AutoMotive News

Digital engine control systems                Traditionally, the term powertrain has been thought to include the engine, transmission, differential, and drive axle/wheel assemblies. With the advent of electronic controls, the powertrain also includes the electronic control system (in whatever configuration it has).                 In addition to engine control functions for emissions regulation, fuel economy, and performance, electronic controls are also used in the automatic transmission to select shifting as a function of operating conditions. Moreover, certain vehicles employ electronically controlled clutches in the differential (transaxle T/A) for traction control.                These electronic controls for these major powertrain components can either be separate (i.e., one for each component) or an integrated system regulating the powertrain...

Engine cylinder capacity:                Engine sizes are compared on the basis of total cylinder swept volume, which is known as engine cylinder capacity. Thus the engine cylinder capacity is equal to the piston displacement of each cylinder times the number of cylinders, VE = Vn / 1000 where        VE = engine cylinder capacity (liter)                     V = piston displacement (cm 3  ) and                       n = number of cylinders                Piston displacement is derived from the combination of both the cross-sectional area of the piston and its stroke. The relative importance of each of these dimensions can be demonstrated by considering how they affect performance individually.               ...

Engine-performance terminology                To enable intelligent comparisons to be made between different engines’ ability to pull or operate at various speeds, we shall now consider engine design parameters and their relationship in influencing performance capability. Piston displacement or swept volume                When the piston moves from one end of the cylinder to the other, it will sweep or displace air equal to the cylinder volume between TDC and BDC. Thus the full stroke movement of the piston is known as either the swept volume of the piston displacement. The swept or displaced volume may be calculated as follows:  V = πd⌑2L / 4000 Where        V = piston displacement (cm3)                          π = 3.142                 ...

Piston-engine cycles of operation The internal-combustion engine:                The piston engine is known as an internal-combustion heat-engine. The concept of the piston engine is that a supply of air-and-fuel mixture is fed to the inside of the cylinder where it is compressed and then burnt. This internal combustion releases heat energy which is then converted into useful mechanical work as the high gas pressures generated to force the piston to move along its stroke in the cylinder. It can be said, therefore, that a heat-engine is merely an energy transformer. To enable the piston movement to be harnessed, the driving thrust on the piston is transmitted by means of a connecting rod to a crankshaft whose function is to convert the linear piston motion in the cylinder to a rotary crankshaft movement.                 The piston can thus be made to repeat its movement to and fro, due to the c...

Future Developments in Automotive Transmission Systems: 1.  The CVT will gradually replace the conventional automatic transmission due to its high fuel efficiency and smooth gear shift. 2.  The technology of semi-automatic transmission systems will also be improved to perform smooth gear shift and extend the cars' lifetime, without losing fast acceleration and fuel efficiency. 3.  The torque converter with fluid coupling may be improved, or may no longer be used for cars in the future due to its low-efficiency power transfer. 4.     5. Shift-by-wire totally eliminates mechanical lever shifting, keeping both of the driver's hands on the wheel.  The clutch is used only for starting and stopping. Once the vehicle is in motion, Auto-Shift operates like an automatic transmission, with the efficiency of a manual transmission. 6. Adaptive transmission control:   ATC has also been invented by using the computer to recognize and memorize different drivers' styl...

Continuously Variable Transmissions (CVT)                CVT is an “infinite speed” transmission that can change step-less through an infinite number of effective gear ratios between maximum and minimum values. Unlike traditional automatic transmissions, continuously variable transmissions don't have a gearbox with a set number of gears, which means they don't have interlocking toothed wheels. The word gear in CVT refers to a ratio of engine shaft speed to driveshaft speed. Moreover, CVTs change this ratio without using a set of planetary gears. Different types of CVTs : 1.     Pulley-based CVTs 2.     Toroidal CVTs 3.     Hydrostatic CVTs                The most common CVT design uses a segmented metal V-belt running between two pulleys. Each pulley consists of a pair of cones that can be moved clos...

Semi-Automatic Transmission        The two most common semi-automatic transmissions are- 1.     Dual-clutch Transmission 2.     Sequential Transmission Dual Clutch Transmission:                A dual-clutch transmission, commonly abbreviated to DCT uses two clutches but has no clutch pedal. Sophisticated electronics and hydraulics control the clutches, just as they do in a standard automatic transmission. In a DCT, however, the clutches operate independently. One clutch controls the odd gears (first, third, fifth, and reverse), while the other controls the even gears (second and fourth) as shown in the figure. Using this arrangement, gears can be changed without interrupting the power flow from the engine to the transmission.                  A two-part transmission shaft is at the heart of a DCT. Unlike a conventional manual gearbox,...

Comparison between Manual & Automatic Transmission:                Both automatic transmission and manual transmission accomplish exactly the same thing, but they do it in a totally different way. Advantages of manual transmission over automatic transmission: 1. It is easier to build a strong manual transmission than an automatic one. This is because a manual system has one clutch to operate, whereas an automatic system has a number of clutch packs that function in harmony with each other. 2. Manual transmissions normally do not require active cooling, because not much power is dissipated as heat through the transmission. 3. Manual gearshifts are more fuel-efficient as compared to their automatic counterpart. Torque converter used to engage and disengage automatic gears may lose power and reduce acceleration as well as fuel economy. 4. Manual transmissions generally require less maintenance than automatic transmissions. An automatic ...

Automatic Transmission                The concept of an automatic transmission is new in India. An automatic transmission is a motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears.  In this transmission system, the gears are never physically moved and are always engaged to the same gears. Automatic transmissions contain mechanical systems, hydraulic systems, electrical systems, and computer controls, all working together in perfect harmony manually. Main Components of an Automatic Transmission: 1.        Planetary Gear Sets             2.        Clutches and Bands 3.        Torque Converter 4.        Valve Body 1 .  Planetary Gear Sets  ...

Manual Transmission                The first transmission invented was the manual transmission system. A manual transmission, also known as a manual gearbox or standard transmission (informally, a "manual", "stick shift", "straight shift", or "straight drive") is a type of transmission used in motor vehicle applications. It generally uses a driver-operated clutch, typically operated by a pedal or lever, for regulating torque transfer from the internal combustion engine to the transmission, and a gear-shift, either operated by hand (as in a car) or by foot (as on a motorcycle).                 In a manual transmission, the driver needs to disengage the clutch to disconnect the power from the engine first, select the target gear, and engage the clutch again to perform the gear change. Components of Manual Transmission The diagram below shows a very simple two-speed transmission in neutral: ...

Types of Transmission System 1.       Manual Transmission 2.       Automatic Transmission 3.       Semi-automatic Transmission:- a)        Dual-clutch Transmission b)        Sequential Transmission 4.       Continuously Variable Transmission

Transmission system Introduction                       Need For a Transmission                The need for a transmission in an automobile is a consequence of the characteristics of the internal combustion engine. Engines typically operate over a range of 600 to about 7000 revolutions per minute (though this varies, and is typically less for diesel engines), while the car's wheels rotate between 0 rpm and around 1800 rpm.               

Comparison between MacPherson Double Wishbone Suspension Systems                Two of the most popular suspensions systems for passenger cars today are the double-wishbone suspension system and the MacPherson strut suspension system. While it is more usual to see the double-wishbone system at the rear end of the car, MacPherson’s solution normally finds its place at the front end of the car. Both types of suspensions have their own sets of benefits and limitations, thus let us look at both the advantages and disadvantages of both systems, starting with the simpler of the two, the MacPherson struts.   MacPherson Struts:                The struts are designed with more simplicity, and thus takes up less space horizontally. As a result, passengers get more compartment place in the car. They also display low un-sprung weight, an advantage that reduces the overall weight of the vehicle as well as ...

Components of Suspension System 1.      Control Arm:  A movable lever that fastens the steering knuckle to the frame of the vehicle. 2.      Control Arm Bushing:  This is a sleeve that allows the control arm to move up and down on the frame. 3.      Strut Rod:  Prevents the control arm from swinging forward and backward. 4.      Ball Joints:  A joint that allows the control arm and steering knuckle to move up and down and sideways as well 5.      Shock absorbers or Struts:   prevents the suspension from bounce after spring compression and extension 6.      Stabilizer Bar:  Limits body roll of the vehicle during cornering 7.      Spring:  Supports the weight of the vehicle Common Problems of the Suspension System Shocks and Struts:       Ball joints:   ...

Suspension System Introduction                The suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Suspension systems serve a dual purpose — contributing to the car's road-holding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants comfortable and reasonably well isolated from road noise, bumps, and vibrations, etc.                 These goals are generally at odds, so the tuning of suspensions involves finding the right compromise. It is important for the suspension to keep the road wheel in contact with the road surface as much as possible because all the forces acting on the vehicle do so through the contact patches of the tires. The suspension also protects the vehicle itself and any cargo or luggage from damage and wear. Principle of Suspension System 1.   ...

Mechanical Advantage                Gear teeth are designed so that the number of teeth on a gear is proportional to the radius of its pitch circle, and so that the pitch circles of meshing gears roll on each other without slipping. The speed ratio for a pair of meshing gears can be computed from the ratio of the radii of the pitch circles and the ratio of the number of teeth on each gear.                Two meshing gears transmit rotational motion.                The velocity v of the point of contact on the pitch circles is the same on both gears and is given by v=r A w A   =r B W B                Where input gear A has radius r A  and meshes with output gear B of radius r B , therefore, w A  /   w B =   r B /   r A =   N B /   N A    ...