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Can a really simple, no PC ECU be created? Think screw driver programmed ECU.

In slack @kb1gtt commented about a 555 based ECU. @mck1117 mentioned the bosch D-jetronic was a discrete components ECU. I see the D-jetronic is fairly well defined in the below. link.
https://www.sw-em.com/bosch_d-jetronic_injection.htm
This looks like it uses the distributor to create astable pulses, then some circuits create the fuel injector mon-stable pulses. I feel that with a hot wire MAF, you could make a better design. I like the option of being linked to the crank angle, but I don't like that this adds complications. If we negate the crank angle sync, at least for now, I think we could make a fairly simple ECU. Basically MAF to small circuit, to fuel injector. You could adjust rich vs lean with a potentiometer. A second potentiometer could be used to adjust for XTau compensations. Eventually an IAT or CLT could also modify the analog signal to increase or decrease the pulse length at times. For now, I'm tempted to make an uber simple design, then add features to it at a later date.

If a MAF is used to create an analog voltage, you could potentially use an 555 chip configured as an astable oscillator to create the varying duty cycle that creates the varying pulses for the fuel injector.

The below MAF is aprox $20 USD, and would work for smaller engines.
https://www.aliexpress.com/item/32825683844.html?spm=a2g0o.productlist.0.0.564b7b9fxdpXMz&algo_pvid=88f5218f-93df-4ad9-a213-1e12e7fcb0b5&algo_expid=88f5218f-93df-4ad9-a213-1e12e7fcb0b5-7&btsid=0ab6fa7b15907064739767637e46df&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
Basically send that signal into this circuit, and you have pulses based on the amount of air flow.
https://electronics.stackexchange.com/questions/463012/555-pwm-motor-driver-controlled-by-external-analog-signal Take note that 555's are commonly found in 18V variants, so you do not need a 5V or 3.3V regulators. Just clamp your 12V to be below 18V and your good to go with a 555 circuit.

Any how, I just wanted to create some discussion points that will survive longer term than slack.

I will remind you of a recent post, by you, recommending precision and control when running an engine: https://rusefi.com/forum/viewtopic.php?p=36927#p36927

The cost of adding an stm32f0 and 5v/3v regulator is essentially zero.

This guys has actually made a 555 ECU https://forum.cxem.net/index.php?/topic/133271-555-%D0%B2-%D0%BA%D0%B0%D1%87%D0%B5%D1%81%D1%82%D0%B2%D0%B5-%D1%8D%D0%B1%D1%83-%D0%B4%D0%BB%D1%8F-%D0%BC%D0%BE%D1%82%D0%BE%D1%86%D0%B8%D0%BA%D0%BB%D0%B0/

I'm trying to simulate the 555 in a monostable pulse configuration. I've seen designs that use a crank pulse to trigger a monostable 555, which drives the injector. As a baby step, I'm trying to get a monostable simulation working, which I then plan to modify into a variety of circuits that I've seen people post. I've tried QUCS and LTSpice to get make a basic and text book monstable 555 simulation. However I'm failing to get it to simulate as expected. Does anyone have any suggestions on why the below does not work?

In this one from LTSpice I expect that on the falling edge of trig for the output to change for about 2mS. However it appears to echo the 10mS. The output seems to simply echo the trigger pulse. Perhaps I typo'ed some where? I'm not sure why it's not playing nice. This is based off this tutorial that I'm working from.
https://www.electronics-tutorials.ws/waveforms/555_timer.html

Looks like this is feasible. See below snap shot of a LTSpice simulation which shows a analog MAF signal being used to vary a fuel pulse from around 1 mS up to about 10mS. The pulse is triggered via a single pulse on the crank. R13 could be a POT which could allow you to adjust rich vs lean ratio. This still need some work, the crank pulse needs to be very short, which can probably be done via cap coupling, and the MAF is a 12V signal. I think most MAF's are 0.5V, so it would likely need an op-amp to scale the signal up. However the core concept appears to work.
https://github.com/jharvey/555ECU/raw/master/Docs/simulations/LTSpice/555ECU/555_ECU2.png