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Afr settings

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Good day.

I have a question about setting my lambda at idle.

I have a 2006 Chrysler 300, i just built a 6.1 based 7.0 stroker, with a supercharger.. the factory stoich target 0.0694 or 14.4 afr which i feel is a bit lean for a blower set up? (Correct me if im wrong). But tochange this i see there are 2 ways to go about it.

1st i can change the fueling in ve tables to get it to where i want to be. But my concern it the ecu will be looking for the stock settings and use the o2 sensors to bring it back to what it want to see.

2nd can i change the factory stoich settings to a value id like to see to, for example from 0.0694 to 0.0715 or about 14.0 afr, and will that cause me other issues?

Thank you for your input on this subject

Steve,

Generally speaking adding a supercharger won't warrant a change to air/fuel targets under conditions similar to how the vehicle operated in stock form. At idle the supercharger isn't creating boost in the intake manifold, engine output is minimal, and there really there isn't a need to enrich the engine to combat high heat.

On a related note, when discussing the air/fuel target, the stoich point of a fuel is 1.0 lambda, then depending on the fuel type and composition, the stoich AFR will be a constant value based on the properties of the fuel you're using. For example 14.7 AFR for 0% ethanol gasoline, about 14.1 for 10% ethanol gasoline. Stoich point is not something you generally want to change, unless you're changing the composition of the fuel used in the vehicle.

That said, you're on the right track when you talk about tuning the engine computer to a new air/fuel target under certain conditions rather than just fudging the VE table. For example, at wide open throttle if the ECU is targeting 12.0 AFR and you want to target 12.5 AFR instead, changing the target from 12.0 to 12.5 will generally get you close to your desired result. Only then if you're still not actually hitting your target would you want to consider altering the VE table, and you'd only want to do so until actual AFR matches target AFR. If you only fudge the VE table, and don't update the air/fuel target, you will end up fighting the factory control strategies.

Have a great day,

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