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On-board diagnostics, or EOBD, European on-board diagnostics.
Software on a vehicle ECU that allows it to evaluate the data it receives from the various stations and sensors on a vehicle. If faults are found they are stored for subsequent retrieval via a serial interface and a suitable diagnostic tester.
Provides the following functions when connected to the vehicle.
Object code is plain text (human readable) written for a computer program that has been converted by a compiler into a form that a computer can read - into object code.
In a petrol engine, we want to use as high a compression ratio as possible. However, the higher we go, the hotter the compressed gasses become. This leads to a situation where it is the temperature of the induced air that is firing the engine rather than the spark.
Detonation is extremely bad for a petrol engine, as must be avoided. Modern engines are designed with the correct compression ratio, so we just need to be careful to use fuel with the correct octane rating.
More commonly referred to as the 'speedo', this is a device, a gauge, that records speed and distance travelled by the vehicle. American and British vehicles use the old Imperial system of miles per hour (mph). Irish and European vehicles use the metric system, and kilometers per hour (kph).
Odometer readings may be used to determine service intervals. However, you should note that many plant vehicles do a lot of work without travelling any significant distance, (for example, tracked excavators, site dumpers). These types of vehicles may use an 'hours in use' meter, powered by the vehicle battery whenever the vehicle is in use.
Finally, many plant machines have no battery fitted, and they rely on service intervals based on time: days, weeks, months etc.
This is a measure of the resistance in an electrical circuit, and it is measured in ohms.
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One of the most fundamental laws of electricity, discovered experimentally by the German mathematician, George Simon Ohm. He discovered that for conditions of constant temperature, the current through a conductor is directly proportional to the potential difference between its ends. This is normally expressed mathematically by the famous formula V = IR, Voltage = Current x Resistance.
Overhead Valve (also referred to as a cam in crankcase arrangement) - an engine arrangement where the inlet and exhaust valves are on top of the engine, but are operated by a camshaft that is down in the engine crankcase.
Opening of the valves is achieved by means of lobes on the camshaft, cam followers or tappets following the profile of these cams, and pushrods transmitting operating forces from the camshaft to the valve rockers.
This arrangement is in contrast to an overhead cam arrangement, where the camshaft is on top of the engine and operates the valves directly.
In construction plant fitting, especially in small plant engines, oil alert systems are fitted to engines. They consist of a float with a permanent magnet, and a reed switch to which the primary winding of the magneto ignition circuit is connected.
In the event of a drop in oil level (often, even a small drop in level), the float and magnet sink, causing the contacts in the reed switch to close, thus running the ignition primary circuit to ground, causing the engine to stop.
This event can also be caused by operating the engine on a sloping surface. When dealing with four-stroke small plant engines, if one fails to start, it is advisable to first check the oil level, then check with the operator to ensure that the engine was being run on level ground. If the oil level is even slightly low, or the engine is operated on a sloping surface, the oil alert switch will often cause the primary winding to be sent directly to ground, causing the failure of the ignition circuit.
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If we want to introduce oil somewhere, we must leave room for it, and this room is called 'oil clearance', or room for the oil to get between two moving parts.
Oil is introduced into vehicle components for 1, 2 or all 3 of the following reasons: