![]() It is at the rear end of the throttle blade. TP - Throttle Position - This sensor provides input signals to the ECM as it reacts to throttle shaft rotation, telling the ECM where the throttle is, as well as if it's opening or closing, and how fast it's opening or closing. It's that probe in the front cylinder head, on the left side. The ECM uses the signals from this sensor to determine if the engine is at operating temperature, or still warming up. It's located in the throttle body.ĮT - Engine Temperature - This sensor provides input signals to the ECM as it reacts to the engine temperature of the front cylinder head. The ECM uses the inputs from this sensor to help calculate how much oxygen exists in a quantity of air. For example, hot air contains less oxygen than cool air. IAT - Intake Air Temperature - This sensor provides input signals to the ECM as it reacts to the temperature of the air entering the engine. It's located in the intake manifold on top, just behind the throttle body. The ECM uses the inputs from this sensor to help calculate how much air is entering the engine. Ambient barometric pressure reflects changes in atmospheric pressure caused by weather conditions or changes in altitude. Intake manifold pressure reflects changes in engine speed and load. MAP - Manifold Absolute Pressure - This sensor provides input signals to the ECM and reacts to intake manifold pressure and ambient barometric pressure. It's that thing that's in the way when you change your oil filter. The ECM also uses these inputs to determine what stroke the engine is in so it can deliver the fuel and spark at the desired time. ![]() On Softails, it's located under the seat, on baggers it's under the side panel.ĬKP - Crank Position Sensor - This sensor provides input signals to the ECM that indicate engine rpm. SYSTEM COMPONENTSĮCM - Electronic Control Module - Sometimes called an ECU, or Electronic Control Unit, is a small microprocessor-controlled box, or "the brains" of the system that collects all of the input signals from the sensors, and makes decisions based on those sensor inputs, and then sends output signals to deliver fuel and spark to the engine. Still with me? OK, let's dig into the components that make up the system, what they do, where they are, and what they are commonly called. Sequential Port Fuel Injection - Injector nozzles are positioned in the manifold near the intake valve and are precisely timed to deliver fuel to each cylinder. Open Loop - The ECM monitors sensors positioned on the intake side of the engine and does not monitor the end result of internal combustion at the exhaust. Speed/Density - An Electronic Control Module (ECM) monitors manifold air pressure, air temperature, throttle position and engine rpm to manage fuel delivery. ![]() The Harley-Davidson ESPFI system is known as a Speed/Density, Open Loop, Sequential Port Fuel Injection system, that controls both fuel flow and spark timing. Ready? OK, let's start out with some terms. In this segment, we'll attempt to explain the components and operation of the ESPFI systems offered on 2001 and later Softail, 2002 and later Touring, 2004-2005 Dyna, and 2002 and later V-Rod motorcycles. Shop All Motorcycle Parts & Accessories.Pulse width control of each injector improves performance over multiport injection. The ECM controls the injectors by pulse width, the length of time the injector sprays fuel into the port. Most of today's engines have sequential fuel injection systems. ![]() This system is more efficient than a multiport system because changes to the fuel mixture are instantaneous. Sequential fuel injection systems fire each injector individually. Due to its design, a problem with one driver will cause a misfire in more than one cylinder. The fuel charge in some cylinders momentarily sits, but engines rotate so quickly the delay is negligible. A six-cylinder engine would fire three injectors on the first revolution and then fire the other three on the next. A four-cylinder engine may fire the #1 and the #3 injectors on the first crankshaft revolution and then fire the #2 and #4 on the second revolution. Multiport injection systems fire the injectors in groups. However, there is a difference in the way these systems operate. Multiport and sequential fuel injection systems both inject atomized fuel into a port just before the intake valve.
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