Gliding is an

energy-efficient driving Energy-efficient driving techniques are used by drivers who wish to reduce their fuel consumption, and thus maximize fuel efficiency. The use of these techniques is called "hypermiling". Simple fuel-efficiency techniques can result in reduction ...

mode achieved by turning off the

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which 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 combus ...

while the vehicle is still moving in order to save fuel. This is differentiated from coasting, which means running the vehicle in idle mode by disengaging the engine from the wheels, either by disengaging the clutch or setting the transmission or gearbox to neutral position.Konrad Reif, Karl E. Noreikat, Kai Borgeest: ''Kraftfahrzeug-Hybridantriebe''. Gliding and coasting use the accelerated

kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...

reserve stored in the vehicles mass, i.e. inertia, to keep the vehicle moving. This energy, however, is being lost due to forces that resist movement, such as air-drag, rolling resistance and gravity. The functionality, being an integral concept of

hybrid electric vehicle A hybrid electric vehicle (HEV) is a type of hybrid vehicle that combines a conventional internal combustion engine (ICE) system with an electric propulsion system ( hybrid vehicle drivetrain). The presence of the electric powertrain is intende ...

s, is performed automatically by the engine controller. For vehicles with a conventional internal combustion engine, coasting can be performed manually; gliding requires having a gear box.bosch-presse.de
''Erweitertes Start/Stopp-System von Bosch spart noch mehr Kraftstoff'', retrieved 14 September 2013 Manual gliding or coasting is illegal in some states. An extra button to stop the engine was shown in 1979 on

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, but never became a feature in mass production of any vehicle. In 1980 research was made on the IRVW II. A so-called ''eClutch'' (electronic controlled clutch) uses an

actuator An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover". An actuator requires a control device (controlled by control signal) a ...

to disengage the clutch when the driver releases the accelerator. A

start-stop system A vehicle start-stop system or stop-start system automatically shuts down and restarts the internal combustion engine to reduce the amount of time the engine spends idling, thereby reducing fuel consumption and emissions. This is most advanta ...

turns the engine off when the vehicle is stopped. Gliding is turning off the engine while the vehicle is still moving. Safety relevant components like

power steering A power steering is a mechanical device equipped on a motor vehicle that helps drivers steer the vehicle by reducing steering effort needed to turn the steering wheel, making it easier for the vehicle to turn or maneuver at lower speeds. Hydraul ...

vacuum servo A vacuum servo is a component used on motor vehicles in their braking system, to provide assistance to the driver by decreasing the braking effort. In the US it is commonly called a brake booster. A vacuum servo also known as a power booster o ...

might be required to be electrically powered, but in most vehicles these components are driven by the combustion engine, only. The fuel saving is depending more on the road terrain and traffic conditions. It is assumed to save up to 7% fuel in the NEDC driving cycle; in real road traffic conditions, the savings is estimated to be up to 10%.

Coasting

Coasting is continuing the vehicle to move by disengaging the clutch or by selecting neutral gear, with the proviso that it is not necessary to do so in order to facilitate easy control of the vehicle. Having the clutch disengaged at low speeds or when the engine would provide little or no

engine braking Engine braking occurs when the retarding forces within an engine are used to slow down a motor vehicle, as opposed to using additional external braking mechanisms such as friction brakes or magnetic brakes. The term is often confused with seve ...

is not classified as coasting, it is merely facilitating easier car control. It may also be seen as driving the vehicle at a higher speed than the idle speed of the engine and then disengaging the engine from the wheels by setting the transmission or gearbox to neutral position or disengaging the clutch, maintaining the engine in idle mode.

Gliding a conventional vehicle

Pushing the clutch pedal disengages the engine from the powertrain like wheels, drive shafts and gearbox. Releasing the accelerator makes the engine slow down to idle. Turning off the ignition has further effects. Pulling the key causes locking of the steering wheel. Some vehicles switch off headlights or brake lights when the ignition is turned off. After the engine is stopped, applying the brake takes a longer time or giving a few pushes to the brake releases the reserve of the

, causing a loss of the brake support. In addition, belt-driven

fails immediately. Real hybrid vehicles have electric-driven support of power steering and brake. Bigger engines and engines with a higher

compression ratio The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values. A fundamental specification for such engines, it is measured two ways: the stati ...

can cause damage to components of the

powertrain A drivetrain (also frequently spelled as drive train or sometimes drive-train) is the group of components that deliver mechanical power from the prime mover to the driven components. In automotive engineering, the drivetrain is the components o ...

at a rough start over clutch from gliding vehicles kinetic power or trailing drag. Using a higher gear decreases the torque force on the powertrain. By turning off the ignition the engine control unit (ECU) needs to detect the engine shafts position. Some ECUs need several rotations of the

camshaft A camshaft is a shaft that contains a row of pointed cams, in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines (to operate the intake and exhaust valves), mechanically controlled ignition systems ...

to detect ignition and injection timing. Starting the engine in cold start temporarily takes more fuel until operation temperature of the engine is detected by the ECU. Gliding vehicles equipped with

torque converter A torque converter is a type of fluid coupling that transfers rotating power from a prime mover, like an internal combustion engine, to a rotating driven load. In a vehicle with an automatic transmission, the torque converter connects the power ...

-based

automatic transmission An automatic transmission (sometimes abbreviated to auto or AT) is a multi-speed transmission used in internal combustion engine-based motor vehicles that does not require any input from the driver to change forward gears under normal driving c ...

s causes damage due lack of lubrication. Also, restarting the engine by clutch from the vehicle's kinetic energy or drag is not possible. It is required to use the starter. Gliding a vehicle with a turbo engine makes the remaining heat from the exhaust cause damage in the bearing of the turbo.{{cite web , url=https://www.youtube.com/watch?v=VKKT5yNQymQ , title=Was sorgt für Peugeot-DPF-Problem? VW-Standard-Fehler Kraftstoffleitung & verbaute Qashqai-Sicherung - YouTube , website=

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Unsynchronized transmissions require double clutching and can not get the gear in at differing vehicle and engine speeds.

References and Remarks

Driving techniques Energy conservation Transport economics

Coasting

Gliding a conventional vehicle

See also

References and Remarks