Richness on the V12

I 'm looking to bring a few more richness to the mixture using the potentiometer from the EFI ECU from my V12. I dont know if it is clockwise or not.
Does someone know the answer?

Salut Michel,

CCW: Rich
CW: Lean

How did you come to the conclusion that it needs to be adjusted though?

Salut Aristides,

Merci de l’info!
because of the color of the sparkplugs, too white :grin:

Is it a digital-p engine ?
Doing arbitrary adjustments might work, but you should really check what your ECU is doing via the feedback monitor socket. Details on the Book.

Problem with CW or CCW, do you mean looking down at ecu or up at ecu?

You need a voltmeter reading, if the volts go up, its going rich. If the volts go down, its going lean.

Another thing I do that helps determine a good setting without a voltmeter, using the feedback sockets, let it idle in Park fully warmed up. It will be idling in open loop with preset mixture. When you pull the little 2 socket plug, it will force it into closed loop using the O2 sensors and ECU mixture setting. If the idle goes UP in rpm, then it’s running too rich. If the idle goes DOWN in rpm, it’s running too lean. What should happen, there will be a split second stumble as it changes, and then the idle rpm should be the same. You will notice it fluctuating up and down a tiny bit, this is normal.

Put the plug back in, make the adjustment, give it a good 15 seconds or so, and then pull the plug again.

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Aristides, Greg,
The engine I’ve used on my E is a Marelli one, the ECU is a " Non Cat" one . I’ve simplified the wiring looms and I do not have the monitor socket anymore… :flushed:

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I guess you still have O² sensors?
I also used Greg’s system and it’s a very good indicator.
Did you also remove the open loop bypass plug?

Since you don’t have the feedback monitor socket you would need a gas analyser.

No O2 sensor on the noncat v12 suche the one I have.

Depending on how the loom was modified, removing the closed loop jumper and the park/neutral wiring could lock in open loop…
Also if ECM is looking for oxygen sensor signals, it defaults to a .5v signal via high value voltage divider resistors. That would also be less than ideal.
My understanding was that all EFI V12s used oxygen sensors, just later were heated.

There were some early NonCat NonO² versions for some markets.
But I never heard of a NonO² Marelli.

Yes, and I don’t know how different it would be from the default open loop mode.
IIRC, when I was experimenting with my 16CU, if I disconnected the O² sensor the feedback monitor voltage would oscillate very fast around 1.8V.

Here is the list from some of the ECU V12 ref:

Mine uses the DAC6338