Quote Originally Posted by LinkMTech View Post
the ECU will pull the injector low for about 2.5ms and it's pulse width will vary about 8%
On all of the fuel injectors I've ever put a 'scope on, the pulse varies a heck of a lot more than 8%. I'd even venture to say that any injector's pulse width would vary 8% at a steady state just to keep the closed loop program in the ECM happy. It's possible this bike has something else going on that keeps the fuel injector pulse practically steady, but I tell ya, that's something I haven't heard of lately.

The -20% control will delay the ON time of the output signal to the injector but supposed to keep the OFF time unchanged for reduced pulse width.
The +20% control should keep the ON time intact but delays the OFF time of the output signal for increased pulse width.
If it was me, I don't think I'd delay the start of the pulse. If you delay the pulse width at the start, the fuel might not be there in time for the intake valve to open. Remember, it takes X amount of time for an injector to open and start spraying that nice cone shape properly, whereas the closing an injector is much more of a solid event, at least that's what I've seen from the high speed video from one of my relatives at GM (neat video too, can see practically every tiny little droplet of atomized fuel in the spray pattern). I think I would shorten up the tail end of the pulse. If anything, at least the fuel will be sitting there on the intake valve or at least in the intake stream, ready to be sucked in, even if it is pooled up on the intake valve, which in any halfway decently designed intake system, will get swirled up and re-atomized by the swirl and heat of the valve.

But, be all that as it may be, it's nearly impossible to determine what the ECM will determine should be the NEXT pulse width. If it was me, I think I'd try a system that would LAG by one pulse event. Keep tabs on the previous pulse, modify that pulse width, shoot that pulse width on the next event, while at the same time, using a timer, measuring the current pulse width, while again, using a timer, to keep track of the current pulse width and stop it as required.
But then again, as fast as today's ECMs operate, it may (and probably will) still flag a failure and go to open loop, because you're messing with the pulse width, thereby the air/fuel ratio, which the ECM will eventually see in the O2 sensor. Unless, you plan on running open loop continuously...which in that case...never mind...Go for it! Just remember that a stoich A/F ratio of 14.7:1 with 20% of the fuel removed is an A/F ratio of about 17.6:1...lean enough to make donuts out of piston heads and make sticks out of exhaust valves and instantly put ports in your otherwise smooth cylinder walls!