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Load Axis increments for boosted applications

Practical Standalone Tuning

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Hi everyone, I have a question on load points, On the G4x plug in for S15 SR20DET wanting to know what load points to use on the Y axis as Andre shows using up to 180KPA on turbo 86 as his desired boost is only 70 KPA positive boost pressure but if desired boost is 25PSI/175kpa and beyond and the table resolution on allows 20 increments you cant continue to increase the Y axis by a value of 20kpa as you run out of increments.

Current table config I have at the moment while messing around with PClink is -100 -80 -60 -50 -40 -20 0 20 40 60 80 100 120 140 160 180 200 225 250 275.


Start with the bare minimum, tune it, then only if you find some area between cells is not being taken care of by the linear interpolation then add a new row into that particular area. With Link you can add and remove rows/columns to a table without messing up any of the existing tuned cells. And they don't need to be even breakpoints either. You can have finer breakpoints around areas where the VE is changing rapidly due to VVT or whatever and larger breakpoints when into decent boost.

But it looks like some of your problem is you are also confusing MAP with MGP. A fuel table using MAP would start at 0 (total vacuum), and for 175kpa boost would need to go up to 275kpa. A fuel table using MGP would start at -100 and would only need to go up to 175 for 175kpa boost. You show your numbers starting at -100 but going to 275 which would be 40psi boost.

Thanks Adam, appreciate that and yep that clears it up as my fuel target table is MAP and the Fuel table is MGP.

I was playing with a base map file on the side when i asked this question as the tuner who has tuned the car recently has only allowed 35psi (Largest increment) on the Target table so that means its only allowing a target table to 20psi (35-14.5=20.5 positive pressure) even though the car is running 22-23psi.

The fuel table increments start at -11.9 (Vac), 0 (atmo), 23psi (positive pressure). thought this should go to at least 25-26psi to account for boost spikes and allow enough safety margin.

Thanks Adam for the help

Note just because your fuel table axis stops at 23psi doesn't mean you cant go above that. The ecu will still factor boost into the fuel equation (i.e if you double the boost the ecu will automatically double the fuel). It is only if your VE changes significantly above 23psi that you would need to add another higher boost row to trim that.

Similarly with your target table only going to 20psi - you would only need to add another row if you actually want to target a different lambda above that last row. Say for instance you have a target of 11.0AFR at 20psi but you run the engine to 25psi - it will still target 11.0AFR at 25psi.

Thanks Adam, does that only apply in closed loop?

No, it applies at all times.

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