True Twin Scroll Turbo & Manifold Design Discussion

[Dose Pipe Sutututu]

I'll try to minimise on the ramble as much as possible.

I've notice these days on the markets there are a few options for twin scroll turbos for the humble RBs, but what I've notice is that the manifold choices available which sometimes confuses me on what the best possible setup is.

1. Manifolds that group Cylinders 123 and 456 together and have 1x external wastegate mount (not true twin scroll manifold as the exhaust pressure clashes at the collector -> gate mount)

2. Manifolds that group Cylinders 123 and 456 together and have 2x external wastegate mount (true twin scroll manifold, separate gas flow for grouped cylinders, mimising exhaust back pressure )

3. Manifolds that group Cylinders 123 and 456 and have no gate mount, makes use of the turbo's waste gate

Imagine the previous with external waste gates blocked off & a turbo like the below from a WRX:

Point 1, the purpose of a twin scroll manifold is to purely group the exhaust gases so that there is less exhaust back pressure & chances of other post fired cylinders sucking back the exhaust gases. If the collector merges the 2x groups, is there really a point in that manifold might as well just have a 6 to 1 collector instead of a split collector

Point 2: Ideally the right setup, but the most expensive and the most complicated (usually A/C lines are removed etc.)

Point 3: The V Band clamp on the housing would eliminate the need to run 2x gates and make the manifold more simple, I've seen weldies here but not the off the shelf kit as so.

Now, I like the ideal of Point 3, but I have yet to see an off the shelf turbo with such housing with a V Band clamp on it, I have see people weld them on, but that's another cost to add. i prefer off the shelf kits because of cost and aesthetics. With Point 3 what are the Cons to it? At the moment I only see Pros to it because:

1. No need cut and shut turbo exhause housing
2. True twin scroll, exhaust gases from cylinder 123 and 456 ever only meet in the exhaust housing
3. Looks more "stock" (I'm ready to cop ccriticism on this)
4. Minimises pipe work, ultimately leads to a nicer setup.

Ideally, what setup would yield the best response and torque?

[GTSBoy]

Well, maybe you're a little off base. It's not about "back pressure". Grouping the pulses together is literally about grouping the pulses together. There is an even spread of 3 pulses in each group, separated by the same numbers of degrees of rotation. This gives a slightly better response by nozzling each group separately onto the turbine.

These pulses are not just static pressure. They are also a burst of gas travelling at rather high speed. There is a lot of velocity pressure involved. So realistically, for any given twin scroll manifold that had just the one wastegate offtake, as long as the wastegate offtake from each half of the manifold was not directly connected to each other (ie ideally if there were separate short pipes from each half that merged together where the wastegate mounts) then the pulses are still going to travel direct to the turbine as required.

And that is exactly what your top photo shows, and that is perfectly fine with me.

You have to remember that there are two operating modes here. 1) The engine is not on boost yet. The wastegate(s) is(are) closed. All the flow is twoards the turbine. The pulses will travel past the wastegate offtakes. Maybe there'll be some leakage of each pulse via the wastegate connection to the other group of three, but it won't be heaps. 2) The engine is on boost. When on boost the exhaust manifold pressure is pretty high and some of the gas is always making the turn to flow towards the wastegate. The exhaust pulses now have a lot more velocity energy and will still travel towards the turbine, and a portion of gas will flow to the wastegate. That flow towards the wastegate will have its own velocity pressure, and as the direction of that flow is towards the wastegate itself, there will be only a small amount of "leakage" back towards the other group of 3 from each pulse.

I simply wouldn't worry about it. I'm sure that a true double wastegate design is the best overall, but the margin is probably reasonably small.

[The Dan]

Weld wastegate pipe onto turbine housing and have no gate pipe off the manifold. Better response, more power, end story

[Roy]

I have my own thoughts on how to mount a wastegate. Will be poutting it to test soon and hopefully will work waaay much better then the current 6boost-Turbosmart arrangment

[Dose Pipe Sutututu]

Weld wastegate pipe onto turbine housing and have no gate pipe off the manifold. Better response, more power, end story

That was what I was thinking, as per Point 3. That 3076 for a WRX has a V Band clamp on the exhaust housing for an external gate. Nice and clean setup, no need to cut and shut a $2k turbo. In saying that, I have yet to see one adapted to a RB.

[NYTSKY]

My last two turbo setups had the gate off the turbine housing, you can make it look great if you have a good fab/welder guy.

[Dose Pipe Sutututu]

My last two turbo setups had the gate off the turbine housing, you can make it look great if you have a good fab/welder guy.

heya NYTSKY, sorry I meant to say off the shelf turbo for a RB motor with a V Band clamp as below. I have seen a several setups where wastegates mounts are welded to the turbine housing. I have yet to see anything below used on a RB motor.

[gotRICE?]

I have my own thoughts on how to mount a wastegate. Will be poutting it to test soon and hopefully will work waaay much better then the current 6boost-Turbosmart arrangment

Lets see a MSPaing Jig! Share share!

[The Dan]

I've got 3 we've done here if you want photos

[Dose Pipe Sutututu]

I'm guessing there isn't an off the shelf housing with a v band mount for an external wastegate?

[NYTSKY]

That housing is used on a specific motor/turbo arrangement. I highly doubt one would be made just for an aftermarket RB application.

Especially when one can be fabricated so easily.

Im having two 38mm gates on my next manifold, single entry Vband. Was going to be T4 divided but couldnt get a housing to suit my turbo in time.

Anyone put two gates on a single entry manifold before?

[black bnr32]

atp turbo has housings with a v-band gate

the famous pics of the turbo f1 bmws from the 80s have twinscroll manifolds with single gates

Edited January 29, 2012 by black bnr32

[wolverine]

I have an ATP 0.82 T3 TS but they also make T4 flanged versions with V-band outlets as stated above.

I bought the turbo through streettotrack but procharge can also supply the housings if you are looking for an alternate.

[meet07]

So how would you go about welding a wastegate onto a twin scrolled turbocharger like the borg warner s366. Would you then weld something like 2 x 38mm tial gates on each side of the divided housing?

I would like to see pictures of these setups. We dont see much of these setups here in the states.

[GTR_JOEY]

I'll have pics up soon of a twin scroll manifold with twin 38 mm gates plumbed into a 4 inch exhaust.. Running a BWs300sx 83/75 on a 26

Its will look awesome but is a real head ache to make happen

Edited January 29, 2012 by GTR_JOEY

[Weapon]

Weld wastegate pipe onto turbine housing and have no gate pipe off the manifold. Better response, more power, end story

I respectfully disagree, my first kit was from ETM and had the Tial 44mm mounted from the housing (GT3582R) The thing never controlled boost past 4500rpm. Fail

I am quite happy with my custom steam pipe manifold running a single 60mm gate with a Precision Billet 6262 and it holds 1.3 bar solid all day every day

Edited January 30, 2012 by Weapon

[wolverine]

Was it the gate size or the design that made a difference?

[The Dan]

I respectfully disagree, my first kit was from ETM and had the Tial 44mm mounted from the housing (GT3582R) The thing never controlled boost past 4500rpm. Fail

I am quite happy with my custom steam pipe manifold running a single 60mm gate with a Precision Billet 6262 and it holds 1.3 bar solid all day every day

Not sure why. We have them control boost perfectly on everything from GT3076's running 1 or even 2 bar up to GT4508's running 3.5 bar. All on 2.5 and 3L 6 cyl engines

It's good that you got your setup working properly but I don't know that the fact the gate pipe was welded off the housing was the cause.

[bigmikespec]

Thought I would boot this thread in the backside with a link to a photo of someones good work: http://www.eagletalon.net/pictures/index.php/2006/Red-Car/wastegate/IMG_1002

[R31Nismoid]

Doesn't look like true twin scroll/twin gate?

Having a single gate with a twin feed will still not be a "true" setup when the gates are not independantly controlling.