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Inspired by acurafans recent rotating exhaust cylinder.
I was noticing the other day that those little little finger trap puzzles that kids sometimes play with have an interesting property in that they can change in diameter with a change in length.
I propose a trap assembled out of thin Stainless
Steel strips with an actuator ring affixed to one end of the tube section. As the actuator is moved in or out the diameter of the tube is adjusted as well. By calibrating the movement to RPMS, throttle position etc. one could create a continuously variable exhaust back pressure regulation system.
Adjustments of the fit of the strips would allow this section of pipe(enclosed within another pipe) to also act as a muffler much like a standard perforated high performance muffler in use today.
inspiring idea.
Rotating-cylinder_2...ry_20exhaust_20size
[jhomrighaus, Feb 12 2007]
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Great idea, certainly more practical and creative than mine. [+] |
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Combining it with a muffler is a good idea. Sealing the finger-trap would be possible, but not easy. Making it a muffler solves that problem entirely. [+] |
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I don't understand how back pressure could be beneficial. |
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you need a little bit, and the amount changes depending on the operating state of the engine. In general most engines are saddled with overly restrictive systems, however even on a very free flowing system there is still some back pressure. I will find more detail later but i believe it has something to do with creating a smooth laminar flow in the exhaust manifolds and pipes. |
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It has clearly been demonstrated that an engine running with no headers does not perform as well as one with headers(reduced HP and torque). |
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I went from a single 1 7/8" pipe on my car to a dual 2 1/4" setup and lost about a second or two off my 0-60 time (all off of the low end of the engine). Too little backpressure will do that. That's why I've been trying to come up with something to regulate backpressure like [jhom] and [acurafan], but nothing's gotten in the oven long enough to even halfbake. |
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Would a simple valve in a large exhaust pipe work? |
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Possibly, but its keeping the pressure regulated to a certain amount that is unknown to me that keeps me from baking it and installing it. And the dual exhaust did help me out on the top end, and lets me get a little better mileage on the highway, so I'm not just going to go back to single exhaust. And it just sound much better with the current setup. |
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[Hunter], is the dual exhaust a true dual exhaust system or a single pipe that splits in two? If it's the latter, you could put a throttle with a butterfly valve in either one of the exhausts after the pipe splits in two, and rig it so that you could open and close the throttle from inside the car. At low rpms you could keep the throttle closed so that all of the exhaust would have to exit through the other pipe and at high rpms (or when cruising on the highway since you said it improved your millage) you could fully open it so that you would get the full flow of both of the exhausts. Of course, this would require a whole lot of work. |
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It's not true dual, it splits after the cat. And my hope was to come up with an automatic system that I wouldn't have to adjust constantly for optimum atvantage. I think about the best I've got so far is to get a piece of metal shaped sort of like a Pringles potato chip, weld a stop inside the pipe, place the bottom edge of the "chip" against that stop, and connect the "chip" with the top of the pipe farther upstream by a spring. If i use identical setups in both pipes, it should retain the sound/look/feel that I want with improved function. One of these days i just need to get a couple sections of pipe, do some math to get the elliptical shape i need for the "chip", and figure out what the best exhaust pressure would be, then I'll see whether all of this is worth it or not. |
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