Cooling System Operation
When the engine is cold the thermostat is closed, preventing the coolant from circulating through the radiator. Coolant is able to circulate through the heater core, expansion tank, and on the MINI COOPER S, the oil cooler.
The MINI COOPER S has a pressurized expansion tank, and allows coolant to enter the top via the heater core pipe, and exit the bottom of the tank to join the heater core return pipe.
Scheme 2
As the coolant temperature increases the thermostat gradually opens. This allows a bleed of coolant from the bottom hose into the cylinder block via the coolant pump, and allows hot coolant to flow to the radiator via the top hose. The flow of hot and cold coolant is balanced to maintain the optimum engine temperature. When the thermostat opens fully, the full flow of coolant passes through the radiator.
Scheme 3
Supercharger Operation
The supercharger is a positive displacement pump. Its purpose is to increase air pressure and density in the intake manifold. The supercharger is matched to the engine by its displacement and belt ratio (driven from the crankshaft).
The concentrated charge of air provided by the supercharger results in a more powerful combustion stroke in the engine's cylinders, resulting in improved performance over non-supercharged engines.
The supercharger incorporates a specially designed bypass valve. This is actuated by a vacuum pipe near the throttle body and re-circulates the supercharger air when boost is not required.
During typical driving conditions the intake manifold is under pressure for only 5% of the time.
For the remaining time the intake manifold is under vacuum (negative pressure), allowing for better fuel economy and a quieter ride.
Inside the supercharger the helix angled rotors and specially designed inlet and outlet port geometry reduce pressure variations. This results in a smooth discharge flow and a lower level of noise during operation. The way in which the ducting to and from the supercharger is mounted also plays a major role in reducing noise.
Scheme 4
Scheme 5
Scheme 6
Operation
When the compressed air mass leaves the outlet of the supercharger, the molecules of air are tightly packed together which generates heat. The air is forced into the inlet of the intercooler and is passed through many elongated tubes.
The ram air effect takes place as the vehicle moves forward and outside air passes externally over the elongated tubes cooling the compressed charge sufficiently before leaving the intercooler.
Principle of Operation
The input shaft incorporates fixed 1st, 2nd, 3rd and 4th speed input gears forming a single component. 5th gear is splined to the input shaft and secured with a lock nut. The output shaft assembly contains all free rotating output gears and synchronizer assemblies.
Modes of Operation
The transmission control is incorporated into the EMS 2000. The EMS 2000 does not control the transmission ratio directly but does provide all of the intelligence relating to the required position of the ratio control motor. It also provides the intelligence for how fast it should be operated.
The EMS 2000 controls the transmission in one of four modes
- Drive mode (normal CVT driving).
- Sport CVT mode or Low CVT mode.
- Manual mode.
- Fault mode.
In the CVT modes, the control system operates by deriving a target engine speed based on current vehicle speed and driver demand. In manual mode, the system derives a target engine speed based on the vehicle speed and the current gear ratio. Having obtained an engine speed target, the system calculates the appropriate ratio control motor position and instructs the GIU to deliver this position.
The engine load calculation will depend on two factors
- The vehicles road speed.
- The driver's demand (throttle position).
The EMS 2000 also needs to control the speed of the ratio control motor in order to protect the transmission from damage due to drive belt slippage. This is more likely to occur at low transmission oil temperatures, and when the transmission is delivering a large change in ratio (for example, after a manual gear change, or sudden throttle movement in Drive mode).
Four speeds are used by the Ratio Control Motor. The motor is accelerated as appropriate to ensure the motor does not lose its reference, thereby compromising system control. The EMS 2000 also knows the maximum torque that the belt can transfer across all possible ratio ranges. It is extremely important that the belt is not allowed to slip on the pulleys, as this would cause excessive wear.