MULTI PORT FUEL INJECTION SYSTEMS By Prof S

MULTI - PORT FUEL INJECTION SYSTEMS By Prof. S. D. Gandhi

A Typical Fuel Delivery System

Drawbacks of a carburettor 1. No Altitude compensation 2. Mal-distribution of fuel 3. Variation in air fuel ratio 4. Inaccurate metering of fuel 5. Does not meet emission norms,

Drawbacks of a carburettor 6. Can not control Rise in Engine Idle RPM as engine warms up. 7. No temperature compensation 8. No compensation for Exhaust gas Recirculation. 9. No compensation for Positive Crankcase ventilation. 10. No compensation for Canister Purge.

Drawbacks of a carburettor 11. System supplies fuel a few revolutions of crank-shaft even after the engine is switched off (Dieseling). Modified designs require a separate anti-dieseling solenoid in the carburettor. 12. The carburettor gives correct air fuel mixture at only one speed corresponding to the venturi design.

Drawbacks of a carburettor 13. Fuel atomization depends upon the velocity of air in the venturi. 14. Wall wetting effect occurs. 15. At high altitude, Carburettor Icing may occur at the nozzle. 16. No compensation for the evaporative emission control

Petrol Injection is adopted for the following reasons • To have uniform distribution of fuel in a multi-cylinder engine. • To meet emission norms / standards • To improve breathing capacity i. e. Volumetric efficiency • To reduce Detonation

Petrol Injection is adopted for the following reasons • To Improve Driveability for all operating conditions. • To provide system diagnosis when malfunction occurs. • To Improve engine performance. • To Reduce wastage of fuel during deceleration and over- speeding of engine.

Petrol Injection is adopted for the following reasons • To Precisely time the injection of fuel. • To Precisely meter the fuel. • Adaptability to different operating conditions.

Methods of Petrol Injection

THROTTLE BODY INJECTION

THROTTLE BODY INJECTION

MULTI-POINT FUEL INJECTION

MULTI-POINT FUEL INJECTION

D-MPFI System • The D- MPFI system is the manifold fuel injection system. In this type, the vacuum in the intake manifold is first sensed. • In addition, it senses the volume of air by its density.

D-MPFI System • As air enters into the intake manifold, the manifold pressure sensor detects the intake manifold vacuum and sends the information to the ECU.

D-MPFI System • The ECU in turn sends commands to the injector to regulate the amount of petrol supply for injection. • When the injector sprays fuel in the intake manifold the petrol mixes with the air and the mixture enters the cylinder.

L- MPFI SYSTEM • The L-MPFI system is a port fuel injection system. • In this type, the fuel metering is regulated by the engine speed and the amount of air that actually enters the engine.

L-MPFI SYSTEM • The Air Flow Sensor measures the amount of air and sends information to the ECU. • speed sensor sends information about the speed of the engine to the ECU.

L-MPFI SYSTEM • ECU processes the information and sends commands to the injector, in order to regulate the amount of petrol supply for injection. • When injection takes place, the petrol mixes with the air and the mixture enters the cylinder.

MPFI Electronic Control System Sensors (Input) Air Flow Meter Cold Start Injector Time Switch To Cold Start Injector To Injectors (Output) Ignition Signal Electronic Control Unit (ECU)

MPFI- Electronic Control System • The MPFI-electronic control system is shown in the form of block diagram. • The sensors that monitor intake air temperature, the oxygen, the water temperature, the starter signal and the throttle position send signals to the ECU.

MPFI- Electronic Control System • The air-flow sensor sends signals to the ECU regarding the intake air volume. • The ignition sensor sends information about the engine speed. • ECU processes the signals and sends commands to the injectors, to control the fuel injection.

Electronic Control Module(ECM) Control functions The ECU/ECM evaluates the sensor inputs using data tables and calculations to determine the output of the actuating devices. • Injection volume control • Injection timing control • Ignition timing control

Electronic Control Module(ECM) Control functions • Evaporative emission control • Engine / vehicle speed control • EGR control

Electronic Control Module(ECM) Control functions • Injection 1. 2. 3. 4. 5. volume control Starting and Post start Enrichment Warm- up Enrichment Acceleration Enrichment Full Throttle Enrichment Overrun Fuel Cut-Off

Electronic Control Module(ECM) Control functions • Injection volume control 6. Altitude Compensation 7. Closed- Loop Lambda Control 8. Idle Speed Control 9. Engine- Speed Limitations 10. Enrichment to avoid Detonation

MPFI- Fuel System • In MPFI- fuel system, the fuel is supplied by the fuel pump. At the time of starting, the cold start injector is operated by the cold start injector time switch. • The cold start injector injects fuel into the air intake chamber, thus enriching the air-fuel mixture. • The pressure regulator regulates the pressure of the fuel. • The injectors receive signals from the ECU and inject the fuel into the intake manifold.

MPFI- Air Induction System • The MPFI- air induction system is shown in the block diagram. • The air cleaner, the air- flow meter, the throttle body and the air valve supply a proper amount of air to the air intake chamber and intake manifold • The quantity of air supplied is just what is necessary for complete combustion.

FUEL INJECTION CONTROL LAMBDA ( ) CLOSED LOOP CONTROL: - The sensor/ O 2 sensor signal is processed by the ECU. The ECU determines the required injector pulse width to maintain the air: fuel ratio within the control window. A sub-system of fuel control system is closed loop control. Lambda is defined as the excess- air factor that indicates the deviation of the actual air: fuel ratio from theoretically required ratio. Quantity of Air supplied = ---------------------------Theoretical required (14. 7: 1 for petrol)

LAMBDA ( ) CLOSED LOOP CONTROL: The sensor or exhaust gas O 2 sensor is installed in the exhaust upstream of the catalytic converter. The sensor responds to O 2 content of exhaust gas. The signal from sensor serves as feedback to the fuel control system. This provides control over air: fuel ratio to remain within the limited catalytic converter window for optimum catalyst performance. The target is to stay close to = 1.

Catalytic Converter Efficiency (%) Conversion efficiency of Catalytic Converter as a Function of Excess Air Factor λ

LAMBDA ( ) CLOSED LOOP CONTROL: - The system will operate in the closed-loop mode under the following conditions: • Coolant temperature above a specified value • Timing out of the start- up delay timer in the logic module • Generation of a valid oxygen sensor signal to the logic module • Operation of the vehicle under drive / idle or cruise conditions.

FUEL INJECTION OPEN LOOP CONTROL: - The system will remain in open- loop mode under the following conditions. • Cold engine (until the oxygen sensor generates a signal) • Park –neutral idle operation • Wide – open throttle position • Deceleration • Absence of oxygen sensor signal for a specified period of time

Idle speed control valve

An electric fuel pump & a pump-sender unit

A pressure-vacuum gasoline filler cap.

This fuel injector design is equipped with a Pintle type needle valve for precise fuel control

Top feed and bottom feed injectors

Grouped injectors in multiport injection

A typical Air-flow Sensor

A Mass Airflow Sensor

Knock Sensor Mounted on Engine Block Consists of Piezo-ceramic Measuring Element which responds to noise oscillations

High Pressure Sensors for Petrol and Diesel Systems Senses absolute pressure of fuel in common rail.

Crank Angle Sensor Mounted in close proximity of flywheel Senses engine speed

Air Temperature Sensor Measures air temperature in manifold

Throttle Potentiometer Sensor Mounted on throttle valve Inform ECM about idle position, deceleration, rate of acceleration & throttle open.

Oxygen (Lambda) sensor Placed in exhaust manifold It is ceramic device that senses contents of exhaust gases

Advantages: • • • MPFI system provides accuracy and adaptability in order to minimize exhaust emissions and fuel consumption Better driveability for all operating conditions Minimized evaporative emissions System diagnosis when malfunction occurs. Avoids detonation.

Advantages: • • • MPFI system provides Combustion of Homogeneous charge Higher power output than conventional engine Better Volumetric Efficiency Better Thermal Efficiency as higher compression ratio can be employed Very lean mixtures with air: fuel ratio of 40: 1 can be effectively used.

Disadvantages of MPFI system: Systems are very costly. Systems are too complicated. Minor software glitches may cause problems. System failures can be repaired by experts only, so maintenance cost is high.

Gasoline Direct Injection System Layout

Future trends: • More and more dependence on microprocessors to control the car emissions. • With simultaneous research in materials technology, electronics and software the future seems to be very bright for use of GDI(Gasoline Direct Injection) Engine Management systems.

Future trends: • Gasoline (Petrol) engines have more potential for Fuel Efficiency improvements compared to the diesel engines The gasoline engine has a 30 to 40% potential for fuel economy improvement over the standard stoichiometric, 4 -valve, PFI engine.

Differences between PFI and TBI PFI TBI Fuel is injected into the port. Fuel is injected into the center of the throttle body. PFI uses top feed injector Fuel injector need not be flushed TBI uses bottom feed injector Fuel injector needs to be flushed continuously- to prevent formation of air bubble. Fuel injectors are equal to the number of cylinders 1 or 2 Fuel injectors are used.

Differences between PFI and TBI Port Fuel Injection Throttle Body Injection PFI is comparatively high pressure injection (differential pressure = 2 to 3. 5 bar) TBI is comparatively low pressure injection (differential pressure = 0. 7 to 1 bar ) Costly fuel pump is required to generate the required pressure Cheaper fuel pump is sufficient to generate the required low pressure.

Differences between PFI and TBI Port Fuel Injection Throttle Body Injection All cylinders receive equal quantity and quality of air: fuel mixture Mixture mal-distribution may occur. More accurate fuel injection control is obtained. Therefore increased fuel economy is obtained Less accurate fuel injection control gives moderate fuel economy. Very low exhaust emission is achieved to meet the strict emission norms. Exhaust emission is above the permissible emission norms.

Differences between PFI and TBI Port Fuel Injection Throttle Body Injection Better throttle response as fuel is injected on hot back side of intake valve and shorter length of travel for fuel – to enter the engine cylinder Moderate throttle response as the fuel is injected at the throttle body and longer length of travel for fuel to enter the engine cylinder. This is costly system. This is a cheaper system.

Differences between PFI and TBI Port Fuel Injection Throttle Body Injection Hither power output due to low resistance at intake manifold and higher volumetric efficiency. Lower power output due to lower volumetric efficiency caused by bulky injector body at the throttle body.

Engine Technology and Fuel Economy Improvement Outlook • As mentioned earlier, gasoline engines have more potential for FE improvements compared to the diesel engines. • The diesel engines have already achieved high levels of fuel economy from going to direct injection (DI), adopting 4 -valve technology and turbochargers. • It is estimated that the gasoline engine has a 30 to 40% potential for fuel economy improvement over the standard stoichiometric, 4 -valve, PFI engine. •

Engine Technology and Fuel Economy Improvement Outlook On the other hand, the fuel economy of HSDI engines can be improved by 15 to 25% over that of the currently produced HSDI car engines. The gasoline engines as discussed above would be using a variety of technologies to improve fuel economy in the coming years. GDI engines are likely to make more inroads in the passenger car market.

Engine Types The Indian passenger cars are largely powered by gasoline engines. During the year 2007, the market share of gasoline passenger vehicles was 76%. All the gasoline car engines are PFI engines with 3 -way catalytic converters and presently no GDI engine car is produced in the country. The engine and vehicle technologies that can be adopted on Indian passenger vehicles in a period of 2 to 3 years include; variable valve timing and lift on gasoline engines, HSDI in place of IDI diesel engine, multi- valve diesel engines, turbocharging and CRDI fuel injection, idle stop-start system (more likely in combination with integrated starter/generator). In the 4 to 5 years period the following technologies could be implemented; GDI Engines, integrated starter-generator, CVT, 6 - and 7 - gear transmission on larger vehicles, and HEVs in larger urban vehicle segment

MPFI Electronic Control System

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