Launceston Driving School
Producing Safer Drivers!
The LDS Blog
|Posted on 2 December, 2019 at 18:00|
How Does A Car Work?
OK, we know a car, and in fact most other vehicles – buses, trucks, motorbikes…. All turn fuel, diesel or petrol, into motion. To get from here to there, you know you need to put fuel in your car regularly, because if you don’t, it’ll stop, and you will stay stopped until your lack of fuel is remedied which usually involved a lot of crying, begging, pleading and walking.
There are things you should know about the mechanical side of owning a car because one day, perhaps when you call the RACT, you will be asked to describe why your car stopped. Wouldn’t it be better if there were things you can do that will keep your car running? Good news! There are things you can do, and knowing a little bit about your car will help you understand why you have to do what you do.
Your Car Has Systems
Before we look at how it all works, there are several systems that are inter-related and which contribute to you getting home.
The fuel system, which includes fuel gauge, fuel tank, carby or fuel injectors, and in late model cars electronic bits that you really don’t want to know about!
The cooling system, which is not the air-conditioning! This system keeps the engines operating temperature at a safe level and includes the radiator, radiator hoses, overflow tank, the radiator cap and the engine temperature gauge. This is one system you can monitor and add coolant if necessary.
The oil or lubrication system is a vital part of your engine. It includes the oil, the oil pump and the oil pressure light on your dashboard. If the oil light ever comes on, stop immediately, because your engine is in imminent danger of catastrophic failure which will be expensive! This is another system you can monitor and add oil if necessary.
The next areas of your car should only be played with by qualified mechanics.
The electrical system provides your lights and the spark to fire up your engine. It includes your battery, the starter-motor, the alternator, the alternator light, the spark plugs, the distributor, all the wiring and fuses etc etc. There are so many bits on your car that use electrickery, including your air-con, entertainment system, electric seats, and so much more, and most of the time, everything works, most of the time! There is not a lot you can do if this system fails except call the RACT.
The next system is the transmission, which transfers the energy created by the engine, to make the wheels turn at your command. It includes the gearbox – manual and automatic – drive-shafts, axles, differentials, CV joints, the clutch and the gear stick for a manual, or the gear selector in an automatic.
All the above systems work together to move your car. Some you control, others happen in the background working to keep you mobile. But they are all important, and any one can fail, bringing your car to a grinding halt.
How Does My Car Work?
When you turn the key to start your engine, just the right amount of fuel is fed into one of the pistons in your engine. In a 4 cylinder car, there are 4 of them – one per cylinder, hence the title. In a six cylinder car, there are 6 pistons, and a V8 has 8. The mechanics of an engine are pretty amazing with each piston going up and down, driven by the fuel exploding in the combustion chamber to drive the piston down. The combined controlled explosions rotate a crankshaft to which the pistons are connected, and this rotation is transmitted to the wheels by the transmission.
In a car with a manual transmission, you control the rate this rotational power is transmitted by selecting the right gear for the right speed. We need gears because a physical force called torque is generated, and the efficiency of the whole system is affected by the weight of the car, the amount of power being created by the engine, the outside environment – level ground, or going uphill or downhill – and inertia. From standing still, to get the car rolling, more power is needed to overcome inertia so the ratio of power to speed is high. As speed increases there is a physical limit to how fast a car can go in the gear which is used to get going, so we need to change to the next gear which allows the car to go quicker for less power, and so it goes until you are in the higher gear, and going much faster. If you find you need to slow down, the higher gears are not conducive to lower speeds as the physical force mentioned before, torque, is insufficient and the car may actually stall, or cut out, so you need to engage a lower gear..
So bottom line is you need to be in the right gear for the right speed. So when you need to slow for a corner for example, to maintain your momentum, and keep the engine working efficiently, you need to get into a lower gear.
The gears in a manual transmission mesh directly with the engine, so to ‘change gear’, up or down, so from 1st to 2nd to 3rd to 4th, or from 4th to 3rd to 2nd to 1st, as the driver, you will need to disengage the engine from the transmission to effect the gear change, and that’s where the ‘clutch’ comes in.
When you depress the clutch pedal (with your left foot, and only your left foot), you are disengaging the engine from the transmission.
You would also use the clutch while stationary to start the engine and select the gear required - 1st or Reverse, or when stationary while waiting at a stop sign or traffic light.
So a typical sequence might go like this;
Clutch is in - start engine – select 1st gear – clutch is out – car is in motion – at appropriate speed clutch in – change from 1st to 2nd gear – clutch out – at correct speed – clutch in – change from 2nd to 3rd gear – clutch out – at correct speed – clutch in – change gear from 3rd to 4th – clutch out.
So now we are driving down the street, listening to the engine, always ready to change gear, up or down as appropriate. Or, you could have a car with an automatic gearbox.
In an automatic gear box, the car can sense what speed you are doing, what demand you are making on the engine, and the automatic gear change system, will select the right gear for the speed for you. And if you suddenly demand extra speed, it will sense this demand and change gear to enable you to get to speed quicker, for example when overtaking another car.
Automatic gearboxes are much more user friendly and are the preferred system for most people, especially for city dwellers that are exposed to much more stop-start traffic than out in the countryside. The main downside for automatics is slightly higher fuel consumption, though with computer assisted gear-changes and management systems, fuel consumption is getting better every time a new model comes on the market..
Starting The Engine
For a car with a manual gearbox, before you look to start the engine, first confirm your park-brake is applied. You can start the engine with the gearshift in ‘Neutral’, which is in effect no gear. Or you can start the engine in any gear, provided you have depressed the clutch pedal to disengage the engine. If you can move the gear-stick around loosely, it’s probably in neutral. If it feels stiff and hard to move, it’s probably in gear. So depress the clutch pedal and to find neutral you will move the gear shift so it is in the centre of its area of movement, which is usually represented by the 'H' pattern on the gear-shift knob.
If you try to start the engine, in gear, with no clutch, the car will try to jerk forward, even with the hand brake applied. This is because as the starter- motor tries to turn over the engine to fire it up, if the engine is still directly engaged with the transmission, the motion will be transmitted to the wheels. So as a matter of habit, whenever you are starting a manual car, always ensure you have the clutch pedal depressed, even if you know the gear-shift is in neutral. The starter-motor is a very strong electric motor which can move a car forward, or backward, whichever way the gear-shift is pointed, and if a person or child walks in front or behind a car which is starting, the potential for injury or worse is very high. So remember, starting a manual, park brake is applied, check gear-shift is in neutral, clutch pedal depressed, then, hit the starter.
In a car with an automatic gearbox, it will only start if you have the selector in P (Park) or N (Neutral). If you have selected D (Drive) or L (Low) or 1 or 2, the engine will not start, it will not even turn over. You will still ensure your Park-brake is applied, and you should also apply pressure to the foot brake pedal with your right foot, and only your right foot!
Why? To be sure, to be sure! It’s all about instilling safe practices and habits.
Getting The Car To Move
So in our automatic car, after checking the Park-brake is on, and your right foot has positive pressure on the brake pedal and the gear selector is in Park, start the engine. Getting the car in motion in an automatic is as easy as, after checking the Park Brake is still applied, and your right foot has positive pressure on the Foot Brake, moving the gear selector from Park to Drive, then releasing the Park Brake. Now the only thing holding you is your right foot. If you slowly ease the pressure on the Brake pedal, you will feel the car slowly start to move. If you release the Brake pedal completely, the car may move quicker, depending on the slope of the surface you are on. And to move even quicker, you would move your right foot from the Brake to the Accelerator pedal.
In normal driving your right foot will be on the brake OR accelerator, so you will be trying to go, or trying to stop, in either a manual or automatic car.
In a manual car, checking the Park Brake is on, the gear stick is in Neutral, your left foot has the clutch pedal in and with right foot applying positive pressure to the Brake pedal, start the engine.
Now select 1st gear, release the Park Brake. You are holding the car stationary with left foot on clutch and right foot on brake. Let’s assume the ground is level. Now you are ready to roll – ease your foot off the clutch. As the clutch pedal comes up you will feel the engine and transmission engage and the car will start to move forward without you touching the accelerator. Now gently apply pressure to the accelerator pedal, imagine there is an egg under your right foot. The accelerator pedal will feed more fuel into the engine, making it run faster, and so the car will pick up speed.
At the correct speed, you will push the clutch in and simultaneously ease your foot off the accelerator pedal, then move the gearstick from 1st to 2nd gear, then as the clutch pedal comes up, your will reapply pressure to the accelerator and just like the above sequence you’ll soon be in 4th gear going down the road doing 50kph.
The manual car will require much more practice, but you will get to the point where you will do a gear change without thinking, and you will sense what gear you need to be in for any situation. – cornering, going uphill, towing a load or passing another car.
So whether you are driving an automatic or a manual car, with the help of your driving instructor and lots of practice you will soon be doing the things that get you from zero to whatever kph safely and stress free.