Exhaust valves
There is some merit to this although it's effect on mileage has yet to be credibly tested but here it is; exhaust valves create backpressure at low RPM's (when the engine is cycling smaller volumes of exhaust per minute) but open to allow full use of the cavernous exhaust pipe, it allows the engine to get a small bump in hp lower in the rev range, my question is has anybody tried exhaust valves to nurse the engine during acceleration at lower speeds for the purposes of mileage/fuel-conservation? I intend to give this a go on my next vehicle but would like to know what others know/have experienced about this subject.
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exhaust valves
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The motorcycle engine underwent a full-spectrum dynamometer test to evaluate it's best performance at all rpm's as a function of exhaust back-pressure,then a look-up menu was burned into the ROM chip which allowed the computer to modulate a servo motor linked to the muffler's valve; enabling the engine to always remain in the sweet-spot. If you've got a loose $100,000 you want to throw at a chassis dyno,you'd be able to do this to your car.:p |
Or you can use in-cylinder pressure sensors.
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If you are doing a single cylinder engine, you can purchase the sensing spark plug for about $1K and cludge your own data logger using slower commonly available electronics and do multiple cycle overlays. But, that's just what I would do. |
You could actually do the same thing with a piggyback chip like the UniChip-Q, to which you can add auxiliary maps to precisely control things like extra injectors, nitrous and even a flapper valve.
Just tune it once on the dyno, you're done. |
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in-cylinder sensor
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On-road data collection.
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A baseline run followed by a set exhaust valve run yields a pair of pressure traces that allow you to determine a gain or loss. No need to calculate BSFC as combustion pressure is all the feedback you need. A pair of runs takes 5 minutes or less. A well thought out set of runs can yield a reasonably extrapolated pressure map with which to program an engine map. Again, there is no need to carry the burden of a dyno cell instrument set. In-cylinder pressure will tell you if the exhaust back pressure is beneficial or detrimental. I would probably add a stepper actuator to the exhaust back pressure valve to make "fanning" the back pressure during runs possible. This reduces the number of runs during your data gathering. |
...or, you can buy software programs that simulate just about 100%-functions of an engine in operation...at any load...under any weather conditions.
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This.
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Aerohead, do you remember approximately what kind of a difference that setup made for that motorcycle?
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