Interesting info on exhaust back pressure and torque
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I'm going to go with what he said a couple times, it depends. I would have been much more influenced if he had shown dyno charts on the same engine with varying pipe sizes instead of just speaking to theory. I fully agree that exhaust velocity is critical. If you check the exhaust diameter on most modern cars they actually get smaller as they get further from the engine, that's to keep exhaust velocity up as the exhaust cools. And his theory on needing large exhausts when you have large valve overlap is kind of against most of the theory I've heard on that. Valve overlap is the period when both intake and exhaust valves are open, and you can actually suck part of the intake charge out the exhaust valve with a system that is designed wrong. In that case I would think you would want a little back pressure. But on a more standard cam profile I would agree, back pressure isn't necessarily a good thing.
I think this is a discussion that will take place as long as we have internal combustion engines.
I think this is a discussion that will take place as long as we have internal combustion engines.
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the most complete burn of the gas/oxygen in the TIME its allowed to BE in the engine will give the most power. Back pressure keeps the gas/oxygen in the engine longer. A log allowed to burn more of itself in the TIME its allowed to BE in the stove gives off more heat.
2008 M109R, 2016 FJR1300, 1999 VMax, 2009 Suzuki AN400 Burgman
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Love PINK FLOYD...I used 'comfortably numb' as background music in one of my old GoPro videos...I had used epoxy to glue the GoPro to the top of my helmet when I rode along the backroads...I will see if I can attach it...the Pink Floyd music was in the last 6 minutes of the video...
https://www.youtube.com/watch?v=1iL8n_kPRFE
https://www.youtube.com/watch?v=1iL8n_kPRFE
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Here's an example, now there are a lot of variables that most people are going to get hung up on but the basics of air flow and resonance apply from the smallest engine to massive diesels as well as carburetors and EFI. Also adding forced induction (which is the same as exacerbating the actual size of the engine) will drastically effect power vs restrictions that cause back pressure.
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My apologies to all the Pink Floyd fans..I posted the wrong video...the last 5 minutes of this video should have PINK FLOYD's Comfortably Numb in the background
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