[E4ODnut]

Olympiadis,
Now we are talking.

I have some experience tuning, primarily Megasquirt but I did use the Haltech E6K when I first started this hobby, some would say an obsession. No matter, all programmable EFI systems are similar in basics. I use speed density, batch fired. This is because I am limited in my tuning resources. I don't have access to a dyno, so all my tuning is on the road, or on the water as the case may be. I use WB EGO feed back and EGT for tuning reference only. I only use EGT as a "sanity check". If I was serious about it then I would need thermocouples for each cylinder, which is not practical for me. I'm also of the belief that EGT tuning has it's place, but because it is much more application specific, I prefer to reference EGO. I have feature that can can calculate fuel burn in litres per hour so I can monitor fuel consumption at any given load.

I tune mainly for economy and reliability. Power output is important, but definitely not a priority. I also run open loop only. Some people may prefer to use closed loop but I agree with the camp that says you give up some control with closed loop, and it is often used as an excuse for sloppy tuning. I don't use EGR.

In the days before EFI and the feed back it can provide, a lot of dedicated tuners made relatively primitive technology perform very well across the complete power band. If I can improve even a small amount on this with the late '80s/early '90s technology I'm using I'll be quite satisfied.

Tuning for best power is relatively easy, and I stress relatively. Best economy is a lot harder. I agree with your theory that the best way should be to aim for minimum pulse width (leanest mix) then adjust spark to suit. This isn't as easy as it would appear. It's especially difficult to do this on the road. I'm finding a bit easier to do it on the boat, almost like a dyno because it's easier to hold a given load. In both cases, using a conservative spark map, I try to hold a given cruise load and lean the mix until I get a "lean surge", then fatten it up a bit until the surge is gone. I note the EGO feed back. Then I try to hold the same load and advance or retard the timing to see if I gain or lose power and note the EGO feed back. I'm finding that I can vary the timing a lot before performance or EGO changes much. I don't reference throttle position at all but prefer to use Manifold Absolute Pressure as an indication of engine load. I tune at or near sea level only but I do have barometric pressure compensation if necessary.

So far I've found that at loads under ~ 75 KPA MAP, EGTs are not an issue and it is almost impossible to induce detonation with any sane ignition timing. I tune for target AF ratios of between 16:1 and 17:1 below ~ 80 KPA. I reason that with pressures above that I am in need of some serious power and ramp up to ~ 13:1 at ~ 90 KPA and ~ 12:1 at 100 KPA. Some of my engines like it a bit richer, some a bit leaner, but not a whole bunch.

As for WOT spark tuning I just revert to the old stand by of "advance until it pings, then back off a couple of degrees". I may be leaving some power, or economy on the table. but without I dyno I don't know. At least I'm comfortable that I won't hurt the engine this way.

I have knock detectors on the engines, but these have to be calibrated by ear, so they just serve as one more open loop feed back. All of my sensors can be data logged, which is the most valuable tool in my arsenal.

The drill is, come up with some realistic base settings, go for a drive and data log. Go home analyze the logs, make changes, go for another drive. Repeat. It never ends, but that's the fun part.