You'd think so, but I recall reading a while back that throttle-body fuel injection systems are quite insensitive to injection timing. You can spray fuel in almost anytime you please and it is so turbulent that even if it is deposited on the walls of the inlet tract, it evaporates and is well-atomized when it makes it to the combustion chamber.WJBertrand said:It would be surprising to me if Yamaha were using a "waste squirt" from the injectors similarly to a waste spark. Any kind of wast squirt would seem to have quite negative effect on both fuel mileage and emissions.
And fuel injectors don't inject all their fuel in a momentary burst - they stay open for some period of time with duration determining mixture - this duration (called pulse width) may be fairly big compared to the total time of the four-stroke cycle. (I recall reading that injector pulse width may be up to 85% of the total cycle time for high-RPM/full-throttle situations; in this case the injector would be delivering fuel 85% of the time and would be delivering across all the four-stroke cycles.) So the idea that fuel injection is a quick/short injection right into the combustion chamber is more apt to direct-injection, not to throttle-body injection. Throttle body injection is, in some ways, more similar to a carb than a direct injection and obviously carbs have no timing with respect to intake valve opening.
Anyone following this might find this discussion interesting - it indicates there are a wide variety of approaches to timing of fuel injection.
http://mdhmotors.com/fuel-and-air-induction-systems-diagnosis/
- Mark