| of that question the past few days : I had on my Sport 600's back in the day 3 inch random tech downpipes and later SZ 2.5 inch super splits w/a 3 inch flange. My experience led me to believe that I had less lag with the super splits ( but maybe at the sacrifice of top end ). The sport 600's were so laggy without manifolds, I preferred the super splits even if it meant the sacrifice of some top end power. In general the super split / divorced pipe will give more mid range and the 3 inch dump / straight pipe I think will allow for more peak rwhp. The top end gain realized though can be small depending on setup and most will opt for the midrange increase to get torque / minimize turbo lag. If you use the SZ expansion downpipe because of the free flower exhaust (the diameter of the turbine side increases faster than the regular super split design ) and the fact that the exhaust is cooler because there is less back pressure - you get the best of both worlds. --- this is purely conjecture --- If one would re-tune ( change ignition timing ) alongside 'significant' downpipe changes ( for example stock to 3 inch SZ expansion or 2.5 super split inch to 3 inch dump ) - I don't see how an application with more back pressure will outperform an application with less backpressure. That being said, I am assuming that it makes sense to think that a lower back pressure environment would allow for cooler cylinder temps and allow for ignition timing changes from the base program ? This would allow the user to reclaim the torque on the bottom end ( if timing is advanced ) or create faster spool up ( if timing is retarded ) ? I never looked into retuning the timing maps with significant down pipe changes before but I plan to once I get Nistune.
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