My intervals are determined by peaks and low spots in my AFR.

I datalog so I get an AFR line in a graph with RPM, throttle position, MAF voltage, (boost and EGT are optional).

I'll do a pull with corrections set to 0 and check the datalog. my intervals will be determined by where AFR comes to a high or low point. If I set a correction point at the low area leading into a high point, an interval at the peak, and then another at the low point coming off the peak, I can then: pull the low points up to even them out with the high point so now the AFR will be steady across the 3 points, OR bring the high point down to make all three even (or pretty close). If I set the first point to my desired AFR and then bring all the peaks and low points into line, the car is tuned. The SAFC will fill in the blanks between the the points I set, and because between the low and high is pretty close to a line, the interpolation the SAFC uses will get it pretty close.

With fewer points if there is a change in my tune due to drastic weather changes, I only have to move a few points, and usually close to an even amount to each correction point to bring the entire AFR up or down.

You can roughly (but carefully) tune a car with 2 correction points at the low and high RPM pints in open loop to get the beginning and ending points to the desired AFR, and then knock down the high points and bring the low points up to get the AFR where it needs to be across the entire range.

The SAFC will not adjust fuel in closed loop, BUT IT WILL adjust fuel/ecu compensation by playing with the corrections in open loop. This has a direct effect on the tuning in open loop. With no tuning in open loop I end up with about 17-18* total timing under high loads, and the tune will wander as the fuel trims set.

If I tune at idle in low throttle and the low RPMs in closed to bring fuel trims close to 0%, the tune won't wander and I end up with timing in the 13-14* range under high loads, which is much better for pump gas. I used to taper the AFR rich past 5k as the RPMs came up, but with the timing tapering off now I don't have to.

Every car and engine management system is different, but fuel injection technology is basically the same car to car. It took me a while to figure out this car, but it's well worth the effort, and tuning myself has saved me a ton of money and kept my engine together for sure.

www.zeitronix.com <----- the bomb if you want to tune your self