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Scott33

Ignition table load input

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I will be tuning a turbo direct injection engine where it may be necessary for me to change the boost levels from race to race.  Rather than retune the engine, my plan is to use TPS as the main load axis in the fuel table and use a 4d table to compensate based on MGP, or possibly MAP/BAP if I can make it happen.  This is the suggested setup for turbo engines with unreliable MAP pressures, so at least I'm not going too far off the beaten path.

My question is what to do for the ignition table load input.  The manual suggests using MAP, as opposed to MGP, which I guess makes sense as it should be more related to the quantity of air entering the chamber, while MGP is more useful for determining how efficient the engine is.  (Side note - the VW GTI Force map uses MGP as the load axis for ignition).  It seems there's another input that is reasonably related to how much air is going into the engine, or at least related to how much air we THINK is going into the engine -- Inst Fuel Consumption.

Would tuning based on fuel quantity be a reasonable idea, or should I just stick with MAP?  Or should I go with MAP + TPS as suggested by the help file?

 

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I would tune the engine as per normal using MGP for the main fuel axis (assuming mild cams and not ITBs)

Tune for the max boost you are ever likely to run and then you can mover the boost from nothing to full with no worries.

For the Ignition MAP would be the preferred option.

 

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9 hours ago, Scott33 said:

Is MGP still the preferred load axis for fuel?

Yep.  For Ign MAP is probably the most correct indicator of cylinder pressure but I often find it easier to use the same axis on both the fuel and ign tables as you dont lose your spot when you are on the dyno switching between fuel & ign tables.  So I usually put MGP on both tables.  If I was doing a high boost pikes peak car or something I might consider the options more closely...

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