Stop-start system

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On / off button for the stop-start system in a Citroën Berlingo

A stop-start system or start-stop system , also known as an automatic start-stop system , is an automatically operating system for reducing fuel consumption when the vehicle is stationary (e.g. when stopping at traffic lights), especially in city traffic. It switches off the engine when stationary under certain conditions and starts it again automatically. It is used in several car models and scooters , but currently (as of April 2011) not in motorcycles . In the operating instructions for Opel models, the start-stop system is referred to as the start / stop system , and in the Citroën and Peugeot as the stop & start system .

functionality

Systems up to approx. 2000

In order to achieve fuel savings with otherwise unchanged engines after the first oil shock, the automatic start-stop system was invented by Toyota in the mid-1970s . The engine was automatically switched off by an electronic device after 1.5 seconds of idling.

At the beginning of the 1980s, the automatic start-stop system was also introduced by Audi and VW . The engine could be switched off at the push of a button without switching off the ignition. The prerequisite was that the engine had already reached operating temperature. When the clutch was actuated, the engine was restarted by the starter without using the ignition key. This system, which was combined with other measures such as an electronic gearshift and fuel consumption indicator, aerodynamics package and 5-speed gearbox with a particularly long-ratio fifth gear (referred to as 4 + E ), worked reliably, but did not meet with much customer acceptance. It was used, for example, in the VW Santana B2 and the Audi 100 C2 . The Italian manufacturer Fiat followed a similar path in 1983 : The Regata 70 ES (ES for Energy Saving ) had an on / off switch for the engine and could be restarted by pressing the accelerator pedal. The Opel Ascona C had since 1985 also a start-stop system and a transmission with a longer translation ( "Already gear"), with the same functionality as Audi and VW. From 1994, the VW Golf III Ecomatic was equipped with an automatic start-stop system and an automatic clutch that switched off the engine every time the accelerator was released. He also had an automatic swing use mechanism .

Systems from around 2000

In 1999 the Volkswagen Group took up the concept of a start-stop system again in the low-energy vehicles VW Lupo 3L and Audi A2 3L . This function was combined with the standard automated manual transmission . The automatic engine shutdown only takes place in the economy mode of the automatic transmission if the footbrake is pressed for longer than three seconds. In addition to various temperature specifications (outside, intake air and coolant temperature), the low beam had to be switched off for this system to work.

A new generation of start-stop systems followed in the 2000s. As a result of the discussion on global warming, as well as stricter legal requirements for CO 2 emissions from motor vehicles, many automobile manufacturers have been offering start-stop systems since then. The designation "blue" or "eco" is often referred to in conjunction with other components in the vehicle description (including BlueEFFICIENCY at Mercedes-Benz , BlueMotion - formerly also Ecomatic - at Volkswagen , GreenLine at Škoda , Blue Drive at Hyundai and ECOnetic at Ford , ecoFLEX at Opel - but there are also Opel ecoFLEX models without a start-stop system - or EfficientDynamics at BMW , PUR O2 at Fiat , i-stop at Mazda , micro hybrid drive (mhd) at smart , DRIVe at Volvo , e-HDi at PSA Peugeot Citroën or Ecomotive at Seat ).

Modern systems switch the motor on engagement of idling and release of the clutch from. When the clutch pedal is pressed, the engine starts again; in automatic transmissions, the reduction in pressure in the brake system when the footbrake is released causes the engine to start. These systems only work if certain temperature specifications are adhered to (engine, outside temperatures in a certain range, e.g. between 3  ° C and 30 ° C). The systems do not work if, for example, the battery is severely discharged, if the internal temperature has not yet reached the value preselected by the air conditioning system, if there is no longer enough vacuum in the brake booster or in heating mode. Opening the seat belt buckle or the bonnet or driver's door also prevents the automatic engine stop. When the engine is switched off, an automatic engine start is also carried out if the battery voltage is very low or there is no longer any vacuum in the brake booster or if you want to let the vehicle roll downhill.

In combination with start-stop systems, some vehicle manufacturers use more powerful starters and batteries with more capacity , for which AGM batteries are preferred . The use of starter generators was also discussed.

Advanced systems

Energy can be stored in so-called super capacitors . You can absorb and release energy quickly; they also relieve the battery. Citroën and Peugeot's e-HDi diesel engines have been using these capacitors since 2010.

Potential savings

According to ADAC estimates , such systems can save between 2 and 3 percent of fuel, according to BMW, significantly more in city traffic. When comparing two systems in the same test vehicle, Siemens found savings of 4 to 7%.

Other studies show that the potential savings with start-stop systems depend on the driving profile. Based on the New European Driving Cycle NEDC with a high proportion of simulated city driving, savings of 4.3% to 12.1% for a Mercedes SL 500 with the Smart ForFour Diesel and Mercedes A 200 can be assumed. With the Smart, the savings in the NEDC are around 0.185 l per 100 km.

Individual evidence

  1. Guido Gluschitsch: Start-stop system also in the scooter. In: derstandard.at . February 8, 2010, accessed December 30, 2014 .
  2. ^ Bob Dunham: Automatic on / off switch gives 10-percent gas saving . In: Bonnier Corporation (Ed.): Popular Science . October 1974, p. 170 (English, google.com [accessed February 14, 2012]).
  3. VW Santana Formula E at http://www.santanagx5.de. In: santanagx5.de. January 2007, accessed March 13, 2019 .
  4. Listino Fiat Regata. In: quattroruote.it. Retrieved August 25, 2016 (Italian).
  5. focus.de June 9, 2010
  6. ↑ Switch off the engine when it is red - a short turn helps save fuel. N24, July 30, 2008, accessed on July 12, 2010 : “For its automatic start-stop system, BMW determined a saving of three percent in the EU test cycle. "That is significantly more in pure city traffic."
  7. Rampeltshammer, Beer u. a .: Direct petrol injection and starter generator - practical experience and measurement results with a test vehicle. Conference "Hybrid Drive - The Future of Automobile Drive?"; 16.-17. June 2005, Berlin
  8. Klaus Schreiner: Basic knowledge of the combustion engine. 2nd edition, Springer Fachmedien, Wiesbaden 2015, ISBN 978-3-658-06187-6 ; The calculations in section 6.16 are based on map data in the MTZ for the period between 2004 and 2005