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Simple and Easy to Understand: The March's Idling Stop System

Known as the "Eco-March," the new March aims to have the best fuel economy among compact cars. Its main feature is the Idling Stop system. Here we will explain the mechanism of the Idling Stop system as simply as possible.

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2011/02/07

The March's Idling Stop system was brought up in the previous article "The present and future of compact cars - on the streets of Takamatsu in Kagawa, Japan's smallest prefecture." Take a March for a ride and the silence of the engine when idling is sure to make you a believer. What's more, when you go to give it some gas, it almost feels as though the car has anticipated your intention and revved up the engine for you. No, it's certainly not as simple as the system just stopping and starting the engine. Here we will explain the mechanism of the Idling Stop system as simply as possible.
Known as the "Eco-March," the new March aims to have the best fuel economy among compact cars. Its main feature is the Idling Stop system. The system improves fuel economy by automatically stopping the engine when the car stops, and restarting it when the driver removes his or her foot from the brake. By using the Idling Stop system along with other fuel economy improving technology, the March achieves a best in class*1 fuel economy of 26.0km/L*2 *3.
At first glance, the Idling Stop system is a simple function that stops and restarts the engine, but incorporated into it is an innovative design concept created by the engineers. If a car featuring the Idling Stop system cannot be driven in the same manner as cars the driver is used to, undue stress will be placed on the driver. For this reason, with the March Nissan aimed for an Idling Stop system that "does not disturb the driver." The driver receives the benefits of improved fuel economy without ever even noticing that the Idling Stop system is working.
Let's not forget that the March is a compact car aimed at people from all walks of life. As it is a compact car, starting with cost there are all sorts of restrictions, and it was necessary to create an Idling Stop system appropriate for a compact.

For a Quick Start

The key to creating an Idling Stop system that does not disturb the driver is the speed of restarting the engine. With the new March's Idling Stop system, when the car is stopped at a stoplight etc, with the engine stopped and the driver with his or her foot on the brake, the engine restarts within approximately 0.4 seconds of the driver releasing the brake. When starting off from a light that has just gone from red to green it usually takes about one full second for the driver to release the brake and step on the accelerator. Therefore 0.4 seconds is fast enough for the system to go unnoticed.

By using an electric oil pump that transmits oil pressure almost instantly to reduce time loss, as well as a large-scale starter and high performance battery, the new March greatly reduces engine start time. Additionally, the CVT's (Continuously Variable Transmission) electric oil pump reduces the time needed for driving force transmission.

Another of the March's Idling Stop system's features is the reliability of the 0.4-second engine start time. In order for the engine to always start in only 0.4 seconds, the stopping position of the pistons within the engine is controlled. Using the engine's inertial force and the momentum of the compressed air, the pistons are always stopped in the ideal position.

When the Idling Stop system is active the engine is stopped, but the internal computer is not. This also contributes to the speed of restart.

The Idling Stop System Isn't Always Active?

The new March's Idling Stop system does not automatically activate when the car stops. For example, on a steep hill with a gradient of more than 6%, or after an initial start in the winter when the engine coolant temperature is still low, the Idling Stop system does not activate. In other words, in situations where it is possible that the restart and initial acceleration cannot be accomplished smoothly the engine does not stop. When the Idling Stop system is activated, the air conditioning automatically switches to ventilation. In cases where the in-car temperature greatly exceeds the set temperature, or where the fuel economy will actually be made worse (when frequently starting and stopping), the Idling Stop system is also setup to not activate. In this way it was developed with the customer's ease and freedom of use in mind.

However, in the majority of cases when stopping the car, the Idling Stop system does activate. In other words, we have increased the number of situations in which the system can be utilized to the greatest possible extent, keeping the engine running only when it is absolutely unavoidable. This is because we want to use the Idling Stop system as much as possible and therefore maximize the reduction of fuel consumption.

Additionally there was concern that, when accelerating from an Idling Stop with the engine off, on a hill the car would roll back during the time needed to restart the engine. In response, we used a new lock system to control the amount of roll back and increase stability when starting up hill. The lock system locks the CVT's 1st and 2nd gear clutch preventing the tires from turning, making use of the Idling Stop system possible on hills with a gradient up to 6%.

The March can also use its Idling Stop system when waiting to make a right turn. In this case, the engine restarts when the wheel is turned. This is because when turning right the majority of drivers begin turning the wheel before releasing the brake. By detecting the driver's intention through the turning of the wheel, this set-up allows for an imperceptible engine start and makes it possible to the use the Idling Stop system when turning right.

The New Serena's Quiet Idle-Stop System

With "ECO Model Change" as its slogan, the new Nissan Selena also features an Idling Stop system. Serena does not use the starter system used by the March and many other cars, but instead utilizes the ECO Motor (Energy Control Motor) system. The ECO Motor is a setup where the engine is restarted directly via the belt. By using the belt system, the crank's coupling pulley is rotated directly, improving start time and reducing engine noise.

As a family car, the low engine noise is a major benefit for the Serena. At Nissan we are always striving to create the most ideal Idling Stop systems, fit to the characteristics of each car.
hattori.jpgEditor: Nissan Automobiles Power Train Development Section (New March Idle-Stop System Development)
Motoyuki Hattori
*1 1.0-1.5L Class. Not including hybrid cars. (Current as of Dec. 2010 Research by Nissan)
*2 10·15 Mode fuel consumption rate (Ministry of Land, Infrastructure, Transport and Tourism test value). The fuel consumption rate is a value based on fixed test conditions. The actual fuel consumption rate will vary based on customers' usage environment (weather, traffic etc) or driving method (sudden acceleration, air conditioning usage).
*3 12G, 12X