THE CONSTANT ENERGY IGNITION SYSTEM

Figure 1.1 shows a type of electronic ignition distributor that has been in use forn many years. The distributor shaft is driven from the engine camshaft and thus rotates at half engine speed. Each time a lobe on the rotor (reluctor) passes the pick-up probe a pulse of electrical energy is induced in the pick-up winding. The pick-up winding is connected to the electronic ignition module and when the pulse generator voltage has reached a certain level (approximately 1 V) the electronic circuit of themodule will switch on the current to the ignition coil primary winding.

Fig. 1.1 Reluctor and pick-up assembly

As the reluctor continues to rotate, the voltage in the pick-up winding begins to drop and this causes the ignition module to ‘switch of’ the ignition coil primary current; the high voltage for the ignition spark is then induced in the ignition coil secondary winding. The period between switching on and switching off the ignition coil primary current is called the dwell period. The effective increase in dwell angle as the speed increases means that the coil current can build up to its optimum value at all engine speeds. Figure 1.2 shows how the pulse generator voltage varies due to the passage of one lobe of the reluctor past the pick-up probe. From the graphs in this figure may be seen that the ignition coil primary current is switched on when the pulse generator voltage is approximately 1 V and is switched off again when the voltage falls back to the same level. At higher engine speeds the pulse generator produces a higher voltage and the switching-on voltage (approximately 1 V) is reached earlier, in terms of crank position, as shown in the second part of Fig. 1.2. However, the ‘switching-of ’ point is not affected by speed and this means that the angle (dwell) between switching the coil primary current on and off increases as the engine speed increases. This means that the build-up time for the current in the coil primary winding, which is the important factor affecting the spark energy, remains virtually constant at all speeds. It is for this reason that ignition systems of this type are known as ‘constant energy systems’. It should be noted that this ‘early’ type of electronic ignition stillincorporates the centrifugal and vacuum devices for automatic variation of the ignition timing.

Engine-Related Systems

The engine systems that are surveyed are those that are most commonly used, namely ignition and fuelling, plus emission control. A major purpose of these system surveys is to identify common ground in order to focus on the components of the systems that can realistically be tested with the aid of reasonably priced tools, rather than the more exotic systems that require specialized test equipment. By examining three ignition systems it should be possible to pick out certain elements that are commonly used. In the process of examining a number of other systems we shall see that certain basic principles are common to several types of systems that are used on vehicles. In effect, there is a good deal of knowledge that can be transferred across a considerable range of technology.

Common technology

Changes in electronics technology and manufacturing methods take place rapidly and for some years now,microcontrollers (mini-computers) have formed the heart of many of the control systems found on motor vehicles. Microcontrollers, in common with other computers, contain a control unit and presumably in order to avoid any possible confusion, the ‘black box’ that used to be known as the Electronic Control Unit (ECU) is now commonly referred to as the Electronic Control Module (ECM). In this book, the term electronic control module (ECM) is used when referring to the control module that was formerly known as the ECU. As vehicle systems have developed it has become evident that there is a good deal of electronic and computing technology that is common to many vehicle electronic systems and this suggests that there is good reason for technicians to learn this ‘common technology’ because it should enable them to tackle diagnosis and repair on a range of vehicles. Indeed, many manufacturers of automotive test equipment are now producing equipment which, when supported by information and data about diagnostic trouble codes (fault codes), provides the knowledgeable technician with the support that should enable him/her to go forward in to the 2000s with a degree of confidence in their ability to maintain and repair modern systems. We will now look at a representative selection of commonly used modern systems in order to enable us to ‘tease out’ the common elements that it will be useful to learn more about.

Turbocharger pada Motor Bensin Daihatsu Tipe CB-23

Turbocharger adalah suatu komponen yang dipasang pada kendaraan bermotor yang bertujuan untuk meningkatkan daya dari motor dengan melakukan penambahan rapat massa udara yang lebih banyak dibandingkan dengan cara pengisian biasa. Turbocharger terdiri dari sebuah turbin dan sebuah kompresor. Banyak yang mengharapkan daya dari kendaraannya dapat meningkat dengan memasang perangkat. Diharapkan dengan memasang perangkat tersebut, daya dari motor akan meningkat dan juga akselerasinya. perangkat yang dipakai dalam hal ini adalah turbocharger. Dengan penambahan turbocharger, akan membuat campuran udara dengan bahan bakar semakin sempurna atau semakin homogen sehingga pembakaran akan semakin sempurna. Perangkat turbocharger ini mempunyai kelebihan dariperangkat lain yang bertujuan untuk meningkatkan daya. Turbocharger ini digerakkan oleh tekanan gas buang, yang pada umumnya tekanan gas buang dan panas dari gas buang ini tidak dimanfaatkan atau langsung dibuang begitu saja.