HEXA

ENGINE

F. Fuel System :

Introduction to VARICOR System :

1. This engine uses DELPHI high-pressure pump

and a common rail for supplying all the

cylinders with high-pressure diesel through the

electronically-controlled fuel injectors. High

pressure results in better atomization which

leads to complete combustion.

2. Common-rail is a key to better diesel engine

performance, since more accurate high

pressure injection results in more efficient fuel

combustion. It also injects the fuel only when it

is required thereby increasing fuel efficiency. It

helps the engine to create a perfect blend of

power and fuel economy.

3. The brain of the VARICOR engine is the ECU

(Electronic Control Unit) which keeps the

VARICOR engine functioning at its optimal

capacity. It continuously receives signal from

various sensors to calculate the timing and

quantity of fuel required by the engine with

complete flexibility. Besides the ECU also

controls Engine cooling electric fans, A/C,

EGR, VNT and diagnosis etc.

4. In addition to the other sensors, the ECU also

receives continuous inputs from the rail

pressure sensor which monitors fuel pressure.

The ECU can thus keep the system pressure

at an optimal value as per the engine speed,

load and various operating conditions. For

example, if the pedal is pressed, depending on

the amount of pedal depression, the

accelerator pedal sensor immediately sends a

signal to the ECU. The VARICOR System has

“Drive by wire” technology where in Driver

demand translation is done through ECU.

5. The ECU determines the load required by the

engine to meet the driver demand. It then

sends a signal to the high pressure pump

through the IMV

(Inlet Metering Valve)

to send

the exact amount of fuel to common rail to

meet the requirement. The Inlet Metering

Valve determines the quantity of fuel required

to be pumped to the rail depending on the

engine speed & load and pressurizes the same

thus avoiding wastage of fuel. This helps in

improving the fuel consumption.

6. The ECU also tells the injectors exactly when

and how much to inject, to produce the amount

of power actually needed.

The high pressure pump has an internal lift

pump to draw the fuel from the fuel tank.

(In

case, the pedal is released abruptly the excess

fuel is recycled back into the fuel tank via the

injectors, through the venturi and fuel return

lines).

8. The desired amount of fuel is pumped into the

common rail after taking into account the

current fuel pressure

(as detected by the rail

pressure sensor and sent to the ECU).

9. The fuel gets distributed through the rail to the

individual electronically controlled injectors into

the cylinders.

10.The fuel is injected into the combustion

chamber at the specified time and pressure.

As a result it increases the power output and

vastly enhances the fuel efficiency.

11.In

addition the ECU commands the injectors to

inject a small amount of fuel in to the cylinder

before the main injection happens. This pilot

injection helps to reduce the instantaneous

combustion which causes the traditional Diesel

‘Knock’. As a consequence there is far less

noise, vibration and harshness that is

conventionally associated with DI diesel

engines.

12.This entire process happens in tiny fractions of

a second.

13.Finally to control the emission, the EGR

(Exhaust Gas Recirculation)

valve along with

EGR cooler does its bit to reduce nitrogen

oxides and particulate matter content in the

emissions by effectively managing exhaust gas

and unburned fuel by returning it to the

combustion chamber for further combustion

events.

14. The VARICOR System is equipped with Fuel

filter & fuel prefilter cum s

edimentor

designed

to filter out external particles & separate water

from Diesel. The water sensor in Sedimentor

gives an alarm to the Driver through a

Dashboard indicator when the water level

increases which indicates presence of water

in fuel.