Tuning With An Air/Fuel Gauge

[chaseincats]

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 July 24, 2021 by chaseincats

[chaseincats]

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.

[Captain Obvious]

There are no microswitches in the ECU.

[TomoHawk]

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.

[madkaw]

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 ? 

[TomoHawk]

I had an old AFM that had a dead sopt in the resistive track.  there was no way to fix it or revive it.  Another AFM fixed that.

[chaseincats]

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.

[Zed Head]

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.

 

[chaseincats]

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.

 

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

[TomoHawk]

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. 

[chaseincats]

good god this again

Edited September 13, 2021 by chaseincats

[TomoHawk]

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.