How To ?s for Tuning

@BobPhx will be happy - new oscilloscope in my hands :grin:

Now that I’m not panicked with valve/injector clicking noises, I’m moving to tuning.

Notes and Considerations:

  • I’ve removed the AAV
  • I’ve removed all the emissions stuff
  • I replaced the small little trumpet intakes to allow for more air
  • New O2 sensors
  • I’ve slightly increased the throttle gap and related switches to increase idle from a stumbling 450 to smooth 550
  • When the front is jacked up, the engine starts but stalls shortly after - thinking fuel pump issues and that plays into tuning questions and thoughts

1. How do I tell if the ECU has entered closed loop?
I’ve dug around and there’s lots of questions and discussions on this topic, what is open and closed loop, etc., but couldn’t find a definitive guide. I’m looking at The Book now which may have answers. I think the first thing I’m worried about is the fuel richness under this new configuration. With the scope, I was going to start by looking at the 4-pin diags in the trunk that shows the ECU adjustments from the O2 sensors. I think I know how to do that. The car needs to come to temperature and then based on various sensor readings, the ECU will switch to closed loop. I’m trying to figure out the key determinant/s I can check that tell me I’m in closed loop versus open loop.

2. Are there other ways to work with idle adjustments without an AAV other than opening the throttle a touch?
After all the changes, the idle actually is much happier than is was before, even after all the work and rebuild and tuning I did with the AAV. It’s very smooth now. I’m looking at this because opening the throttle increases the fuel richness and that will impact the readings. I think I just need to make sure that A and B throttles are adjusted the same, and then from there if the A or B fuel map is outta whack, go from there, but I like having options.

Cool - as always - love any constructive criticism, thoughts, new directions, etc :grin:

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Good call on the scope :smiley:

Couple of thoughts:

  1. I don’t know the answer, but remember that Marelli cars are weird. The PRNDL doesn’t control open vs. closed loop, and the ECU service harness is a bit different than Lucas. This thread has some details:
    Open v closed loop at idle

  2. You could easily create a way to increase idle speed with an adjustable vacuum leak downstream from the throttle body. All the EAV and AAV do are create leaks which speeds up the idle. So maybe some sort of hidden petcock. Remember the filter the inlet side, possibly plumb into the airbox like the EAV does. Maybe something in parallel with the EAV that allows you to bypass it. Also I know several others have created “manual” AAVs which allow adjustable idle speed.

As far as I know, and as Bob said, on later cars with heated oxygen sensors, the ECU is always on closed loop except at start up or when the ECU gets no signal from the sensors.

In theory, opening the throttles a touch should not have any ill effects.
But without the AAV or an alternative adjustable air intake source, adjusting the idle will be a very complicated job.
Any kind of adjustable valve will do the job.

Also, without the AAV cold starts could be a bit problematic.
You will need a second EAV in conjunction with a thermostat, or something similar to allow more air when cold.
I used a caterpillar thermostat from a water heater, with it’s sensor inside the V, a fuel return valve as an air valve connected to the big port at the intake manifold and a relay to drive it. Somewhat complicated but has the added benefit that I can adjust when it will switch Off according to the engine’s temperature.
Then I used that valve to also increase the idle when the car is in D via the gear inhibit switch.
Now I have 750 rpm when in P or in D.

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