Types of Fuel Injection Schemes

Direct (cylinder) injection Port injection

Manifold riser injection

Direct fuel injection

GDI (Gasoline Direct Injection)

inlet port and manifold riser injection

These terms include designs in which the injection nozzles are located to spray fuel into the valve port (right) or into the induction manifold adjacent to the valve port (left).

A Schematic diagram of the electronic fuel injection system

Signals and controlled variables at the ECU

QL Intake air quantity, ϑL Air temperature, n Engine speed, P Engine load range, ϑM Engine temperature, VE Injected fuel quantity, QLZ Auxiliary air, VES Excess fuel for starting, UB Vehicle-system voltage.

1 Fuel lank, 2 Electric fuel pump, 3 Fuel filter, 4 Fuel-pressure regulator, 5 Solenoid-operated fuel injector, 6 Air-temperature sensor, 7 ECU, 8 Throttle-valve actuator, 9 Throttle-valve potentiometer, 10 Canister-purge valve, 77 Carbon canister, 12 Lambda oxygen sensor, 13 Engine-temperature sensor, 14 Ignition distributor, 15 Battery, 16 Ignition-start switch, 17 Relay, 18 Diagnosis connection, 19 Central injection unit.

Mono-Jetronic schematic diagram

D-Jetronic schematic diagram

Functional schematic diagram of the K-Jetronic

A Schematic diagram of the K-Jetronic: Mechanical multipoint port fuel-injection system (without electronic control unit).

The Schematic diagram of the K-Jetronic system with closed-loop lambda control (with electronic control unit)

1 Fuel tank, 2 Electric fuel pump, 3 Fuel accumulator, 4 Fuel filter, 5 Warm-up regulator, 6 Injection valve, 7 Intake manifold, 8 Cold-start valve, 9 Fuel distributor, 10 Air-flow sensor, 11 Timing valve, 12 Lambda sensor, 13 Thermo-time switch, 14 Ignition distributor, 15 Auxiliary-air device, 16 Throttle-valve switch, 17 Electronic control unit, 18 Ignition and starting switch, 19 Battery.

1 Fuel tank, 2 Electric fuel pump, 3 Fuel accumulator, 4 Fuel filter, 5 Primary-pressure regulator, 6 Fuel-injection valve, 7 Intake manifold. 5 Cold-start valve, 9 Fuel distributor, 10 Air-flow sensor, 11 Electro-hydraulic pressure actuator, 12 Lambda sensor, 13 Thermo-time switch, 14 Engine-temperature sensor, 15 Ignition distributor, 16 Auxiliary-air device, 17 Throttle-valve switch, 18 Control unit, 19 Ignition and starting switch, 20 Battery.

The Schematic diagram of a KE-Jetronic system with lambda closed-loop control.

Principle of the L-Jetronic (simplified)

A Schematic diagram of an L-Jetronic system with lambda closed-loop control.1 Fuel tank, 2 Electric fuel pump, 3 Fuel filter, 4 ECU, 5 Injection valve, 6 Fuel rail andpressure regulator, 7 Intake manifold, 8 Cold-start valve, 9 Throttle-valve switch, 10 Air-flow sensor, 11 Lambda sensor, 12 Thermo-time switch, 13 Engine-temperature sensor, 14 Ignition distributor, 15 Auxiliary-air device, 16 Battery,17 Ignition and starting switch.

1 Carbon canister, 2 Shutoff valve, 3 Canister-purge valve, 4 Fuel-pressure regulator, 5 Injector, 6 Pressure actuator, 7 Ignition coil, 8 Phase sensor, 9 Secondary-air pump, 10 Secondary-air valve, 11 Air-mass meter, 12 Control unit (ECU), 13 Throttle-valve sensor, 14 Idle actuator, 15 Air-temperature sensor, 16 EGR valve, 17 Fuel filter, 18 Knock sensor, 19 Engine-speed sensor, 20 Engine-temperature sensor, 21 Lambda oxygen sensor, 22 Diagnosis interface, 23 Diagnosis lamp, 24 Pressure differential sensor, 25 Electric fuel pump.

A Schematic System diagram of Motronic MS with integrated onboard diagnostics.

Motronic block diagram

THE STRATIFIED-CHARGE ENGINES

Effect of Mean Effective Pressure and Fuel Consumption on coefficient of air excess at constant speed

SFC: Specific Fuel Consumption, MEP: Main Effective Pressure

Influence of air ratio on exhaust emissions

The Russian Gaz-52 stratified-charge spark-ignition engine

The cylinders are fed with two separate carburetted mixture streams through separate inlet valves. The main inlet valve supplies a relatively weak charge, while a small quantity of rich mixture is fed through the small inlet valve into the pre-combustion chamber

The IFP Renault-CNRS variable fuel/air ratio process. In this stratified-charge engine, the rich mixture is fed into the inlet port through a separate tube. The encircled numbers illustrate the different sparking plug positions tested

The IFP Renault-CNRS system. One method of feeding a mixture supply of two different mixture ratios

A possible solution, using a special carburettor or metering device having two or more throttles. The main throttle valve would function in the usual manner, controlling the main portion of the weak-mixture charge. A smaller metering system supplies the rich-mixture tube through its own throttle valve, and a third throttle valve regulates the con-nection between the large and small metering systems

The Schlamann stratified-charge engine

Honda CVCC (compound vortex controlled combustion), pre-chamber stratified charge engines

In the Honda engine a valve controls the supply of a rich carburetted mixture to the pre-chamber, while the main inlet valve controls the supply of a weak mixture to the main part of the combustion chamber. An alternative system is to use fuel injection into the pre-chamber, and admit either air or a weak carburetted mixture to the main chamber

Texaco controlled combustion system TCSS, single-chamber stratified charge engine

The GDI consists of the following four basic features

1) Upright straight intake ports,(A strong down-flow is generated along the intake cylinder liner during the intake stroke)

2) High pressure fuel injection pump,(A swash type axial plunger pump for high volumetric efficiency is used for the high pressure fuel injection which provides high pressure fuel directly injected into the cylinder)

3) High pressure swirl injector,(An electro-magnetic injec-tor was developed to achieve accurate and precise control of injection quantity and timing)

4) Curved lop piston.(The top land configuration is modi-fied to provide a cavity, right under the spark plug tip, which is aimed to strengthen the air motion generated by the Upright Straight Intake Port and also to lead a concentrated fuel spray)

High pressure swirl injector

Detail of curved top piston

GDI (Gasoline Direct Injection) Engine

Stratified combustion injects fuel on the compression stroke, just prior to ignition, making for high economy but low power. Homogenous combustion injects fuel on intake as in a conventional engine.

The GDI (gasoline direct injection) engine injects the fuel directly into the cylinder, and controls the injection tim-ing carefully according to the operation range to achieve combustion in the ultra-lean range.

Comparison of the PFI and GDI mixture preparation systems

In the PFI engine, fuel is injected into the intake port of each cylinder, and there is an associated time lag between the injection event and the induction of the fuel and air into the cylinder

The GDI engine offers the potential for leaner combustion, less cylinder-to-cylinder variation in the air-fuel ratio and lower operating BSFC values

Comparison of the fuel quantity required to start GDI and PFI engines at different ambient temperatures

The theoretical advantages of the GDI engine over the contemporary PFI engine are summarized as follows

1) Improved fuel economy (up to 25% potential improve-ment, depending on test cycle) resulting from:-less pumping loss (unthrottled, stratified mode);-less heat losses (unthrottled, stratified mode);-higher compression ratio;-lower octane requirement;-increased volumetric efficiency;-fuel cut-off during vehicle deceleration (no manifold film).

2) Improved transient response:-less acceleration-enrichment required (no manifold film).

3) More precise air-fuel ratio control, -more rapid starting;-less cold-start over-fueling required.

4) Extended EGR tolerance limit.5) Selective emissions advantages.

-reduced cold-start UBHC emissions; -reduced CO, emissions.-Enhanced potential for system optimization.

Although the GDI engine provides important potential advantages, it does have a number of inherent problems

1) difficulty in controlling the stratified charge combustion over the required operating range;

2) complexity of the control and injection technologies required for seamlessload changes;

3) relatively high rate of formation of injector deposits and / or ignition fouling;4) relatively high light-load UBHC emissions;5) relatively high heavy-load NOx emissions;6) high local NOx - production under part-load, stratified-charge operation;7) soot formation for high-load operation;8) increased particulate emissions;9) three-way catalysis cannot be utilized to full advantage;10)increased fuel system component wear due to the combi-nation of high-pressure

and low fuel lubricity;11)increased rates of cylinder bore wear;12)increased electrical power and voltage requirements of the injectors and drivers;13)elevated fuel system pressure and fuel pump parasitic loss.

Typical GDI engine system layout.

Fuel injection systems for full-feature GDI engines must have the capability to provide both late injection for stratified-charge combustion at part load, as well as injection during the intake stroke for homogeneous-charge combus-tion at full load

The Schematic illustration of the Mitsubishi GDI combustion system (a) fuel injection strategies, (b) piston geometry, (c) the combustion mode calibration.

The Mitsubishi GDI Combustion System

The Mitsubishi GDI Combustion System

The Mitsubishi GDI engine system layout

Toyota GDI Combustion System

Combustion chamber configuration of the Toyota

GDI engine.

Zone (a) of the cavity is designed to be the mixture formation area, and is positioned upstream of the spark plug. The wider zone (b) is designed to be combustion space and is effective in promoting rapid mixing. The increased width in the swirl flow direction was reported to enhance the flame propagation after the stratified mixture is ignited. The involute shape (c) is designed to direct the vaporized fuel towards the spark plug. The intake system consists of both a helical port and a straight port, which are fully independent. An electronically activated SCV (swirl control valve) of the butterfly-type is located upstream of the straight port. When the SCV is closed, the resulting swirl ratio is reported to be 2.1. The helical intake port utilizes a vari-able-valve-timing-intelligent (VVT-i) cam-phasing system on the intake camshaft. These valves are driven by a DC motor so that the desired valve opening angle can be controlled according to the engine operating conditions.

Toyota GDI engine system.

Toyota GDI engine system.

Detailed SCV operating map of the Toyota GDI engine.

Nissan GDI Combustion System

NEODi (Nissan Ecology Oriented performance and Direct Injection)

The engine can operate in both the stratified-charge mode and the homogeneous-charge mode, and a 30% reduction in cold-start UBHC (unburned hydrocarbons) emissions relative to the base-line PFI engine

The engine could be operated with stable combustion using a mixture leaner than an air-fuel ratio of 40, resulting in a 20% improvement in fuel economy when compared with a baseline PFI engine that operates with a stoichiometric mixture.

The Nissan 1.8L Inline4 GDI engine system.

The homogenous charge combustion process injects the fuel in the intake stroke to gain time for evaporation and mixing before ignition. With stratified charge combustion, the fuel is injected in the compression stroke to prevent excessive diffusion of the mixture while the liquid-phase evaporates, with the aim of positioning the mixture in the vicinity of the spark plug.

Mercedes-Benz GDI Combustion System

The Mercedes-Benz GDI combustion system has a verti-cal, centrally mounted, fuel injector. Dynamometer tests of the Mercedes-Benz GDI combustion system for a range of injection pressures from 4 to 12 MPa indicate that the fuel consumption, UBHC emissions and COV (coefficient of variation) of IMEP (indicated mean effective pressure) are minimized at 8 MPa.

Mazda GDI Combustion System

The direct gasoline injection engine can manage both fuel economy improvement and high power output by changing stratified charge operation injected in the compression stroke and homogeneous operation injected in the induction stroke. Swirl air motion, which remains the mainstream, is effec-tive in medium load from the point of view of mixture dispersion. However, tumble air motion attenuating the mainstream at the end of the compression stroke has the advantage of keeping the mixture stratification near the spark plug in light load. A hemispherical piston cavity coincides the mixture transportation route of the fuel spray in these air motions.

1) In light load, swirl air motion enables stable and adequate mixtureformation and leaner mixture operation.

2) A wider and deeper piston cavity can trap the curved fuel spray precisely, and realize the optimized mixture formation over a wide range of engine load and speed