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At different Rpms, different sized exhaust tubes are more desirable than others. For instance, at low rpms you would want a small diameter exhaust pipe to give some backpressure and increase low rpm torque, while at high rpms you would want a large diameter exhaust pipe to be able to let out the exhaust
gases quickly and easily. I propose connecting the exhaust tube to a cylinder that has multiple holes and a shaft in the middle, much resembling the cylinder of a gun. The exhaust tube would be connected to one hole and sealed completely via using electricity to magnetize both the cylinder and tube to make them sealed. Once the rpms change and a different sized hole is more desirable, the electricty flow stops, the shaft is turned, then the magnets are re-engaged. The actual holes would all be the same size to make sure that both tubes are completely sealed (the first part of the exhaust has to stay the same size, therefore can only fit with one hole) however, each hole is cone-drilled so that each will match the first part and then the cone will make it smaller/ larger.
Yamaha Exup
http://en.wikipedia.org/wiki/EXUP
[Mister Sketchly, Feb 11 2007]
V-ball valve
http://www.pbmvalve...-control-valve.html
Design which allows accurate flow control [gardnertoo, Feb 11 2007]
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Surely there is a much simpler way to have a nozzle which changes diameter in direct proportion to your engine's RPMs. I envision a continous area changing ball valve that does the same thing (although it's not exactly a circular nozzle)... this could be a ball valve, like the one found on your kitchen faucet, but controlled by a trim motor attached to an RPM sensor. |
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yes, [quantum], I thought similar, except to use the variable expansion valves used in aircon (A/C) units. |
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However, this would be a cheap and nasty compared to the quality results that can be achieved with a whole different exhaust optimised for each setting. I would suggest a linear arrangement to avoid scraping the bottom exhaust on the road. |
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[quantum] has the right idea: it is called a V-ball valve. See link for one design. The V shaped slot in the ball allows a much finer control of flowrate than the standard on/off ball valve. |
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I've thought about ways to accomplish the same thing quite a bit, and one problem I've run into is that it is not a direct RPM/exhaust size relationship, but it varies with manifold pressure as well. Both work together to produce exhaust pressure, so the best way to control it would be from a pressure sensor in the exhaust upstream of the contraption, if you go the electrical route. I thought about inserting a section of pipe into the exhaust with a sort of trap door on a hinge, forming basicall a pressure regulator. And then I found something that I think is similar in the JC Whitney catalog, but tis unclear as to exactly how it works, so I'm not sure. I'm not calling this baked, because its a completely different method to accoplish the same thing.
One problem I could see in this design is the moment that the cylinder rotates. There could potentially be a major spike (or dip) in backpressure when the holes are not lined up exactly, but good solution nonetheless. |
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//There could potentially be a major spike (or dip) in backpressure when the holes are not lined up exactly//
Some kind of blow-off valve would work fine to relieve the pressure when the holes aren't lined up. Is something really considered baked if it's a different solution? I've seen many ideas bunned that are simply other ways of doing things that can be done a different way. |
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I didn't say that I boned the idea (I didn't bun or bone either way)and I did't call it "baked". I'm just a pessimist and I look at why things might not work and potential problem areas, and I throw in similar ideas that I've seen before that may or may not contribute to the idea at hand. |
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I think that the blow-off valve wold work, as long as it was routed back into the pipe downstream to avoid any exhaust gettin released under the cabin (illegal in most areas). |
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So is this kind of like a variable expansion expander? |
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