Service Advisor Customer Service Skills SERVICE ADVISOR. Technical for Non-technical - Engines INDUCTION

Transcription

1 Service Advisor Customer Service Skills SERVICE ADVISOR Technical for Non-technical - Engines INDUCTION

2 Objectives Welcome to the technical for non-technical modules. We will discuss engines, transmissions and drivetrains in the next three sessions. In this session we discuss engines and during this session we will: Explain the basic workings of an engine. Explain how valves work. Explain the four strokes - including injection systems. Discuss fuel and octane ratings. Explain the various types and ratings of oils. Objectives Enjoy the learning experience!

3 Engines Where did it all begin? Engines Nikolaus August Otto (10 June 1832) was the German inventor of the first internal-combustion engine to efficiently burn fuel directly in a piston chamber. Though the concept of four strokes, with the vital compression of the mixture before ignition, had been invented and patented in 1861 by Alphonse Beau de Rochas, Otto was the first to make it practical.

4 Engines A diagram The diagram below is for reference for the technical jargon that we will discuss during this session. It shows an inline-4 cylinder engine with dual overhead cams. Engines

5 Engines Engines How does it work? The most accurate description for how an internal combustion engine works! The basic way all internal combustion engines work is to take a mixture of fuel and air, compress it, ignite it either with a spark plug or by self-ignition (in the case of a diesel engine), allow the explosion of combusting gasses to force the piston back down and then expel the exhaust gas.

6 Engines Engines How does it work? The vertical movement of the piston is converted into rotary motion in the crank via connecting rods. The crank then goes out to the gearbox via a flywheel and clutch, and the gearbox sends the rotary motion to the wheels, driving the vehicle forwards.

7 Engine Layouts Here are some illustrations of the most common types of cylinder layout you'll find in engines today. Singles Singles are typically used in motorbikes, jet-skis, chainsaws etc. V-twins are also found in motorbikes. Engine Layouts

8 Engine Layouts Here are some illustrations of the most common types of cylinder layout you'll find in engines today. Inline-fours Inline-fours are the mainstay of car engines, as well as being found in some motorbikes. Inline fives have made a semblance of a come-back while the V5 is very unusual and is not used as a mainstream layout. Engine Layouts Straight four Flat four

9 Engine Layouts V6 and V8 engines The straight line 6 cylinder and V6 has the benefits of being smoother than an inline-four but without the fuel economy issues of a V8. Boxer engines are found in a number of vehicles. Engine Layouts Straight line 6 V 8

10 Engines Engines Internal combustion engines how do they work? We will discuss the differences between a 2 and 4 stroke engine and then explain how a 2 and 4 stroke engine work. Almost every car sold today has a 4-stroke engine. So does a lot of motorbikes and other mechanical equipment. There are still a lot of 2- stroke engines about in smaller motorbikes, smaller lawnmowers, leafblowers and such. Difference The difference between the two engine types is the number of times the piston moves up and down in the cylinder for a single combustion cycle. A combustion cycle is the entire process of sucking fuel and air into the piston, igniting it and expelling the exhaust.

11 2 Stroke Engines 2 Stroke Engines How does it work? A 2-stroke engine is different from a 4-stroke engine in two basic ways. 1. The combustion cycle is completed within a single piston stroke as oppose to two piston strokes. 2. The lubricating oil for the engine is mixed in with the petrol or fuel. The simplicity of a 2-stroke engine lies in the reed valve and the design of the piston itself. The picture on the left below shows a 4-stroke piston (left) and a 2-stroke piston (right). The 2-stroke piston is generally taller than the 4-stroke version, and it has two slots cut into one side of it. These slots, combined with the reed valve, are what make a 2-stroke engine work the way it does. 4 Stroke Piston 2 Stroke Piston

12 2 Stroke Engines How does it work continuous... As the piston (red) reaches the top of its stroke, the spark plug ignites the fuel-air-oil mixture. The piston begins to retreat. As it does, the slots cut into the piston on the right begin to align with the bypass port in the cylinder wall (the green oblong on the right). The receding piston pressurises the crank case which forces the reed or flapper valve (purple in this animation) to close, and at the same time forces the fuel-air-oil mixture already in the crankcase out through the piston slots and into the bypass port. This effectively routes the mixture up the side of the cylinder and squirts it into the combustion chamber above the piston, forcing the exhaust gas to expel through the green exhaust port on the left. Once the piston begins to advance again, it generates a vacuum in the crank case. The reed or flapper valve is sucked open and a fresh charge of fuel-air-oil mix is sucked into the crank case. When the piston reaches the top of its travel, the spark plug ignites the mixture and the cycle begins again. 2 Stroke Engines

13 4 Stroke Engines The principle behind any reciprocating internal combustion engine; If you put a tiny amount of high-energy fuel (like petrol) in a small, enclosed space and ignite it, an incredible amount of energy is released in the form of expanding gas. You can use that energy to propel a piston. You can also use it for more interesting purposes. For example, if you can create a cycle that allows you to set off explosions like this hundreds of times per minute, and if you can harness that energy in a useful way, what you have is the core of a car engine! 4 Stroke Engines

14 4 Stroke Engines Petrol Engines - How does it work? The piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. This is the intake stroke. Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful. When the piston reaches the top of its stroke, the spark plug emits a spark to ignite the petrol. The petrol charge in the cylinder explodes, driving the piston down. Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe. Now the engine is ready for the next cycle, so it intakes another charge of air and gas. 4 Stroke Engines

15 4 Stroke Engines Diesel Engines - How does it work? Mechanically, 4-stroke diesels engines work identically to four-stroke petrol engines in terms of piston movement and crank rotation. It s in the combustion cycles where the differences come through. First, during the intake cycle, the engine only sucks air into the combustion chamber through the intake valve not a fuel/air mix. Second, there is no spark plug. Diesel engines work on self-ignition, or detonation the one thing you don t want in a petrol engine! 4 Stroke Engines

16 Valves Valves let the air/fuel mixture into the engine and the exhaust out of the engine. The camshaft uses lobes (called cams) that push against the valves to open them as the camshaft rotates and springs on the valves return them to their closed position. This is a critical job and can have a great impact on an engine s performance at different speeds. 4 Stroke Engines Valves

17 Camshaft Basics Camshaft How does it work? The key parts of any camshaft are the lobes. As the camshaft spins, the lobes open and close the intake and exhaust valves in time with the motion of the piston. There is a direct relationship between the shape of the cam lobes and the way the engine performs in different speed ranges. Camshaft Basics

18 Camshaft Basics Camshaft How does it work? To understand why this is the case, imagine that we are running an engine extremely slowly at just 10 or 20 revolutions per minute (RPM) so that it takes the piston a couple of seconds to complete a cycle. It would be impossible to actually run a normal engine this slowly, but let s imagine that we could. Camshaft Basics At this slow speed, we would want cam lobes shaped so that: Just as the piston starts moving downward in the intake stroked (called top dead center, or TDC), the intake valve would open. The intake valve would close right as the piston bottoms out. The exhaust valve would open right as the piston bottoms out (called bottom dead center, or BDC) at the end of the combustion stroke, and would close as the piston completes the exhaust stroke.

19 Camshaft Basics Camshaft How does it work when we increase engine speed? When you increase the RPM, the configuration for the camshaft does not work well. If the engine is running at 4,000 RPM, the valves are opening and closing 2,000 times every minute, or 33 times every second. At these speeds, the piston is moving very quickly, so the air/fuel mixture rushing into the cylinder is moving very quickly as well. Camshaft Basics When the intake valve opens and the piston starts its intake stroke, the air/fuel mixture in the intake runner starts to accelerate into the cylinder. By the time the piston reaches the bottom of its intake stroked, the air/fuel is moving at a pretty high speed. If we were to slam the intake valve shut, all of that air/fuel would come to a stop and not enter the cylinder. By leaving the intake valve open a little longer, the momentum of the fast moving air/fuel continued to force air/fuel into the cylinder as the piston starts its compressions stroke. So the faster the engine goes, the faster the air/fuel moves, and the longer we want the intake valve to stay open wider at higher speeds this parameter, called valve lift is governed by the cam lobe profile.

20 Valve Timing Technology The Jargon Because of the nature of fuel injection, carburetors, the 4-stroke cycle and valves, the internal combustion engine only really works really well at one particular range of speeds. Valve Timing Any higher or lower and you start to affect fuel efficiency, reliability and power. To overcome this issues, and to make engines more useable throughout their revolution (RPM) ranges, manufacturers invented various different types of variable valve timing. The idea is simple alter the timing and/or size of the intake and exhaust ports at different engine RPM s to ensure that the engine is as efficient as possible throughout its range of operating speeds.

21 Suzuki VVT Suzuki VVT How does it work? The VVT system goes a step further and allows a continuously variable engine operating profile, so rather than simply having economy and power modes, there s an infinite number of positions in between that can be selected on-the-fly in fractions of a second. This means that the engine can be kept in its sweet spot for a far broader range of operating conditions and demands. VVT

22 Suzuki VVT Suzuki VVT How does it work continued To keep the engine in its sweet spot, VVT doesn't have two sets of cam lobes, rather it can dynamically adjust the timing of the entire camshaft instead. This means that whilst the actual duration that the valves are open never changes, their timing in relation to all the other engine operations can be adjusted. In a simple engine, the timing belt or chain from the crankshaft loops up and around a camshaft pulley that turns the camshaft. With VVT, the timing belt loops around a pulley that contains hydraulic fluid or oil. The camshaft itself has vanes on the end of it that sit inside the fluid, so in this system, the camshaft is not directly linked to the timing belt pulley. By altering the oil pressure through a series of valves, the position of the camshaft vanes can be altered inside the pulley housing.

23 Fuels Fuels Petrol is a distilled and refined oil product made up of hydrogen and carbons a hydrocarbon. It is designed to be relatively safe to handle, if you are careful. It does not spontaneously combust without extreme provocation. When you have a petrol fire, it is not the petrol itself that is burning, it is the vapour and this is the key to fuelling an engine. The carburetor or fuel injectors spray petrol into an air stream. The tiny particles of petrol evaporate into a vapour extremely quickly, and combined in a cloud with air, it becomes extremely combustible. The smaller the particles from the carburetor jet or fuel injectors, the more efficiently the mixture burns. Only around 25% of the fuel s energy is converted into actual usable power, the rest being lost to heat.

24 Fuel Injection How does it work? Compared to carburetors, fuel injectors themselves are incredibly simple. They are basically electro-mechanically operated needle valves. The image on the right shows a cutaway of a representative fuel injector. When a current is passed through the injector electromagnetic coil, the valve opens and the fuel pressure forces petrol through the spray tip and out of the diffuser nozzle, atomising it as it does so. Fuel Injection

25 Fuel Injection How does it work continued When current is removed, the combination of a spring and fuel back-pressure causes the needle valve to close. Fuel Injection This gives an audible tick noise when it happens which is why even a quiet fuel-injected engine has a soft but rapid tick-tick-tick-tick noise as the injectors fire. This on-off cycle time is known as the pulse width and varying the pulse width determines how much fuel can flow through the injectors.

26 Fuel Injection How does it work continued When fuel-injection was first introduced, it was fairly simple and used a single injector in the throttle body. As you would expect though, technology marches on and the latest technology is direct injection, also known as GDI (gasoline direct injection). In this instance, the injectors are moved into the combustion chambers themselves rather than the intake manifold. This is nearly identical to the direct injection system used in diesel engines. Essentially, the intake valve only allows air into the combustion chamber and the fuel is sprayed in directly through a high-pressure, heat-resistant injector. The fuel and air mix inside the combustion chamber itself due to the positions of the intake valve, injector tip and top of the piston crown. Fuel Injection

27 Fuel Injection Types of fuel injection Indirect fuel injection: The injector sprays fuel into the intake manifold creating an air/fuel mixture. Fuel Injection Direct injection system: Separates the injector completely away from the intake manifold. Fuel is metered independently to air intake through the manifold. Direct Fuel Injection

28 Fuels Fuels Where does petrol come from? Gasoline is made from crude oil. The crude oil pumped out of the ground is a black liquid called petroleum. This liquid contains hydrocarbons and the carbon atoms in crude oil link together in chains of different lengths. It turns out that hydrocarbon molecules of different lengths have different properties and behaviours. For example, a chain with just one carbon atom in it (CH4) is the lightest chain, known as methane. Methane is a gas so light that it floats like helium. The different chain lengths have progressively higher boiling points, so they can be separated out by distillation. This is what happens in an oil refinery, crude oil is heated and the different chains are pulled out by their vaporization temperatures. Certain chains are blended together and used for gasoline. All of them vaporize at temperatures below the boiling point of water. That s why if you spill gasoline on the ground, it evaporates very quickly. The illustration on the next page explains the concept.

29 Fuels Fuels Where does petrol come from? Following on from the previous page, the chains next in line is kerosene, followed by diesel fuel and heavier fuel oils (like heating oil for houses).

30 Fuels Fuels Where does petrol come from? Next come the lubricating oils. These oils no longer vaporize in any way at normal temperatures. For example, engine oil can run all day at 121 degrees C without vaporizing at all. Oils go from very light (like 3-in-1 oil) through various thicknesses of motor oil through very thick gear oils and then semi-solid greases. Chains above the C20 range form solids, starting with paraffin wax, then tar and finally asphaltic bitumen, which used to make asphalt roads. All of these different substances come from crude oil. The only difference is the length of the carbon chains!

31 Fuels Fuels What is Octane? The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. One of the strokes in our 4 stroke engine is the compression stroke, where the engine compresses a cylinder-full of air and gas into a much smaller volume before igniting it with a spark plug. The amount of compression is called the compression ratio of the engine. A typical engine might have a compression ratio of 10-to-1. The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase power of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel.

32 Fuels Fuels What is Octane continued 93-octane petrol is petrol that contains 93-percent octane and 7-percent heptane (or some other combination of fuels that has the same performance of the 93/7 combination of octane/heptane). Heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well you can compress it a lot and nothing happens. It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.

33 Engine Oils What Does Oil Actually Do? Engine oil performs many functions. It stops all the metal surfaces in the engine from grinding together and tearing themselves apart from friction, and it transfers heat away from the combustion chamber. Engine oil must also be able to hold in suspension, all the nasty byproducts of combustion like silica (silicon oxide), acids and friction material. Engine Oils Finally, engine oil minimises the exposure to oxygen and thus oxidation at higher temperatures. It does all of these things under tremendous heat and pressure. The life of your engine depends in no small part on the quality of the oil you put in it oil is its lifeblood.

34 Engine Oils What Does the Grade of Oil Mean? As oils heat up, they generally get thinner. Single grad oils get too thin when hot for most modern engines which is where multi-grade oil comes in. The idea is simple use science and physics to prevent the base oil from getting too thin when it gets hot. The number before the W is the cold viscosity rating of the oil, and the number after the W is the hot viscosity rating. So a 5W40 oil is one that behaves like a 5-rated single grade oil when cold, but doesn t thin any more than a 40-rated single grade oil when hot. Engine Oils

35 Conclusion During this session we discussed the following; Basic workings of an engine, explained how valves work, how injection systems work, fuel and octane ratings and explained the various types and ratings of oils. Objectives

36 End End This concludes the e-learning module on the Technical for nontechnical engine section Thank you for your participation!