load points

how do you know what the idle and cruise points should be if you are not familiar with the engine?

I suggest you take the Understanding AFR course offered here, if you haven't yet.

Idle AFR is usually what makes the engine run happily. The will vary with cam overlap, for exemple. Stock engine will be happy to run with stoich (lambda 1), while modified engine could run better with a richer mixture. Just be careful that you don't foul the plug with an overly rich mixture.

For cruise, stoich is what I target. Some tuner will go a bit leaner for better fuel economy. You can do trial and error, just listen for knock. Also, too lean will make the car run poorly.

Hi everyone, I have a question on this also (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.

cheers

I guess I didn't understand the question from Shaun haha!

For load points, I don't think you need to be super picky to start with. You usually want more resolution around idle and cruise region (at least for a street driven car). Don't forget the ECU will always interpolate when you are sitting between two cells. If for any reasons, you have a dip in lambda while transitioning from one cell to another, now you would simply rescale your table to add a load point between those two cells, then adjust your fueling in that new cell.

Ok thanks just wasn't sure how far of a gap the load points could be. If you wanted to run 30psi positive pressure the gap between every increment above 100kpa could be 50kpa or higher.

Just wanted to see how tuners go about that. Cheers

Hi Wal,

Experience counts a lot for laying out the spacing on the tables (also the number of sites that the table is able to accommodate has an influence). You will get to a point where you know how the ECU that you are using handles the interpolation between load sites and from this a knowledge of how close you need to put the sites for correct operation.

Some engines you can have a gap between RPM sites of 1000 as the table smooths out and is linear between points, especially higher in the Engine Speed range.

You will usually end up needing to have more sites in the transient regions of the map such as coming out of idle where a small change in throttle position results in a large change in the air mass entering the engine. Where the engine transitions into boost is also an area that typically needs to have more sites available to manage the rapidly changing conditions in the inlet manifold.

I will normally start with a few more sites than actually needed in the areas that I expect will need to have a finer resolution for control, map the engine through those regions and then, if needed, remove the extraneous sites from the map once I have the table built. I will always do a run through these regions after having done so to ensure that I haven't removed too much.