Sailing (motor vehicles)

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Representation of sailing with motor vehicles. Speed ​​50 km / h. Upper picture "Sailing" (engine off), lower picture "Idle sailing" (engine idling). Manually shown with a conventional vehicle.

In a motor vehicle, the term sailing describes the function of switching off the internal combustion engine while driving and decoupling it from the drive train. This has the advantage that existing kinetic energy to use for locomotion, rather than in the form of drag power to lose. In hybrid vehicles , this function is part of the drive concept, to which the engine management system automatically changes. The coasting function can be used in conventional switching vehicles with internal combustion engines. The stop button for switching off the internal combustion engine was presented at the IAA 1979 , but did not become standard equipment in vehicles. The so-called eClutch (electronic clutch) automatically activates the clutch pedal via an actuator when the driver takes off the accelerator pedal.

In contrast to the start-stop system , in which the engine is only switched off when the vehicle is stationary, the engine is switched off when sailing when coasting. Safety-relevant functions such as power steering or brake booster are secured via the on-board network. The use of the sailing function depends on the driving profile of a route. It is assumed that up to 7% fuel can be saved in the NEDC, and up to 10% in real traffic.

Automatic sailing

With so-called idle coasting , the drive train is decoupled at higher speeds as soon as the driver takes his foot off the accelerator and does not brake; the combustion engine is not switched off, but continues to idle . In addition to coasting at idle, the engine is switched off in hybrid vehicles, which further reduces consumption.

Sailing with a conventional vehicle

If the clutch is operated manually, the existing kinetic energy can be used by pressing the clutch. The overrun cut-off is canceled by idling. If the ignition is switched off, this has further effects. Removing the ignition key also causes the steering lock to click into place . Some vehicles switch off the function of the headlights or brake lights when the ignition is switched off. When the engine is at a standstill, the vacuum-fed brake booster fails after the brake is operated several times. Belt-driven steering aids ( power steering ) fail immediately. For this reason, real hybrid vehicles use electric steering aids and electric brake boosters. Heavy and higher compression engines can cause damage to the drivetrain due to high forces if the vehicle is started roughly via the clutch of the rolling vehicle. A higher gear reduces the load on the drive train. Engine control units that are switched off by the ignition lose the memory due to the engine's angle of rotation and sometimes require several revolutions of the camshaft to control the engine with injection and ignition timing again. When starting a cold start , a larger amount of fuel can be consumed for a short time than with a comparable operation of a warm-up engine.

Vehicles with converter automatic transmissions can cause damage when sailing. Starting by towing is not possible; the starter must be operated. With a turbo engine, coasting can damage the turbo charger's slide bearing, as it is exposed to the temperatures of the exhaust gases and is cooled by the engine oil. In the case of unsynchronized transmissions that require double clutches, the gear cannot be engaged if the engine speed does not come close to the driving speed for this gear.

See also

References and comments

  1. ↑ a b Konrad Reif, Karl E. Noreikat, Kai Borgeest: automotive hybrid drives . Vieweg + Teubner Verlag 2012, ISBN 978-383482-050-1 . P. 16
  2. ↑ a b c bosch-presse.de Extended start / stop system from Bosch saves even more fuel (accessed on September 14, 2013)
  3. ^ IAA 1979 - Porsche 928 S.
  4. ↑ pressrelations.de The eClutch saves fuel and increases comfort (accessed on September 19, 2013)
  5. ↑ bmwgroup.com press release from May 6, 2013 (accessed on September 15, 2013)
  6. ↑ porsche.com  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. (PDF; 10.7 MB) 911 (accessed September 15, 2013)@1@ 2Template: Dead Link / www.porsche.com  
  7. ↑ BMW offers coasting in the automatic transmission , Porsche in the dual clutch transmission .
  8. ↑ https://www.youtube.com/watch?v=VKKT5yNQymQ