twin scroll question

[rr06rs]

While we all know that the pairing of 1/4 and 2/3 is the correct way it should be done, has it ever been determined which primary pairings should be on the inner or outer side of the turbine? While most manifolds that I've seen put 1/4 on the passenger side, making it flow to the inner side of the blades on a conventionally mounted dsm turbo, I've seen them both ways such as is the turbo is mounted flipped, facing the compressor to the driver side, or even with the 1/4 pairings flipped in a case where its bottom or top mounted, or even forward facing. Would this have any role in spool characteristics or even overall power output considering how the exhaust pulses are hitting the inner or outter most part of the inducer?

 

[talonDSMerr]

If your engine is healthy and the cylinders have relatively equal compression, it would be the same in either configuration. The turbine would not know the difference.

 

[rr06rs]

What about the exhaust pulses and firing order. Going by that theory, pairing the correct primaries would have no affect on power or spool, which we know isn't the case.

 

[rlacasse1]

If your engine is healthy and the cylinders have relatively equal compression, it would be the same in either configuration. The turbine would not know the difference.

x100,000,000

What about the exhaust pulses and firing order. Going by that theory, pairing the correct primaries would have no affect on power or spool, which we know isn't the case.

No, not quite.

The whole point of pairing the correct primaries is so that you have a more consistent flow, if that makes sense.

The way it is done, a cylinder on one set of primaries will fire, then a cylinder on the other set of primaries will fire. The constantly go back and forth like that to provide consistent, timed exhaust pulses.

If primary didn't matter, then what would happen is one pair of primaries would get two exhaust pulses then be dead while the other pair got two pulses.

Does that make sense? They have to be paired correctly to provide the optimal flow of exhaust over the turbine.

 

[Steve93Talon]

Think of it this way - you can swap plug wires within a coil, but you can't swap them between 2 different coils.

 

[talonDSMerr]

What about the exhaust pulses and firing order. Going by that theory, pairing the correct primaries would have no affect on power or spool, which we know isn't the case.

Then you should think through the firing order of a 4-cylinder engine. 1-3-4-2. You are pairing 1-4 and 2-3, so the outlet of each side of the divided manifold will see an exhaust pulse every 360* of crank rotation. This is true regardless which side of the turbine they are directed towards.

Walking through step-by-step:

Firing order: 1-3-4-2-1-3-4-2-1-3-4-2-1-3-4-2
Side of turbine getting exhaust pulse: right left right left right left right left right . . .

There really is no difference which one goes to the left/right of the turbine housing if 1-4 and 2-3 are paired. Both sides create the same pattern of exhaust pulses and the same amount of exhaust.

 

[T-mun]

What he says above is what i've always been telling my buddy, but he keeps saying that the inner turbine wheel should be from cylinder 1&4 for better spool. I would say the most important aspect is no cross contamination & equal length runners to get the most out of the twin scroll setup, which cylinder on which side of the turbine doesnt matter as long as the pulse are in sequence.

 

[1MeanTSI]

Orientation won't make a difference in spool times. I had a twin scroll on my 1g for a little while.