Whoa, Nice concept!
I follow your concept, see if I have it right.But for accelerating and hill climbing, it can be hard to tell what's best. If you are accelerating hard, the bar is down at 25 mpg or so, which seems bad, but in fact the engine may be operating very efficiently--using a lot of energy but storing the result as kinetic energy of the car. You may be better off opening the throttle pretty wide (where the engine is efficient), accelerating quickly, and then suddenly leveling off your speed, rather than gently sneaking up on the desired speed, even though the latter looks better on the indicator.
Awesome!Mike Dabrowski 2000 said:Hi CHRS
Dont mean to jump on your thread, but think you may have uncovered another thing MIMA can do.
That's a good data point. It might be that we have to time the interval between pulses, rather than counting pulses in a fixed time, in order to get enough resolution on the velocity signal to also calculate a good acceleration signal. Is that within the capability of your hardware, or should I start thinking about an extra circuit to do that function?Mike Dabrowski 2000 said:Will have to see what kind of acceleration resolution I can get from the VSS, to know how good we can compute acceleration from the signal, I did a quick look at the VSS signal with my scope, and it goes from 0 HZ when the car is stopped to about 55HZ at 40MPH, and it is a linear change.
Right--the amount of fuel injected should be linearly related to the MAP signal, as long as the fuel/air ratio is held constant. But when you enter lean-burn, the mixture is suddenly drastically changed. So there's an unknown nonlinear relationship between fuel per cycle and MAP. Furthermore, there are other factors that affect whether you go into lean burn, at least including what gear you are in. If all I wanted was a general indication of doing well or poorly on MPG, it would be fine. But I actually want something truly proportional to fuel use, because what I want to do is compare gently accelerating in lean burn to open-throttle acceleration.The map is the mixture determining signal that the ECM uses to control the fuel injectors, and is very sensitive indicator of engine load....
It certainly doesn't directly indicate efficinecy--it gives a rough nonlinear indication of fuel consumption per revolution. But for efficiency we need fuel consumption per power out. That's where my adjustments factor in--to take numbers on fuel consumption and change to efficiency. But I'm not sure it's worth correcting for accleration if we can't get the fuel consumption number more accurately to start.It should be a good indicator of engine efficincy...
As primarily an analog electronics guy, I'm amused when "simple hardware" involves multiple chips each with millions of transistors, but of course from a practical point of view that is simpler than an analog circuit with a few transistors that needs pots adjusted for every 10 degree temperature change....The simplest hardware to determine what the MPG bargraph is showing was suggested in the past, just capture the video image,from one of those mini tv cameras like I used for my rear MPG display, which has AGC to compensate for lighting changes. Do a simple OCR scan of the captured frame to decode the MPG numbers. May be able to do a progressive frame grab with a PIC microcontroller,kind of like the Snappy frame grabbers of several years ago. I happen to have 2 of those in my parts bin..