Your Drive Train Explained

Written by Kevin Schappell

The drive train serves two functions: it transmits power fromrepparttar engine torepparttar 102755 drive wheels, and it variesrepparttar 102756 amount of torque. "Power" isrepparttar 102757 rate or speed at which work is performed. "Torque" is turning or twisting force. Multiple ratio gearboxes are necessary becauserepparttar 102758 engine delivers its maximum power at certain speeds, or RPM (Rotations Per Minute). In order to userepparttar 102759 same engine RPM's at different road speeds, it is necessary to changerepparttar 102760 "Gear Ratio" betweenrepparttar 102761 engine andrepparttar 102762 drive wheels. Just like a bicycle,repparttar 102763 car has to switch gears in order to move at a wide range of speeds. Unlike your bicycle,repparttar 102764 car's drivetrain also has to allow you to back up. (Well, you could push it backwards if you ate your Wheaties) There are actually two sets of gears inrepparttar 102765 drive train;repparttar 102766 transmission andrepparttar 102767 differential. The transmission allowsrepparttar 102768 gear ratio to be adjusted, andrepparttar 102769 differential letsrepparttar 102770 drive wheels turn at different speeds. Manual transmissions usually have four or five speeds, and often have "overdrive", which means thatrepparttar 102771 output shaft can turn faster thanrepparttar 102772 input shaft for fuel economy onrepparttar 102773 highway. Some use an electric clutch and a switch that controls whetherrepparttar 102774 overdrive is engaged or not. An interesting development on a few cars isrepparttar 102775 "clutchless" manual transmission, which uses a stick shift and an automatic electric clutch. Speed and position sensors, mini computers, and throttle controls keeprepparttar 102776 engine from over-revving whenrepparttar 102777 driver shifts gears. As with many automotive "inventions", this is an old idea, which may now reach feasibility due torepparttar 102778 computer revolution. Automatic transmissions commonly use three forward gears to blend speed and torque. Inrepparttar 102779 case of a three-speed transmission, first gear delivers maximum torque and minimum speed for starting. Second gear offers medium torque and speed for acceleration and hill climbing. Third gear allows maximum speed with minimum torque for highway travel. A reverse gear permits backward movement. A transmission is a speed and power-changing device installed at some point betweenrepparttar 102780 engine and driving wheels of a vehicle. It provides a means for changingrepparttar 102781 ratio between engine RPM (Revolutions Per Minute) and driving wheel RPM to best meet each particular driving situation. Some types of drive train layouts use a "Transaxle", which is simply a combination ofrepparttar 102782 transmission andrepparttar 102783 differential. These are usually found on front wheel drive cars, but are also used on mid- and rear-engine cars. Some exotic cars have their engine inrepparttar 102784 front, and a transaxle inrepparttar 102785 rear ofrepparttar 102786 car for better weight balance. Torque is derived from power. The amount of torque obtainable from a source of power is proportional torepparttar 102787 distance fromrepparttar 102788 center of rotation at which it is applied. It is logical, then, that if we have a shaft (in this case,repparttar 102789 crankshaft) rotating at any given speed, we can put gears of different sizes onrepparttar 102790 shaft and obtain different results. If we put a large gear onrepparttar 102791 shaft, we will get more speed and less power atrepparttar 102792 rim than with a small gear. If we place another shaft parallel to our driving shaft and install gears on it in line with those onrepparttar 102793 driving shaft, we can obtain almost any desired combination of speed or power withinrepparttar 102794 limits ofrepparttar 102795 engine's ability. That is exactly what an automobile transmission does by means of gears and other devices. There are two types of transmissions; manual and automatic. If you have a manual transmission, you have to shiftrepparttar 102796 gears yourself, usually with a stick located on your console andrepparttar 102797 clutch pedal. If you have an automatic transmission,repparttar 102798 mechanism changes without any help from you. This is accomplished through a system that works by oil pressure. Each shift ofrepparttar 102799 gears is controlled by a shift valve;repparttar 102800 gears shift change depending on speed,repparttar 102801 road, and load conditions.

The Engine Explained

Written by Kevin Schappell

The engine isrepparttar heart of your car, but instead of pumping blood,repparttar 102754 engine pumps air and fuel. The engines main function is to convert air and fuel into rotary motion so it can driverepparttar 102755 wheels ofrepparttar 102756 car. How does it do that ??.... Well let's start with a cutaway ofrepparttar 102757 engine and see allrepparttar 102758 major parts then we will get intorepparttar 102759 actual mechanics. Pistons: Most common engines have 4, 6, or 8 pistons, which move up and down inrepparttar 102760 cylinders. Onrepparttar 102761 upper side ofrepparttar 102762 piston is what is calledrepparttar 102763 combustion chamber whererepparttar 102764 fuel and air mix before ignited. Onrepparttar 102765 other side isrepparttar 102766 crankcase, which is full of oil. Pistons have rings which serve to keeprepparttar 102767 oil out ofrepparttar 102768 combustion chamber andrepparttar 102769 fuel and air out ofrepparttar 102770 oil. Crankshaft: The crankshaft is connected torepparttar 102771 pistons via a connecting rod. Asrepparttar 102772 piston moves up and down inrepparttar 102773 cylinder it rotatesrepparttar 102774 crankshaft and convertsrepparttar 102775 straight line motion into rotary motion. Valve train: The valve train consists of valves, rocker arms, pushrods, lifters, andrepparttar 102776 camshaft. (shown in above picture in blue, yellow, and green) The valve train’s only job is that of a traffic cop. It lets air and fuel in and out ofrepparttar 102777 engine atrepparttar 102778 proper time. The timing is controlled byrepparttar 102779 camshaft, which is synchronized torepparttar 102780 crankshaft by a chain or belt. Now that we have a general overview ofrepparttar 102781 parts involved let's talk about what happens. Most automotive engine today are 4-stroke (or 4-cycle) engines, meaning they have four distinct events which make uprepparttar 102782 cycle. ·Intake stroke: The camshaft opensrepparttar 102783 intake valve andrepparttar 102784 piston moves downrepparttar 102785 cylinder. This creates vacuum and sucks in air and fuel intorepparttar 102786 combustion chamber aboverepparttar 102787 piston. ·Compression stroke: Asrepparttar 102788 piston starts moving back uprepparttar 102789 cylinderrepparttar 102790 intake valve closes and seals offrepparttar 102791 combustion chamber. The causesrepparttar 102792 air and fuel to compress. ·Power stroke: Asrepparttar 102793 fuel is compressed andrepparttar 102794 piston nearsrepparttar 102795 top ofrepparttar 102796 cylinderrepparttar 102797 spark plug fires and ignitesrepparttar 102798 fuel and air. This explosion pushesrepparttar 102799 piston back downrepparttar 102800 cylinder and drivesrepparttar 102801 crankshaft. ·Exhaust stroke: Afterrepparttar 102802 piston reachesrepparttar 102803 bottom ofrepparttar 102804 cylinder,repparttar 102805 exhaust valve opens andrepparttar 102806 gasses left over fromrepparttar 102807 fuel and air are sent out torepparttar 102808 exhaust system. Put these four events together inrepparttar 102809 above order and you have a complete cycle. Are you asleep yet? That's enough theory, let's talk aboutrepparttar 102810 real world and problems you might encounter withrepparttar 102811 above mentioned parts. Pistons: Remember I talked aboutrepparttar 102812 rings, which sealrepparttar 102813 combustion chamber fromrepparttar 102814 crankcase. The rings over time tend to wear out. When they wear they allowrepparttar 102815 fuel and air to enter intorepparttar 102816 oil and dilute it. This dilution reducesrepparttar 102817 oils ability to lubricate your engine and can cause premature wear. Also ifrepparttar 102818 rings wear down they can allow oil fromrepparttar 102819 crankcase to enterrepparttar 102820 combustion chambers. This will result in oil being burned and exiting your tailpipe as grayish/white smoke. If your car spews grayish white smoke and it does not go stop inrepparttar 102821 first few minutes after start-up you might have warn rings. Ifrepparttar 102822 smoke goes away after start-up look torepparttar 102823 valve train section. Crankshaft: The crankshaft rides on bearings, which can wear down over time. The bearings supportrepparttar 102824 crankshaft and alsorepparttar 102825 rods, which connectrepparttar 102826 pistons torepparttar 102827 crankshaft. A loud medium pitched knocking noise inrepparttar 102828 engine points to warn bearings most ofrepparttar 102829 time. This is usually a costly repair and involves removingrepparttar 102830 crankshaft and either machiningrepparttar 102831 surface whererepparttar 102832 bearings ride, or replacingrepparttar 102833 entire crankshaft. To prevent this type of problem, use a high quality oil, change your oil at suggested intervals (3 months or 3000 miles is a safe number) and always maintain your oil level between oil changes.

Cont'd on page 2 ==> © 2005
Terms of Use