2015 Nissan Murano Active Grille Shutter

The 2015 Nissan Murano introduced a seemingly simple, yet cleverly engineered feature aimed at improving fuel efficiency and aerodynamic performance: the Active Grille Shutter (AGS) system. While it might appear as just another piece of plastic behind the grille, the AGS is a sophisticated piece of engineering designed to reduce drag and optimize engine operating temperature. Let's delve into the technical details of how this system works.

What is an Active Grille Shutter?

At its core, an Active Grille Shutter is a system of electronically controlled louvers positioned within the vehicle's front grille. These louvers can open and close based on various sensor inputs and a pre-programmed control strategy. When closed, the shutters significantly reduce airflow into the engine compartment. This seemingly counterintuitive action can actually improve fuel economy and enhance engine performance under certain driving conditions.

Components of the 2015 Murano AGS System

The 2015 Murano's AGS system consists of several key components working in concert:

• Grille Shutters: These are the movable louvers themselves, typically made of a durable plastic composite material resistant to heat, impacts, and road debris. Their design is crucial for both effective airflow blockage when closed and minimal restriction when open.
• Actuator Motor: An electric motor that drives the opening and closing of the grille shutters. It's a relatively compact unit, designed for reliable and precise operation over a wide range of temperatures and conditions. The Murano uses a DC motor with a worm gear reduction to provide sufficient torque.
• Control Unit (ECU): This is the "brain" of the AGS system. It receives input from various sensors and uses a pre-defined algorithm to determine the optimal position of the grille shutters. This ECU is typically integrated with the vehicle's main engine control unit (ECU).
• Sensors: Multiple sensors provide the necessary data for the ECU to make informed decisions. Critical sensors include:
  • Coolant Temperature Sensor: A primary input, indicating the engine's current operating temperature.
  • Ambient Air Temperature Sensor: Provides information about the external temperature, influencing the cooling needs of the engine.
  • Vehicle Speed Sensor: Crucial for determining aerodynamic drag reduction needs.
  • Engine Load Sensor (MAP/MAF): Gives the ECU an indication of how hard the engine is working.
  • (Potentially) Radiator Outlet Temperature Sensor: Some implementations include a sensor after the radiator to monitor cooling efficiency.
• Linkage and Mechanical Components: A system of linkages and levers connects the actuator motor to the grille shutters, translating the motor's rotational motion into linear movement of the louvers. These components must be robust and precisely engineered to ensure smooth and reliable operation.

How the System Works: Aerodynamic Benefits

The primary benefit of the AGS system is the reduction of aerodynamic drag. At higher speeds, a significant portion of a vehicle's energy is expended overcoming air resistance. By closing the grille shutters, the AGS system streamlines airflow around the front of the vehicle. This reduces turbulence and minimizes the amount of air entering the engine compartment, which is an area of significant drag. The reduced drag translates directly into improved fuel economy, especially at highway speeds. This is because the engine needs to work less hard to maintain a given speed.

Consider this scenario: a Murano traveling at 65 mph. With the AGS open, air rushes into the grille, impacting the radiator, engine block, and other components. This creates turbulence and increases drag. However, with the AGS closed, the air is forced to flow smoothly over the front of the vehicle, reducing the drag coefficient and improving fuel efficiency. The exact amount of fuel savings is dependent on various factors like speed, driving conditions, and overall vehicle condition, but the improvement is measurable.

How the System Works: Thermal Management Benefits

Beyond aerodynamics, the AGS system also plays a role in engine thermal management. When the engine is cold, the AGS can remain closed to help it reach its optimal operating temperature more quickly. This is particularly beneficial in cold weather conditions, as it reduces the time it takes for the engine to warm up, improving fuel economy and reducing emissions. Faster engine warm-up also translates to quicker cabin heating, enhancing passenger comfort.

Once the engine reaches its optimal operating temperature, the ECU will modulate the position of the grille shutters to maintain that temperature. If the engine starts to overheat (due to high engine load or hot ambient temperatures), the AGS will open fully to allow maximum airflow through the radiator, providing maximum cooling capacity. This dynamic control allows the system to optimize engine temperature for both performance and efficiency.

Furthermore, the AGS can help maintain a more stable engine temperature in stop-and-go traffic. By closing when the vehicle is stationary, it prevents excessive cooling of the engine by the ambient air, helping to avoid temperature fluctuations.

Control Logic and Decision Making

The ECU's control logic is complex and takes into account multiple factors. Here's a simplified overview:

1. Engine Start-up: Typically, the AGS will be closed upon engine start-up, especially in colder temperatures, to accelerate engine warm-up.
2. Low Speed/Low Load: At low speeds and under light engine load, the AGS may remain closed or partially closed to reduce drag and maintain engine temperature.
3. High Speed/High Load: At higher speeds or under heavy engine load, the AGS will open to provide maximum cooling to the engine.
4. Temperature Thresholds: The ECU uses temperature thresholds to trigger changes in the AGS position. For example, if the coolant temperature exceeds a certain limit, the AGS will open.
5. Fault Detection: The system also incorporates fault detection mechanisms. If a sensor fails or the actuator motor malfunctions, the ECU will likely trigger a warning light on the dashboard and may disable the AGS system to prevent potential engine damage. In most cases, the shutters will default to the open position in the event of a failure to ensure adequate cooling.

Potential Issues and Maintenance

While the AGS system is relatively reliable, it is not immune to problems. Common issues include:

• Actuator Motor Failure: The actuator motor can fail due to wear and tear or exposure to the elements.
• Sensor Malfunctions: Faulty temperature or speed sensors can provide incorrect data to the ECU, leading to improper AGS operation.
• Linkage Problems: The linkages connecting the actuator motor to the shutters can become damaged or disconnected.
• Debris Obstruction: Road debris can sometimes get lodged in the grille and prevent the shutters from opening or closing properly.

Maintenance is generally limited to visual inspection to ensure that the shutters are free from obstructions and that the linkages are intact. In some cases, the actuator motor may need to be lubricated. If a sensor or the actuator motor fails, replacement is typically the only option.

Conclusion

The Active Grille Shutter system on the 2015 Nissan Murano represents a smart application of technology to improve fuel efficiency and optimize engine performance. By dynamically controlling airflow into the engine compartment, the AGS system reduces drag, accelerates engine warm-up, and maintains optimal engine temperature. While seemingly a minor component, the AGS plays a significant role in the overall efficiency and performance of the vehicle. Understanding the technical details of this system provides valuable insight into the sophisticated engineering behind modern vehicles and the ongoing efforts to improve fuel economy and reduce emissions. As aerodynamic improvements continue to play a key role in vehicle design, similar AGS systems will likely become even more prevalent in future models.