Quote:
Originally Posted by Nigel_S
Does it suggest the pairing of the pipes in the tri-y header?
Seems to me that for a 32" to end of secondary header you need 1 pared with 4 but for a 32" to end of primary you want 1 pared with 3, but I've never noticed that written or implemented...
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That's a very good question. I
think the double-length version will have the same cylinder pairing as the equivalent single-length design, but I'm not entirely sure, and it can't hurt to ask...
One of the interesting things from PipeMax is that the lengths calculated for the "3-step" header (small primary -> large primary -> secondary in length ratios) look very similar to the "hybrid tri-y" designs I posted earlier in this thread, the small primary:large primary:secondary length ratio is 2:1:1... and they all seem to use sequential pairing instead of even-spaced pairing. On a side note, pairing 1 with 3 and 2 with 4, is equivalent to 1 with 2 and 3 with 4 - in either case, each secondary pipe gets two pulses in a row.
Quote:
Originally Posted by Nigel_S
"I think the magic number may be 27" instead of 32"." - mine have a range from 26.5 to 31.5, measured from the valve to end of secondary. (different engine)
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Indeed - magic number for the specific engine, obviously, give or take an inch or so. I say 27" because it's in the overlap point between the "EGT corrected" calculations given a bit of uncertainty in valve timing, for the low to mid RPM ranges, and it's also darn close to the acceptable range for the high-rpm, high-EGT VTEC cam results. I believe my calculations should apply fairly well to any of the Honda D16Y engines though, if they're running stock cams -
minor variation in cam timings didn't seem to change the recommended length by more than about an inch, but aggressive aftermarket cams would definitely change things - not that that should be an issue for most people on this forum
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