The EST (Electronic Shift Transfer) system is classified as a “Part Time 4WD” system. This all-wheel drive system allows you to drive a car using one of three transmission modes:
1. Drive only to the rear wheels (all-wheel drive control switch position: “2H”).
2. Drive to front and rear wheels (all-wheel drive control switch position: “4H”).
3. The drive is carried out on the front and rear wheels with the inclusion of a reduction gear (position of the all-wheel drive control switch: “4L”).
When changing the position of the four-wheel drive control switch, the corresponding signal is received in the electronic control unit of the EST system, after which the control system switches to the specified mode.
AWD control circuit
Note: in the figure, the abbreviations indicate: TCCM – electronic control unit for the EST system; EMC – electromagnetic clutch; N – neutral gearbox / span.
The EST system includes an electromagnetic clutch and a transfer case motor mounted in the transfer case body. An electromagnetic clutch allows you to transmit torque to the front and rear wheels or only to the rear, and the transfer case motor is responsible for engaging the reduction gear.
All models with an EST system have a front axle connection system (CADS). The use of the front axle connection system made it possible to reduce noise, vibration and fuel consumption while driving, when the drive is carried out only on the rear wheels (all-wheel drive control switch position: “2H”), since the front driveshaft does not rotate. CADS allows you to connect or disconnect the front axle at speeds up to 80 km / h.
Front axle connection system
The EST system includes a front axle connection system – CADS (Center Axle Disconnect System). The system is designed to disconnect or connect the front axle when necessary.
The use of CADS on a car allows you to abandon the use of automatic wheel couplings that were installed on Hyundai Galloper and Kia Sportage cars:
– The automatic wheel couplings that were installed on the Hyundai Galloper made it possible to connect the front wheels at speeds up to 40 km / h, and to turn off the front wheels it was necessary to drive 1-2 meters with the rear house, which creates certain inconvenience in their use.
– The automatic wheel couplings with a vacuum drive that were installed on the Kia Sportage made it possible to connect the front wheels at speeds up to 80 km / h, but the service life of these couplings was not high, due to their design features.
Elements of the front axle connection system. 1 – front axle gearbox, 2 – front axle connection system block, 3 – vacuum drive, 4 – gear extension cord, 5 – vacuum tank, 6 – electromagnetic valve.
Front axle connection mechanism
Front axle connection system diagram
CADS allows you to connect or disconnect the front axle at speeds up to 80 km / h. A similar system have cars Mitsubishi Pajero, Mitsubishi Challenger, Isuzu Bighorn.
When changing the position of the all-wheel drive control switch, the electronic control unit of the EST system sends a corresponding signal to the electromagnetic valves of the front axle connection system, which control the vacuum drive of the clutch located in the front axle connection system block. Coupling connects or disconnects the internal drive shaft and the output shaft of the front axle gearbox.
After the all-wheel drive control switch is set to “2H”, the EST system will transmit torque from the engine only to the rear wheels of the car, and thanks to the front axle connection system, the internal drive shaft will be disconnected from the output shaft of the front axle gearbox, so the front universal joint the shaft will not rotate, which reduces noise, vibration and fuel consumption while driving.
EST System Modes
Under normal conditions, it is recommended to use the rear-wheel drive only. Changing the operating mode of the EST system is done using the all-wheel drive control switch located on the center console.
The four-wheel drive control switch has 3 positions: “2H”, “4H” and “4L”.
The drive is carried out only on the rear wheels. Recommended for use under normal driving conditions (on good roads).
1. Drive to front and rear wheels. It is recommended to use when driving on wet roads and also covered with ice or snow. This position gives a more stable ride..
2. When this mode is selected, the four-wheel drive indicator lights up..
1. The drive is carried out on forward and back wheels with a reduction gear. This mode is used to obtain maximum power and traction: when climbing steep slopes, descending from steep slopes and when driving on poor roads, for example, covered with mud.
2. When this mode is selected, the downshift indicator lights up.
Attention: it is not recommended to use four-wheel drive when driving under normal conditions. The use of all-wheel drive will lead to increased fuel consumption and rubber wear..
2Н4Н or 4Н2Н
Switching is performed at a speed of no more than 80 km / h without pressing the clutch pedal (models with manual transmission) or shifting the selector to the “N” position (models with automatic transmission).
Switching is performed on a stationary car with the clutch pedal depressed (models with manual transmission) or after the selector is in the “N” position (models with automatic transmission).
Rodionov Alexander, Goncharenko Mikhail, Moscow
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