Another injected Elan
Posted: Thu Jan 01, 2015 7:40 pm
Here are some photos of my injected Elan. It is running quite well, but I spend all my time adjusting it anyways.
The throttle bodies are from the Kawasaki GPz-1100 Motorcycle. I threaded them with my mini lathe and made up adapters to connect them to the Weber flanges on the cylinder head. The cold air box is a piece of PVC drainage pipe (very elegant, no ?) and the intake side adapters for the throttle bodies connect to it via standard plumbing slip joints.
The fuel system is closed-end, I pulse-width-modulate the drive to the fuel pump to control the pressure sensed by this transducer: I think this is much more elegant than having to run a return line back to the tank. It also reduces current draw, which is a consideration since I am still using a 20 amp Lucas generator. The system pressure is set by software, which is much more flexible than a mechanical regulator.
I made up a surge tank by machining an extension for an SU carburetor float bowl that fits between the body and the lid. I replaced the needle valve with a larger one I found that is intended for use with a Chevy truck carburetor since I didn't think the flow rate of a single SU carburetor would be enough for the twink. You can see part of the surge tank in this shot, it is in the nose and bolted to the air cleaner housing.
The surge tank is fed by the usual mechanical pump on the engine, since it has a float valve, there is no need for a tank return line. The high pressure pump is bolted to the floor of the nose so it gets some positive head from the tank.
Instead of an idle air controller valve, I decided life would be simpler (because of the independent throttle bodies) if I just made the mechanical throttle stop adjustable, to this end I have a small stepper motor linear actuator as seen here:
Having closed loop idle speed control really makes driving the car more enjoyable.
The control computer is my own design, I based it on the Motorola 68332 32 bit microcontroller, which is a fossil, but has a nice coprocessor for generating timing signals. This latter makes sequential injection very easy. I also is NOT a BGA package, it was hard enough hand soldering a 132 pin flat package to the circuit card. I adapted some open source software to run on my machine. Despite the independent throttle body setup, I am getting good results with the speed-density control algorithm. I generate a manifold air pressure signal by searching for the minimum value over an engine cycle.
The throttle bodies are from the Kawasaki GPz-1100 Motorcycle. I threaded them with my mini lathe and made up adapters to connect them to the Weber flanges on the cylinder head. The cold air box is a piece of PVC drainage pipe (very elegant, no ?) and the intake side adapters for the throttle bodies connect to it via standard plumbing slip joints.
The fuel system is closed-end, I pulse-width-modulate the drive to the fuel pump to control the pressure sensed by this transducer: I think this is much more elegant than having to run a return line back to the tank. It also reduces current draw, which is a consideration since I am still using a 20 amp Lucas generator. The system pressure is set by software, which is much more flexible than a mechanical regulator.
I made up a surge tank by machining an extension for an SU carburetor float bowl that fits between the body and the lid. I replaced the needle valve with a larger one I found that is intended for use with a Chevy truck carburetor since I didn't think the flow rate of a single SU carburetor would be enough for the twink. You can see part of the surge tank in this shot, it is in the nose and bolted to the air cleaner housing.
The surge tank is fed by the usual mechanical pump on the engine, since it has a float valve, there is no need for a tank return line. The high pressure pump is bolted to the floor of the nose so it gets some positive head from the tank.
Instead of an idle air controller valve, I decided life would be simpler (because of the independent throttle bodies) if I just made the mechanical throttle stop adjustable, to this end I have a small stepper motor linear actuator as seen here:
Having closed loop idle speed control really makes driving the car more enjoyable.
The control computer is my own design, I based it on the Motorola 68332 32 bit microcontroller, which is a fossil, but has a nice coprocessor for generating timing signals. This latter makes sequential injection very easy. I also is NOT a BGA package, it was hard enough hand soldering a 132 pin flat package to the circuit card. I adapted some open source software to run on my machine. Despite the independent throttle body setup, I am getting good results with the speed-density control algorithm. I generate a manifold air pressure signal by searching for the minimum value over an engine cycle.