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Hi guys on testing the accel enrichment i saw that a few seconds after each throttle opening event there was a very high drop in afr or a lean spot can you please explain what that is ?

Attached Files

I would say decel fuel cut.

i can understand if its fuel cut but the afr drops way below the target and im no pro tuner or anything but if i studied that lg file i would have identified that as a concern ? please do correct me if im wrong

If I'm understanding your question correctly, the issue is simply what I addressed in the actual webinar - You aren't going to achieve a 100% perfect flat line for your AFR response during a transient throttle event. The aim is to use the lambda trace along with noting how the engine responds to the throttle input (is it crisp and smooth or is it hesitant) to judge the next direction for our tuning.

In general once the accel enrichment tuning is optimised you will still see a slight lean spike immediately after the throttle opening but provided the engine's response is crisp this is the main concern.

Hi ... please note that the lean spike in question is not that when the throttle is opened ... i remember where you had tried yo get that line smoother but said to take engine feel into consideration and i am by no means disputing that , the lean spike that i am referring to is the second one at aprox 2 seconds after closing throttle ,

please see attached image

and should there then be 2 lean spikes ? one on throttle opening and again after the throttle had been closed ?

You will note on the image that in that screen capture of the log file there are 2 throttle opening events , but 4 lean spots 2 that occurs with throttle opening and another 2 after the throttle had been closed ....

The second lean area would be as a result of the over run fuel cut out becoming active. This will turn back off as the rpm approaches idle speed however there is some latency in the wideband response time, particularly at very low exhaust mass flows. This is relatively normal behaviour. The lambda would have continued to track back to target if I hadn't opened the throttle again so quickly.

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