cribbj wrote:
Mark, I'm trying to keep the stock ECU's in the system, but firing into dummy loads for the injectors & coils. I need to keep them in order to pass an annual OBD2 scan to get a state inspection, and renew the registration on the car.
An aftermarket box will be running in parallel with the stockers and will actually be running the engine.
To keep the stock ECU's happy, they need MAF signals, which in this case is just a 1.0 to 4.5v analog signal, proportional to the airflow. No PWM'ing required.
My other strategy (besides installing mini-MAF's) is to try & synthesize a MAF signal from the MAP+IAT+RPM+TPS, but I'm a real dummy when it comes to embedded processors and other fancy electronics. Apparently other Real Smart Guys have already tried this, and have had very mixed results. Hence my reticence, and interest in looking for other alternatives.
Ok. 1.0V to 4.5V should be pretty easy to fake from nearly any ECU you buy. They all have a PWM out signal that you can tie to somehting that should be useful, englab lets you tie to anything you please. I know you don't want PWM but nobody I know of has a true analog output but it's VERY easy to convert the PWM to analog, it's just a resistor and a capacitor:
http://www.instructables.com/id/Analog- ... o-Voltage/You can buy something pre-made or solder it up and heat shring it in-line. Very easy either way.
then you just enter the correct PWM dutycyle in the control table for the voltage you want. 1V = 7.2% (of 13.7V) and 4.5V=32.8%.
Once you know what ECU you're using we just need to figure out the best option for setting up the PWM output.
Thinking about it you could probably just use the injector drive signal is worse comes to worse....it is a PWM tied to load, RPM,etc so filter it, add a voltage divider to get it in the right range and you've got synthetic MAF. This is real parts not programing so there will be a little trial and error type tuning which is why it wouldn't be my first choice but it will produce the signal you need without needing to program anything.