Cylinder deactivation

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The cylinder deactivation is a system developed at the end of the 1970s to reduce the fuel consumption of gasoline engines .

In driving situations with low power requirements, the fuel supply is interrupted or no fuel is injected. The valves of the deactivated cylinders are kept closed in order to avoid gas exchange losses. This measure was able to reduce fuel consumption by up to 15% at the end of the 1990s. Depending on the system, either a complete cylinder bank ( V engines ) or individual cylinders (individual cylinder deactivation) can be switched off. The system is mainly used because of a certain minimum smoothness, mainly in engines with at least eight cylinders. But it is also used in smaller engines, such as the three-cylinder EcoBoost engine of the Fiesta ST of the eighth model series with a displacement of 1.5 liters .

With hybrid drives, the entire combustion engine is switched off and operated in electric mode; here one speaks of an "engine shutdown".

functionality

Two methods are used to control the torque : quantity and quality control.

  • The quantity control used primarily in " homogeneous " gasoline engines works largely with a constant ratio of air to fuel. A reduction in the amount of air results in a lower amount of fuel and thus a lower indicated torque. In conventional engines, a throttle valve is used to reduce the amount of air . In the low load range, the throttle valve is closed very far, which is why there are throttle losses : The air is blocked through the small opening and thus brakes the piston. This deceleration can only be compensated to a limited extent by increasing the amount of fuel (see stoichiometric fuel ratio ). Cylinder deactivation provides a remedy here. In order to obtain the same torque when individual cylinders are switched off, more petrol must be burned in the remaining fired cylinders. Due to the fixed combustion air ratio, more air is required, which is why the throttle valve can be opened further. The throttling losses therefore also decrease in these cylinders that are still working, and some fuel can be saved. The friction and pumping losses of the unfired cylinders that continue to move along remain in place.
  • The quality control regulates the ratio of air and fuel ( combustion air ratio ) and thus determines the torque; it is mainly used in diesel engines. In principle, the same amount of air is always used here and the torque is controlled by regulating the amount of fuel injected directly. There is no throttle. This is why the consumption advantage of diesel engines is greater, especially in the low load range.

Since in gasoline engines with fully variable valve train and in diesel engines the torque is regulated without a throttle valve at all, cylinder deactivation is almost pointless with these engine types.

Use in motor vehicles

Daimler had offered cylinder deactivation in the 5-liter V8 version of the S-Class and CL ( M 113 engine) as an option until around 2005. The technology had previously been used in the comparatively short-lived M 137 V12 engine. The Mercedes sister AMG wanted to reduce the consumption of their models by 30 percent by 2012; To do this, in 2011 they brought a new gasoline direct injection V8 engine to the SLK 55 AMG , which uses a further developed version of cylinder deactivation and at times only works with four cylinders. Cylinder deactivation is also used in the Mercedes E63 AMG (2017) .

Other manufacturers that use cylinder deactivation have been the Hemi V8 engines (5.7 liter displacement) from Chrysler, Jeep and Dodge since 2005 .

At Honda, the technology is sometimes even used in four-cylinder engines such as the Honda Civic Hybrid . GM uses them under the name "Active Fuel Management" in various V8 and some V6 engines. One of the appropriately equipped models is the Chevrolet Camaro SS introduced in 2010 .

The technology has also been used in four-cylinder engines from the VW Group since 2012 under the name "Active Cylinder Termination" (ACT). Audi has also been using cylinder deactivation in the 4.0 biturbo V8 since 2012 and installs these engines in the Audi S6 , Audi S7 , Audi RS7 and Audi S8 .

With the introduction of the new Fiesta ST from spring 2018, the new three-cylinder Ford EcoBoost with a displacement of 1.5 liters will also receive cylinder deactivation.

If cylinders are switched off in partial load operation, this is also known as “dynamic downsizing ”.

Web links

Wiktionary: cylinder deactivation  - explanations of meanings, word origins, synonyms, translations

literature

  • Peter A. Wellers, Hermann Strobel, Erich Auch-Schwelk: Vehicle technology expertise. 5th edition, Holland + Josenhans Verlag, Stuttgart 1997, ISBN 3-7782-3520-6 .

Individual evidence

  1. ↑ Cylinder deactivation : fun with eight, save with four. Handelsblatt, July 17, 2009, accessed on June 1, 2018 .
  2. ↑ Tom Greenway: Business printed matter. Mercedes E 63 AMG. SPIEGEL ONLINE, July 22, 2011, accessed June 1, 2018 .
  3. ↑ heise Autos: VW brings cylinder deactivation to the 1.4 TSI
  4. ↑ Rainer Golloch: downsizing of internal combustion engines, VDI-Book, 2005, p.75