Tuning With An Air/Fuel Gauge

[chaseincats]

That's what we're trying to figure out.  It happens every few weeks and is fixed by kicking the pedal a few times.

[Patcon]

It really is a shame O2 sensors dont work since all modern cars use them to adjust the fuel mixture (sarc) 😣

[Captain Obvious]

6 hours ago, chaseincats said:

I thought the ecu (fuel injection brain if you dont want to call it that) was a bunch of microswitches on the s30s, no?

@madkawThat's an interesting idea with the afm sticking.  I don't want to switch the car to megasquirt because it runs fantastically 95% of the time especially after this tuning thread.

There are no switches (electro-mechanical devices) inside the ECU. There are lots of transistors (which can be used to "switch" current paths, but there is nothing elecrro-mechanical. Nothing moves inside the box except electrons.

And as for it being a "computer" or not... I would say "not". To me, a "computer" would be a programmed device running a sequence of decision making steps, and the old analog ECU's do none of that. There are no "steps", and there are no decisions.

I have not, however, looked up or researched in any way what a "computer" is by definition. But I can tell you there is nothing programmable inside the ECU's, at least through the end of the first gen Z run. Some of the later ZX's have embedded computers inside, but nothing before the ZX.

[Captain Obvious]

Oh yeah, and yes... A sticking AFM is an interesting idea.

If it's sticky and not opening as far as it should be, you'll run lean. Just seems kinda hard to believe it would be intermittent like that. But whatever... It's better than anything I've got at this point which is absolutely nothing! 

[TomoHawk]

If you want to measure temperature, you use a temperature sensor or thermometer, and read the value directly, the same for pH (of a water or liquid) to directly measure pH., a pressure sensor or gauge to directly measure pressure, etc., but there is nothing like a sensor that directly measures the air-to-fuel ratio in the cylinder.

They use the oxygen sensor and presume that if there is no oxygen in the exhaust gas, it must mean a 14.7 air/fuel mixture.  So you could calibrate the ECU to any oxygen value and make it mean 14.7, then complain the engine runs badly!

[Captain Obvious]

4 hours ago, Zed Head said:

The ECU's are analog computers and use capacitors to control injector open duration.  No ones or zeros.  The algorithms are hard-wired in, no programming possible.  You can only change the characteristics of the inputs to manipulate the outputs.

@Zed Head Not really pertinent to the conversation at hand, but actually I think there's a lot of gray area involved here. I haven't actually scoped deep enough into the ECU to know exactly how they do things, but I believe they are more sophisticated than just using capacitors for duration. I think there ARE actually ones and zeros.

You'll notice in the functional description you posted for the ECU, they mention "frequency conversion". To me, that means they are converting the analog signals to a frequency signal (V to F), and then doing "calculations digitally". Now it might not be a computer, but I do think there are adders, timers, counters, multiplexers, summers, integrators, all that kind of stuff. And all that can be done with non-programmable logic circuits.

So even though it might not be programmable, I DO think they are converting signals to "digital" and using ones and zeros derived from a highly accurate resonator circuit. It's much more accurate than an R-C time constant.

[TomoHawk]

5 minutes ago, Captain Obvious said:

There are no switches (electro-mechanical devices) inside the ECU. There are lots of transistors (which can be used to "switch" current paths, but there is nothing elecrro-mechanical. Nothing moves inside the box except electrons.

And as for it being a "computer" or not... I would say "not".

Well...  there is that one big integrated circuit in a metal can which does all the complicated stuff.

When I had computer 101, we learned that a computer had a CPU, short-term memory (RAM), long-term memory (hard/floppy drive) and can start & stop programs at will until you turned it off.  Micrprocessors in cars are similar because they have a CPU and memory (RAM and flash memory) ( think of the Arduino things) and only operate one kind or system or devices in a vehicle (engine, transmission, electrical (lights/security/heat/windows) entertainment, etc.  Each begins running a single, but very sophisticated, program when you turn on the main power, and runs it until the power is turned off.

[TomoHawk]

On 6/27/2021 at 7:25 PM, Patcon said:

Get some compressed air and cool the ECU when it does it and see what happens

You can get a cryo-freeze spray for electronics, but I don't know who sells that now.

[TomoHawk]

1 hour ago, chaseincats said:

 

 

7 hours ago, chaseincats said:

I thought the ecu (fuel injection brain if you don't want to call it that) was a bunch of microswitches on the s30s, no?

@madkawThat's an interesting idea with the afm sticking.  I don't want to switch the car to megasquirt because it runs fantastically 95% of the time especially after this tuning thread.

You must be thinking of old computer peripheral or I/O adapter cards, that use the microswitches to set up the port settings, card address, etc.

Edited September 13, 2021 by TomoHawk

[TomoHawk]

If you are interested in a less electronic way to tune the fuel injection, Autospeed.com has some good technical articles you read and try:  One uses an accelerometer in stead of the S-O-P  method.

BTW-  the accelerometer is also useful for determining shift points.

https://www.autospeed.com

Edited September 13, 2021 by TomoHawk

[Zed Head]

23 hours ago, Captain Obvious said:

So even though it might not be programmable, I DO think they are converting signals to "digital" and using ones and zeros derived from a highly accurate resonator circuit. It's much more accurate than an R-C time constant.

My post was basically a regurgitation of things I picked up from various other posts on the forum.  Odds are almost certain that you're correct.  My main point was that you can't really "tune" or adjust anything between the inputs and the outputs.  It's all hardwired/soldered in.

I did take the opportunity to dig up a neat article about the history of A/D conversion.  I think I've mentioned in the past that most of my electronics experience is just dendrites of knowledge taking me just far enough to solve a problem.  Many gaps.  Like a piece of Swiss cheese, it will support some weight but it's definitely not solid.  Kind of squishy. 

https://www.analog.com/media/en/training-seminars/design-handbooks/Data-Conversion-Handbook/Chapter1.pdf

[TomoHawk]

It looks like you could only make changes to how the L-Jet ECU works if you had the original Bosch circuit diagrams and operation flowchart.  But at least you can fool around with small changes in the coolant sensor.