Idling Stop Technology | i-stop

Idle stop systems save fuel by shutting down a vehicle’s engine automatically when the car is stationary and restarting it when the driver resumes driving. Especially in urban areas, drivers often let their car’s engine idle at traffic lights or when stopped in traffic jams. Switching off the engine to stop it idling in these situations enhances fuel economy by about 10% under Japan’s 10-15 mode tests.

Conventional idling stop systems restart a vehicle’s engine with an electric motor using exactly the same process as when the engine is started normally. Mazda’s ”i-stop”, on the other hand, restarts the engine through combustion. Mazda’s system initiates engine restart by injecting fuel directly into a cylinder while the engine is stopped, and igniting it to generate downward piston force. This system not only saves fuel, but also restarts the engine more quickly and quietly than a conventional idle-stop system.

• Piston stop position control and combustion restart technology

In order to restart the engine by combustion, it’s vital for the compression-stroke pistons and expansion-stroke pistons to be stopped at exactly the correct positions to create the right balance of air volumes. Consequently, Mazda’s ”i-stop” effects precise control over the piston positions during engine shutdown. With all the pistons stopped in their optimum position, the system restarts the engine by identifying the initial cylinder to fire, injecting fuel into it, and then igniting it. Even at extremely low rpm, cylinders are continuously selected for ignition, and the engine quickly picks up to idle speed.

Thanks to these technologies, the engine will restart with exactly the same timing every time and will return to idle speed in just 0.35 seconds, roughly half the time of a conventional electric motor idling stop system. As a result, drivers will feel no delay when resuming their drive. With the ”i-stop”, Mazda can offer a comfortable and stress-free ride as well as better fuel economy.

INTERVIEW QUESTIONS:GERNAL:

• Explain the Second Law of Thermodynamics.
  The entropy of the universe increases over time and moves towards a maximum value.

 

• How do you measure temperature in a Wet Bulb Thermometer?
  Wet bulb temperature is measured in a wet bulb thermometer by covering the bulb with a wick and wetting it with water. It corresponds to the dew point temperature and relative humidity.

 

• What is Bending moment?
  When a moment is applied to bend an element, a bending moment exists in the element

 

• What are the points in the Stress Strain curve for Steel?
  Proportional limit, elastic limit or yield point, ultimate stress and stress at failure.

 

• Define Reynolds number.
  Reynolds number is the ratio of inertial force and viscous force. It is a dimensionless number. It determines the type of fluid flow.

 

• What is a Newtonian fluid?
  A Newtonian fluid possesses a linear stress strain relationship curve and it passes through the origin. The fluid properties of a Newtonian fluid do not change when any force acts upon it.

 

• How many Joules is 1 BTU?
  1 BTU is equal to 1055.056 joules.

 

• What is PS?
  PS is Pferdestarke, the German unit for Horsepower.

 

• Explain Otto cycle.
  Otto cycle can be explained by a pressure volume relationship diagram. It shows the functioning cycle of a four stroke engine. The cycle starts with an intake stroke, closing the intake and moving to the compression stroke, starting of combustion, power stroke, heat exchange stroke where heat is rejected and the exhaust stroke. It was designed by Nicolas Otto, a German engineer.

 

• Explain the nomenclature of a 6203-ZZ bearing.
  6 is the type code, which shows it is a single-row ball bearing, 2 is the series, means light, 03 is the bore, which is 17 mm and ZZ is the suffix meaning double shielded bearing.

 

• What is Gear ratio?
  It is the ratio of the number of revolutions of the pinion gear to one revolution of the idler gear.

 

• What is Annealing?
  It is a process of heating a material above the re-crystallization temperature and cooling after a specific time interval. This increases the hardness and strength if the material.

 

• Define Torque.
  Torque is defined as a force applied to an object that results in rotational motion.

 

• What is Ductile-Brittle Transition Temperature?
  It is the temperature below which the tendency of a material to fracture increases rather than forming. Below this temperature the material loses its ductility. It is also called Nil Ductility Temperature.