ignition timing

[Gnarbunkle]

The technical description on FI in the service manual has a bit of a description on how it works. My understanding is that each cylinder has 2 fuelling maps, one used at light throttle openings and injector duty is determined by rpm and the inlet air pressure sensor. At high throttle settings, the other map is chosen and this time injector duty is controlled by rpm and the throttle position sensor. Final injector duty is based on the above plus a "correction factor" from "various inputs". Various inputs are atmospheric pressure, coolant temp, gear position etc. This is all well and good for for a completely stock bike, but when you fit an aftermarket exhaust, gut the airbox, change cams, velocity stacks, gearing etc then those stock fuelling maps are off the mark. A modded GPS does not change the fuelling maps, its' effect is to change the output from the various "correction factors" by giving a false gear position signal. A PC is a mid priced "go-between" box to restore correct fuelling and will do so if set up on a dyno. An aftermarket ECM is a more expensive option and gets rid of the "go-between" the fuelling maps need to be generated on a dyno. I have the poor mans option: factory ECM and no PC, the GPS has been modded and the A/F set to 12.7 across the band. Yep its' cheap, its dirty and seat of the pants feeling is that it works for me. <i></i>