Digital electronic ignitions

At the turn of the 21st century digital electronic ignition modules became available for small engines on such applications as chainsaws, string trimmers, leaf blowers, and lawn mowers. This was made possible by low cost, high speed, and small footprint microcontrollers.

 Digital electronic ignition modules can be designed as either

 capacitor discharge ignition (CDI)    or 

inductive discharge ignition (IDI) systems.

 Capacitive discharge digital ignitions store charged energy for the spark in a capacitor within the module that can be released to the spark plug at virtually any time throughout the engine cycle via a control signal from the microprocessor. This allows for greater timing flexibility, and engine performance; especially when designed hand-in-hand with the engine carburetor.

ACC

 What is ACC (Adaptive Cruise Control) in automobile. Need , How it works   (operation) ?

Adaptive cruise control (ACC) is an available cruise control system for road vehicles that automatically adjusts the vehicle speed to maintain a safe distance from vehicles ahead.

it is also called by more than 20 unique names that describe that basic functionality. 

This is also known as Dynamic cruise control.

Control is based on sensor information from on-board sensors. 

Such systems may use a radar or laser sensor or a camera setup allowing the vehicle to brake when it detects the car is approaching another vehicle ahead, then accelerate when traffic allows it to.

Mark splitup

 

Module	Topic Area	% Marks in University Exam
1	Fundamentals:	15
2	Sensors	15
3	Fuel injection and Ignition	15
4	Safety and comfort	15
5	Electric vehicles and hybrid vehicles	20
6	Vehicle Intelligence	20

steering system

 There are two main types of steering gears used for most modern vehicles: 

the rack and pinion steering gear and 

the recirculating ball steering gear.

In most cars, small trucks and SUVs on the road today, there is a rack and pinion steering system. This converts the rotational motion of the steering wheel into the linear motion that turns the wheels and guides your path. 

The system involves a circular gear (the steering pinion) which locks teeth on a bar (the rack).

 It also transforms big rotations of the steering wheel into small, accurate turns of the wheels, giving a solid and direct feel to the steering.

ABS

 Anti-lock braking system (ABS) is an automobile safety system that allows the wheels on a motor vehicle to maintain tractive contact with the road surface according to driver inputs while braking, preventing the wheels from locking up and avoiding uncontrolled skidding.

 • ABS generally offers improved vehicle control and decreases stopping distances on dry and slippery surfaces. 

• ABS modulates the brake line pressure independent of the pedal force, to bring the wheel speed back to the slip level range that is necessary for optimal braking performance.

Braking system

 Braking system in automobile . Need , How it works   (operation) ?

The function of the brake system is to stop the vehicle within the smallest possible distance and hence this is done by converting the kinetic energy of the vehicle into the heat energy which is dissipated into the atmosphere.

The brake system in an automobile can be classified into these following categories:

    • Mechanical Brake

    • Disc Brake

    • Hydraulic Brake

    • Power-assisted Brake

    • Air Brake

    • Electric and

    • Hand brake System

Suspension system

Suspension system in automobile . Need , How it works   (operation) ?

Suspension is the system of tires, tire air, springs, shock absorbers and linkages that connects a vehicle to its wheels and allows relative motion between the two.

Suspension systems must support both roadholding/handling and ride quality which are at odds with each other. 

* roadholding=  the ability of a vehicle to remain stable when moving, especially when cornering at high speeds.

* handling =Automobile handling and vehicle handling are descriptions of the way a wheeled vehicle responds and reacts to the inputs of a driver, as well as how it moves along a track or road

The tuning of suspensions involves finding the right compromise.

 It is important for the suspension to keep the road wheel in contact with the road surface as much as possible, because all the road or ground forces acting on the vehicle do so through the contact patches of the tires. 

The suspension also protects the vehicle itself and any cargo or luggage from damage and wear. The design of front and rear suspension of a car may be different. 

Charging system

Charging systems deliver electrical energy to power your vehicle while it’s running and sustains the battery’s charge. 

Your vehicle’s charging system consists of three parts: 

the battery, the alternator, and the voltage regulator. 

The battery supplies the necessary electrical power to start your engine.

 The alternator generates the electrical currents to power everything electrical in the car, while the regulator controls the voltage of the currents. 

The voltage regulator also makes sure the battery stays fully charged. 

When the battery has lost its charge, the voltage regulator will signal the alternator to recharge the battery.

 

drive train

 

What is a Drive train ?

The drivetrain of a motor vehicle is the group of components that deliver power to the driving wheels. 

This excludes the engine or motor that generates the power.

In contrast, the powertrain is considered to include both the engine or motor and the drivetrain.

components in front of car

 

Autotronics

 Autotronics could be described as an artificial word that combines automotive sector and electronics content. 

It has without doubt been at the heart of every meaningful automobile industrial breakthrough recorded in the last two centuries and is continually transforming maintenance operations with endless discovery of new techniques.

capacitor discharge ignition (CDI)

  capacitor discharge ignition (CDI) 

Capacitive discharge digital ignitions store charged energy for the spark in a capacitor within the module that can be released to the spark plug at virtually any time throughout the engine cycle via a control signal from the microprocessor. This allows for greater timing flexibility, and engine performance; especially when designed hand-in-hand with the engine carburetor.

Electronic ignition

 Electronic ignition

The disadvantage of the mechanical system is the use of breaker points to interrupt the low-voltage high-current through the primary winding of the coil; the points are subject to mechanical wear where they ride the cam to open and shut, as well as oxidation and burning at the contact surfaces from the constant sparking. They require regular adjustment to compensate for wear, and the opening of the contact breakers, which is responsible for spark timing, is subject to mechanical variations.

In addition, the spark voltage is also dependent on contact effectiveness, and poor sparking can lead to lower engine efficiency. A mechanical contact breaker system cannot control an average ignition current of more than about 3 A while still giving a reasonable service life, and this may limit the power of the spark and ultimate engine speed.

Electronic ignition (EI) solves these problems. In the initial systems, points were still used but they handled only a low current which was used to control the high primary current through a solid state switching system. Soon, however, even these contact breaker points were replaced by an angular sensor of some kind - either optical, where a vaned rotor breaks a light beam, or more commonly using a Hall effect sensor, which responds to a rotating magnet mounted on the distributor shaft. The sensor output is shaped and processed by suitable circuitry, then used to trigger a switching device such as a thyristor, which switches a large current through the coil.

Digital electronic ignitions

mechanically timed ignition (distributor)

 Most four-stroke engine  have used a mechanically timed electrical ignition system. The heart of the system is the distributor. The distributor contains a rotating  cam driven by the engine's drive, a set of breaker points, a condenser, a rotor and a distributor cap. External to the distributor is the ignition coil, the spark plugs and wires linking the distributor to the spark plugs and ignition coil

   

The system is powered by a lead-acid battery, which is charged by the car's electrical system using a dynamo or alternator. The engine operates contact breaker points, which interrupt the current to an induction coil (known as the ignition coil).

The ignition coil consists of two transformer windings — the primary and secondary. These windings share a common magnetic core. An alternating current in the primary induces an alternating magnetic field in the core and hence an alternating current in the secondary. The ignition coil's secondary has more turns than the primary. This is a step-up transformer, which produces a high voltage from the secondary winding. The primary winding is connected to the battery (usually through a current-limiting ballast resistor). Inside the ignition coil one end of each winding is connected together. This common point is taken to the capacitor/contact breaker junction. The other, high voltage, end of the secondary is connected to the distributor's rotor.

The ignition firing sequence begins with the points (or contact breaker) closed. A steady current flows from the battery, through the current-limiting resistor, through the primary coil, through the closed breaker points and finally back to the battery. This current produces a magnetic field within the coil's core. This magnetic field forms the energy reservoir that will be used to drive the ignition spark.

As the engine crankshaft turns, it also turns the distributor shaft at half the speed. In a four-stroke engine, the crankshaft turns twice for the ignition cycle. A multi-lobed cam is attached to the distributor shaft; there is one lobe for each engine cylinder. A spring-loaded rubbing block follows the lobed portions of the cam contour and controls the opening and closing of points. During most of the cycle, the rubbing block keeps the points closed to allow a current to build in the ignition coil's primary winding. As a piston reaches the top of the engine's compression cycle, the cam's lobe is high enough to cause the breaker points to open. Opening the points causes the current through the primary coil to stop. Without the steady current through the primary, the magnetic field generated in the coil immediately collapses. This high rate of change of magnetic flux induces a high voltage in the coil's secondary windings that ultimately causes the spark plug's gap to arc and ignite the fuel.

The spark generation story is a little more complicated. The purpose of the ignition coil is to make a spark that jumps the spark plug's gap, which might be 0.025 inches (0.64 mm) (it also has to jump the rotor-to-distributor-post gap). At the moment the points open, there is a much smaller gap, say about 0.00004 inches (0.001 mm), across the points. Something must be done to prevent the points from arcing as they separate; if the points arc, then they will drain the magnetic energy that was intended for the spark plug. The capacitor (condenser) performs that task. The capacitor temporarily keeps the primary current flowing so the voltage across the points is below the point's arcing voltage. There is a race: the voltage across the points is increasing as the primary current charges the capacitor, but at the same time the points' separation (and consequent arcing voltage) is increasing. Ultimately, the point separation will increase to something such as 0.015 inches (0.38 mm), the maximum separation of the points.

In addition to staying below the arcing voltage, the ignition system keep the voltage across the points below the breakdown voltage for an air gap to prevent a glow discharge across the points. Such a glow discharge would quickly transition to an arc, and the arc would prevent the spark plug from firing. The minimum voltage for a glow discharge in air is about 320 V. Consequently, the capacitor value is chosen to also keep the voltage across the points to be less than 320 V. Keeping the points from arcing when they separate is the reason the ignition coil includes a secondary winding rather than using just a simple inductor. If the transformer has a 100:1 ratio, then the secondary voltage can reach 30 kV.

The ignition coil's high voltage output is connected to the rotor that sits on top of the distributor shaft. Surrounding the rotor is the distributor cap. The arrangement sequentially directs the output of the secondary winding to the appropriate spark plugs. The high voltage from the coil's secondary (typically 20,000 to 50,000 volts) causes a spark to form across the gap of the spark plug that in turn ignites the compressed air-fuel mixture within the engine. It is the creation of this spark which consumes the energy that was stored in the ignition coil's magnetic field.

The flat twin cylinder 1948 Citroën 2CV used one double ended coil without a distributor, and just contact breakers, in a wasted spark system.

battery & coil operated ignition

 Battery and coil-operated ignition

With the universal adoption of electrical starting for automobiles, and the availability of a large battery to provide a constant source of electricity, magneto systems were abandoned for systems which interrupted current at battery voltage, using an ignition coil to step the voltage up to the needs of the ignition, and a distributor to route the ensuing pulse to the correct spark plug at the correct time.

The Benz Patent-Motorwagen and the Ford Model T used a trembler coil ignition system. A trembler coil was a battery-powered induction coil; the trembler interrupted the current through the coil and caused a quick series of sparks during each firing. The trembler coil would be energized at an appropriate point in the engine cycle. In the Model T, the four-cylinder engine had a trembler coil for each cylinder; a commutator (timer case) delivered power to the trembler coils. The Model T would be started on battery but then switched to an alternator.

An improved ignition system was developed by the Dayton Engineering Laboratories Co. (Delco) and introduced in the 1910 Cadillac. This ignition was developed by Charles Kettering and was a wonder in its day. It consisted of a single ignition coil, breaker points (the switch), a capacitor (to prevent the points from arcing at break) and a distributor (to direct the spark from the ignition coil to the correct cylinder).

The points allow the coil magnetic field to build. When the points open by a cam arrangement, the magnetic field collapses inducing an EMF in the primary that is much larger than the battery voltage and the transformer action produces a large output voltage (20 kV or greater) from the secondary.

The capacitor suppresses arcing at the points when they open; without the capacitor, the energy stored in the coil would be expended at an arc across the points rather than at the spark plug gap. The Kettering system became the primary ignition system for many years in the automotive industry due to its lower cost, and relative simplicity.

switchable ignition

 The output of a magneto depends on the speed of the engine, and therefore starting can be problematic. Some magnetos include an impulse system, which spins the magnet quickly at the proper moment, making easier starting at slow cranking speeds. Some engines, such as aircraft but also the Ford Model T, used a system which relied on non rechargeable dry cells, (similar to a large flashlight battery, and which was not maintained by a charging system as on modern automobiles) to start the engine or for starting and running at low speed. The operator would manually switch the ignition over to magneto operation for high speed operation.

To provide high voltage for the spark from the low voltage batteries, a 'tickler' was used, which was essentially a larger version of the once widespread electric buzzer. With this apparatus, the direct current passes through an electromagnetic coil which pulls open a pair of contact points, interrupting the current; the magnetic field collapses, the spring-loaded points close again, the circuit is reestablished, and the cycle repeats rapidly. The rapidly collapsing magnetic field, however, induces a high voltage across the coil which can only relieve itself by arcing across the contact points; while in the case of the buzzer this is a problem as it causes the points to oxidize and/or weld together, in the case of the ignition system this becomes the source of the high voltage to operate the spark plugs.

Ignition system

Purpose ?

An ignition system generates a spark or heats an electrode to a high temperature to ignite a fuel-air mixture in spark ignition internal combustion engines, oil-fired and gas-fired boilers, rocket engines, etc. The widest application for spark ignition internal combustion engines is in petrol (gasoline) road vehicles such as cars and motorcycles.

Compression ignition Diesel engines ignite the fuel-air mixture by the heat of compression and do not need a spark. They usually have glowplugs that preheat the combustion chamber to allow starting in cold weather. Other engines may use a flame, or a heated tube, for ignition. While this was common for very early engines it is now rare.

Main classification falls into two category (These are old systems)

     Magneto  systems 

    Battery and coil-operated ignition

   

some other terms related  (relatively modern ) are 

          Switchable systems

Mechanically timed ignition

Electronic ignition

        capacitor discharge ignition

Digital electronic ignitions

magneto ignition

Magneto ignition system

a petrol engine needs a high voltage at spark plug for igniting air-fuel mixture.

the magneto ignition system produces that high voltage as follows

An ignition magneto, or high tension magneto, is a magneto that provides current for the ignition system of a spark-ignition engine, such as a petrol engine. It produces pulses of high voltage for the spark plugs. The older term tension means voltage.

The use of ignition magnetos is now confined mainly to engines where there is no other available electrical supply, for example in lawnmowers and chainsaws. It is also widely used in aviation piston engines even though an electrical supply is usually available. In this case, the magneto's self-powered operation is considered to offer increased reliability; in theory, the magneto should continue operation as long as the engine is turning.

Firing the gap of a spark plug, particularly in the combustion chamber of a high-compression engine, requires a greater voltage (or higher tension) than can be achieved by a simple magneto. The high-tension magneto combines an alternating current magneto generator and a transformer. A high current at low voltage is generated by the magneto, then transformed to a high voltage (even though this is now a far smaller current) by the transformer. In the type known as a shuttle magneto, the engine rotates a coil of wire between the poles of a magnet. In the inductor magneto, the magnet is rotated and the coil remains stationary. As the magnet moves with respect to the coil, the magnetic flux linkage of the coil changes. This induces an EMF in the coil, which in turn causes a current to flow. One or more times per revolution, just as the magnet pole moves away from the coil and the magnetic flux begins to decrease, a cam opens the contact breaker (called “the points” in reference to the two points of a circuit breaker) and interrupts the current. This causes the electromagnetic field in the primary coil to collapse rapidly. As the field collapses rapidly there is a large voltage induced (as described by Faraday's Law) across the primary coil.

As the points begin to open, point spacing is initially such that the voltage across the primary coil would arc across the points. A capacitor is placed across the points which absorbs the energy stored in the leakage inductance of the primary coil, and slows the rise time of the primary winding voltage to allow the points to open fully. The capacitor's function is similar to that of a snubber as found in a flyback converter. 

A second coil, with many more turns than the primary, is wound on the same iron core to form an electrical transformer. The ratio of turns in the secondary winding to the number of turns in the primary winding, is called the turns ratio. Voltage across the primary coil results in a proportional voltage being induced across the secondary winding of the coil. The turns ratio between the primary and secondary coil is selected so that the voltage across the secondary reaches a very high value enough to arc across the gap of the spark plug. As the voltage of the primary winding rises to several hundred volts, the voltage on the secondary winding rises to several tens of thousands of volts, since the secondary winding typically has 100 times as many turns as the primary winding.

The capacitor and the coil together form a resonant circuit which allows the energy to oscillate from the capacitor to the coil and back again. Due to the inevitable losses in the system, this oscillation decays fairly rapidly. This dissipates the energy that was stored in the condenser in time for the next closure of the points, leaving the condenser discharged and ready to repeat the cycle.

On more advanced magnetos the cam ring can be rotated by an external linkage to alter the ignition timing.

In a modern installation, the magneto only has a single low tension winding which is connected to an

external ignition coil which not only has a low tension winding, but also a secondary winding of many

thousands of turns to deliver the high voltage required for the spark plug(s). Such a system is known as an "energy transfer" ignition system. 

Initially this was done because it was easier to provide good insulation for the secondary winding of an external coil than it was in a coil buried in the construction of the magneto (early magnetos had the coil assembly externally to the rotating parts to make them easier to insulate—at the expense of efficiency). 

In more modern times, insulation materials have improved to the point where constructing self contained magnetos is relatively easy, but energy transfer systems are still used where the ultimate in reliability is required such as in aviation engines.

inertia type

starter - pre engaged type

 

Starting & charging systems operation-

Starting system in automobile . How it works   (operation) ?

The starting system:

• Uses a powerful electric motor to drive the engine at about 200 RPM 

(fast enough to allow the fuel and ignition systems to operate).

• Drives the engine through a pinion gear engaged with a ring gear on the flywheel.

• Disengages as soon as the engine starts.

fig 

There are 2 types 

1. pre engaged     

2. inertia type (uses bendex gear)

The engine-components

Explain various engine components ?

An engine comprises of a few hundred components : small and big, stationary and moving, metallic
and  non-metallic , casted and forged and made by other processes.

The components of an engine can be grouped under 2 categories.

1. Stationary or Structure forming components. (which forms the mechanism)

2. Moving or mechanism forming components.

Important mechanism forming components are as follows:-

piston , piston rings, gudgeon pin , connecting rod

crank , crankshaft

camshaft ,

valves, valve operating mechanism , timing gears

chain and sprocket

belts and pulleys

flywhhel

Important structural components are as follows :

cylinder block ,

cylinder head ,

gaskets

cylinder liner

crankcase

inlet manifold, exhaust manifold.

Oil pan

resonator

muffler (silencer)

vibration damper

bearings

fasteners

turbocharger

Spark plug for SI /Petrol engine ,

Fuel injector / pump for CI /Diesel engine

 

fig 1

fig 2

fig 3

Car Engine Parts

The core responsibility of the engine is to transform energy from fuel with a spark (in petrol

engine), to create the power to move.

This internal combustion creates tiny, contained explosions to produce movement.

While many of us think of the engine as one major component, it’s actually made up of several

individual components working simultaneously.

Car engines are designed around sealed, resilient metal cylinders.

Most modern vehicles have between four and eight cylinders, though some vehicles can have as

many as sixteen.

The cylinders are made to open and close at precisely the correct time to bring in fuel to combine

with the spark for burning internally, and to release the exhaust gases produced.

While there are several components on an engine, a list of the most essential car engine parts and

their functions are given below see diagram 1,2 and 3

Engine Block–

This is the very core of the engine.

Often made of aluminum or iron, it has several holes to contain the cylinders as well as provide

water and oil flow paths to cool and lubricate the engine.

Oil paths are narrower than the water flow paths.

The engine block also houses the pistons, crankshaft, camshaft, and between four and twelve

cylinders—depending on the vehicle, in a line, also known as inline, flat or in the shape of a V.

Pistons –

Are a cylindrical apparatus with a flat surface on top.

The role of the piston is to transfer energy created from combustion to the crankshaft to propel the

vehicle.

Pistons travel up and down within the cylinder twice during each rotation of the crankshaft.

Pistons on engines that rotate at 1250 RPM, will travel up and down 2500 times per minute.

Inside the piston, lie piston rings that are made to help create compression and reduce the friction

from the constant rubbing of the cylinder.

Crankshaft

The crankshaft is located in the lower section of the engine block, within the crankshaft journals

(an area of the shaft that rests on the bearings).This keenly machined and balanced mechanism is connected to the pistons through the connecting

rod.

Similar to how a jack-in-the-box operates, the crankshaft turns the pistons up and down motion into

a reciprocal motion, at engine speed.

Camshaft –

Varying from vehicle to vehicle, the camshaft may either be located within the engine block or in

the cylinder heads.

Many modern vehicles have them in the cylinder heads, also known as Dual Overhead Camshaft

(DOHC) or Single Overhead Camshaft (SOHC) and supported by a sequence of bearings that are

lubricated in oil for longevity.

The role of the camshaft is to regulate the timing of the opening and closing of valves and take the

rotary motion from the crankshaft and transfer it to an up and down motion to control the movement

of the lifters, moving the pushrods, rockers, and valves.

Cylinder Head–

Attached to the engine through cylinder bolts, sealed with the head gasket.

The cylinder head contains many items including the valve springs, valves, lifters, pushrods,

rockers, and camshafts to control passageways that allow flow of intake air into the cylinders during

the intake stroke as well as exhaust passages that remove exhaust gases during the exhaust stroke.

Timing Belt/Chain –

The camshaft and crankshafts are synchronized to ensure the precise timing in order for the engine

to run properly.

The belt is made of a heavy-duty rubber with cogs to grasp the pulleys from the camshaft and

crankshaft.

The chain, similar to your bicycle chain wraps around pulleys with teeth.