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Old 05-20-2008, 11:20 AM   #1 (permalink)
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Chysler patent raises technical question about injector accuracy

I hope this is an appropriate place for this question. I think it is.

I think a major advantage of MPGuino is that it reads the injectors directly. It's pretty clear that doing indirect calculations based on OBD2 airflow data (e.g., SG) will yield results that aren't always perfectly accurate. And I think a high level of accuracy is actually important, given the intended use of these products.

For example, I would really like to know what happens when I add cargo, or change tires, or drive into a headwind, or do all sorts of major and minor aero mods. I won't have confidence in these observations (and therefore I won't bother making them) unless I have an instrument that delivers impressive accuracy.

I figure reading the injectors is a great way to do that. But I'm posting here because I just stumbled across a patent that raises interesting questions.

The patent was published in 2000, and it belongs to Chrysler. It's called "Method for calculating fuel economy using manifold air pressure (MAP) and fuel rail temperature."

Here's the abstract: "A method for determining an approximate, instantaneous fuel economy of a gasoline powered motor vehicle. The method involves determining a nominal fuel flow through fuel injectors of the vehicle's engine under static pressure conditions and adding to this value a determined additional quantity of fuel flow through the injectors which is caused by dynamic conditions such as engine rpm, vehicle speed, etc. The additional quantity of fuel flow is determined in part by monitoring a pressure drop across the intake manifold of the vehicle. The temperature of the fuel and the octane rating of the fuel are estimated and used to help determine a fuel density value. The fuel density value is then used to determine a total volume of fuel used. The total volume of fuel used is then ratioed with distance information to provide a fuel economy value."

They're monitoring the injectors, but they're saying that some other factors (e.g., fuel temperature and manifold pressure) need to be taken into account in order to improve the accuracy.

Anyway, I just thought this might be interesting to ponder. I'm sure MPGuino is going to have terrific accuracy (at least compared to SG, which is going to be the typical comparison, I think). But questions about this might arise, so it might be good to think about whether there's knowledge in this patent that can be used to improve MPGuino, or to help users understand how to use MPGuino more effectively.

The patent is here:

I notice there are lots of other patents in this field, but this one struck me as particularly interesting and perhaps relevant to MPGuino.

I'm very curious about what folks think of this.

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