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I commend you on the effort. It is an interesting area of study and I hope you continue. However, I do have some comments/concerns about the paper.
First, and minor, reference [3]. It is very doubtful that you are achieving +/- .1% flow measurements from the electrical pulse width controlling the injectors. When commercial automotive fuel systems are tested gravimetrically, the variation is already larger.
Also, it is a mistake to assume that this method is readily applicable to modern fuel efficient designs. Consider, some systems intentionally alter injectory opening and closing times conditionally, others will leave the injectors on some cyls closed while still cycling others.
Second, I have some real concerns about your basic mathmatical model. My prediction would be that it would generate a fairly innacurate instrument of engine efficiency, and this seems to actually match your own data.
Consider figure 7, efficiency calculated from dyno readings. It does rougly match the expected V/P curve for a conventional combustion engine. And also, as expected, you have an 'efficiency island' near peak torque. However, your efficiency island is elongated from typical engine efficiency models.
Mathmatically, this deviation in the curve should be exaggerated by under sampling and an EKF techique, and that is what we see in your data. Consider figure 6. You point out that peak matches, but that is the lowest possible hanging fruit, like finding lambda 1.0 on a UEGO sensor. The question is, what is the typical error as we move away from the easily identifiable set point?
Based on your included data, pretty high. Notice how much larger and elongated the efficiency island is on figure 6. The expected V/P slope is not even really visible on the chart. If we did a scatter plot of point to point deviation between the two it would appear that, aside from peak, the instrument would almost always over estimate efficiency, and in a non-trival operational envelope, extremely so.
My third concern is that the paper never really establishes a link between the acheived measurement and the stated goal. Look at part of your first paragraph:
"optimal control to make great reductions in emissions and fuel consumption"
Now, we could debate rather or not your measurement of engine efficiency is accurate enough to be of value. But the more fundemental question is, is the data even really connected to either fuel consumption or emissions?
Virtually everyone in the field knows that every conventional combustion engine has a fuel economy sweet spot - wide open throttle (so there is no induced vaccuum reducing VE) at peak torque.
But this is not an available decision for routine operation of a vehicle. In fact, most people here (myself included) go out of our way to avoid this point of operation, because it is terrible from both the perspective of emissions and *operational* fuel economy.
At peak torque wide open throttle, the mixture is generally quite rich, to keep CHTs and pressure down so that destructive abnormal combustion does not occur. But this also means that the vehicle is operating way out side of the cat efficiency envelope, making emissions soar.
I'm not saying this to discourage you. Just the opposite. You are attempting to inexpensively measure a very narrow definition of effiency. What I am suggesting is that you try an experiment to demonstrate rather or not your target metric is of any practical use in either the area of fuel economy or emissions.
Good Luck!
-jjf
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