Quote:
Originally Posted by Ryephile
While I have some personal experience with Burns products, nobody beyond Burns' staff has direct access to X-design. As such, they are the only people that can answer the question regarding if they are able to add fudge factor for variable cam phasing and/or lift. To my knowledge, a well designed header has to be designed to specific application [i.e. torque and rpm...and cam angle] to work ideally.
I'd rather not comment on things like stepped primaries and other exotic reversion theories at this point, as I don't have enough research experience to make a qualified statement. I haven't read, seen, or experienced any stepped, coned, or otherwise crazy concepts make a significant change in performance. The most important aspects seem to be the collector volume and primary dimensions.
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I've read only that they boost top with little to no negatives on the bottom (same thing with long-primary super-short secondary 4-2-1 venturi-merge collected headers on NASCARs), and seen one dyno result on a 2.0L L4 where they did just that, as well as just seen them applied to Aussie V8 Supercars, F3 and F1 engines.
It's that the explanations for why they do it are different.