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Old 04-20-2010, 05:10 PM   #1 (permalink)
dcb
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pimp mobile - '81 suzuki gs 250 t
90 day: 96.29 mpg (US)

schnitzel - '01 Volkswagen Golf TDI
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runtime efficiency?

I was thinking about a sort of "efficiency" readout, though I'm not sure it makes sense.

i.e. if you input your vehicle weight/cDA/rolling resistance, then (not accounting for hills/wind) a mpguino type device could conceivably:

make a guess at how much work was done/is being done by looking at the change in speed.

compare it to the fuel that was/is used to do that work in that amount of time

print out the percentage of work that was actually done vs what the fuel could have done in a %100 efficient engine/vehicle.

But given the influence of hills/wind (and even deceleration) I'm not entirely sure how useful it is. Also it is a little misleading to factor in the cda, your engine can be at peak efficiency but still the whole package is a dog.

I do think something like this could be useful where you have no bsfc clue, or other variables (like a slipping torque converter) and are trying to optimize your acceleration curve.

I also considered a simplified scheme where it simply looks at the change in speed vs fuel used, and comes up with a number that doesn't map directly to anything but you can still look for a peak value, and focus on how to get the greatest change in speed (regardless of your cda/weight) for the least fuel when accelerating. Except for the completely synthesized units, I think this might be easiest to implement and offer the most realistic value. But without CDA, your peak will be a speed dependant moving target.

Any of this make sense? Am I missing something obvious?

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WINDMILLS DO NOT WORK THAT WAY!!!

Last edited by dcb; 04-20-2010 at 05:16 PM..
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