Start-stop system


A start-stop system is a technology that automatically shuts down and restarts a vehicle's internal combustion engine to reduce idle time, with the aim of lowering fuel consumption and emissions. The system is most beneficial in urban environments, where vehicles frequently stop and start, such as at traffic lights or in congestion.
Originally developed for hybrid electric vehicles, start-stop systems are now found in a range of conventional vehicles without hybrid powertrains. Reported fuel economy improvements for non-hybrid vehicles range from 3–10%, with some estimates as high as 12%. According to the United States Department of Energy, idling in the United States consumes more than of fuel annually.
Start-stop operation varies by vehicle type. In manual transmission vehicles, the system typically activates when the gear is in neutral and the clutch is released, and restarts the engine when the clutch is pressed. Automatic systems monitor engine load and accessory demand, and may override stop-start functionality under certain conditions, such as use of air conditioning or low battery charge.
To support engine-off functionality, accessories traditionally powered by a serpentine belt—such as air conditioning compressors and water pumps—may be redesigned to run electrically. Some vehicles, such as the Mazda3 equipped with the i-ELOOP system, use a supercapacitor to temporarily power accessories when the engine is off.
Start-stop technology has also been implemented in two-wheel vehicles, such as Honda scooters sold in Asian and European markets.

Characteristics

Start-stop technology was introduced in Europe first because of regulatory differences: 25 percent of the New European Driving Cycle is spent idling, while only an estimated 11 percent of the United States Environmental Protection Agency test is spent idling. Start-stop activation depends on specific driver inputs as well as operating conditions. The engine must have reached the proper temperature to ensure adequate light-off of its catalytic converter and proper lubrication for an effortless restart.
In a car with a manual transmission, engine shutdown typically occurs when braking to a complete stop, shifting the gearbox to neutral, and releasing the clutch. Cars with automatic transmissions shut down upon braking to a full stop; the shutdown is activated by pressing the foot brake pedal when the car comes to a halt. If the car is slowed initially by manual use of the automatic gearbox and final stoppage is achieved by using the handbrake, the engine will not shut down.
A start-stop system only shuts down the engine when it is warm. Most of an engine's wear occurs during cold starts, so the system avoids unnecessary shut downs when the engine is still cold.

Enhanced components

The system needs to be implemented in conjunction with modifications and reinforcements on many of the car's components in order to reinforce the engine and electrical system durability and long-term wear resistance, as added stopping and starting cycles impose increased loads on those systems. To accomplish similar levels of durability, comfort and user experience to that of older cars without the system, the car's manufacturer can include any of the following enhancements in the car's industrial design:
  • The engine main bearings are coated with special polymers that have properties of dry lubricants, such as polyamide. This aids the lack of the motor oil film and hydrodynamic lubrication when the crankshaft stops, preventing metal-to-metal contact that would otherwise produce accelerated wear on the bearing surfaces.
  • The main battery is either absorbent glass mat or enhanced flooded battery technology, both supporting an increased number of charging cycles and increased load. This is important because all the car's electrical system must be maintained by the battery after the alternator stops generating current. Often the battery will be labeled as supporting or specifically designed for start-stop.
  • The starter is reinforced and designed to withstand continuous use without wearing too fast or overheating.
  • An independent cooling circuit is added in conjunction with an electrical runoff water pump that keeps on running when the main mechanical pump goes out. This ensures the coolant supply to heat sensitive engine components like turbocharger bearings and to keep cabin temperature in wintertime.
  • Special sensors and engine control units can be added to ensure proper system running conditions, and to keep parameters between tolerance like a good battery charge, essential to guarantee future starts.

    History

Carbon monoxide emissions and the fuel shortage/oil crisis of the 1970s pushed car manufacturers to find solutions to reduce gas consumption. The first vehicle to use the automatic on/off switch was the six-cylinder Toyota Crown in 1974 and was already claiming a 10% gas saving in traffic. In the 1980s, the Fiat Regata "ES" with the City-matic system and Volkswagen Polo "Formel E" also used similar devices. The Volkswagen Group also adopted it in the Golf Ecomatic in 1994 and in the Volkswagen Lupo "3L" and the Audi A2 "3L" in 1999. Though these early implementations were considered rather disconcerting by many drivers, and high pricing failed to yield these cars much commercial success, both the Volkswagen Lupo and the Audi A2 were more efficient than any production car available in the US at the time of their release.
Since European emission standard Euro 5, more and more vehicles include a start-stop system, whatever the price level, as reducing idling also reduces vehicles' emissions of CO2, a prime cause of global warming.
Manufacturers continued to refine the system. In 2010, Valeo declared that its second Start-Stop generation would appear in the same year. This new generation would be called "i-StARS".The Valeo system is included in Citroën, Land Rover, Peugeot, Smart, and Volvo, while the Bosch system is included in Fiat, Nissan, SEAT, and Volkswagen, with various motorization including essence and diesel. Bosch developed a system for automatic cars.
The Mazda Smart Idle Stop System uses combustion start instead of electrical start. By sensing the position of the pistons in the cylinders, the engine is stopped in a configuration that allows immediate starting by combustion. Mazda claims quieter and quicker engine restart within 0.35 seconds.
The Kia ISG EcoDynamics system uses Bosch, Valeo, and Varta components.

Manufacturers

Alexander Dennis

Some Alexander Dennis Enviro200 MMC and Enviro400 MMC buses are equipped with stop-start systems that will stop the engine at bus stops.

Bentley

Stop-start technology was fitted to a Bentley for the first time in 2016 on the Bentayga model. Bentley's system stops the engine when the car is stopped or moving slowly.

BMW

is including the technology across many of its cars and the MINI line for 2008 as part of its Efficient Dynamics brand. BMW has been interested in ways to reduce parasitic losses on engines, so the company took the technology a step further. Instead of using an Integrated Starter Generator, BMW has used an enhanced starter which is a conventional starter, developed by Robert Bosch GmbH, that can withstand the increased number of engine-starts in a stop-start vehicle.
BMW has developed the system such that the alternator is not activated most of the time. This means that electrical components in the vehicle are normally running on battery power. When the battery needs to be charged or when decelerating or braking, the alternator is activated to recharge the battery. Since this battery experiences very different load characteristics than a normal car battery, BMW used an absorptive glass mat type instead.
Due to the use of regenerative braking, some have started calling this type of system a micro hybrid, a step below a mild hybrid system where the ISG can be used to assist the engine or even drive the vehicle.

Citroën

introduced a more refined system in its C2 and C3 models by 2006, named "Stop and Start". The Citroën implementation combines a SensoDrive automated gearbox and an electronically controlled reversible alternator or integrated starter-generator. An ISG, also known as "integrated starter-alternator", combines the role of the starter and alternator into one unit; manufacturers include Valeo and Denso.

Daihatsu

Daihatsu's "Eco Idle" idling stop mechanism was first installed on some grades of the Daihatsu Move and Move Conte, and gradually became standard for all Daihatsu's kei class vehicles. The system installed in the Mira e:S was the world's first for CVT vehicles with petrol engines. By applying the brakes and automatically stopping the engine when the speed is or less, the fuel consumption is improved by increasing the idling stop time. In addition, by reducing the number of dedicated parts, it achieved additional weight reduction and "compactification".

Fiat Chrysler Automobiles

introduced the Robert Bosch GmbH made system in the end of 2008 in the Fiat 500. Starting in September 2009, Alfa Romeo also introduced this system in its Alfa Romeo Mito series utilising Fiat Powertrain Technologies 1.4 L Turbo petrol MultiAir engines.

Ford

Late in 2010, Ford announced that its start-stop system, already used in its hybrids as well as several mainstream models in Europe, would be introduced in North America with the 2012 models, initially with 4-cylinder engines and later proliferating into V6s and V8s. Eventually, the system became available in all Ford vehicles.
In 2013, it announced that start-stop technology would be brought into the second generation Ford Fusion models, and it built start-stop systems into the Ford F150 2015 model for the first time as a standard feature rather than an option. Formerly, only the 2.7-liter turbocharged V-6 version came with stop-start, which requires a more robust absorbent-glass-mat battery that can better handle the constant cycling and the heavier draw from vehicle accessories with the engine off.