ODBII Program Car for better gas milage

It is theoretically possible to flash the ECM through the OBD II system to improve fuel mileage, but there are some things to keep in mind:

1) You will not have any warranty coverage on the ECM, including emissions performance warranty. 2) You will not have any warranty coverage on any parts that are affected by any reprogramming. For example, if a lean-misfire damages a part, there will be no warranty coverage. 3) There is no inexpensive easy way to return the ECM to its original programming if you are not satisfied with the results, like if the engine runs poorly, or has so little power that it becomes undrivable. 4) Any improvement in fuel mileage will result in reduced performance and/or engine and component life. 5) The folks who originally programmed the ECM are pretty knowledgeable about the vehicles they designed, and so there is a pretty good likelihood that given the overall design of the vehicle and taking into account the vehicle weight, transmission, differential, and engine operating characteristics, they have balanced fuel economy, engine performance, and component longevity in their programming. 6) There is a good chance that an ECM that has been re-programmed by a do-it-yourselfer will not comply with emissions requirements, so the vehicle will probably not pass the state OBD II emissions test. 7) Fuel has different characteristics in different parts of the country and during different parts of the year. The vehicle is programmed to take this into account, and any new programming should also take this into account. 8) If the vehicle has an automatic transmission, reprogramming the transmission ECM may also have to take place because of engine operating characteristics. 9) The re-programming may make traction control and electronic stability control malfunction.

Other than these few issues, there is nothing to stop someone with a thorough understanding of how every component and sensor is controlled by the ECM and the effect of variable signals from those sensors on stoichometric efficiency couldn't go and do and re-program the ECM.

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stoichometric = not a word - or perhaps a buzzword only. Exactly what do you have in mind? There are people out there that know a thing or two about chemistry .

...in automotive applications used to describe complete combustion of the air-fuel mixture:

OK, my bad typing... the word should have been "stoichiometric", not "stoichometric".

Does this program not have a means to back up the existing settings so that they can be restored?

The authors of this program have obviously gotten around that. If they can alter the settings, I would imagine they can copy them off to a configuration file for backup. Worst case scenario: write them down by hand before making any changes.

Reminds me of a show I saw on TV somewhere. A team was designing and building an updated Shelby Cobra. The body was together, and the engine had arrived and was installed. Problem: the ECM needed to be tweaked, and all the text displayed on the little monitor was in Japanese... which nobody could understand. It took them all night to get it straightened out.

I'd be curious to see how the software works.

Since the ECM is programmed to answer if-then statements like

"If MAF voltage = A and throttle position = B and coolant temp = C and intake air temp = D and brake light switch position = E and transmission gear selector position = F and transmission gear position = G and the position of the evaperative emissions purge valve is H and the signal from sensor 1 bank 1 is I and the signal from sensor 1 bank 2 is J and the signal from sensor 2 is K then injector # x pulse duration is L and ignition timing advance is M, for all possible values of variables A thorugh K"

I imagine that it is not easy to come up with the solutions for L and M that will make the car more efficient than the solutions that the factory engineers came up with.

If you know how to solve that equation, then you have the knowledge to be able to possibility make the car more efficient than the factory engineers did. Otherwise, I think the results would be similar to what would happen if I tried to make a Swiss watch more efficient.

Hey, don't sell yourself short, Ray! You might get the watch to sing "Cuckoo!" at 7 min 23 sec past the half hour. Or something equally useful. ;-) (IOW -- for our slower readers -- I agree.)

LOL! It would be interesting to see if anyone could actually get better fuel mileage while preserving performance, and drivability without increasing NOx, CO, and HC emissions.