Paul

The temperature compensation was only an idea.

Not a good one as it turns out.

Ah ha, just, re-read your comment.

Obvious---the pot alters the mixture proportionally to 555 increasing or
decreasing the pulse width across the whole range.

The temp sensor is another input, hence the need for computamebobs, that we
don't want.

Here's another idea (so don't shoot me if no good)
Could the MAP output be also used to drive a PFM for the fuel pump?
Someone was working on that a while back.

Clive.

Yes I think that could be made to work. However I, like Dave Leonard prefer a
full return system for several reasons. One of which it is known to work.

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I have given this a bit more thought since Clive mentioned it again.

One 555 with input from a crank angle sensor and manifold pressure might work.

It looks like one of the cheapest fuel injection systems of all as you need the fuel pump anyway. The fuel injected is both pulse width modulated by manifold pressure and proportional to engine RPM by pulse rate. It is the product of RPM and manifold pressure. Easy to check on the bench as all you need is a hand vacuum pump to simulate manifold pressure and a pulse generator to simulate the crank angle sensor.

One problems is controlling the power supply voltage to the fuel pump. The voltage regulator in most alternators maintain the supply at 13.9 volts more or less which may be sufficient.

The simple mechanical passive injectors themselves are available in a wide variety from Kinsler.

http://www.kinsler.com/page--Home-Page--13.html


Paul Lamar