Motor Overview
I’ve always wanted to make a engine control unit (ECU). So when the i came into possession of a old 2 stroke lawn mower motor, i took the opportunity to play around with electronic engine management and direct fuel injection.
After checking the motor ran, i pulled it apart to work on the modifications. Basically i took a fuel system out of a car, attached it to the side side of the motor and put the injector in the cylinder head. I know this wouldn’t last long term. But i was just wanting to play around and see if i could 😛
This setup was pretty basic and had the carburetor only controlling the air flow while a sensor measured the air flow setting. A sensor on the crankshaft that determined the point in the intake stroke the exhaust port closed i.e. when to inject the fuel. A basic 12v driver circuit to run the injector. And finally the Arduino Micro-controller, the brains of the operation. Its job was to calculate the time the injector should be open, based on the air flow valve sensor. Then to activate the injector for the pre-calculated amount of time when the crankshaft sensor is activated. The ignition i kept standard as i didn’t want to take on too much at once and have too many variables.
In the end i never did get it to run. The most i got it to do was shoot fireballs out the exhaust, which I think was from injecting way too much and too late.
Looking back i think it could have actually been pretty close to running with just advancing crank sensor position and reducing the injector on-time a bunch. Also an exhaust with some decent back pressure would have also helped with pre-charge pressure.
Possible changes for future iterations:
- Have an actual Fuel map and ideally a O2 sensor
- A better, faster Injector driver circuit
- More precise injector timing for better fuel control
Year: ~2009/2010
injector in top of milled cylinder
Cylinder with Injector installed
jmc projects & Ideas 