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Understanding AFR: The AFR Target MAP

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The AFR Target MAP


00:00 So far we have discussed how the AFR will effect the performance and tuning of the engine.
00:05 In this next section we are going to look at how we can bring this together throughout the engine’s operating envelope.
00:12 We do this with an AFR Target MAP.
00:16 The AFR target MAP is really just a 3D table of load vs RPM that matches the same break points that we have used in the main fuel table.
00:25 This gives us a table that we can fill in with our desired AFR targets for different areas of the engines operation.
00:33 We are going to be using this map when the time comes to actually tune the car but before we get that far, we are going to spend a little time and break the engine operation down and discuss each section in detail.
00:47 Here you can see an example of an AFR target MAP.
00:51 We have RPM on the x axis and load in manifold pressure on the Y axis.
00:57 In this case the load increases as we move up the table but some ECUs work the opposite way and load increases as we move down through the table.
01:06 This should be pretty obvious by looking at the numbers on the load axis.
01:11 You can see that we have highlighted areas on the map to represent idle, cruise, high rpm vacuum, and full load n/a which also corresponds to a zone known as transition for turbocharged or supercharged engines.
01:27 As we move into positive boost pressure we have two zones labelled medium boost and high boost.
01:33 You can see we also have a couple of dead zones, and finally the starting zone.