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Making small fuel map changes after dynoing

Practical Dyno Tuning

Discussion and questions related to the course Practical Dyno Tuning

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Is it best when making any fuel map changes to fine tune that you do so in open loop? Or even when creating your fuel map? Then once you have everything how you want, turn close loop on?

There are two ways of adjusting the fuel map and really the difference is down to understanding the implications.

If you choose to disable the closed loop fuel control then the measured AFR is what is being generated based on the fuel map and hence if there's an error then you need to adjust the map to correct it. This would be the most typical way of tuning the fuel table.

If you're using closed loop control then you need to take into account any error between your target and measured AFR BUT you also need to consider what the closed loop trims are doing. For example if your AFR is on target but you have a +5% STFT then this means that the number in your fuel table is 5% too low. To correct this you would add 5% to the relevant cell and your fuel trims 'should' be back at zero.

STFT? Thanks for the response Andre!

STFT = Short Term Fuel Trim

Depending on the system the software may use other names like Lambda Feedback, Lambda Short Trim or Closed Loop Control Trim.

Sorry for confusion. David has nailed it.