Mechanical Fuel Injection Systems | Jerk Fuel Injection System | Distributor Fuel Injection System | Constant Pressure Common Rail System

Mechanical fuel injection systems

In the year of 1927 Bosch brought the first mechanical hydraulicfuel injection system for truck diesel engines. This made diesel engines familiar among people. In1932 the complete fuel system consisting of nozzle holder assembly, nozzle, filter system was introduced.

Jerk pump injection system

01 - FUEL INJECTION SYSTEM - Jerk pump injection system

The jerk pump controlled system has a single reciprocating type pump for each fuel injection. The pump is separately mounted on the engine block. The pump is driven by an accessory shaft. The pump plunger has a constant stroke with a variable effective stroke. The injector is connected to the pump by suitable tubing.

The injector is opened by lifting the needle valve automatically by fuel pressure. When the fuel pressure in the system falls below a certain value, the spring loaded injector needle valve terminates fuel injection.

Multicylinder in line pump unit is produced by a number of manufacturers under license from ROBERT BOSCH Company of Germany. It is characterized by having one pump with a delivery valve and a injector for each cylinder in the engine.

Distributor fuel injection system

01 - FUEL INJECTION SYSTEM - Distributor fuel injection system

There are several types of distributors fuel injection system. One type provides a high pressure metering pump with a distributor which delivers fuel to the various cylinders. Another design provides a low pressure metering and distributor. High pressure needed for injection is provided by the injection nozzles which are cam operated.

In these systems, the metered fuel is directed to the proper cylinder by the rotating distributor with drilled passage ways. The distributor is driven by the camshaft of the engine.

Distributor pump system is used by General motors, Volkswagen, Cummins and others. It is characterized by having one pump to supply fuel to outlets leading to each engine cylinder.

Constant pressure common rail system


The constant pressure common rail system was developed by M/s.Vickers company. This system consists of a high pressure pump which distributes fuel to a common rail or header to which each injector is connected. A spring loaded bypass valve on the header maintains a constant pressure of 330 to 530kscm in the system and returns all excess fuel to the supply tank.

The fuel injectors are operated mechanically. The metering and timing of fuel injection are accomplished by the spray valve. The amount of fuel injected into the cylinders is controlled by the lift of the needle valve in the injector. The duration of injection depends on the length of time the valve is off its seat.

The quantity of fuel injected depends on the duration, size and number of holes in the nozzle tip and fuel pressure and air pressure in the cylinder.

The nozzles must therefore be closely matched to ensure equal distribution among the cylinders. The common rail system tends to be self-governing. That is if the speed falls, an increased quantity of fuel is injected. Remember, supply pressure is independent of engine speed.

Hybrid Drive Trains | Hybrid Vehicles

Hybrid vehicles

The term Hybrid drive denotes such vehicle drives with more than one drive source. Hybrid drives can incorporate several similar or dissimilar types of energy stores and/or power converters.

The goal of the hybrid drive developments is to combine different drive components, such that the advantages of each are utilized under varying operating conditions in such a manner that the overall advantages outweigh the higher technical and cost outlay associated with hybrid drives.


Hybrid drive trains

Hybrid drive trains are broadly classified into series and parallel depending on the configuration of the power source.



In a series drive train, only the electric power is coupled to the wheels. The second power source converts fuel energy into electric power. This electric power is then passed in a series fashion through the electric drive and motor to the wheels. Typically an IC engine is coupled to an alternator to provide the fuel based electric power. The engine alternator combination is often referred to as an auxiliary power unit.

Series hybrid engines have the following characteristics

The engine and the energy storage devices are closely coupled. More efficient, satisfying light load power demands.


In the parallel hybrid drive trains, two power sources operate in parallel to propel the vehicle. Power from the electric motor and internal combustion engine are combined via the vehicle transmission to satisfy the road power demand.

Parallel hybrid engines have the following characteristics

Drive train losses between the engine and the engine and the road are minimal. Generally more efficient and satisfying high power demand.

Parallel hybrids have speed coupling between the road and the engine. Series hybrids do not have speed coupling. Both series and parallel hybrids can be operated with engine to road power decoupling. Both parallel and series hybrids can be implemented with large engines and small energy storage or vice versa.

Series and parallel combined system

This combined system called the dual system having a generator and a motor, features characteristics of both the series and parallel systems, and the following systems are possible.


Switching system

This implies the application and the release of the clutch switches between the series and parallel system. For driving by the series system, the clutch is released, separating the engine and the generator from the driving wheels. For driving with the parallel system, the clutch is engaged, connecting the engine and the driving wheels.

Since city driving requires low loads for driving and low emission, the series system is selected with the clutch released. For high speed driving where the series system would not work efficiently due to higher drive loads and consequently higher engine output is required, the parallel system is selected with the clutch applied.

Split system

This system acts as the series and parallel systems at all times. The engine output energy is split by the planetary gear into the series path and the parallel path. It can control the engine speed under variable control of the series path by the generator while maintaining the mechanical connection of the engine and the driving wheels through the parallel path.