Modern Automotive Engines – Trends & Technologies 1.1 Introduction The advent of Automotive Electronics has brought a new dimension to the field of automotive research. The prime motive of this involves making an Automobile more fuel efficient without compromising with performance and also Eco friendly. Modern IC Engines are not an exception in this respect. Some of the trends observed in Engine designs are Engine Design trends: The location of various parasitic loads has been changed like engines with Over Head camshaft arrangement. Some of the parasitic loads have been made independent of engine like Steering Assist Hydraulic pump. Even combining Alternator and Starter motor (ISG) is a new development. Unorthodox IC Engines like Wankel engine, Air engine and Grail engine have also paved new opportunities for research. Material trends: Previous IC engines were manufactured by casting or forging of ferrous metals. But the need to improve power to weight ratio has made way for use of aluminium alloys for cylinder blocks, cylinder heads and intake manifolds are made of magnesium. Parts such as engine covers, intake manifolds, and oil pans are being manufactured by powder metallurgy by using plastic or composite materials which are less dense and reduce engine noise and vibration. Ignition & Fuel Supply trends: Distributor less ignition system are replaced by coil-on-plug or direct ignition
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Modern Automotive Engines – Trends & Technologies
1.1 Introduction
The advent of Automotive Electronics has brought a new dimension to the field of
automotive research. The prime motive of this involves making an Automobile more fuel
efficient without compromising with performance and also Eco friendly. Modern IC Engines
are not an exception in this respect. Some of the trends observed in Engine designs are
Engine Design trends: The location of various parasitic loads has been changed like
engines with Over Head camshaft arrangement. Some of the parasitic loads have been
made independent of engine like Steering Assist Hydraulic pump. Even combining
Alternator and Starter motor (ISG) is a new development. Unorthodox IC Engines
like Wankel engine, Air engine and Grail engine have also paved new opportunities
for research.
Material trends: Previous IC engines were manufactured by casting or forging of
ferrous metals. But the need to improve power to weight ratio has made way for use
of aluminium alloys for cylinder blocks, cylinder heads and intake manifolds are
made of magnesium. Parts such as engine covers, intake manifolds, and oil pans are
being manufactured by powder metallurgy by using plastic or composite materials
which are less dense and reduce engine noise and vibration.
Ignition & Fuel Supply trends: Distributor less ignition system are replaced by coil-
on-plug or direct ignition system. In this ignition system ignition coil sits directly
above each spark plug. Modern IC Engines have ECU’s capable of monitoring
exhaust gases by the help of oxygen sensors and control the air fuel mixture
accordingly by electronic actuators.
1.2 Technology in Modern IC Engines
The various new technologies introduced in IC Engines are explained here
o Drive by Wire Throttle System: This system eliminates the mechanical linkage
between Accelerator pedal and Throttle. A accelerator pedal module based on Hall
effect sensor or a rotary potentiometer detects the driver input and through ECU sends
signal to electric motor (BLDC) to adjust the throttle position accordingly. TPS is also
included in the control loop for a closed loop operation. A major advantage of this
system is that it can be integrated with ESP, ACC and TC since throttle position can
be controlled irrespective of driver input. In case of failure of the system ‘limp home
mode’ will be activated setting the throttle in a fixed position to maintain uniform
vehicle speed.
o Variable valve timing (VVT): Traditional Valve mechanism use fixed valve timing
which is a compromise between low and high Engine speed. A typical VVT engine is
capable of varying Valve timing & lift of valve according to engine speed. The engine
has 2 camshafts for operating intake valves and operating exhaust valves. Each
camshaft has two lobes per cylinder for high and low rpm, with two intake valves and
exhaust valves. Each set of two valves are controlled by one rocker arm which has a
slipper follower mounted to the rocker arm with a spring .The Engine speed sensor,
the ECM, oil pressure switch forms a closed loop which pushes a sliding pin under the
slipper follower on each rocker arm to switch to the high lobe causing high lift and
longer duration at high rpm. VVT improves Engine fuel efficiency, Torque and
Engine responsiveness.
o Common Rail Direct Injection (CRDI): The fuel is supplied directly to a common
rail from where it is injected directly onto the pistons which ensures the onset of the
combustion in the whole fuel mixture at the same time. CRDI provides highly
accurate and uniform distribution of air/fuel ratio at all engine operating condition and
better engine response
o Multi point Fuel Injection (MPFI): In this system each cylinder has number
of injectors to supply fuel in the cylinders as compared to one injector located
centrally to supply fuel in case of single point injection system. MPFI with direct
injection provides allows higher compression ratios and more efficient fuel intake,
which deliver higher performance with lower fuel consumption.
o Integrated Starter/Generator (ISG): In this system the Starter motor also acts as a
alternator and stores energy in the battery when the engine is running. At idling
condition the ECM signals the engine to stop and start as required and the alternator
drives the engine to start. Regenerative braking can also be implemented in this
system for higher fuel efficiency without effecting driver comfort.
o Cylinder deactivation: This system enables the ECM to cut off fuel supply to some
cylinders (Normally in 6-8 cylinder engines) at low load condition to reduce the fuel
consumption. This system is not suitable for 3-4 cylinder engines because it may
greatly reduce the engine performance. The ECM signals the VVTi to close the intake
and exhaust valve creating an air spring in the combustion chamber and hence no load
is supported by the cylinder.
Safety Systems
2.1 Introduction:
At the time of launch of first affordable road car in the year 1909 Ford Model
T [1] people were fascinated about this indigenous locomotive which can carry people
from one place to another with minimum human effort. With top speed of just 40 to
45kmph [1] safety of the passengers were least of the concerns. But as the industrial
age has emerged and flourished in both developed and developing countries car
design and driver attitude has changed greatly. According to WHO September 2012
reports about 1.3 million people die each year on roads worldwide. Road traffic
injuries are the leading cause of death among young people, aged between 15 and 29
[2] which is a very disturbing fact. Over 90% of the deaths on the roads occur in low-
income and middle-income countries, which have only 48% of the world’s registered
vehicles [2] which includes India. Even with these alarming figures common
commuters are more aware of traffic congestion then road fatalities, so it is the duty of
the car designers to prioritise safety of cars over speed, acceleration and aesthetics.
Modern car safety systems are widely branched into active and passive safety
system. The prime motive of these systems is to assist the driver to avoid any
impending danger to passengers as well as pedestrians in driving condition or in a
worst case scenario damp the effects of an accident to the passengers. Various active
and passive systems installed in modern cars are explained here.
Passive Safety System:
In occurrence of a collision the vehicle deformation occurs within 0.1-0.2
seconds but braking maneuver will take few seconds [3]. Hence the occupants will
subjected to very thrust in the direction of motion and in case of absence of any
restraints the occupants will be subjected to injury due to vehicle interior trims.
Primary objective of a passive safety system is to safe guard the occupant by a
combination of restraint and by collision damping to the passenger cabin. Based on
these two methods following safety measures are implemented in modern cars.
o Vehicle Structure: This category mainly deals with the crashworthiness of the
vehicle body. In case of frontal, rear or side impact the vehicle body is designed to
absorb the crash energy by deforming with minimal deformation of the passenger
cabin. This is realised by understanding the various crash scenarios and vehicle
behaviour in these crash scenarios.
Figure 2.1 [4]
From Figure 1 it can be understood that the two vehicles with different front hood
length have to absorb same energy, because of this the SUV becomes much stiffer
then the Sedan and hence passenger in SUV is injured more in this case. Both the
front and the rear of the car act as a crumple zone and hence are made less stiff to
absorb crash energy. To inhibit the effects of side impact modern cars have side doors
with beam, cells, padding and other energy absorbing medium. Modern vehicles are
also provided with safety cages which are built around the passenger cabin to provide
protection in case of vehicle roll over.
o Restraint System: Modern automobiles are fitted with occupant restraint systems,
like seat belt with pre-tensioner and airbags to reduce passenger injuries and fatalities
at the occurrence of a crash. Seat belts are the primary restraint systems whereas air
bag is supplementary to the seat belt. Type of seat belt also greatly affects the
occupant safety because insufficient restraint might still be dangerous. The various
seat belt restraints are shown in the figure 2.
Figure 2.2 Left to Right Lap Strap, 3 point, Belt in seat, Five point Harness [5]
Three point Harness is best restraint for passenger cars since they support both torso
and shoulder region. They are easy to detach. Seat belt pre tensioner arrests the slack
of the seat belt in case of sudden deceleration which pulls the occupant firmly on the
seat when crash occurs. Air bags have three basic functions which are slowing the
driver deceleration by deflating at a controlled rate, preventing the driver and
passenger head from colliding with the internal trims and supplementing the seat belt
constrain to reduce occupant chest compression. Airbag operates by detecting crash
with the help of accelerometer sensors, and calculating the severity of the crash and
deploying the airbag if necessary.
Active Safety System
As the name suggests this safety system is a drive assistance system controlled
by various electro mechanical devices to prevent accidents either by cautioning the
driver or by overriding driver command. The various Active safety systems include
ABS, TCS, ESP, TPMS, ACC and Parking Assist.
o Tire Pressure Management System (TPMS): Tire is the most crucial part any
automobile in all the aspects imaginable. The contact patch defined by the tyre on the
ground can define vehicle handling & stability, Fuel economy, Acceleration, Top
Speed and many more. Many times Tire is the most neglected part by any automobile
owner. Tire pressure defines the geometry of the contact patch, roll resistance and
cornering stiffness. TPMS continuously monitors the pressure in individual tires and
notifies the driver in case of under inflation or sudden drop in tire pressure. TPMS
consists of Tire pressure sensor, Control Module, radio frequency transmitter and
receiver. The pressure sensor is mounted on the tire rim hence each sensor is fitted
with independent batteries having a low discharge rate. Tire pressure is detected at
intervals of time and transmitted to the receiver by low frequency radio signal. The
signal from receiver is then amplified, conditioned, converted from analog to digital
and rendered to the control module. The control module detects any pressure drop and
notifies the drive through Warning lamp.
o Adaptive Cruise Control (ACC): ACC is intended to reduce driver fatigue while on
long drives on highways where any mishandling will lead to fatality. It allows a driver
to set a desired speed similar to ordinary cruise control but if a vehicle immediately
ahead of the equipped vehicle is moving at a slower speed, then throttle and braking
of the host vehicle is controlled to match the speed of the slower vehicle as per the
driver defined gap. The defined speed is automatically re attained when the roadway
ahead is unobstructed, either due to slower vehicle ahead leaving the lane or the driver
of the host vehicle changing to a clear lane. The current ACC Systems monitor the
road ahead using either radar or Lidar (laser radar).The operating modes of an ACC is
shown in figure 2.3.
Figure 2.3 Various modes of ACC operation [Refer 7]
o Antilock Braking System (ABS): This system is primarily addressing the problem of
wheel locking due to sudden application of brakes under driver panic. A wheel under
locked condition may lead to under steer or over steer and finally lead to fatalities.
Major components of an ABS include Brake Module, Wheel Speed Sensor and
Hydraulic Modulator with solenoid valves and Brake assembly. ABS control module
analyses wheel speed sensors data and detects any wheel approaching lock condition.
It signals the hydraulic modulator to release the brake pressure momentarily on the
locked wheel using solenoid assembly. The control strategy for ABS is shown in
figure 2.4.
Figure 2.4 ABS Control Strategy [Refer 8]
2.2 Active Safety System-Passive Safety System, A comparison
Active Safety System
o Technology: The technology used in Active safety system is highly advanced
compared to passive safety system. The control algorithms have to deal with a lot of
variables and either affected by driver attitude, vehicle stability or the road
environment. The sensors used in Active safety range from Wheel speed sensors