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Old 09-30-2012, 09:23 AM   #97
roger 04 rt OP
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Joined: Nov 2011
Location: Massachusetts
Oddometer: 2,108
How the Motronic handles spark advance has been something of interest. When the data in the last post was collected, I also collected ignition timing data, plotted below, for reference and for those who are interested. This data is for the Motronic MA 2.4, Pink Coding Plug.

Unlike fueling which can be modified externally, spark advance is under the control of the Motronic's internal program so can't be modified without an ECU chip replacement.

The charts below show spark advance compared to RPM and to throttle angle. In the RPM chart you can see that advance is increased with RPM, reaching a maximum of about 43 degrees above 4000 RPM.

In the TPS chart though you can see that the maximum advance is only for throttle angles below 18 degrees (80 degrees is WOT), and is then reduced for wider throttle angles. From 50 degrees to wide open throttle the advance is limited to 20 degrees.

The other thing worth noting is that while the spark is advanced with RPM up to certain throttle angles, there are a lot of points scattered well off the curve. This shows that there are other factors that the Motronic uses in its timing calculations.

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