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AFR target table using Alpha-N

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Andre, (and other knowledgeable persons)

I am trying to create an AFR target table but using Alpha-N as the load source. My ECU (Performance Electronics) requires the same load source for all its tables. The engine is an Ford FE (Big Block - 468") using a Borla ITB system. It will tune and run better using the Alpha-N system. The manifold does contain a vacuum source and the ECU allows vacuum compensation, but we've learned it still works better using Alpha-N. The engine at idle produces about 60kpa. The camshaft is relatively mild and the purpose of the engine is for cruising, not ultimate performance.

I've watched your webinars 065, 089 and 163 which address AFR and target tables but most of the discussion and examples are based on a MAP load source. The concepts are the same however a MAP source doesn't easily convert to a TPS source. As you are aware, the airflow changes drastically with the throttle opening and is not linear. You just can't cut and paste a MAP example into a TPS based table.

Do you have any examples or help on setting up a table and using TPS as the load source.



I would target Lambda 1.0 for 40% or less throttle at any RPM above 2000. I would Target Lambda 1.0 for 20% or less throttle from 0 - 2000 RPM. Above those TPS values I would taper to the same target Lambda for WOT (.88-.92 depending on engine).

Sometimes you may need to fiddle with the target Lambda around idle to get a smooth running engine (might want leaner or richer -- just try both directions and see what the engine wants...). Often with V8's there is substantial extra uncombusted air supplied by the cam overlap, so a lean reading value (1.05 or higher) is OK, if the engine is running smoothly. Or you may need to request a richer target lambda, so the VE table remains smooth. It depends if the ECU is running closed loop to the target, or just using that to calculate how much fuel mass to add for the calculated air mass.

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