this is the beginning of explaining the original MPI injection that came with the 4G63 turbo engine, by no means is this a complete explination, but I hope you can help me explain it by asking the questions you have
this is a very general explinaion
I guess the place to start is the main relay, its is the power distribution center of the whole system
before OBD1&2 all the manufacturers had a free hand on how to do things, some came with serial data, some didnt, the reason that is important is because you need serial data to build a scanner tool like we have today, so in the early wild days of computer design, we had to train to use the power distribution schematics to repair fuel injection problems
this is the main relay schematic with the key off and 'at rest'
this is the main relay with the key in start position
and this is the main relay with the key in 'run' position
there are 4 things needed to happen to make the engine run ( you can count that on one hand!)
you need air/fuel mixture intake, you need compression, you need ignition (spark) and you need timing, so I guess we should break down just the ignition
This is the CAS
all it is is a camera, really, two light emmiters are in the plasitc housing, the disc rotates between the two light emmiters and two photo diodes, the windows in the disc turn the photo diodes on and off by allowing the light to shine through the windows
I originaly thought this may have been a hot wire set up but I stand corrected, it is a korman votex set up
Some early Mitsubishi models also used the KV sensor. Ultrasonics (sound waves with a frequency higher than the human ear can hear) are used to detect the pressure changes. A small speaker sends a fixed ultrasonic tone through the vortex area of the sensor to a microphone. The greater the number of vortices, the greater the turbulence and the more the tone is disrupted before it reaches the microphone. The sensor’s electronics then translate the amount of tone distortion into a frequency signal which indicates air flow.
The 1983 – 86 Mitsubishis have a four-pin connector and the 1987 to 1990 versions have a six-pin connector. The early units also contain an integral air-temperature sensor while the later ones also have a built in barometric-pressure sensor. From 1991 onwards Mitsubishi started using a redesigned KV sensor with an eight-pin connector which replaces the ultrasonic generator with a pressure sensor which measures fluctuations in air pressure directly.
the is a barometer to sense the altitude and air temp sensor to adjust for hot and cold air
The air flow meter is just that; it’s not an air mass meter - it needs other sensors to gain information on air density and temperature so the ECU can make the necessary compensations. An air temperature sensor is fitted inside the Karman vortex air flow meter, but it is absolutely nothing to do with the meter itself.The system also uses a barometer ( high alititude sensor). The frequency of the Karman vortex square wave varies according to the density of the incoming air and for altitude using the barometer
and last but not least there is the injectors themselves, after all the inputs are made to the ECU, information is computed into the proper injector pulse width, the injectors are preset in size by how many pounds per hour of fuel the injector can pass into the cylinder, but to correct for engine load and speed, the ECU controls how long to hold the injector open by using a bianayr number to switch the injector on and off
I will be posting how to test and understand all these pieces with hand held, low buck tools if anybody is intrested
