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Glossary of terms you will come across during your Phase 2 training.


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> means greater than -example 2 > 1

< means less than - example 1 < 2

≤ means less than or equal to.

≥ means greater than or equal to.

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Lambda, a letter from the Greek alpahbet. In automotive engineering, it is used to represent the stoichiometric ratio of the amount of air required to burn a fuel. For example, for diesel, the value is approximately 14.5:1, meaning that it takes 14.5 parts of air to burn 1 part of diesel.

The stoichiometric ratio for petrol is approximately 14.7:1.

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Pi, Greek letter used to represent how many times the diameter of a given circle will fit into its circumference. This is constant at 3.142. Apprentice cp fitters use this figure for many calculations, for example: when calculating the capacity of an engine; when calculating centrifugal force and when calculating the peripheral speed of a cutting disk.

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1104D Perkins common rail engineThis is a Perkins designation, and refers to the 1100 series engine. The '4' refers to a four cylinder engine, and the 'D' refers to the common rail engine.

This engine has full electronic control of the fuel system - common rail with electronic injectors. 

As of April, 2012, we operate 3 of these engines.

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The 1106C Perkins diesel engineThis designation refers to the 1100 series Perkins engine. The '6' refers to the number of cylinders, and the 'C' refers to the fuel injection system, which is mechanical, based around a rotary fuel injection pump. This engine is the forerunner of the 1100D common-rail engine. Currently, the section is equipped with 6 1106C engines and 3 1104D engines.

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Typical 12V electrical training boardDuring the electrical module, one of the suggested exercises is to construct various electrical circuits such as parking lamps, headlamps (including relays) and glow plug circuits (including solenoid control).

In order to facilitate this exercise, we use 12V electrical training boards. These are boards of steel construction, with a working tray and a base that can accommodate a 12V battery.

This set up allows apprentices to construct the various circuits, and connect the board to an engine fitted with an alternator.

This set up allows each apprentice to wire up all the basic electrical circuits and components found in a typical plant vehicle.

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Typical 12 volt electrical test lampThis consists of a 12V lamp, with two different terminals. One terminal (the earth terminal) consists of a short cable and a crocodile clip. The other terminal is at the pointed end of the tool. It is used by fastening the crocodile clip to a good earth point, and then using the sharp end of the took to probe wires. If the wires are live, the lamp will glow.

During the induction phase of the course, you will be issued (at your own expense) with a 12V test lamp.

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Typical diodeOne of a series of diodes (the 1N4000 series). They are popular, 1 amp, general purpose, silicon rectifier diodes.

During the Phase 2 course, we use these diodes to make half-wave rectifiers, full-wave rectifiers, and to suppress voltage spiking on 30 amp relays in circuits such as the time-delay circuit built as part of the Electrical Module.

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Crowsfoot injector removal toolCrow's foot tool that allows you to tighten injector pipe unions with a 3/8" torque wrench.
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The 3 effects of electicity.

3 Effects of electricity:

  1. Chemical change  - For example, the electrolyte in a battery changes from sulphuric acid (H2SO4) when the battery is charged, to water, H2O, when the battery is discharged.
  2. Heat - For example, current passed through a bulb causes the filament to glow white hot. This is incandescent heat.
  3. Magnetism - for example, when we pass electrical current through the commutator and the field windings of a motor, like poles come into close proximity. These poles repel each other, giving us the motoring action.
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DIN numerical wiring code:

  • 15: Battery live supply controlled by the ignition switch (often referred to as 'live under key').
  • 30: Battery live or battery positive (+)
  • 31: Battery earth or Ground (-)

Other codes you will come across on Phase 2 training include:

  • 85: End of coil (for example, the end of the coil windings on an electromagnetic relay)
  • 86: Start of coil (for example, the start of the coil windings on an electromagnetic relay)
  • 87: To load (for example, on an electromagnetic relay, battery positive is supplied to terminal 30 on the relay. That leads to a set of contact points, and the far side of those contacts is terminal 87, which leads to whatever load the relay is serving.

Understanding European DIN Codes (PDF document download)

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Injector clamping boltInjector clamp bolt.
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Also written as 50 Hz or 50Hz.

This is the frequency at which mains electricity in Ireland is delivered at.

We know that in an AC circuit, rather than flow constantly in one direction, the electrons move rapidly back and forth. The rate at which these electrons move back and forth is referred to as the frequency of the supply. In Ireland, the mains AC supply has a frequency of 50 Hz. In other words, the electrons in our homes move back and forth in the wires 50 times every second when a circuit is closed.

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From Wikipedia:

555 chipThe 555 Timer IC is an integrated circuit (chip) implementing a variety of timer and multivibrator applications. The IC was designed by Hans R. Camenzind in 1970 and brought to market in 1971 by Signetics (later acquired by Philips). The original name was the SE555 (metal can)/NE555 (plastic DIP) and the part was described as "The IC Time Machine". It has been claimed that the 555 gets its name from the three 5-kohm resistors used in typical early implementations, but Hanz Camenzind has stated that the number was arbitrary. The part is still in wide use, thanks to its ease of use, low price and good stability. Read more...

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A4 lever arch folderThis is a hard covered folder for holding any course notes you may write up, and for any diagrams you may draw.

It is important to get into the habit of writing up your notes on a regular basis. To that end, you are supplied with a spiral notebook and black and red pens. During induction, you will also purchase a geometry set and a pack of markers.

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A4 refill padsDuring your phase 2 training, it is important that you take and write good notes on the course material. You should also get used to drawing detailed diagrams of vehicle and machine components.

In order to help you do this, you will be issued, free of charge, a spiral notebook and an A4 refill pad. As you fill these pads and notebooks, you will be given new replacement items, also free of charge.

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Advanced Automotive Engineer.

This is a qualification awarded by the Institute of the Motor Industry.

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Anti blockier system, or anti-lock braking system, an electronically controlled system that senses the relative speeds of road wheels in order to determine whether braking wheels have locked up and began to skid. If they have, the system overrides the braking effort supplied by the driver, and frees the brakes until the wheel begins to turn again (stop skidding).

The system is informed by speed sensors at the wheels. These same sensors can be used to feed into a traction control system.

Check here for more information.

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Acceleration is simply a change in speed.

Acceleration can be positive - an object speeds up, or it can be negative - an object slows down.

The kind of acceleration we all experience every day is the acceleration produced by gravity - 9.81m/s2, referred to as 'g' in engineering calculations.

For example, in order to calculate the weight of an object, we multiply its mass by the acceleration produced by gravity:

W=m.g

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Acid-proof apronDuring Phase 2, you will spend a lot of time working with lead-acid batteries. In order to protect your body and clothing from acid, you will be issued with an acid-proof apron.

You will also be issued with acid-proof gloves to protect your hands against acid.

You should wear the gloves, apron and your safety goggles whenever you work with lead-acid batteries.

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Acid-proof glovesDuring Phase 2, you will spend a lot of time working with lead-acid batteries. In order to protect your hands from acid, you will be issued with acid-proof gloves.

You will also be issued with an acid-proof apron to protect against acid spillages.

You should wear the gloves, apron and your safety goggles whenever you work with lead-acid batteries.

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This alerts the operator or the service technician that an electronic system malfunction is currently present. Refer to the term Diagnostic Code in this glossary.
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Ackermann angle

Imaginary lines drawn through the king pin and the track control rod end on each side of a vehicle will intersect at a point just in front of the rear axle of that vehicle. The angle they make with each other is known as the Ackermann angle.

The purpose of the angle is to allow the front wheels to turn through different angles when cornering. This is because the inside wheel always needs to turn through a bigger angle in order to get around the corner without scrubbing.

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Word formed by using the first letter of other words, for example:

RAM-Random Access Memory

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Pressure sensors - active sensorsUnlike a passive sensor, an active sensor needs a power supply. There are 3 terminals on a pressure sensor. One is a supply, one is ground, and the third sends a signal back to the ECM.

Here, we can see the example of a pressure sensor. There are 3 terminals. We know this is an active sensor because it has these 3 terminals.

  1. Pin A is a 5 volt supply into the sensor.
  2. Pin B is common, meaning it is grounded to 0 volts.
  3. Pin C sends a signal back to the ECM. From this signal, the ECM calculates the pressure acting on the sensor.
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In certain course modules, such as the small plant module, there are activity sheets for you to download. Once you do this, you should work your way through the sheet, carrying out all the activities listed, and researching answers to all the qeustions asked by searching this website, your own course notes and the world wide web.

The small plant module covers a large range of machinery, so it can be very difficult to cover everything.

Acitvity sheets will guide you to study all matters related to health and safety, theory and practical work. If you do all activity sheets, you will not come across anything in the practical or theory exams that you have not already researched as you worked your way through the activity sheets.

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Acupuncture probe in useA needle-like probe used in automotive diagnostics when probing wires and connector blocks for electrical signals.

It is very easy to cause damage to wires, their insulation and to connector blocks when trying to diagnose electrical problems. You must make good metal to metal contact with electrical circuits to analyse them, but it is essential you do not cause any damage when doing so.

An acupuncture probe is smooth and pointed, allowing you to slide the probe into connector blocks without causing damage. The probe then connects to your voltmeter or oscilloscope by way of the standard 4mm connector.

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This denotes a self-learning system.
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This is a software process that is performed in the ECM that optimises engine performance.
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Sometimes, course participants may feel they can add more to an explanation given in this glossary. In cases like this, they can add comments. See the comment at the bottom of this entry. (Please note: comments are only visible to registered users who are logged in.)
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Address bar in a browser windowThis is the part of a browser window into which you can type the URL (the web address) of a website. If you know the exact URL of a site, you should type it in here.
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From the Aerial Platform Hire website:

Aerial Platform Hire is Ireland's leading work platform rental company. Founded in 1980 we offer for hire self propelled boom and scissor lifts manufactured mainly by JLG industries, the worlds largest manufacturer of powered access equipment. We also offer Telescopic Handlers from JLG and Manitou Buggiscopics. Hire is available from strategically located depots in Clane, Co. Kildare and Mallow, Co. Cork. We deliver machines throughout Ireland from both of these depots.

Read more...

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Across Flats. A term used to describe measuring a bolt head. Note: This term does not describe the shank of the bolt, just the head, and hence what size spanner is required to open the bolt:
Across the flats
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A UK based engineering company established for over 45 years specialising in the manufacture of vocational automotive related training products.
They supply to motoring organisations, technical colleges, diagnostic equipment manufacturers, motor manufacturers, and Schools.

Visit their website

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Absorbed Glass Matte (AGM) Batteries

AGM Batteries are lead acid batteries. They use a separator consisting of fiberglass between the plates to hold the electrolyte in its place with capillary action.

In other words, the electrolyte is not in free-flowing liquid form, it is held in these absorbent mats. This is a safer arrangement, as it makes the battery "spill proof" - an important feature in the event of an accident or the vehicle over-turning. This type of battery also has a lower internal resistance. This increases the output voltage, and decreases charging time, AGM batteries are also often referred to as 'maintenance-free'. 

All battery charging over a certain voltage causes significant gassing. In flooded lead-acid batteries, these gasses are vented to the atmosphere. This results in a loss of electrolyte, which must be replenished during routine maintenance.

AGM batteries recombine these gases produced internally, back into the electrolyte, thus eliminating the need for topping up the electrolyte level during routine maintenance, hence the term 'maintenance-free'. 

These batteries are often VRLA, meaning that, should excess gas pressure build up during charging/discharging, these gasses are vented to the atmosphere.

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Air is a gas that is the main component of the earth's atmosphere. It is a mixture of many different gasses such as nitrogen (78%), oxygen (20%) and carbon dioxide (1%). There are much smaller traces of other gasses such as freon, neon, argon, helium, carbon monoxide and helium.
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This is the number of parts of air mixed with 1 part of fuel in an engine. There is an ideal, or optimum or stoichiometric ratio, which is 14.7 parts of air to one part of petrol, or 14.5 parts of air to one part of diesel.

An air fuel mixture with more air is said to be a 'lean' mixture, and a mixture with less air is said to be a 'rich' mixture.

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Do not confuse 'air gap' with 'spark gap', they are two entirely different things.

Air gap between a flywheel and an ignition coil.Air gap normally refers to the clearance between a revolving object and a stationary coil or pick-up sensor.

In the diagram on the right, we can see a magneto ignition coil and a flywheel. The correct air gap between them is 0.4 mm, with a tolerance of + or - 0.2 mm. This means that an air gap of between 0.2 mm and 0.6 mm is acceptable.

In magneto ignition systems, the air gap is the clearance between the laminated iron core of the ignition coil and the revolving flywheel which has a permanent magnet mounted on it.

In this case, the ignition coil is able to produce a HT spark because the magnetic lines of force from the permanent magnet on the flywheel move rapidly across the coil windings. This induces a current in the primary windings. When we suddenly open the circuit in the primary windings, the magnetic field associated with the current in the primary windings collapses, inducing the HT spark in the secondary windings.

The air gap between the coil and the magnet on the flywheel is vital if we are to produce a good quality HT spark.

If the air gap is too small, the flywheel can physically contact and damage the laminated iron core of the ignition coil. This is a common fault in small plant petrol engines. Always check this gap during service.

If the air gap is too big, the magnetic lines of force (magnetic flux) tend to splay out into space, and do not act on the windings of the ignition coil, thus causing the coil to produce a weak spark.

Other components where air gaps are essential are items such as inductive ABS wheel sensors. If the air gap is too large, the sensor is incapable of producing a signal of sufficient amplitude, and this will cause the control system to log a fault code and to display a warning lamp.

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This is when a diesel fuel system draws air in through a loose or badly sealed connection. The air that is drawn in can prevent the smooth running of the engine, or prevent the engine from starting at all.

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Allen keysHexagonal keys or wrenches used to loosen and tighten allen head bolts, like the ones shown below:

allen head bolts