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Twin scroll Brain teaser

Off Topic Discussion

If it's not really about tuning or wiring. Then it belongs in here.

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People say twin scroll turbo runners should be paired with 1 and 3 cylinders and 2 and 4 cylinders when used on a 4 cylinder 4 stroke engine with a firing order of 1 3 4 2 but the theory doesn't compare in practice because the firing order could be 2 1 3 4 or 4 2 1 3 or 3 4 2 1... it doesn't make any difference, they are all the same order but at different times in the 4 cycles of a 4 stroke engine. Question is: what is the correct explanation for a twin scroll turbo?.

So what they have asked for is that each scroll has two cylinders that fire in order (ie, 180 deg apart). Think about the pulses and how they would interact if they were 360 degrees apart?

Hey Tony, actually the correct runner design for a '1-3-4-2' 4 cylinder would be to collect the runners from #1 and #4 into one scroll and #2 and #3 in the other.

This gives consistent pulses into each scroll every 360 degrees of crank rotation. If it was #1 and #3 paired then you'd get two pulses 180 degrees apart and then nothing for 360 degrees. The same goes for the other scroll. I hope that makes some sense?

Cool thanks. Yes makes sense.