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Old 04-29-2012, 05:02 AM   #80
roger 04 rt OP
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Joined: Nov 2011
Location: Massachusetts
Oddometer: 2,291
Yesterday afternoon I disconnected the Wideband O2 sensor so that I could measure the "raw" or Open Loop, Air Fuel Ratio (AFR) of the Motronic MA 2.4., with Pink Coding Plug. And then measure the Open Loop effect of the BoosterPlug. The motorcycle is running 93 Octane E10 fuel, which is important since it has shifted the curves upward by about 4%, meaning running 4% leaner.

In all the charts, there are two marker lines, one is at 14.7:1 (normal Closed Loop stoichiometric) and 13.8:1 (my richer Closed Loop target that creates more power). In the first photo there are two charts: the top chart is Open Loop, the lower Open Loop plus BoosterPlug.

The top chart below shows Open Loop AFR, after the Motronic is reset, and from a Cold start. For the first three minutes, you can see the AFR moving from 13:1 to the low 15s as the bike oil warms up. If I were running pure gas, the warmup would be in the 14.7 range, but E10 leans out the mixture. Much of the cruising time, the AFR is between 15:1 and 16.5:1--fairly lean. Notice in the histogram inset chart that the bulk of AFRs are between 14:1 and 16:1, even including acceleration.

The in the lower chart, the bike is warm, the Motronic is still reset but a BoosterPlug has been connected, dropping the air inlet temperature (AIT) signal to the Motronic by 20C. There is a similarly large spread of AFRs, but now they run between 13:1 and 15:1, about 6-7% richer. I was surprised at how much the AFR varies in Open Loop operation.

For comparison, look at the next photo, the conditions are reset Motronic, no BoosterPlug and Closed Loop at 13.8:1. The upper run is the first test run after reset and the lower run is the second run after reset. Since the Motronic is only Closed Loop about half the time in these charts, and comparing these two runs to the first photo (Open Loop conditions), you see Adaptation, the learning of Closed Loop applied to Open Loop conditions, and in the second run looking at the even tighter spread of AFRs, further Adaptation.

Some conclusions:

1) E10 fuel results in leaner Open Loop operation
2) Open Loop fueling results in a wide variation of AFRs
3) The BoosterPlug does enrichen the fueling tables by 6-7%
4) Closed Loop operation tightens the fueling range
5) Closed Loop operation allows the Motronic to correct for E10, aging injectors and air filters, and variations in battery voltage and fuel pressure.
6) The Motronic is a learning, adapting engine controller that takes what it measures in Closed Loop operation and applies it to adjust Open Loop fueling. (The mechanisms and degree could be examined further.)
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