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Originally Posted by RobertSmalls
The biggest problem I see is with the inputs for the road load equation: M, Ma, Cd*A, Crr. M varies quite a bit. For example, my car sheds 27kg as the fuel tank runs from full to empty. I've removed some parts and added others, so if I wanted to know my car's mass, I'd have to have it weighed.
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Very true, although mass loss through fuel burn is something that is directly measurable (since we're measuring fuel consumption after all). Harder is mass change due to passengers, but if the model is good enough we can identify all these things.
I might add that the 27kg mass change is perhaps negligible when considering that the true mass of the vehicle is probably unknown, and other (important) parameters such as air density, wind speed and direction, air temperature, engine temperature, oil temperature, tire pressure, etc... are not included in the model. It's not really that important though, as all these factors tend to average out, leaving you with good results even if you have more uncertainty than you would like.
Some of these above parameters we can easily include in the model once we have the measurements. I'd be especially interested to know if we can get an idea of absolute air pressure changes based on the MAF.
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My Cd*A changes with every aeromod I do, and Crr depends on tire temperature, pavement type, and too many other factors. I think the best approach here is to have the user do a high-speed neutral coast to discern Cd*A and a low-speed coast to determine Crr. I think lots of EcoModders would like to have a precise datalogger to help calculate these numbers.
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One of the beautiful things about observers is that we can estimate all those parameters. High-speed/low-speed tests are a great way to have a first order approximation, but they miss some essential information that we can reconstruct with a parameter estimating observer.
That being said, an online observer and a parameter estimation observer are slightly different, and I haven't yet written the code to do that with this model. The first order approximation is good enough for my purposes right now.
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I would love to study the BSFC of the first-gen Honda Insight. I'd love to quantify the effect of lean burn, find the optimal rate of acceleration, and study exhaust and intake mods.
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You can lean burn on the Insight? Cool. I had no idea. How do you do this? What are you using to measure the effects of lean burning? Do you have a CHT or EGT gauges?
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How long does it take to fill the 2GB SD card?
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Quite a while, although it's speed dependent. Figure roughly 1MB/min, and you've got an idea of how long you can go before emptying the card.