaust manifold pressures from finding their way into the other cylinder on its overlap period. "

 

But . . . A/R is only a static ratio, nothing more. It doesn't give any indication as to the actual volume of the housing. In my case, the T4 housing I'm using is considerably larger than anything T3, nevermind the A/R. This being the case, I was reluctant to jump into something too large - not right away, anyway.


The twin scroll setup eliminates the dramatic transition from the primary tube diameter into a large open flange. Abrupt changes like this reduce pulse energy.