The reasoning behind having a TPS in a fuel injection system is to provide the FI information as to how much air is flowing into the engine. Optimal fuel air ratio is 14.7 to 1, so for the FI to be able to provide the correct amount of fuel, it has to "know" about how much air is being ingested. The relative position of the throttle plates allows that estimation to mathematically calculated so proper fuel flow rate can be delivered. By adjusting the TPS, you are in effect tricking the FI to think you are flowing more or less air than what you really are. This is a way that you can richen or lean the mixture slightly. By increasing the TPS position, the FI thinks the throttle is open more than it really is, so it provides a bit more fuel to each cylinder. Conversely, closing the TPS would make it lean out. The surge is a classic lean condition, and therefore is addressed and improved upon by richening the mixture. I have mixed emotions on the effects of the idle mixture screws on the ECU concerning their effectiveness at partial throttle openings. If this were a carbureted bike, they would be contributing. The reason I am mixed on it is these are electronic controls and not mechanical like fuel screws on carbs. Fuel screws on carbs are still exposed to engine vacuum so they keep feeding even if the engine is not idling. A FI system technically does not need this because the fuel curve can be programmed electronically and not determined by the fuel screw, float height, Jet Needle, Needle Jet, Clip position slide cut away or CV slide spring rate/preload or main jet. You get the idea......... Much easier to adjust or create a fuel curve on an FI bike. Anyhow....... hope this clears up some of the confusion, without creating more. RSRBOB
