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Tuning With An Air/Fuel Gauge


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26 minutes ago, Captain Obvious said:

Understood about the timing. Maybe you'll get lucky and it will never happen again. (Suuuuuuure).

And I'm not proposing any theories yet... I'm just trying to come up with something, anything. to maybe point in the right direction. I'm thinking that if you do the "START with engine already running" a couple times and nothing changes, then maybe it REQUIRES the engine to actually come to a stop to reboot. Injectors need to stop injecting, coil needs to stop coiling... all that.

On the other hand, if you do that test and the lean condition DOES go away, then there might be some info to be gleaned from the fact that the engine does not need to a complete stop in order to make the lean boot go away. Vibrations don't need to stop, starter does not need to suck a big hit of current from the battery. Alternator doesn't need to bootstrap. That kind of stuff.

Just fishing at this point.   LOL

Haha sounds good.

I just went to check and this is my ECU's version label like we were talking about: unnamed.jpg

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I'll see what I have for ECUs here. I don't know if I can tell anything from the label, but I'll look.

So here's to hoping the lean boot thing just doesn't come back, but in reality what will probably happen is that it'll occur when you're dressed nice and don't want to go popping the hood and pulling wires off and all that.  Haha!

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  • 2 weeks later...
Posted (edited)
On 6/29/2021 at 8:07 AM, Captain Obvious said:

I'll see what I have for ECUs here. I don't know if I can tell anything from the label, but I'll look.

So here's to hoping the lean boot thing just doesn't come back, but in reality what will probably happen is that it'll occur when you're dressed nice and don't want to go popping the hood and pulling wires off and all that.  Haha!

I removed/opened my ecu for my new problem here: https://www.classiczcars.com/forums/topic/65578-sudden-engine-shutoff/?tab=comments#comment-624753.  But since we were discussing what my ECU looked like, here it is too lol

 

front 3.jpgback.jpg

Edited by chaseincats
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OK, so that's an original 78 ECU and there's no software in it. In other words... I don't think there's anything inside that can that would cause a lean-boot that would last the length of the drive and then be reset by a reboot. Still sounds like a software issue to me.

And with that in mind... Something we haven't discussed in depth... Jonbill had asked earlier "when it is in this "lean" state, does it feel normal to drive, or hesitant?"

Your A/F meter is the only entity attached to the car that has any software in it. Let's consider the prospect that it's a measurement phenomenon and not "really" occurring?

So can you tell from driving the care while it's in the lean-boot state... Does it feel lean, or does it feel the same as when it's not measuring lean?

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37 minutes ago, Captain Obvious said:

OK, so that's an original 78 ECU and there's no software in it. In other words... I don't think there's anything inside that can that would cause a lean-boot that would last the length of the drive and then be reset by a reboot. Still sounds like a software issue to me.

And with that in mind... Something we haven't discussed in depth... Jonbill had asked earlier "when it is in this "lean" state, does it feel normal to drive, or hesitant?"

Your A/F meter is the only entity attached to the car that has any software in it. Let's consider the prospect that it's a measurement phenomenon and not "really" occurring?

So can you tell from driving the care while it's in the lean-boot state... Does it feel lean, or does it feel the same as when it's not measuring lean?

Gotcha

It absolutely feels hesitant and is a real dog to drive so it shouldn't be the gauge in that case.

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  • 2 weeks later...
Posted (edited)
On 7/10/2021 at 12:42 PM, Captain Obvious said:

Bummer. Was hoping it was just an instrumentation issue.

We're back to where we were before. Keep us posted!

Update: Had lean boot happen today and noticed it while driving.  I ended up kicking the pedal (flooring and dropping it) 4 or 5 times in quick succession and that seemed to fix it.

So my guess is a periodically lazy TPS?

Edited by chaseincats
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  • 1 month later...

Update again: I started the car today and got "lean boot" so I shut it off and restarted to another lean boot - I restarted it a good 4-5 times with no change so I took it out on the road anyway.  It seems the only way to get the car back into regular mode is to leave it in a low gear and floor it/drop the pedal in quick succession - after that I didn't have a problem the rest of the day.

My next guess is one of the microswitches in the ecu is getting tired.  I'll try to give the computer a smack the next time it happens and will see if that does anything.  Also for what its worth, I've noticed this never happens after the car has been sitting for days, it's only after its been parked and restarted after a few hours.

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9 hours ago, chaseincats said:

 

  I'll try to give the computer a smack

S30s don't have computers in them, unlessz you install something.  Neither to modern vehicles; hey have micrcontrollers  The Bosh L-Ject ECU is just a circuit board with transistors, integrated cir cuits, and other discreet electronics.

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You could have had Megasquirt or another programmable ECU by now , but I understand wanting to figure this out . 
Sure your MAF isn’t sticking ? 

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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.

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17 hours ago, chaseincats said:

got "lean boot"

I went to the top of the page and couldn't find what "lean boot" means.

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.

image.png

 

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3 hours ago, Zed Head said:

I went to the top of the page and couldn't find what "lean boot" means.

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.

image.png

 

"Lean boot" is a term coined by @Captain Obvious earlier in this thread to describe the car inexplicably running lean at startup.

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I still don't understand how you can tell the exact air-to-fuel mixture going into the cylinders by measuring the oxygen in the exhaust gas in the exhaust pipe.  There is no such thing as a sensor that measures the air-to-fuel ratio directly so you can show it on a guage, so you are making a lot of big presumptions, as well as presuming the engine is in perfect working order, a complete combustion, etc.

You can measure the amount of air using the density sensor and air speed sensors, and the amount of fuel (approximately) using the fuel pressure and injector timing, then making some calculations to calculate the air/fuel ratio. 

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27 minutes ago, chaseincats said:

"Lean boot" is a term coined by @Captain Obvious earlier in this thread to describe the car inexplicably running lean at startup.

That's strange.  Since the coolant is cold, the mixture ought to be a bit rich.  Please explain how you can get a lean condition for a cold engine, unless it was stopped in a warm state, then retarted before it could cool.

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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.

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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!  LOL

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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!

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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.

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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.

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