Glossary

Driver assistance systems: These invisible co-pilots help drivers in monotonous or difficult traffic situations. They monitor the car’s surroundings with the help of radar, video, and ultrasonic sensors. They help to steer and brake the car when parking, changing lanes, or sitting in traffic. Driver assistance systems can prevent accidents and are precursors to automated driving.

Adaptive cruise control: ACC can accelerate and brake a car autonomously. With the help of a radar sensor, the system maintains both the driver’s chosen speed and a programmed safe distance to the vehicle in front. This helps drivers reach their destination more relaxed, while the more even driving style saves fuel. In the Stop&Go version, ACC can even stop the car completely and restart the engine once traffic gets moving again after a brief pause.

Evasive steering support: Evasive steering support helps drivers avoid obstacles by way of specific steering interventions. This means the maximum steering angle is reached 25 percent faster. Prior to the maneuver, radar and video sensors detect whether the vehicle’s surroundings permit a swerve of any kind.

Automatic emergency braking (rear): It can be difficult to see small children when reversing. Automatic emergency braking (rear) is based on radar and ultrasonic sensors in conjunction with the ESP electronic stability program. At speeds of up to 15 kilometers per hour, the system automatically performs an emergency braking maneuver if it detects a person or an obstacle dangerously close to the rear of the reversing vehicle.

Construction zone assist: The construction zone assist system keeps the car within a narrower lane by way of steering corrections. To do this, the system takes data from video and ultrasonic sensors and calculates a safe distance on either side to vehicles in the neighboring lane as well as to the crash barrier. The video sensor also measures clear spaces ahead of the vehicle. This enables the system to provide a timely warning in case the lane in a freeway construction zone is too narrow for the vehicle.

Driver drowsiness recognition: Drowsiness at the wheel causes imprecise steering maneuvers and lots of steering corrections. The drowsiness recognition system constantly analyzes the driver’s steering behavior by way of the steering angle sensor, so it can recognize signs that the driver is nodding off before it happens. It also takes into account factors such as the time of day and the length of the journey. Tired drivers are warned optically and acoustically, and are reminded to take a break.

Intelligent headlight control: When driving at night or in a tunnel, this system automatically activates the headlights. Outside of built-up areas, it will also automatically switch on the high beams as long as it does not detect any vehicles ahead or any oncoming traffic via the video sensor. This means the road ahead is always ideally lit.

Left-turn assist: When turning left involves crossing the other side of the road, it is easy to overlook oncoming traffic. The left-turn assist system monitors oncoming traffic using two radar sensors in the front of the vehicle. If the gap in traffic is too small to permit a turn, the system prevents the vehicle from moving forward. If a collision with an oncoming vehicle is imminent, the system will stop the turn in time by performing an automatic emergency braking maneuver.

Lane keeping support: The lane keeping support system helps drivers to keep their vehicle within a traffic lane. It uses a video sensor to detect the lane markings to the right and left of the vehicle. If the vehicle’s distance to the lane boundary falls below a defined minimum, the lane keeping support steps in. In vehicles with electric power steering, it steers gently but firmly in the opposite direction in order to keep the vehicle in the lane. In vehicles without electric power steering, it achieves the same effect by utilizing the ESP electronic stability program to brake individual wheels. Drivers can override the function at all times, so they retain control of the vehicle. If they activate the turn signal in order to change lane or turn, the system does not intervene.

Lane-departure warning: The lane-departure warning system alerts drivers to the fact that they are about to unintentionally drift out of the lane by, for example, causing the steering wheel to vibrate. A video sensor detects the lane markings ahead. If the vehicle risks leaving the lane unintentionally, the system sounds a warning. This enables the driver to change course in time. If the driver has activated the turn signal in advance of a lane change, the system sounds no warning.

Lane change assist: Radar sensors fitted in the rear of the vehicle constantly monitor the traffic situation up to 90 meters to the side and behind the vehicle. Prior to a lane change, the function warns the driver, for instance by lighting up a symbol in the exterior rear-view mirrors, if it detects another vehicle either approaching from behind at speed or already in the blind spot.

Traffic jam assist: The traffic jam assist system is based on the sensors and mechanics of ACC Stop&Go and of the lane keeping support. Up to a speed of 60 kilometers per hour, the system automatically follows the vehicle ahead in heavy traffic. Not only does the traffic jam assist accelerate and brake, it also keeps the vehicle in its lane by way of steering interventions. This relieves drivers so they can focus on monitoring the system.

Side view assist: In contrast to the lane change assist with its radar sensors, the side view assist system uses ultrasonic sensors. These permit it to monitor the hard-to-see areas up to four meters to the side and just behind the car. When turning or changing lanes, for instance, the system warns drivers that there is a vehicle in their blind spot by lighting up a symbol in the exterior rear-view mirrors.

Road sign recognition: The road sign recognition system helps drivers to navigate the “road sign jungle.” By way of a video sensor, this system detects all relevant road signs – including speed limits and no-passing warnings – and presents them as information on the cockpit display. This not only ensures drivers are always informed of the current applicable speed limit, it also means they can be warned when they are exceeding it.

Predictive pedestrian protection: Pedestrians are the most vulnerable road users. The proactive pedestrian protection system uses radar or video sensors for early detection of pedestrians who step out into the road without warning and might be hit by the car. The system then reacts faster than any human to automatically perform an emergency braking maneuver. This either avoids an impact or at least reduces the speed of impact and hence the severity of injuries.

Predictive collision warning: This system uses a radar sensor to detect whether there is a risk of collision with an obstacle in the road. It then builds up braking pressure in an instant to prepare the braking system for an emergency braking maneuver. At the same time, it warns the driver of the risk of collision with either an optical or acoustic signal. If the driver then steps on the brakes, maximum braking power is available immediately and the braking distance is much shorter as a result.

Automatic emergency braking: If a radar or video sensor detects a potential obstacle ahead of the car, this system first of all prepares the braking system for an emergency braking maneuver and warns the driver. If the driver doesn’t respond, the system performs a partial braking maneuver in order to increase the time available to react. As soon as the driver steps on the brakes, the system helps to avoid an accident by calculating the braking power needed and increasing the braking power applied should the driver brake too gently. If the driver also fails to respond to the partial braking maneuver and the system detects that a collision is unavoidable, it performs an emergency braking maneuver itself. This helps to greatly mitigate the consequences of the accident.

Smart trailer parking: Maneuvering a car and trailer into a parking space is truly an art. The smart trailer parking system offers a convenient way for drivers to control their vehicle and trailer from the curbside using a smartphone or tablet computer. It is based on electric power steering, the ESP electronic stability program, the electronic gas pedal, and a trailer hitch featuring a trailer angle sensor. Users can select steering angle and vehicle speed with an app. The driver can stand anywhere that offers a good view of the procedure.

Parking aid: Most accidents occur when parking. At speeds of up to ten kilometers per hour during parking maneuvers, ultrasonic sensors integrated into the bumpers constantly monitor the distance to any obstacles in the parking area. Drivers are also warned optically and/or acoustically about other vehicles that are parking. The closer the car gets to an obstacle, the more frequently the acoustic warning is sounded, until it becomes a continuous tone.

Remote park assist: With the remote controlled park assist system, vehicles park themselves as if by magic. All drivers need to do is press and hold a button on their ignition key or smartphone. This tells the vehicle to automatically maneuver itself into the parking space it has previously detected and measured using ultrasonic sensors. However, drivers retain responsibility for the parking maneuver. As soon as they release the button on their ignition key or smartphone, the system immediately stops parking.

Maneuver brake assist: At a speed of up to ten kilometers per hour, ultrasonic sensors monitor the entire area around the vehicle up to a distance of four meters. The system uses this sensor data to detect relevant and non-relevant obstacles and to calculate the path the car should travel. If there is a risk of collision, the driver is warned. If the driver fails to react, the system stops the car itself.

Park steering control: This system uses ultrasonic sensors to detect parallel or perpendicular parking spaces suitable for the vehicle in question and informs the driver. Upon activation, the system then automatically steers the car into the space. The driver remains responsible for accelerating and braking.

Rear cross-traffic alert: When reversing out of a perpendicular parking space, this radar-supported system detects vehicles, bicycles, and pedestrians that are crossing behind the car up to 50 meters away. It then gives the driver an acoustic or optical warning when there is a risk of collision.

Source: Bosch
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ATF: Abbreviation for Automatic Transmission Fluid, which is the lubricating and hydraulic oil used in the automatic transmission.

Belt: On a belt-type CVT, the belt is stretched over two pulleys to transmit torque. There are belts that incorporate steel elements, as well as those that come in chain formats.

CVT: CVT refers to Continuously Variable Transmission. This is a power transmission mechanism that continuously changes the gear ratio using mechanisms other than the gear. The transmission mechanism is made up of a belt that connects the pulleys on the input and output sides. There is an increasing number of CVT that employs a mechanism in which the contact radius between each pulley and the steel belt is changed without steps.

Lock-up: Although the torque converter transmits power through fluids, loss is unavoidable due to the viscosity and slippery property of liquids. Therefore, in areas where gear shift operations are not necessary, the lock-up is a mechanism that is applied in order to enhance transmission efficiency by directly connecting the input and output shafts through a mechanical clutch. In addition, improvements were achieved in fuel efficiency for automatic transmission and vehicles equipped with the system.

Pulley: On a belt-type CVT, the belt is stretched over two pulleys to transmit torque. Changing the groove width of the pulley in turn changes the contact radius with the belt, in a stepless way, causing the gear to shift.

Range of gear ratio: The gear ratio is also known as the reduction ratio, and refers to the ratio of the number of revolutions for the engine that is having its speed reduced through the transmission gear. For the same number of engine revolutions, larger gear ratio provides greater power but lower speed, while conversely, smaller gear ratio provides greater speed but less power. The larger the range of gear ratio, from low to high, the better the acceleration performance during start-up, and the better the fuel efficiency.

Step AT: Automatic transmission (AT) is the overall term for transmission that is equipped with a function that enables automatic changing of the gear ratio in response to the speed of the vehicle and the speed of engine revolution. In recent years, in order to distinguish between AT and CVT, the industry has also begun to apply the term “step AT” to automatic transmission. Step AT refers to a stepwise transmission system for switching gears.

Toroidal CVT: Two discs are placed parallel to one another on the input and output sides, and several power rollers (resembling tops) are wedged powerfully between the two discs. Changing the degree of inclination of the power roller changes the ratio of the number of revolutions of the two discs correspondingly, thereby allowing for variable transmission.

Torque converter: The torque converter is a machine that makes use of the effects of fluid dynamics in order to behave as a mechanical clutch. Unlike fluid coupling, which is a similar device, torque amplification occurs as a result of the difference in revolution between the input and output sides. As such, the automatic transmission, which uses the torque converter, has capability with respect to acceleration during start-up, and is able to start-up powerfully even on an slope.

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A/F: Air/Fuel ratio.

BDC: Bottom Dead Center. When the piston is at the bottom of the cylinder, at its lowest position in the stroke.

BMEP: Brake Mean Effective Pressure. Mean and constant pressure over the piston which would give an engine torque similar to the real mean torque obtained during power stroke.

BSFC: Brake Specific Fuel Consumption. Measure of the fuel efficiency of any prime mover that burns fuel and produces rotational, or shaft, power. It is typically used for comparing the efficiency of internal combustion engines with a shaft output.

CA50: Crank angle position where 50% of the heat is released.

CA70: Crank angle position where 70% of the heat is released.

CAD: Crank Angle Degree.

CAI: Controlled Auto Ignition.

CI: Compression Ignition.

CR: Compression Ratio. Value that represents the ratio of the volume of engine combustion chamber from its largest capacity to its smallest capacity. It is a fundamental specification for many common combustion engines.

DI: Direct Injection.

EGR: Exhaust Gas Recirculation – Help controlling NOx emission.

F/A: Fuel/Air ratio. Mass ratio of fuel to air present in an internal combustion engine

FMEP: Friction Mean Effective Pressure. Theoretical mean effective pressure required to overcome engine friction, can be thought of as mean effective pressure lost due to friction.

HCCI: Homogeneous Charge Compression Ignition.

IMEP: Indicated Mean Effective Pressure. Mean effective pressure calculated from in cylinder pressure, average in cylinder pressure over engine cycle (720° in a 4 stroke, 360° in a 2 stroke).

ISFC: Indicated Specific Fuel Consumption. Specific fuel consumption based on the engine in-cylinder pressures.

Knock: Undesired auto-ignition appearing in unburned area of combustion chamber.

LHV: Lower Heating Value. Determined by subtracting the heat of vaporization of the water vapor from the higher heating value

MFB: Mass Fraction Burned. A normalized quantity with a scale of 0 to 1, describing the process of chemical energy release as a function of crank angle

MFB10: Crank Angle for 10% MFB.

MFB50: Crank Angle for 50% MFB.

MFB90: Crank Angle for 90% MFB.

Pcyl: Cylinder pressure.

PCP: Peak Cylinder Pressure.

rc: Compression ratio.

SA: Spark Advance. spark timing expressed in crank angle degrees (compared to TDC).

SI: Spark Ignition. Common denomination for spark ignited engines.

SOI: Start Of Injection. Injection timing expressed in crank angle degrees (compared to TDC).

Tcyl: Cylinder temperature.

TDC: Top Dead Center. When the piston is at the top of the cylinder, at its highest position in the stroke.

Ti: Injection duration, generally expressed in microseconds.

Vc: Clearance Volume. Volume of the combustion chamber when piston is at TDC.

Vd: Swept volume. Volume of the cylinder between TDC and BDC piston position.

Vt: Total volume. Maximum cylinder volume.

λ: Relative Air/Fuel ratio. Ratio of actual A/F ratio to stoichiometry for a given mixture. λ= 1.0 is at stoichiometry, rich mixtures λ < 1.0, and lean mixtures λ > 1.0.

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