| Auto Glossary Technical Terms |
| Also AFR, is the mass ratio of air to fuel present in an internal combustion engine. If exactly enough air is provided to completely burn all of the fuel, the ratio is known as the stoichiometric mixture, often abbreviated to stoich. AFR. The lower the ratio, the “richer” the mixture Contents. AFR numbers lower than stoichiometric are considered rich. AFR numbers higher than stoichiometric are considered lean. | Air fuel ratio | A/F | |
| It is the mass ratio of the air to the mass of the fuel in the charge mixture of an internal combustion engine. If there is exactly enough air to complete the combustion process of all the fuel, then the ratio is known as the ideal ratio. The lower the ratio, the richer the mixture. When the proportion of the mixture is less than the ideal proportion, the mixture is rich, and when the proportion of the mixture exceeds the ideal proportion, the mixture is weak. | air to fuel ratio | ||
| Also called Manifold Air Temperature (MAT) sensors, and Intake Air Temperature (IAT) sensors. The ACT measures air temperature through changing resistance and sends this information to the onboard computer. The computer uses this and other inputs to calculate the correct amount of fuel delivered. | Air Charge Temperature (sensor | ACT | |
| It is also called the manifold air temperature sensor, and the air inlet temperature sensor. It measures the air temperature by changing the resistance and sends that information to the car’s computer. The computer uses that information and information from other sensors to calculate the amount of air needed. | Air charge temperature (sensitive) | ||
| The majority of vehicles on the road today are equipped with a mass air flow sensor (MAF), also commonly referred to as an air flow meter (AFM). It is a device that measures the amount of air entering the engine and supplies this information to the engine control unit (ECU) to precisely control the engine’s air/fuel ratio. | Air Flow Meter | AFM | |
| Most cars on the road today are equipped with an air flow sensor, called an air flow meter. It is a device that measures the amount of air entering the engine and provides that information to the engine control unit to precisely control the air-fuel ratio. | air flow meter | ||
| Also A/F, is the mass ratio of air to fuel present in an internal combustion engine. If exactly enough air is provided to completely burn all of the fuel, the ratio is known as the stoichiometric mixture, often abbreviated to stoich. AFR. The lower the ratio, the “richer” the mixture Contents. AFR numbers lower than stoichiometric are considered rich. AFR numbers higher than stoichiometric are considered lean. | Air Fuel Ratio | AFR | |
| It is the mass ratio of the air to the mass of the fuel in the charge mixture of an internal combustion engine. If there is exactly enough air to complete the combustion process of all the fuel, then the ratio is known as the ideal ratio. The lower the ratio, the richer the mixture. When the proportion of the mixture is less than the ideal proportion, the mixture is rich, and when the proportion of the mixture exceeds the ideal proportion, the mixture is weak. | air to fuel ratio | ||
| When the piston has reached the lowest point in the cylinder, the connecting rod will be vertical. The piston, therefore, will be at the bottom of its stroke and the connecting rod will be in the dead center position. | Bottom Dead Center | BDC | |
| It is the point at which the piston reaches the lowest point in the cylinder, at which point the connecting rod is in the vertical position. The piston is at the end of the piston travel and the connecting rod is at the dead position of the axis. | bottom dead point | ||
| It is a device used in the automobile uses information of the crankshaft speed and position to control ignition timing, and injection sequencing. The sensor is typically located on the flywheel or on a separate cog. One of the teeth of the flywheel is missing, the one exactly at Top Dead Center of cylinder #1 (the closest to the flywheel). The sensor registers a change and responding to this, sends out a pulse to the ECU. The ECU is then able to calculate the injection and ignition timing. The position sensor may be mounted externally on the crankcase wall, or it may be inside the housing of the ignition distributor. There are two commonly applied versions of this sensor, based on the principle of induction and on the Hall Effect. This sensor is the most important sensor in modern day engines. When it is failing, the engine will not run at all. | Crank Angle Sensor | CAS (2 | |
| The crankshaft angle sensor is a device used in automobiles that uses information about crankshaft speed and position to control ignition timing and the injection sequence. The sensor is usually attached to the flywheel or a separate gear. One of the teeth of the flywheel gear is missing, which is exactly at the top dead point of cylinder #1 (near the flywheel). The sensor registers the change and responds to it by sending a pulse to the engine control unit. The ECU is then able to calculate the injection and ignition timings. In some cars, the sensor can be installed externally on the crankshaft wall or inside the spark distributor housing. There are two types of such sensors commonly used, depending on the principle of induction and the Hall effect. This sensor is one of the most important sensors in modern-day engines. If the sensor fails, the engine will not work at all. | crankshaft angle sensor | ||
| Cold Cranking Amps is a rating used in the battery industry to define a battery’s ability to start an engine in cold temperatures. The rating is the number of amps a new, fully charged battery can deliver at 0° Fahrenheit for 30 seconds, while maintaining a voltage of at least 7.2 volts, for a 12 volt battery. The higher the CCA rating, the greater the starting power of the battery. | Cold Cranking Amps | CCA | |
| It is a measurement system used in the battery industry to determine the capacity of a battery to start the engine in cold weather. The scale is the amount of current in amperes that a new battery can produce at 0°F for 30 seconds, while still maintaining a battery voltage of at least 7.2V. The higher the scale number, the higher the capacity of the battery to rectify the motor. | cold engine rectifier current | ||
| It is the volume swept by all the pistons inside the cylinders of a reciprocating engine in a single movement from top dead center (TDC) to bottom dead center (BDC). It is commonly specified in cubic centimeters (cc or cm3), liters (l), or (mainly in North America) cubic inches (CID). Engine displacement does not include the total volume of the combustion chamber. Engine displacement is determined from the bore and stroke of an engine’s cylinders. The bore is the diameter of the circular chambers cut into the cylinder block. Displacement = π/4 x bore x bore x stoke x number of cylinders. | Cubic Inch Displacement | CID | |
| It is the displacement of the piston inside the cylinders of a reciprocating engine (engine capacity) during one movement from the upper dead point. It is usually specified in cubic centimeters, liters, and in North America in square inches. Engine displacement/capacity does not include the entire combustion chamber volume. The engine capacity is combined by the cylinder bore and the stroke length of the engine cylinders. The bore is the diameter of the circular section of the cylinder block. Engine capacity = i/4 x diameter x stroke length x number of cylinders. | Displacement (capacity) in cubic inches | ||
| A crank position (CKP) sensor is an electronic device used in an internal combustion engine to monitor the position or rotational speed of the crankshaft. This information is used by engine management systems to control the spark/fuel delivery and timing to and other engine parameters. | Crankshaft Position Sensor | CPS | |
| The crankshaft position sensor is an electronic device used in internal combustion engines to monitor the position and rotational speed of the crankshaft. This information is used by the engine management system to control the amount and timing of spark and fuel, as well as other engine factors. | crankshaft position sensor | ||
| Honda CVCC engines have normal inlet and exhaust valves, plus a small auxiliary inlet valve which provides a relatively rich air–fuel mixture to a volume near the spark plug. The remaining air–fuel charge, drawn into the cylinder through the main inlet valve, is leaner than normal. The volume near the spark plug is contained by a small perforated metal plate. Upon ignition flame fronts emerge from the perforations and ignite the remainder of the air–fuel charge. This combination of a rich mixture near the spark plug, and a lean mixture in the cylinder allowed stable running, yet complete combustion of fuel, thus reducing CO (carbon monoxide) and hydrocarbonemissions. This method allowed the engine to burn less fuel more efficiencies without the use of an exhaust gas recirculation valve or a catalytic convertor, | Compound Vortex Controlled Combustion | CVCC | |
| Honda engines that use the system have regular charge inlet and exhaust valves on each cylinder, as well as an additional small inlet valve that provides the air-fuel mixture to space near the spark plug. The rest of the charge, enters the cylinder (a poor mixture than usual) via the primary valve. The space near the spark plug is enclosed in a perforated metal plate. When ignited, the flame front exits the holes and ignites the remainder of the air-fuel mixture. The combination of a rich mixture near the spark plug, and a poor mixture in the cylinder allows for uniform operation, and results in complete combustion of the fuel, thus reducing carbon monoxide and hydrocarbon emissions in the exhaust. This method allows the engine to burn less fuel more efficiently without the need for an exhaust gas recirculation valve or catalyst. | cyclone control multi combustion | ||
| It is an automotive technology used in automotive piston engines that allows the intake andor exhaust valve left to be infinitely varied during engine. It varies the height that a valve opens, in order to improve performance, fuel economy or emissions. When used in conjunction with variable valve timing, variable valve lift can potentially offer infinite control over the intake and exhaust valve timing. | Continuous Variable Valve Lift | CVVL | |
| An automotive technology widely used in piston car engines that allows the intake valve travel and/or exhaust valve travel distance to be continuously changed while the engine is running. It’s a change of valve opening height, to improve performance, fuel economy, or emissions. When used with variable valve timing, the variable valve distance can provide infinite control over the intake and exhaust valve timing. | Continuously changing valve travel distance | ||
| It is an automotive technology also known as Continuous Variable Valve Timing Control (CVTC or CVTCS) that allows the varied intake and/or exhaust valve timing to be infinitely during engine operation. | Continuous Variable Valve Timing | CVVT | |
| It is an automotive technology also known as Continuously Variable Valve Timing Control that allows intake and/or exhaust valve timing to vary infinitely while the engine is running. | Continuous change valve timing system | ||
| It is continuously variable length intake manifold, it serves the same purpose as variable-length intake manifold (VLIM), variable intake manifold (VIM), or variable intake system (VIS), but has a different design. It is an automobile internal combustion engine manifold technology. The principle is simple. The intake manifold of each cylinder is arranged in circular shape and half-recessed into the V-valley. The inner wall is actually a rotor, onwhich the air inlet is located. When the rotor swivels, the position of the air inlet moves in relation to the outer housing of manifold. This varies the effective length of the intake manifold in order to optimize power and torque across the range of engine speed operation, as well as help provide better fuel efficiency. As the DIVA requires a circular construction, it occupies more space (especially height) than other VLIM systems. It is later abandoned by BMW. | Differentiated Variable Air Intake | DIVA | |
| It is a continuously variable intake manifold length system, which serves the same purpose as the variable length intake manifold, variable intake manifold, and variable intake manifold systems, but has a different design. It is a vehicle’s internal combustion engine complex technology. The principle is simple. The intake manifold for each cylinder is designed in a circular shape and has a retractable bottom. The inner wall is actually a rotor, containing the incoming air. When the rotor rotates, the air inlet moves relative to the collector casing. This changes the effective manifold length to improve power and torque across a range of engine operating speeds, as well as improve fuel efficiency. Since the system requires a circular construction, it occupies more space (particularly height) than other variable length intake manifold systems. It was later abandoned by BMW. | Permanently changing drag complex | ||
| Shuts down cylinders in an engine when not needed, typically at a highway cruise. Sometimes called Cylinder Deactivation, Multiple Displacement System (MDS), Active Fuel Management, or Variable Cylinder Management. | Displacement on Demand | DOD (DoD | |
| Disable the engine cylinders when not needed, especially when driving on highways. It is called by several names, including: cylinder deactivation, multi-displacement system, effective fuel management, and cylinder capacity management. | Adjust engine capacity as needed | ||
| DOHC dual overhead cam engine has two camshafts in cylinder head. Cams act directly on valves without rocker arms. One cam operate the intake valves the other operate the exhaust valves. | Dual Over Head Cam | DOHC | |
| It is a system with two camshafts installed in the engine head. The cams are actuated directly on the valves without the use of swing arms. A camshaft to operate the intake valves, and the other shaft to operate the exhaust valves. | Dual overhead camshaft system | ||
| It is a heat engine where an (internal) working fluid is heated by combustion in an external source, through the engine wall or a heat exchanger. The fluid then, by expanding and acting on the mechanism of the engine, produces motion and usable work. The fluid is then cooled, compressed and reused (closed cycle), or (less commonly) dumped, and cool fluid pulled in (open cycle air engine). | External Combustion Engine | ECE | |
| A heat engine in which the active fluid is heated by an external source, via the walls of the engine, or a heat exchanger. The fluid expands and affects the motor, resulting in efficient movement and work. The liquid is then cooled, compressed and reused (closed circuit), which is less commonly the liquid is discarded and another liquid is withdrawn (open circuit). | external combustion engine | ||
| ECM or ECU (electronic control unit) is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance. It does this by reading values from a multitude of sensors within the engine bay, interpreting the data, and adjusting the engine actuators accordingly. | Engine Control Module | ECM | |
| An engine control unit, or electronic control unit, is an electronic control unit that controls multiple actuators in internal combustion engines to ensure their optimum performance. It does this by reading the values of several sensors in the engine compartment, analyzing the data and adjusting the actuators accordingly. | Electronic control unit/engine | ||
| Also called coolant temperature sensor (CTS). It is used to measure the temperature of the engine coolant of an internal combustion engine. The readings from this sensor are then fed back to the Engine control unit (ECU). This data from the sensor is then used to adjust the fuel injection and ignition timing. On some vehicles the sensor may be used to switch on the electronic cooling fan, and/or to provide readings for a coolant temperature gauge on the dash. | Engine Coolant Temperature (sensor | ECT | |
| It is also called coolant temperature sensor. It is used to measure the coolant temperature of an internal combustion engine. The reading from those sensors is sent to the engine control unit. This data from the sensor is used to adjust fuel injection and ignition timing. On some engines, the sensor can be used to operate the electric cooling fan, and/or to give a reading of the temperature gauge on the car’s dashboard. | Engine coolant temperature sensor | ||
| It is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance. The ECU determines the amount of fuel to inject based on a number of sensor readings, to control air/fuel ratio. The ECU can adjust the exact timing of the spark (called ignition timing) to provide better power and economy, and when it detects knock, it can delay the spark to prevent it. The ECU can also control the idle engine speed, and control of variable valve timing. | Engine Control Unit | ECU (2 | |
| An engine control unit is a type of electronic control unit that controls various actuators of an internal combustion engine to ensure optimum engine performance. The engine control unit determines the amount of fuel to be injected based on several sensor readings, to control the air / fuel ratio. The unit can adjust the spark timing (called ignition timing) for better power and fuel economy, and when it senses a smack in the engine it delays the spark to prevent it from happening. The unit can also control the velocity of the empty load, and control the variable timing of the valves. | Engine control unit | ||
| EDTC prevents excessive slip of the driven wheels due to engine drag torque (engine brake). This may occur when driving on slippery road surface if the driver changes to lower gear or suddenly lifts his foot off the throttle. | Engine Drag Traction Control | EDTC | |
| It prevents the driving wheels from slipping due to engine braking. Occurs when driving on a slippery road, which occurs when the gearbox is shifted to a lower gear (higher reduction ratio) or the foot is suddenly removed from the fuel pedal. | traction engine control unit | ||
| In an Engine Management System (EMS), electronics control fuel delivery, ignition timing and firing order. Early EMS systems used analogue computer circuit designs to accomplish this, but as embedded systems became fast enough to keep up with the changing inputs at high revolutions, digital systems started to appear. | Engine Management System | EMS | |
| The engine management system, electronically controls fuel delivery, ignition timing, and the order of the fire. Early engine management systems used analog computer circuits to achieve this, but as existing systems became fast enough to keep up with changing inputs at high rotational speeds, digital systems began to appear. | Engine management system | ||
| An ordinary fixed intake manifold has its geometry optimized (no change in its geometry), is designed for high speed power, or low speed torque, or a compromise between them. Many modern engines turned to variable intake manifold designs , to benefit from supercharging effect creating form pressure waves, such as: Variable Intake Manifold (VIM), Variable Length Intake Manifold (VLIM), 3-stage variable length intake manifold, continuous variable length intake manifold (Differentiated Variable Air Intake “DVAI”), or resonance intake manifold systems. | Fixed Geometry Intake Manifold | FGI | |
| The regular fixed intake manifold has a specific dimension (no change in dimensions or shape), and is designed for power at high speeds, or torque at low speeds. Many modern engines are modified to work with variable-dimension intake manifold designs, to take advantage of the effect of supercharging generated by pressure waves, such as variable intake manifold, variable length intake manifold, three-stage intake manifold, and continuous length variable intake manifold (Variable Variable Air Manifold). ), or reciprocating collector systems. | Dimensionally/shaped fixed intake manifold | ||
| It is the theoretical mean effective pressure required to overcome engine friction, can be thought of as mean effective pressure lost due to friction. Friction mean effective pressure calculation requires accurate measurement of cylinder pressure and dynamometer brake torque. FMEP = IMEPn- BMEP. | Friction mean effective pressure | FMEP | |
| It is the theoretical average effective pressure required to overcome the friction inside the engine, which is the effective average pressure lost due to friction. To calculate the average effective braking pressure, it is necessary to accurately measure the cylinder pressure and the braking torque of the dynamometer (engine power gauge). Frictional effective mean pressure = net graph effective average pressure – braking effective average pressure | Frictional effective medium pressure | ||
| An idle air control actuator or idle air control valve (IAC actuator/valve) is a device commonly used in fuel-injected vehicles to control the engine’s idling RPM. The IAC, actuator is an electrically controlled valve, which gets its input from the vehicle’s ECU. The ECU can control the amount of air that bypasses the throttle when the throttle is fully closed, thereby controlling the engine’s idle RPM. | Idle Air Control | IAC | |
| Empty load air control valve/actuator is a device used in vehicles that use fuel injection to control the engine speed at empty load. The valve is installed so that it bypasses the throttle valve. The actuator is an electrical control valve that gets its input from the vehicle’s electronic control unit. The unit can control the amount of air bypassing the throttle when the throttle is fully closed, thus controlling the engine’s empty load rotational speed. | Empty Load Air Control | ||
| The intake air temperature sensor is mounted to the air duct housing. The sensor detects intake air temperature and transmits a signal to the ECM. The engine computer (PCM) needs this information to estimate air density so it can balance air/fuel ratio mixture. Cold air is denser than hot air, so cold air required more fuel to maintain thesame air/fuel ratio. The PCM changes the air/fuel ratio by changing the length of the injection pulse. | Intake Air Temperature (sensor | IAT | |
| The intake air temperature sensor is mounted on the body of the air collector. The sensor senses the air temperature and sends a signal to the engine control unit. The power train control module needs this information to estimate air density so that it can balance the air/fuel ratio of the mixture. Cold air is denser than hot air, as cold air needs more fuel to maintain the same air/fuel ratio (mass ratio). The unit adjusts the ratio by changing the fuel injection duration. | Intake air temperature sensor | ||
| It is a heat engine where the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine the expansion of the high-temperature and high-pressure gases produced by combustion apply direct force to some component of the engine. The force is typically applied to pistons, turbine blades, or a nozzle. This force moves the component over a distance, transforming chemical energy into useful mechanical energy. | Internal Combustion Engine | ICE | |
| It is a heat engine, in which the combustion of the fuel occurs with an oxidizer (usually air) in the combustion chamber that is an integral part of the effective medium flow circuit. The high-temperature, high-pressure gases generated by the combustion process expand inside the internal combustion engine and directly affect certain parts of the engine. The force usually affects the pistons, turbine blades, or the nozzle. This force moves the part for a certain distance, thus converting the chemical energy of the fuel into useful mechanical energy. | internal combustion engine | ||
| It is the average pressure acting on a piston during different portions of its cycle. IMEPg is the Gross indicated mean pressure calculated over compression and expansion of engine cycle (360 degree in a 4 stoke, 180 degree in a 2 stroke). IMEPn is the Net indicated mean effective pressure calculated over the complete engine cycle (720 degree in 4 stroke, 360 degree in 2 stroke). Direct measurement requires cylinder pressure sensing equipment. | Indicated Mean Effective Pressure | IMEP | |
| It is the average pressure applied to the piston during different phases of its cycle. The average effective pressure (total) is calculated during the compression and expansion stroke during the engine cycle (360° for 4-stroke engines, 180° for 2-stroke engines). The mean effective pressure (net) is the calculated over the entire engine cycle (720° for a 4-stroke engine, 360° for a 2-stroke engine). Direct measurement requires pressure sensors inside the cylinder. | Effective average pressure graphic | ||
| The ISC (Idle Speed Control) system is provided with a circuit that bypasses the throttle valve, and the air volume drawn in from the bypass circuit is controlled by the ISCV (Idle Speed Control Valve). The ISCV uses the signal from the engine ECU to control the engine at the optimum idling speed at all times by setting how much air flows through a bypass passage, from the intake air side, to the manifold side of the throttle body. The control unit reacts to this additional air by metering additional fuel. If the control unit is programmed to maintain a fine control of the idling speed, ignition timing can be used. Advancing the ignition point increases engine speed, just as retarding it decreases it. The ISC system consists of the ISCV, engine ECU, and various sensors and switches. | Idle Speed Control system | ISC | |
| The empty load velocity control system is equipped with a circuit/ bypass/ bypass throttle valve, and the air drawn from the bypass is controlled by the empty load velocity control valve. The valve uses a signal from the ECU to control the engine to reach the optimum empty load speed at all times by adjusting the amount of air to pass in the bypass path, from the air intake side to the intake manifold side of the throttle valve. The control unit responds to this additional amount of air by providing the required fuel. If the controller is programmed to precisely control the empty load speed, the spark/ignition timing can be used. Advance ignition increases speed, and delay decreases speed. The system consists of an empty load speed control valve, an electronic control unit for the engine, several sensors, and switches. | Empty load speed control system | ||
| It is part of ISC (Idle Speed Control) system which is provided with bypasses the throttle valve. The air volume drawn in from the bypass circuit is controlled by the ISCV (Idle Speed Control Valve). The ISCV uses the signal from the engine ECU to control the engine at the optimum idling speed at all times. The valve varies the opening of the bypass passageway, and changes the idle speed to suit. | Idle Speed Control Valve | ISCV | |
| It is part of an empty load speed control system equipped with a bypass/bypass/bypass throttle. The air drawn from the bypass circuit is controlled by the empty load control valve. The valve uses the signal from the engine ECU to control the engine at the optimum free-load speed at all times. The valve changes the bypass opening, and changes the empty load speed to suit the load and operating conditions. | Empty Load Speed Control Valve | ||
| The LBE concept refers to engine operation that is leaner (higher air to fuel mass ratio) than stoichiometric (chemically correct air-fuel ratio). The excess of air in a lean-burn engine combusts more of the fuel and emits fewer hydrocarbons. A lean burn mode is a way to reduce throttling losses, because if the fuel/air ratio is reduced, then lower power (at part load) can be achieved with the throttle closer to fully open. The engines designed for lean-burning can employ higher compression ratios and thus provide better performance, fuel use and low exhaust hydrocarbon emissions than those found in conventional petrol engines. | Lean-Burn Engine | LBE | |
| The concept of a weak mixture burning engine refers to running the engine with a lower mixture (high air/fuel ratio) than the chemically correct ratio. Excess air in weak mixture engines ensures more fuel combustion in the mixture and lower hydrocarbon emissions. The low-mix burn mode is an effective way to reduce throttle loss due to the fact that at lower fuel/air ratio lower power (at medium loads) can be achieved with throttle opening close to full. Engines designed to burn weak mixtures can use a higher compression ratio and thus deliver better performance, higher fuel efficiency, and lower hydrocarbon emissions than conventional gasoline engines. | Weak mixture burning engine | ||
| The majority of vehicles on the road today are equipped with a mass air flow sensor (MAF), also commonly referred to as an air flow meter. The mass airflow sensor is placed in the stream of intake air to measure the amount of air entering the engine and supplies this information to the engine control unit (ECU). The ECU uses this information to calculate engine load, which the ECU uses along with information provided by the oxygen sensor(s) to precisely control the engine’s air / fuel ratio. Air changes its density as it expands and contracts with temperature and pressure. In automotive applications, air density varies with the ambient temperature, altitude and the use of forced induction, which means that mass flow sensors are more appropriate than volumetric flow sensors for determining the quantity of intake air in each cylinder. | Mass Air flow sensor | MAF | |
| Most cars on the road today are equipped with a mass air flow/flow sensor, also known as an air flow meter. The sensor is placed in the intake airflow path to measure the amount of air entering the engine and sends that data to the engine control unit. The ECM uses this data to calculate the engine load, which the unit uses along with the data provided by the oxygen sensor(s) to precisely control the air/fuel ratio. Air changes density with expansion or contraction as a result of heat and pressure. In automotive applications, air density varies with atmospheric pressure, altitude and lubrication usage, which means that the flow mass gauges are more appropriate than the flow volume sensors to determine the amount of air drawn per cylinder. | Mass flow/air flow sensor | ||
| MAP System is one of the sensors used in an internal combustion engine’s electronic control system. It measures changes in the intake manifold pressure resulting from engine load and speed changes. By monitoring the sensor output voltage, the computer can determine the manifold absolute pressure. The data is used to calculate air density and determine the engine’s air mass flow rate, which in turn determines the required fuel metering for optimum combustion and influence the advance or retard of ignition timing. The higher the MAP voltage output the lower the engine vacuum, which requires more fuel, and vice versa. Under certain conditions, the MAP sensor is also used to measure barometric pressure. This allows the computer to automatically adjust for different altitudes. The computer uses the MAP sensor to control fuel delivery and ignition timing. The MAP sensor can also be used in OBD II (on-board diagnostics) applications to test the EGR (exhaust gas recirculation) valve for functionality. | Manifold Absolute Pressure (sensor | MAP | |
| The intake manifold absolute pressure sensor is one of the sensors used in the electronic control system of internal combustion engines. It measures the intake manifold pressure caused by the change in engine load and speed. It measures changes in intake manifold pressure due to changes in engine load and speed. By monitoring the sensor voltage output, the computer can determine the absolute pressure in the collector. The data is used to calculate the air density and to estimate the airflow mass ratio of the engine, which in turn determines the amount of fuel required for optimal combustion and influences the advance or delay of ignition timing. The higher the sensor output voltage, the lower the engine rancidity, which requires more fuel, and vice versa. Under certain conditions, the sensor is also used to measure atmospheric pressure, allowing the computer to automatically adjust the calculations accordingly. The computer uses the sensor to control the delivered fuel and the ignition timing. | Intake manifold absolute pressure sensor | ||
| Also called Air Charge temperature (ACT) sensors, and Intake Air Temperature (IAT) sensors. The MAT measures air temperature through changing resistance and sends this information to the onboard computer. The computer uses this and other inputs to calculate the correct amount of fuel delivered. | Manifold Air Temperature (sensor | MAT | |
| It is also called the air charge temperature sensor, and the air inlet temperature sensor. It measures the air temperature by changing the resistance and sends that information to the car’s computer. The computer uses that information and information from other sensors to calculate the amount of air needed. | Air collector temperature | ||
| Cylinder Deactivation, Displacement On Demand (DOD), or Variable Cylinder Management. | Multiple Displacement System | MDS | |
| It is a measure of the effectiveness of a mechanical system. It is often the ratio between the output power or work output of the mechanical system (transmission system or equipment) to the power input or work output, and due to friction (power lost), the efficiency is always less than one. | Variable Capacity System | ||
| The mean effective pressure is a quantity relating to the operation of a reciprocating engine and is a valuable measure of an engine’s capacity to do work that is independent of engine displacement. Some commonly used MEPs are: brake mean effective pressure (BMEP), indicated mean effective pressure (IMEP “Gross” IMEPg and “Net” IMEPn), pumping mean effective pressure (PMEP), and friction mean effective pressure (FMEP). | Mean Effective Pressure | MEP | |
| The effective average pressure is a quantity related to the reciprocating engine operation and an important measure of the engine’s ability to do work that is independent of the engine’s capacity. Some of the effective medium pressures used are: the braking effective medium pressure, the graphic effective medium pressure (the graphic effective average pressure “total”, the graphic effective medium pressure “net”), the effective medium pressure for pumping, and the frictional effective medium pressure. | Effective medium pressure | ||
| An oxygen sensor (O2S, Heated Oxygen Sensor HO2S, or lambda sensor) is an electronic device that measures the proportion of oxygen (O2) in the gas or liquid being analyzed. Automotive oxygen sensors, make modern electronic fuel injection and emission control possible. They help determine, in real time, if the air–fuel ratio of a combustion engine is rich or lean. Since oxygen sensors are located in the exhaust stream, they do not directly measure the air or the fuel entering the engine but when information from oxygen sensors is coupled with information from other sources, it can be used to indirectly determine the air-fuel ratio. In addition to enabling electronic fuel injection to work efficiencies, this emissions control technique can reduce the amounts of both unburnt fuel and oxides of nitrogen entering the atmosphere. | Automotive oxygen sensors | O2 sensor- O2S | |
| An oxygen sensor (heated oxygen sensor, or lambda sensor) is an electronic device that measures the percentage of oxygen in the gas or liquid being analyzed. Car oxygen sensors. which facilitates the possibility of making electronic fuel injection and modern emissions control possible. It can determine whether the mixture’s air-to-fuel ratio is rich or poor. Since the oxygen sensor is located in the exhaust duct, it does not directly measure the air or fuel entering the engine, but when the information from the oxygen sensors is combined with information from other sources, it can be used indirectly to determine the air-fuel ratio. Based on the sensor data, the fuel injection is controlled. In addition to enabling efficient electronic fuel injection, emission control technology reduces the amount of unburned fuel and nitrogen oxides released into the atmosphere. | oxygen sensor | ||
| In an overhead cam engine (OHC), the camshaft is located in the top of the cylinder head. Push rods are NOT needed to operate the rockers and valves. With the cam in head, the number of valve train parts is reduced. Also the valves can be placed at an angle to improve breathing. The OHC increase high speed efficiency and power output. The OHC can be single overhead cam SOHC, or dual overhead cam DOHC. | Over Head Cam | OHC | |
| In upper cam engines, the complete shaft is located in the upper part of the cylinders. So there is no need to use thrust shafts to operate the swing arms and valves. With the cam in the head, the number of valve train parts is reduced. The valves can also be angled to improve intake and exhaust. Overhead camshafts increase efficiency and power output at higher speeds. Overhead cams can be single camshaft or vertical/double camshafts. | upper camshaft | ||
| Engines with the camshaft in the block are called Overhead Valve (OHV) Engines. | Over head valve | OHV | |
| Engines that have a camshaft in the cylinder block are called cylinder head overhead valve engines, and the valves are operated by means of push arms (connected to the cam), which move the swing arms to drive the valve. | overhead valve | ||
| The positive crankcase ventilation system pulls the crankcase fumes into the intake manifold so they can be burned before entering the atmosphere. The PCV became standard equipment on all vehicles worldwide because of its benefits not only in emissions reduction but also in engine internal cleanliness and oil lifespan | Positive crank case ventilation | PCV | |
| The crankshaft forced ventilation system works by pulling the fumes resulting from the combustion process and leaking from the piston rings into the crankshaft case, and entering them with the drawn charge into the cylinders for re-combustion with the charge instead of taking them out to the atmosphere. The crankshaft forced ventilation system has become standard equipment in the car not only due to the reduction of harmful emissions from the car but also to the internal cleaning of the engine and increase the service life of the oil as well. | Crankshaft case ventilation system | ||
| Mean effective pressure from work moving air in and out of the cylinder, across the intake and exhaust valves. Calculated from in-cylinder pressure over intake and exhaust portions of engine cycle (360 degree in a 4 stroke, 180 degree in a 2 stroke). Direct measurement requires cylinder pressure sensing equipment. PMEP = IMEPg – IMEPn. | Pumping Mean Effective Pressure | PMEP | |
| The effective average pressure of work required to move air into and out of the cylinder, through the intake and exhaust valves. Which is calculated from the pressure inside the cylinder during the intake and exhaust period of the engine cycle (360° for a 4-stroke engine, 180° for a 2-stroke engine). The direct measurement process requires pressure sensors inside the cylinder. The mean effective pumping pressure is equal to the total graphical effective mean pressure minus the net graphical effective mean pressure. | Effective medium pressure for pumping | ||
| Stratified charge combustion engines utilize a method of distributing fuel that successfully builds layers of fuel in the combustion chamber. A stratified charge engine is a type of internal combustion engine, used in automobiles, in which the fuel is injected into the cylinder just before ignition. This allows for higher compression ratios without “knock,” and leaner air/fuel ratio than in conventional internal combustion engines. | Stratified Charge | SC | |
| Layer charge combustion engines use a method of distributing the fuel as successive layers in the combustion chamber. Stratified engines are a type of internal combustion engine used in automobiles, in which fuel is injected into the cylinder before ignition. This allows for a higher compression ratio without slamming, and with a lower air/fuel mixture than that used in conventional internal combustion engines. | stratigraphic charge | ||
| The SDI engine is a design of naturally aspirated (NA) direct injection diesel engine developed and produced by Volkswagen Group. The SDI engine is generally utilized in applications where reliability and fuel economy are of primary concern. These engines lack any type of forced induction, hence the use of ‘suction’ in the title, and as such, their power output is lower when compared with a similar displacement turbocharged engine. | Suction Diesel Injection | SDI | |
| It is a diesel engine that introduces air into the cylinders by pulling the pistons, and injecting diesel fuel directly into the cylinder, developed and produced by the Volkswagen Group. It is used in applications where the goal is to achieve reliability and fuel economy. These engines do not depend on any type of charging, and therefore their power is lower compared to charging engines of the same capacity | Diesel injection by pulling pistons | ||
| The single overhead cam engine has one camshaft in cylinder head, cam act directly on valves or rocker arms can be used. | Single over head cam | SOHC | |
| Single cylinder overhead camshaft engine. The cam directly affects the valves or swing arms can be used. | Single overhead camshaft system | ||
| When the piston has reached the highest point in the cylinder, the connecting rod will be vertical. The piston, therefore, will be at the top of its stroke and the connecting rod will be in the dead center position. | Top Dead Center | TDC | |
| The point at which the piston reaches the highest point in the cylinder, at which point the connecting rod is in the vertical position. The piston is at the beginning of the piston’s journey and the connecting rod is at the dead position of the axis | top dead point | ||
| It is a design of turbodiesel engines, which feature turbocharging and cylinder-direct fuel injection, developed and produced by the Volkswagen Group. The TDI engine uses direct injection, where a fuel injector sprays atomized fuel directly into the main combustion chamber of each cylinder, rather than the pre-combustion chamber prevalent in older diesels which used indirect injection. The engine also uses forced induction by way of turbocharger to increase the amount of air which is able to enter the engine cylinders, and most TDI engines also feature an intercooler to lower the temperature (and therefore increase the density) of the ‘charged’, or compressed air from the turbo, thereby increasing the amount of fuel that can be injected and combusted. | Turbocharged Direct Injection | TDI | |
| It is a design for turbo-diesel engines, featuring turbocharging and direct cylinder fuel injection, developed and produced by the Volkswagen Group. These engines use direct injection, in which the fuel injector atoms the fuel directly into the main combustion chamber of each cylinder, rather than the pre-combustion chamber of older indirect injection diesel engines. The engine also uses forced charging via a turbocharger to increase the amount of air that has the ability to enter the engine cylinders, these engines are characterized by the use of an intercooler to reduce the temperature of the charge (and thus increase the density), or turbo air, thus increasing the amount of fuel that can be injected and burned. | Turbocharged direct injection | ||
| In internal combustion engines, Fuel Stratified Injection (FSI), also known as Petrol Direct Injection or Direct Petrol Injection or Spark Ignited Direct Injection (SIDI) or Gasoline Direct Injection (GDI), is a variant of fuel injection employed in modern two-stroke and four-stroke gasoline engines. The gasoline is highly pressurized, and injected via a common rail fuel line directly into the combustion chamber of each cylinder, as opposed to conventional multi-point fuel injection that injects fuel into the intake tract, or cylinder port. Directly injecting fuel into the combustion chamber requires high pressure injection whereas low pressure is used injecting into theintake tract or cylinder port requires. In some applications, gasoline direct injection enables a stratified fuel charge (ultra-lean burn) combustion for improved fuel efficiency, | Turbocharged Stratified Injection | TDS | |
| It is a design for supercharged diesel engines, featuring turbocharging and direct cylinder fuel injection, developed and produced by the Volkswagen Group. The engine uses direct injection inside the combustion chamber, without the need for the pre-combustion chamber of older indirect injection diesels. Engines also use forced charging via a turbocharger to increase the amount of air that is able to increase the amount of air entering the cylinders, and most of them are characterized by the use of a coolant to reduce the air temperature to increase its density or compressed air from the charger, to increase the amount of fuel that can be injected and burned. | Turbocharged laminar injection | ||
| It is the name given by Ford to engines with the ability to advance or retard the timing of both the intake and exhaust camshafts independently, unlike the original versions of VCT, which only operated on a single camshaft. This allows for improved power and torque, particularly at lower engine RPM, as well as improved fuel economy and reduced emissions. | Twin Independent Variable Camshaft Timing | Ti-VCT | |
| It is a “Ford” designation for engines that are able to independently provide or delay timing for both the intake and exhaust camshafts, unlike the original versions of the variable camshaft timing system, which operated only on a single camshaft. This allows to improve the power and torque of the engine. Especially at low engine speeds, it also improves fuel efficiency and reduces emissions. | Dual cam/camshaft independent variable timing | ||
| The throttle position sensor responds to the accelerator pedal movement. This sensor is a kind of potentiometer that transforms the throttle position into output voltage, and emits the voltage signal to the ECM. In addition, the sensor detects the opening and closing speed of the throttle valve and feeds the voltage signal to the ECM. The ECM receiving the signal from the throttle position sensor determines idle position of the throttle valve. This sensor controls engine operation such as fuel cut. | Throttle Position Sensor | TPS | |
| The throttle position sensor responds to the acceleration/fuel pedal movement. This sensor is a type of potentiometer that converts the throttle position into a voltage output, and sends a voltage signal to the engine control unit. In addition, the sensor recognizes the opening and closing speed of the throttle valve and sends it to the engine control unit. The ECM receives the signal from the throttle position sensor and decides the optimum throttle position. This throttle controls engine operation like a fuel cut. | throttle position sensor | ||
| It is a variable displacement in automobile engine technology that allows the engine displacement to change, usually by deactivating cylinders, for improved fuel economy and reduce emissions. The technology is primarily used in large, multi-cylinder engines. Many automobile manufacturers have adopted this technology under different names: Active Fuel Management (AFM), Multi-Displacement System (MDS), and Active Cylinder Control (ACC). Cylinder deactivation is achieved by keeping the intake and exhaust valves closed for a particular cylinder, the engine management system is also used to cut fuel delivery to the disabled cylinders. | Variable Cylinder Management | VCM | |
| It is an automotive engine technology that allows engine displacement/capacity to be changed, usually by deactivating some cylinders, to improve fuel economy and reduce emissions. This technology is mainly used for large multi-cylinder engines. Many car manufacturers have adopted this technology under several names: Active Fuel Management, Multi-capacity System, Active Cylinder Control. Deactivation of the cylinders is done by keeping the exhaust and intake valves closed for certain cylinders, and the engine management system cuts off fuel from the deactivated cylinders. | Cylinder Control Management | ||
| Variable compression ratio is the technology to adjust internal combustion engine cylinder compression. This is done to increase fuel efficiency while under varying loads. Higher loads require lower ratios to be more efficient and vice versa. Variable compression engines allow for the volume above the piston at ‘top dead center (TDC)’ to be changed. This needs to be done dynamically in response to the load and driving demands. | Variable Compression Ratio | VCR | |
| Changing the compression ratio is a technique for adjusting the pressure of internal combustion engines. This is to increase fuel efficiency with changing engine loads. Higher loads need a lower ratio to improve efficiency and vice versa. Variable compression ratio engines allow the volume above the piston at the top dead point to vary. This needs to be done dynamically to respond to the demands of the load and driving conditions. | Variable compression ratio | ||
| Variable Camshaft Timing (VCT) is an automobile variable valve timing technology developed by Ford. A VCT mechanism varies the phase of the valve opening and closing relative to the crankshaft as a function of engine operating condition. It allows for more optimum engine performance, reduced emission, and increased fuel efficiency compared with fixed camshafts. For twin cam or DOHC engines, VCT was used on either the intake or exhaust camshaft. (Engines that have VCT on both camshafts are now designated as Ti-VCT.) The use of variable camshaft timing on the exhaust camshaft is for improved emissions, and vehicles with VCT on the exhaust camshaft do not require exhaust gas recirculation (EGR) as retarding the exhaust cam timing achieves the same result. | Variable Cam Timing | VCT | |
| Variable camshaft timing is a valve timing technology developed by Ford. The system mechanism works to change the phase of opening and closing the valves for the crankshaft according to the engine operating conditions. The system allows for optimum engine performance, reduced emissions, and increased fuel efficiency compared to fixed camshafts. The system adjusts the timing for all valves operating on one camshaft. For dual camshafts or dual overhead camshaft engines, the system is used on the intake valves camshaft or the exhaust valve camshafts (engines that have a mechanism that changes the valve timing on both camshafts is known as double camshaft independent variable timing). The use of an exhaust camshaft system improves emissions, and vehicles with an exhaust camshaft system do not need an exhaust gas recirculation system as delaying the exhaust cam leads to the same results. | Variable cam timing | ||
| Valve-Event Modulation (VEM) or Variable Valve Actuation (VVA) are general terms that can be used to describe a range of technologies used to add flexibility to the engine’s valve train by enabling variable valve event timing, duration and/or lift. The main types of VVA technologies include valve timing control (VTC), variable valve lift (VVL) and camless valve trains. | Valve-Event Modulation | VEM | |
| Modified valve actuation or variable valve actuation is a general description to describe a group of techniques used to add flexibility to an engine’s usual valve set by changing the factors controlling valve operation by being able to change the timing, duration, or distance of the valves. The main types of technology used include valve timing control, valve opening distance, and camless valve control. | valve actuation adjustment | ||
| They are a series of sounds designed to alert pedestrians to the presence of electric drive vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and all-electric vehicles (EVs) traveling at low speeds. Warning sound devices were deemed necessary because vehicles operating in all-electric mode produce less noise than traditional combustion engine vehicles and could make it more difficult for pedestrians, the blind, cyclists, and others, to be aware of their presence. A small speaker up front plays a pre-recorded engine sound during electric-only vehicle operation, as a warning to pedestrians. | Virtual engine sound system | VESS | |
| It is a series of sounds designed to alert pedestrians to the presence of vehicles powered by an electric motor, such as all types of hybrid cars, and electric cars, which are traveling at slow speeds. Acoustic alarms are essential because electric drive vehicles emit much less sound than internal combustion engine vehicles, which makes it more difficult for pedestrians, blind people, cyclists, animals, and others to sense their presence. It may be a small loudspeaker installed in the front of the car that emits a pre-recorded sound of the engine, which works only during the electric start phase of the car, to warn pedestrians. | Engine sound imitation system | ||
| In internal combustion engines, a Variable Geometry Induction (VGI), variable-length intake manifold (VLIM), variable intake manifold (VIM), or variable intake system (VIS) is an automobile internal combustion engine manifold technology. As the name implies, VGI/VLIM/VIM/VIS can vary the length of the intake tract – in order to optimize power and torque across the range of engine speed operation, as well as help provide better fuelefficiency. This effect is often achieved by having two separate intake ports, each controlled by a valve, that open two different manifolds – one with a short path that operates at full engine load, and another with a significantly longer path that operates at lower load. | Variable Geometry Intake (manifold | VGI/VLIM/VIM/VIS | |
| In internal combustion engines, variable intake manifold dimensions, variable intake manifold dimensions, variable intake manifold, variable intake system are all expressions of a technology for internal combustion engines. As the names indicate, the length of the entry path can be changed in order to improve the power and torque across the engine’s operating speed range, and also helps to provide better fuel efficiency. This is often done with two separate air intake ports, each controlled by a valve, which opens a path for two different manifolds – one with a short path running at full engine load, and the other running at a much longer length during low/low loads. | Dimensionally variable towing complex | ||
| It is a valve train system developed by Honda to improve the volumetric efficiency of a four-stroke internal combustion engine. This system uses two camshaft profiles and electronically selects between the profiles. Different types of variable valve timing and lift control systems have also been produced by other manufacturers (MIVEC from Mitsubishi, VVTL-i from Toyota, VarioCam Plus from Porsche, VVL from Nissan, etc. | Variable Valve Timing and Lift Electronic Control | VTEC | |
| Electronically controlled variable valve opening timing and distance. There are many car companies that have developed systems similar to this system under other names | Electronic control to change the timing and opening of the valve | ||
| Variable Valve Actuation (VVA) or Valve-Event Modulation (VEM) are general terms that can be used to describe a range of technologies used to add flexibility to the engine’s valve train by enabling variable valve event timing, duration and/or lift. The main types of VVA technologies include valve timing control (VTC), variable valve lift (VVL) and camless valve trains. | Variable Valve Actuation Systems | VVA | |
| Variable valve actuation or valve actuation modification, which is a general description to describe a group of techniques used to add flexibility to an engine’s usual valve set by changing the factors controlling valve operation by being able to change the timing, duration, or distance of the valves. The main types of technology used include valve timing control, valve opening distance, and camless valve control. | Variable valve actuation systems | ||
| It varies the height that a valve opens, in order to improve performance, fuel economy or emissions. When used in conjunction with variable valve timing, variable valve lift can potentially offer infinite control over the intake and exhaust valve timing. | Variable Valve Lifts | VVL | |
| Valve lift change is a technology now increasingly used in automotive piston engines. It changes the valve intake height (valve travel) to improve performance, fuel economy or emissions. When used in conjunction with variable valve timing, the system can potentially offer complete control over the timing of the exhaust and intake valves. | Valve Aperture Distance Changing Systems | ||
| In internal combustion engines, Variable valve timing (VVT) is the process of altering the timing of a valve lift event, and is often used to improve performance, fuel economy or emissions. There are many in which this can be achieved, ranging from mechanical devices to electro-hydraulic and camless systems. | Variable Valve Timing | VVT | |
| In internal combustion engines, variable valve timing is a procedure for adjusting valve opening, often used to improve performance, fuel consumption, or emissions. There are many ways to do this, from mechanical systems, to electro-hydraulic systems, or camless systems. | Variable valve timing system | ||
| It is an automobile variable valve timing technology developed by Toyota. It varies the timing of the intake valves by adjusting the relationship between the camshaft drive (belt, scissor-gear or chain) and intake camshaft. Engine oil pressure is applied to an actuator to adjust the camshaft position. Adjustments in the overlap time between the exhaust valve closing and intake valve opening result in improved engine efficiency. Variants of the system,including VVTL-i, Dual VVT-i, VVT-iE, and Valvematic, have followed. | Variable Valve Timing with intelligence | VVT-i | |
| It is a technology for changing valve timing in cars, developed by Toyota. It alters the timing of the intake/intake valves by adjusting the motion between the camshaft actuator (belt, gear, or track) and the charge ingress control camshaft, by applying engine oil pressure acting on the actuator to set the full shaft position. It adjusts the overlap between closing the exhaust valves and opening the intake valves, improving engine efficiency. Many similar and advanced systems have been updated after that. | Intelligent timing variable valve system | ||
| It is a version of Dual VVT-i that uses an electrically operated actuator to adjust and maintain intake camshaft timing. The exhaust camshaft timing is still controlled using a hydraulic actuator. This form of variable valve timing technology was developed initially for Lexus vehicles. | Variable Valve Timing – intelligent by Electric motor | VVT-iE | |
| It is a version of the Dual Variable Valve Timing System that uses an electric motor to drive an electric actuator to adjust and maintain the timing of the intake valve camshafts. Exhaust camshaft timing is still controlled by a hydraulic actuator. This type of valve timing technology was originally developed for Lexus. | Intelligent variable timing valve system by electric motor | ||
| The VVTL-i system is based on the VVT-i system and employs a cam changeover mechanism to change theamount of the intake and exhaust valve lift. | Variable Valve Timing and Lift – Intelligent | VVTL-i | |
| This system is based on a system (Variable Timing Valves System with Intelligence) with the addition of a mechanism that controls the amount of valve opening. | Intelligent variable timing and opening distance valve system | ||
| Wide open throttle (WOT) refers to an internal combustion engine’s maximum intake of air and fuel that occurs when the throttle plates inside the carburetor or throttle body are “wide open”, providing the least resistance to the incoming air. In the case of an automobile, WOT is when the accelerator is depressed fully. | Wide Open Throttle | WOT | |
| In the case of an engine, it means the maximum amount of air/mixture entering the engine at which the air intake throttle is open at the maximum opening so as to provide the least resistance to air intake. As for the car, it is when the pedal is at its maximum distance (on the floor). | full throttle opening | ||
| It refers to an engine, motor, process, or other energy source, that emits no waste products that pollutes the environment or disrupts the climate. | Zero Emission Engine | ZEE | |
| Refers to engines, motors, or actuators, which do not emit any emissions or waste that pollute the environment or change the climate. | Zero Emission Engine |
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