Gary Lewis Posted February 16, 2018 Share Posted February 16, 2018 X crossovers are more common *now* because we have better, cheaper, CNC mandrel tube benders and robotic MIG welders available across both manufacturing and repair shops. It is really the only place to put an aftermarket oxygen sensor in a 'true dual' exhaust. (as opposed to factory bank-1 & bank-2 style) If you've been looking into exhaust you understand that this all has to do with scavenging and that on the whole, long tube equal length headers are going to help top end, where shorties are going to help*loWer* in the rpm range. Also that larger tubes need enough exhaust volume to fill them. (either through displacement or rpm's) In essence you want the shock wave to travel back up the pipe and bounce off the back of the closed exhaust valve. Then the valve can open while the shock wave is helping pull the spent charge through the exhaust port and down the tube. It is a complex equation involving supersonic shock waves, temperature, volume, gas expansion ratios, ect. to determine tube length to the collector. And the distance downstream from the collectors to the crossover. (see Bernoulli effect) **I am not an expert in this but understand the concepts of fluid dynamics from my rocketry experiments** Congrats on your recent purchase! I have an original P220 and find it amazingly reliable and accurate. Edit; lover to lower. Maybe spell check and Valentine's day influence in Chrome? Amen to what Jim said. And, X crossovers are more effective than H's since the gas doesn't have to make a right-angle in its travel to go across to the other side. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted February 16, 2018 Share Posted February 16, 2018 Amen to what Jim said. And, X crossovers are more effective than H's since the gas doesn't have to make a right-angle in its travel to go across to the other side. Flowing *past* the adjacent pipe is what causes low pressure in the adjacent pipe.... https://en.m.wikipedia.org/wiki/Bernoulli%27s_principle Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 16, 2018 Share Posted February 16, 2018 Flowing *past* the adjacent pipe is what causes low pressure in the adjacent pipe.... https://en.m.wikipedia.org/wiki/Bernoulli%27s_principle I see what you are saying. So, an H is better than an X? Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted February 16, 2018 Share Posted February 16, 2018 I see what you are saying. So, an H is better than an X? I don't think so, but I was very clear that I am not an expert on exhaust system tuning. Link to comment Share on other sites More sharing options...
Pebcak Posted February 16, 2018 Author Share Posted February 16, 2018 I don't think so, but I was very clear that I am not an expert on exhaust system tuning.That I've ever heard of from talking to people is the "X" configuration. I'd never heard of the "H" until I started searching recently. On Feb 16, 2018 07:39, "ArdWrknTrk [via Bullnose Enthusiasts]" <redacted_email_address> wrote: Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 16, 2018 Share Posted February 16, 2018 I don't think so, but I was very clear that I am not an expert on exhaust system tuning. I'd always heard/read that X is better than H, but it that probably was due to being able to use both muffler/tailpipe systems for each cylinder. However, if you are looking for scavenging, maybe H is better? Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted February 16, 2018 Share Posted February 16, 2018 I don't think so, but I was very clear that I am not an expert on exhaust system tuning. The pulse does travel into the other pipe. Ideally we are tuning for the low pressure after the wave passes. Dumbing it down... shock waves happen because the molecules of the medium cannot move out of the way fast enough and you have collision instead of expansion. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted February 16, 2018 Share Posted February 16, 2018 I'd always heard/read that X is better than H, but it that probably was due to being able to use both muffler/tailpipe systems for each cylinder. However, if you are looking for scavenging, maybe H is better? Scavenging happens in a header collector.... You sure aren't looking for right angles there. Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 16, 2018 Share Posted February 16, 2018 Scavenging happens in a header collector.... You sure aren't looking for right angles there. That's for sure. There's a finite end to each tube, and the wave created when a pulse comes out of one tube goes back up the other three - on a V8 using equal-length headers. But, if we put a crossover in downstream of the collector does that cause another set of waves that add at some RPM's and subtract at others? Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted February 16, 2018 Share Posted February 16, 2018 That's for sure. There's a finite end to each tube, and the wave created when a pulse comes out of one tube goes back up the other three - on a V8 using equal-length headers. But, if we put a crossover in downstream of the collector does that cause another set of waves that add at some RPM's and subtract at others? Yes, yes you do have secondary waves, and collisions, magnification due to interference, standing waves, reverberation, constantly changing temperatures affecting the local speed of sound, energy (heat *and* velocity) lost due to expansion, ect... This is why I say it is a very complex equation. That is beyond my abilities -or at least desire- to solve for. Link to comment Share on other sites More sharing options...
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