True Twin Scroll Turbo & Manifold Design Discussion

[sneakey pete]

Well thats interesting. Was twin gated on the engine dyno and then welded on gate off housing in car?

 

[GTSBoy]

Surely that setup somewhat defeats the purpose of twin scroll.  The pulses are not so isolated from each other when they're directly joined!

[AngryRB]

5 hours ago, iruvyouskyrine said:

Why?

Well when I had it done it was laggy, maybe too far along the scroll created too much turbulence I'm not sure. But its certainly possible as the actual fabrication of the gate pipe with split right up to the gate was great work from my fabricator. Pics in my old build thread.

[eXquiSit]

It would be similar to those running a single gate with diverted piping to the gate right?

[GTSBoy]

Yes and no.  It is possible to do two pipes to a single wastegate properly.  There was a thread showing that on here recently.  I would also be possible to do it wrongly.  You need to keep both halves of the system isolated from each other when the gate is closed.  If the two pipes from the two halves are open to each other before the gate, then the pressure pulses will leak and ruin the effect, thus making it pointless.  That particular example off a twin scroll housing (above) doesn't look like it would be internally divided in the pipe running to the wastegate.  I therefore suspect that it is not a good implementation.  Obviously it will still work and make lots of power.....but what about the spool behaviour, etc etc?

[iruvyouskyrine]

That video seems like a very weird way to do it. It sort of rolls over both sides of the housing and has a very large diameter gate pipe.

I would look at doing it directly off the housing like a conventional single scroll system. Turbo will be GTX3067 with a tiny (physicslly) rear housing.

[GTSBoy]

That's the problem with trying to do it on twin scroll housings.  On a single scroll housing, you have a spot just downstream of the housing's inlet flange where the scroll is nice and big - nearly the same size as the manifold connection itself.  So you can put a single pipe off of that (or the gate direct onto it) and get the gas to flow properly.  But a twin scroll is already compromised by having the gas paths in that same location squeezed into a tall-narrow shape.  You can only access the short sides of these paths, so can't weld on a round/squarish port for the offtakes.  And they're right next to each other and the offtakes need to be right there in the same spot next to each other.  It's just all so compromised that you'd be better off with gate(s) off the manifold.

[MJTru]

Are these real twin scroll.??

[GTSBoy]

Provided that divider in the wastegate elbow goes all the way to the divided part of the collector, then yes.  It looks like it does.

[owen1r]

I wonder how much of a difference it makes having the pressure communication inside the wastegate, someone go make a simulation pls.

Because I'm wanting to go a similar style manifold, saves a massive headache with piping. 

Edited March 10, 2017 by owen1r

[r32-25t]

Once it's out the gate/s it doesn't matter what happens to it cause it's done it's job and is literally just waste at that point 

[GTSBoy]

That's not what he's asking.  The wastegate is a valve.  When it is closed it SHOULD block off the communication between the two halves of the manifold, and if it doesn't, that's bad.  When it is open, it will impose a pressure drop on the flow passing through it.  It will be like the end of any pipe, any orifice, etc etc.  The pressure pulses that come down the pipe from one half of the manifold will leak into the other half of the manifold because of that.  The question is.....how much does it negatively effect it?

I think it somewhat defeats the purpose of the whole split pulse idea.  But I am willing ti accept that split pulse with turbos is more about getting the thing to spool better.  Once the gate is open, the pulses can probably leak between halves of the system without too much negative effect.  But that's just a gut feeling.

[owen1r]

I would of also thought that you'd struggle to get a good seal between the divider and the wastegate piston with varying brands of wastegates etc. I'd expect there to be a gap of a mm or two.

I'm hoping someone like fullrace will chime in with some data, as I believe they've done plenty of simulations.

[r32-25t]

I've always been skeptical of these single gate twin scroll manifolds 

[MJTru]

I was thinking that it would leak right where the gate valve meets the divided part in the pipe. I assembled the gate and send a camera inside to check if it leaks, by seeing light. It's not perfect but very very close. Make me think what would happen when it heats up on expansion if it would leak even more. Or seal better. I guess in drag racing all that's not to important, but I wanted this style in the event I wanted to use it on another setup. I do agree that my reasoning for this was all the piping/plumbing.
I always get my manifold from Kyle at 6 boost. Hands down the best for the cash.

[czy18e]

I had an etm twin scroll single gate manifold and it worked fine with a Garrett t04z but when I changed to a precision it wouldn't control boost.
I welded it up and went with welding the gate off the turbine housing. Problem solved and 500rpm less lag.

[iruvyouskyrine]

Was the housing single or twin scroll though?

[czy18e]

Both Garrett and Pte were twin scroll.

[iruvyouskyrine]

So you were using a single gate on a twin scroll exhaust housing? Any more pics would be appreciated

[czy18e]

I was using single gate on twin pulse exhaust manifold and changed to single gate off the twin scroll exhaust housing.

Works perfect.

When I was talking to 6 boost they said it was the best way to run also.