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Originally Posted by plusaf
in the old days, messing with the mixture like that would do nasty things like burn exhaust valves... if the hybrid uses exhaust gas O2 sensors, messing around with the mixture might just bring THAT feedback into the loop and counteract it
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I agree. The O(2) sensor and exhaust temperature gage should be controlling the mixture. As for timing, I would expect RPM to be the primary determinant.
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Originally Posted by plusaf
.... i wrote to the eBayer and asked, "i thought the prius' engine control computers limited the rpms to about 4500....
what actual results have been seen with priuses?" if i get an answer (that's printable in a family forum , i'll post it here.)
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I noticed he didn't report any Prius direct results. Without at least a scanner and better yet, supporting instrumentation, I wouldn't be terribly interested in testing what is essentially an inaccurate IAT sensor.
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Originally Posted by plusaf
i LIKE the supercharger idea, though! all other things equal, "fooling the engine" into thinking it's at lower altitude with denser air just means, i'd bet, that it'll put out sea-level levels of power, which might be higher than a mile or two further up.
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With the lower aerodynamic drag from low pressure, the car should scoot.
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Originally Posted by plusaf
i also wondered why, or if, the Atkinson-cycle Prius engine couldn't be "educated" to know the altitude, or maybe just by using a preignition knock sensor, to close the intake valves a LOT sooner at high altitude, regaining the peak compression pressures of sea level, just by more vigorously changing the intake valves' timing....
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The intake valves are variable delay. What I don't know is how much it changes the 8:1 compression side ratio. The expansion ratio remains fixed at 13:1. I suspect the difference in compression and expansion ratio is what gives the high specific energy performance (i.e., HP / lb of fuel).
It looks like the "Oil Control Valve" operates the "Valve Timing Controller Assembly." It may be possible to tap or externally control this signal. Before making any active changes, I'd want to monitor it and several other engine parameters to determine how the ECU operates it. I would expect the low-pressure or 'off' position would have the lowest possible compression ratio to make starting easier. Once running, it should move the valves to a higher ratio.
Once the valve control signal is identified, an ordinary compression tester could measure the ranges: starting ratio and operating ratio. As for increasing the compression ratio, it may be possible to use Echo parts. But I'd rather use a supercharger than make those kind of changes.
Living about 700-800 ft. above sea level, more power doesn't help me and would have a negitive impact on MPG. If I lived in the high plains or a mountainous area, I'd be more interested in supercharging and valving changes.
Bob Wilson