Introduction Accumulation of Large gasoline droplets Air gasoline mixture liquid gasoline Typical Pattern of Mixture Distribution in a Multi-Cylinder Engine 5 October, 20 ENGINES, Morors & Mositity Instructor: Prof.N. Jalaian 1 BITS-Pilani, Hyderabad Campus NEFIntroduction + Ina gasoline injection system, the fuel is injected into the intake manifold or near the intake port through an injector. + The gasoline is supplied to the injector by a pump and sprayed into the air stream in a finely atomized form. * Compared to carburetion, the mixing of gasoline with the air stream is better in this case. * Inboth the cases, throttle valve controls the mixture flow to the intake manifold. * Ina carburetor based multi-cylinder engine, it is difficult to realize uniformity in mixture strength across the cylinders. * This problem is called the maldistribution and can be solved by the port injection system, by having the same amount of gasoline injected at each intake manifold. * Gasoline injection system is preferred over the carburetor for the following reasons: (i) To distribute fuel uniformly in a multi-cylinder engine, (ii) To improve volumetric efficiency, 5 October, 2023 MEFI17 ENaiNes, Motors & Mosittty Instructor: Prof. N. Jalaian 1 BITS-Pilani, Hyderabad CampusTypes of Injection Systems + Fuel injection system can be classified as: + Gasoline direct injection into the cylinder (GDI) + Port injection: (a) Timed, and (b) Continuous + Manifold injection * These systems can be grouped under two heads as single point, and multi-point injection. + Ina single-point injection system, one or two injectors are mounted inside the throttle body assembly. + Fuel sprays are directed at one point or at the centre of the intake manifold. * Single point injection is also called as throttle body injection. + Multi-point injection has one i injection system. jector for each cylinder, and is often called as port 5 October, ME F317 ENatxes, Motors & Mosittty Instructor: Prof. N. Jalaian 2 BITS-Pilani, Hyderabad CampusTypes of Injection Systems (Cont'd) * Continuous injection system: This system usually has a rotary pump that maintains a fuel line gauge pressure of about 0.75 to 1.5 bar. * The system injects fuel through a nozzle located in the manifold immediately downstream of throttle plate. * The timing and duration of the fuel injection is determined by Electronic Control Unit (ECU), depending on the engine load and speed. * Timed fuel injection system: This system supplies fuel through a pump at a low pressure of about 2 bar when engine is running at maximum speed. * The nozzle injects the fuel in the manifold or the cylinder head port at about 6.5 bar or into the combustion chamber at pressures that range from 16 to 35 bar. * This system injects fuel usually during the early part of the suction stroke. * During the maximum power operation, injection begins afier the closure of the exhaust valve and ends usually after the BDC. 5 October, MEFI17 ENaixes, Motors & Mositity Instructor: Prof. N. Jalaian 3 BITS-Pllani, Hyderabad CampusTypes of Injection Systems (Cont'd) Gasoline direct injection into the cylinder (GDI): This is superior and always desirable and better compared to manifold injection. In this case, both low and high volatile fuels can be used and higher volumetric efficiencies can be achieved. However, this may lead to oil dilution during the frequent warmup phases, if the car is used for daily transportation. MEFi17 ENaixes, Motors & Monitity Instructor: Prof. N. Jalailan 4 BITS-Pilani, Hyderabad CampusFuel Injection Methods He ho c= '|| F. Cc Li | ss Cy ke len nen Low pressure Low pressure intake Low pressure direct injection manifold injection semi-direct injection (a) Gasoline injection in four-stroke engines & Mositity Instructor: Prof.N. Jalaian 5 BITS-Pilani, Hyderabad Campus $M MEFSFuel Injection Methods High pressure \\ Low pressure Low pressure intake Low pressure direct injection ‘manifold injection direct injection Low pressure H transfer port injection (b) Fuel injection in two-stroke engines 'Y Instructor: Prof.N. Jalaian 5 — BITS-Pilani, Hyderabad CampusComponents of an Injection System The objectives of fuel injection system are to meter, atomize and uniformly distribute the fuel throughout the air mass in the cylinder. At the same time, it must maintain the required air-fuel ratio as per the load and speed requirement of the engine. To achieve all the above tasks, a number of elements are required. Pumping element: Moves the fuel from the fuel tank to the injector. Metering element: Measures and supplies the fuel in tune with engine’s speed and load. Mixing element: Atomizes the fuel and mixes it with air to form a homogeneous mixture. Metering control: Adjusts the rate of metering in accordance with the engine conditions. Mixture control: Adjusts the fuel-air ratio as demanded by the load and speed. Distributor element: Divides the metered fuel equally among the cylinders. Timing control: Fixes the start and stop of the fuel-air mixing process. Ambient control: Compensates the changes in temp and pressure of either air or fuel. 5 October, 2023 MEFi17 ENaixes, Motors & Mosittty Instructor: Prof... Jalaian 6 BITS-Pilani, Hyderabad CampusElectronic Fuel Injection System zz Modern gasoline injection systems use engine sensors, a computer, and a solenoid operated fuel injectors to meter and inject the right amount of fucl into the engine cylinders. These EFI systems use electrical and electronic devices to monitor and control engine operation. An electronic control unit (ECU) or the computer receives electrical signals in the form of current or voltage from these sensors. ECU uses the data (received from the sensors) to operate the injectors, ignition system, and other engine related devices. As a result, less unburnt fuel leaves the engine as emissions, and the vehicle gives better mileage. ME Fi17 Ew. NES, Morors & Mositity Instructor: Prof.N. Jalaian 7 BITS-Pilani, Hyderabad Campus5¢ EFI Sensors kx Exhaust gas or oxygen sensor: Senses the amount of oxygen in the engine exhaust and calculates the air-fuel ratio. Engine temperature sensor: Senses the temperature of the engine coolant, and help adjust the mixture strength to rich side for cold starting. Air flow sensor: Monitors the mass or volume of air flowing into the intake manifold for adjusting fuel quantity. Air inlet temperature sensor: Checks the temperature of the ambient air entering the engine for fine tuning the mixture strength. Throttle position sensor: Senses the movement of the throttle plate so that the mixture flow can be adjusted for engine speed and acceleration. Manifold pressure sensor: Monitors vacuum in the engine intake manifold so that the mixture strength can be adjusted with changes in engine load. Camshaft position sensor: Senses rotation of engine camshatt/ crankshaft for speed and timing of injection. Knock sensor: Microphone type sensor that detects ping or pre-ignition noise so that the ignition timing can be retarded. ctober, 2023 ME F317 ENaixes, Motors & Mosittty Instructor: Prof. N. Jalaian 8 BITS-Pilani, Hyderabad CampusMerits & Demerits of EFI System kx Merits: * Improvement in the volumetric efficiency due to lesser resistance in the intake manifold. * Manifold wetting is eliminated as the fuel is injected into or close to the cylinder. * Fuel atomization is independent of crank speed, therefore starting will be easier. * Better atomization and vaporization will make the engine less knock prone. * Formation of ice on throttle plate is eliminated. * Distribution of fuel being independent of vapourization, less volatile fuel can be used. * Variation of A/F ratio is almost negligible even when the vehicle takes different positions like turning, moving on gradients, uneven roads, etc. 5 October, MEFi17 ENaiNes, Motors & Mositity Instructor: Prof. N. Jalaian 9 BITS-Pilani, Hyderabad CampusMulti-Point Fuel Injection (MPFI) System | im Throttle body of ¥ Throttle Body Injection (Single Point) a ‘BILITY Instructor: Prof.N. Jalaiah 10 BITS-Pilani, Hyderabad Campus.Multi-Point Fuel Injection (MPFI) System kx Air Intake valve (>) Spark plug Injector aes — = “TU GI) AGOSN Port Injection Multi-point Fuel Injection (MPFI) near Port 5 October, INES, MoroRs & Monitity Instructor: Prof..N. Jalaian 10 B|TS-Pilani, Hyderabad CampusD-MPFI and L-MPFI Systems The D-MPFI system is the manifold fuel injection system. The L-MPFI system is a port fucl injection system. The D stands for Druck (Pressure in German) as D-MPFI depends on vacuum pressure. The L stands for Luft (Air in German) as L-MPFI depends on mass of air. Ga }—__— - F seams cee | wet | He Bagi ow} = a ‘Paging RPM sensor > ina Coa JH D-MPFI Gasoline Injection System som L-MPFI Gasoline Injection System 5 October, ME F317 ENaixes, Morors & Mositity Instructor: Prof. N. Jalaian 11 BITS-Pilani, Hyderabad Campus