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SD map changes affect load

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Howdy folks


I've noticed that changing the speed density maps to richen the afr also changes the load, even tho the boost level remains the same. Obviously this changes many other things that are load dependant such as ignition timing, trans pressures etc, when we're just trying to change the afr.

I can see why the load might change, as we're actually adjusting the airflow numbers, not fuel delivery numbers, which changes the afr as a by product.

I've tuned a couple of cars which have had the fuel pump running out. Adding fuel to the SD map will keep the injectors open longer which in turn will richen the afr, despite the fuel pressure falling.

This is only an interim fix and you can't rely on a failing pump to deliver constantly predictable fuel pressure.

I started this topic to ask a question that I worked out the answer for as I typed it out. Rather than delete it, I may as well post it to help others that run into the same scenario.


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