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Old 11-19-2014, 10:34 PM   #17 (permalink)
Madact
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Location: Adelaide, Australia
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Emerald - '97 Honda Civic CXi
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Quote:
Originally Posted by undeRGRound View Post
Don't think I had any input here, but splitting a 4-2-1 into two 2-1 headers and then running them into an X-Pipe would achieve the ASC design.
I saw the X-pipe thing - both as a better alternative to an H-pipe for bank balancing on V-shaped engines, and the whole "Acoustic SuperCharger" / "The Amazing Campbell X-Pipe" thing... while I think it may have some merit in certain situations, I think it might complicate the design a bit in this case. One thing I was considering was having a an X at about 55-60" and then merging back to a Y at 80"-ish but I'm not convinced it would be worth it.

I'll say straight up that I think a lot of the wilder ASC claims on x-pipe.com can be attributed at least in part to the fact that the Campbell pipes don't have mufflers (and by the photos I could find, cats either - though they say "legal"... but elsewhere on the page they say "pleasure license only" so whatevs). Now the X-Pipe itself is a decent scavenging system, but with those advantages (removing muffler and possibly cat), you give any basically well-designed and built system a chance to really shine

There are some really interesting aspects to X-Pipes though. Consider that in a Y merge, you effectively double the excitation frequency in the pipe after the merge compared with before the merge (as you're adding two sets of pulses 180 degrees out of phase). This will affect any resonance that happens after that point. However, if an X-pipe (mainly) flows across the 'X' between opposite pipes, then each downstream tube will be effectively experiencing the same excitation frequency as the input, which would mean a wider resonance bandwidth (& less sensitivity to downstream pipe length) while still getting the scavenging effect. This could be very useful for high-revving engines, I would expect it to be especially handy on a motorbike.

And of course the flow isn't restricted by changing direction or going down a pipe size, so positive pressure pulse reflection should be lower compared to a basic (i.e. cheaply fabricated) Y merge. And of course the output tone will be much more meaty, as you avoid the frequency doubling effect mentioned... if I was building a big burbly V8 hot-rod, it would be a candidate for sure...

So plenty of interesting aspects, but not necessarily huge gains for a 'street' car with cats, mufflers and low RPMs (unless you believe all the hype ) and quite a bit of added complexity.

If I had a good 1D simulation package I'd plug it in and see how it might go anyway, of course...

Last edited by Madact; 11-19-2014 at 10:42 PM..
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