Enhanced Stop & Start System

Enhanced Stop & Start System: The New Generation of Fuel Economy

In the constant pursuit of reducing fuel consumption and CO2 emissions, automakers have developed numerous technologies. Among them, the Stop & Start system has become a standard. However, a more advanced version is gaining ground: the enhanced Stop & Start system. Much more than a simple engine shut-off when stationary, it represents a significant advancement in efficiency and refinement.

What is the enhanced Stop & Start system?

The enhanced Stop & Start, often associated with mild-hybrid powertrains, is an optimized version of the conventional system. It uses higher-performance components to enable more frequent, faster stops and restarts across a broader operating range. The key elements of this technology are:

• The belt-driven starter-alternator (or MGU - Motor Generator Unit): In many cases, the traditional starter is replaced by a belt-driven starter-alternator. This single component handles both engine restarts and battery recharging. It allows for much smoother, faster, and quieter restarts than a conventional starter.
• The specific battery: The system requires a more robust battery, such as an AGM (Absorbent Glass Mat) or EFB (Enhanced Flooded Battery) type. These batteries are designed to withstand deep discharge cycles and recharge very quickly, particularly thanks to regenerative braking.
• Advanced electronic management: A powertrain control module continuously analyzes multiple parameters (vehicle speed, battery charge level, air conditioning demand, etc.) to determine the optimal moment to shut off or restart the engine, thereby maximizing fuel-saving phases.

Operation and differences compared to a conventional system

The main difference lies in the extent of its action. Whereas a basic Stop & Start only cuts the engine once the vehicle is completely stationary, the enhanced version can anticipate it. Thanks to its intelligence and the power of the starter-alternator, it can activate the "coiling" or "sailing" function.

This function shuts down the internal combustion engine when the driver releases the accelerator at a stabilized speed, letting the car coast. The engine restarts instantly and imperceptibly as soon as the driver touches the accelerator or brake pedal again. This engine-off coasting, impossible with a standard system, yields substantial fuel savings on highways or major roads.

The tangible benefits of the enhanced Stop & Start

The adoption of this technology offers several notable benefits for the driver and the environment:

• Increased savings: By multiplying the opportunities to shut off the engine, including while driving, consumption gains can reach up to 0.7 L/100 km compared to a non-equipped vehicle, representing a noticeable improvement over a conventional Stop & Start.
• Driving comfort: Gone are the sometimes noticeable vibrations and noise of restarts. The starter-alternator ensures transitions that are so fluid they become almost imperceptible, greatly enhancing the driving experience, especially in heavy traffic.
• Durability: The components, from the engine to the battery, are specifically sized to endure tens of thousands of stop/start cycles without premature wear.
• Performance: In 48V mild-hybrid systems, the starter-alternator can also provide a slight torque boost to the combustion engine during acceleration, thereby improving roll-on recovery.

Maintenance and considerations

A vehicle equipped with an enhanced Stop & Start system requires special attention when replacing the battery. It is imperative to use a battery of the same technology (AGM or EFB) as the original one. Failure to follow this recommendation can lead to system malfunctions and a greatly reduced battery lifespan. Furthermore, replacement often requires resetting via a diagnostic tool so that the energy management system recognizes the new battery and adjusts its charging cycles accordingly.

In conclusion, the enhanced Stop & Start system is not a mere gimmick. It is a foundational technology, at the heart of automakers' mild electrification strategy, which delivers tangible gains in energy efficiency and everyday usability.