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Why twin scroll and internal wastegate doesn't work?

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95burgundyesi

15+ Year Contributor
816
9
Feb 8, 2006
Rockford, Illinois
Out of curiosity I have been searching to find a concrete answer or example why turbos ca be ran in twin scroll on say a factory hx35 truck, but will not properly work on a dsm that ran same set up. What would boost control be like?

I know nobody does it, I am just left wondering who has done it, and what was the negative result.
 
Every EVO sold in this country has been twin scroll and internally gated, and many people have adapted those turbos to DSMs (stock and larger). The Borg EFRs have twin scroll internal options. People have used Holsets with the twin scroll internal setups on DSMs. You don't see it much because it's a lot of work to adapt an EVO frame turbo, and anything T3 or T4 usually uses a manifold that's already got gate flanges, so you'd need a custom manifold fabbed.
 
RevShift sold a twin scroll manifold for a DSM designed to work with an internally gated Evo turbo. A quick look at their site I don't see it anymore but I'm sure you could contact them and have one built, I want to say they were around $700.
 
The holsets internal gate only bypasses 1 volute, so essentially 2 cyl would flow more air than the rest. They would be lean and the engine would make uneven power would could cause problems
 
I just "accidentally" made 600awhp on a internally wastegated hx35w, so internal wastegate work just fine. As far as increasing Volumetric Efficiency... I don't believe there is a reasonable argument or data to support the claim an external wastegate is better. Either way there is pressure variance and flow noise.
 
I just "accidentally" made 600awhp on a internally wastegated hx35w, so internal wastegate work just fine. As far as increasing Volumetric Efficiency... I don't believe there is a reasonable argument or data to support the claim an external wastegate is better. Either way there is pressure variance and flow noise.
The amount of power you can make doesn't mean the wastegate is working properly. Boost control, and in a twin scroll, exhaust drive pressure balance are what a properly working wastegate do.
 
The amount of power you can make doesn't mean the wastegate is working properly. Boost control, and in a twin scroll, exhaust drive pressure balance are what a properly working wastegate do.

ok. Didn't think I was challenging either of those points. Just stating internal wastegates work just fine...
 
All Evo's or other factory twin-scroll internal gates have two flappers with decent-sized wastegate holes pulling from each runner, or one large flapper with half-moon shaped holes leading to each chamber underneath.

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The HX35 housing has one flapper pulling from one runner with a dime-sized wastegate hole. It would never control boost enough on a high-boost gasoline application and, as mentioned above, two cylinders would flow different than the other two assuming you're running a true twin-scroll manifold.

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ok. Didn't think I was challenging either of those points. Just stating internal wastegates work just fine...
You were also making what...40psi? At that boost level the wastegate is barely doing anything anyway. Just because it was "done" doesn't mean it's the right thing to do....try running 20psi on your setup without creep and let us know how it works. ;)
 
You were also making what...40psi? At that boost level the wastegate is barely doing anything anyway. Just because it was "done" doesn't mean it's the right thing to do....try running 20psi on your setup without creep and let us know how it works. ;)

If I wanted 20psi... I would run... a stock turbo.
 
If I wanted 20psi... I would run... a stock turbo.
I'm sure next you'll be preaching how stock cams are ideal for all levels of power.

Not that I'm not knocking your achievement- just questioning your logic a bit. Besides- if you're using the twin-scroll turbine housing paired to a single-scroll manifold then it doesn't matter if it's pulling from one runner or not....you've essentially made a twin-scroll turbo into a single-scroll model at that point.
 
All Evo's or other factory twin-scroll internal gates have two flappers with decent-sized wastegate holes pulling from each runner, or one large flapper with half-moon shaped holes leading to each chamber underneath.

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The HX35 housing has one flapper pulling from one runner with a dime-sized wastegate hole. It would never control boost enough on a high-boost gasoline application and, as mentioned above, two cylinders would flow different than the other two assuming you're running a true twin-scroll manifold.

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On that note Justin with internal wastegated twin scrolled turbos, in each side of each scroll is there a port that by passed the turbine and flows to the wastegate opening and in that picture we are seeing the outlet of the hotside? I guess maybe a picture of the Volute/Hot side entrance area of a twin scroll internally gated turbo might work better to further explain.

Thanks
 
I'm sure I'll never find a good pic to illustrate, but yes each side of the hole goes to each side of the divided housing. May be able to see it a little better in this pic of the EFR's internal gate:

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I'm sure next you'll be preaching how stock cams are ideal for all levels of power.

Not that I'm not knocking your achievement- just questioning your logic a bit. Besides- if you're using the twin-scroll turbine housing paired to a single-scroll manifold then it doesn't matter if it's pulling from one runner or not....you've essentially made a twin-scroll turbo into a single-scroll model at that point.

I'm not trying to pick a fight. I don't think my setup is perfect or right for everyone. Truth be told it will probably blow up very soon. Cams have a place, but were not needed for my build.

My original comment was in regard to the increase VE of an external wastegate setup. This is just not supported by any science I can find other than the case studies of those who have invested interest in selling wastegates.
 
I'm sure I'll never find a good pic to illustrate, but yes each side of the hole goes to each side of the divided housing. May be able to see it a little better in this pic of the EFR's internal gate:

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Makes sense now! Thanks again
 
20psi on a stock turbo is not nearly the power of 20psi on a larger turbo. Why is PSI being compared here rather than compressor flow?

The point Jusmx was making is that you cannot run that large turbo on low boost without creep on an internal gate porting only one side of the exhaust runners.
 
^ You're also using a single-scroll manifold on a single-scroll turbo....and the wastegate hole on the HY35 and HE351 is much larger than the HX35.

If you're using a twin-scroll manifold on a twin-scroll HX35, the factory wastegate system will not be enough to control boost. If you're using a single-scroll manifold on a twin-scroll HX35, the factory wastegate system *may* control boost if you're running a high enough boost level
 
Stock cams don't ever have a place but in the scrap pile....

Some guys use to drill a hole through over to the other volute on the HX turbos. Kind of negates the whole twin scroll thing.
 
Haha it seems like the nordicsaab guy isn't having too much trouble making power with stock cams, especially considering that is the highest dyno hx35 here.

The wastegate hole is the same size on an hy as an hx. I have them side by side at home.

I'm not sold that that the single internal gate wounldn't control boost on a t/s setup. It would probably cause one pair to run a bit leaner than others. but really how much. On an 8:1 motor, going from a 1:1 boost to exhaust pressure ratio to a 1:2 causes a loss of 10% ve. I strongly doubt that the the two pairs would be farther apart than that. I might try it for shits and giggles.
 
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