what are the basics of mechanical injection, trying to learn the basics and what does what Options

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[Dave_Darling]

D-jet is not MFI. D-jet is an old, funky, analog electronic fuel injection system. It uses a variety of electronic sensors to determine how much fuel it thinks the engine needs, and opens the injectors for long enough for that amount of fuel to get sprayed into the intake. The injectors are opened for longer times for more fuel, or shorter times for less fuel.

CIS (Bosch K-jetronic) is sometimes called a mechanical fuel injection system. It isn't the same as MFI, though. It is a fuel-pressure-controlled form of injection. The bits and pieces vary the fuel pressure going to the injectors, which continuously spray fuel into the intake. Higher pressures mean more fuel goes in, lower mean less goes in.

MFI (yes, Clay, it went through aero engines in the 30s and 40s) is a purely mechanical system. The MFI pump is a piston pump, much like an engine is. There is one pump piston per engine cylinder, and when the pump piston goes up in its bore, it pushes fuel out of the injector in the intake. The pump is hooked up to, and runs at the same speed as, the camshaft. The pump has a means that lets it vary how much fuel is pushed by each piston for one stroke. Rotate the pump piston one way, it pushes more fuel. Rotate it the other way, it pushes less fuel. That rotation is hooked up to several different things, mostly the throttle position and a mechanical RPM sensor.

Is that simple enough?

Also check the Wikipedia article.

--DD