I’m embarking on a project to fuel inject my 1987 Austin Mini, which has already had an engine swap from a 998 to a 1098, but currently runs on an HS4 1.5″ single carburettor.
This obviously offers a reasonable level of tunability, with the ability to change needles, dashpot damper springs, dashpot oil and mixture adjustment and is relatively easy to set up for quite a reasonable state of tune, especially now that I have an AFR meter installed.
However, I would like to try fitting an MPI system and develop my own ECU for electronic fuel injection. Due to the ‘Siamese ports’ on the A-Series engine causing charge robbing, and only having one fuel injector per two ports, this is apparently something that’s difficult to achieve well, which makes me want to do it all the more.
So, I’ve begun researching and purchasing various parts for this project including an MPI Inlet manifold and throttle body from Ebay:
Now I’ve had a chance to look at one up close, I think I can work out most of the connections and functionality. Fortunately this one comes with all the sensors too so I can start to test those and their interfaces.
This is the Intake Air Temperature sensor (IAT) on the MPI inlet manifold. It is located very close to the inlet port to get the most accurate measurement. The datasheet from Honeywell states that this is a 2,000 Ohm at 25C, Negative Temperature Coefficient (NTC) thermistor temperature sensor. I should be able to build a crude interface for this to a microcontroller using a potential divider.
This is the Manifold Absolute Pressure (MAP) Sensor Rover Part number MHK100600. I haven’t yet been able to find out much information about interfacing with these apart from that they are expensive (~£80). This one has 3 pins, which are likely to be +VE, GND and Signal, probably at 0-5V or 0.5 to 4.5V signal, which will probably relate to 0-1 bar or something similar. I have managed to find a bit of information here: http://www.mgfcar.de/sensor/ and here http://www.tom-seven.stillgame.ch/wiki/doku.php?id=map_sensor#schema_and_signals.