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Closed Loop Lambda vs Base Fuel Map

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In the Syvecs ECU that I'm running, there's both fuel map that uses injector pulse width and also a closed loop table with Lambda targets. My question is how do these 2 tables work together?

It seems that I could simply make changes to the Lambda table to change fueling but where base fuel map come into play? From looking at the settings, it appears that closed-loop is disabled for 8 seconds on startup. Is the base fuel map only used during startup until the O2 sensor warms up and then the ECU switches into closed-loop mode?

Is there any point, post startup where the ECU references the base fuel table or it strictly closed-loop from that point forward?

Thanks for your help.

at no time is any one table in full control of the fueling or even the ignition in an ECU. When cranking you have up to half a dozen compensations involved, such as; pre-crank prime, crank enrichment, post start enrichment, coolant temp compensation, your main fuel table, etc.

Your closed loop won't be active when starting up due to these compensations as it is more important to get the engine running than to hit a target AFR, you'll also find that there is a coolant temp lock out on your closed loop also.

The ECU references the main fuel table initially, then it'll add/subtract and trims that are active before checking the AFR measured and comparing this to the target lambda, if there is any variance then it'll apply a trim of it's own before measuring the the AFRs and feeding back into the closed loop again.

What engine are you working on?

Thanks for the reply Chris. I'm working on a 2.3 litre Ford Ecoboost engine. The one that's the in Mustang and Focus RS.

So what based one what you're saying, the ECU will compare the closed loop target against the measured lambda value and then make changes to to the fuel trim tables in order to more closely hit that lambda target in the future? So assuming that the base fuel table is fairly close, the ECU will can essentially "auto-tune" itself as the car is driven more?

Would you mind posting the map up? I'd like a look at it as I've a few customers with the mk3 Focus RS.

It wouldn't auto-tune unless the ECU was programmed to apply any trims to the map. For tuning the closed loop needs to be deactivated and tuned as best as you can and make sure your target AFR map is where you want it before activating the closed loop control.

here's a webinar Andre hosted on activating the closed loop control on a Link ECU, different platform, same principles apply:


Watching the webinar now Chris. Great stuff.

Thank you.

Which part of the calibration are you wanting to see?

I've attached a screenshot of the Lambda fueling targets that I'm using in my car.

Attached Files

Which part of the calibration are you wanting to see?

I've attached a screenshot of the Lambda fueling targets that I'm using in my car.

Attached Files

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