Real time 4WD

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Real Time 4WD (German: real-time all-wheel drive) was built by Honda develops and refers to a technique for the all-wheel drive a car.

This all-wheel drive system is one of the systems that automatically switch on. With good traction, only the front wheels are driven. As soon as these have a higher speed than the rear wheels (e.g. when driving on snow or when starting off on wet roads), torque is transmitted to the rear wheels. If the speeds of the front and rear wheels equalize again, the power transmission to the rear axle is gradually reduced again.

premiere

The Real Time 4WD was first launched in Europe in 1989; at the time in the Honda Civic Shuttle EE4 facelift, and from 1996 in the CR-V. Honda did not develop this all-wheel drive system to ensure that the car was off-road, but to increase the safety of the occupants.

function

The most important components of the system are two oil pumps built into the rear axle drive ("dual pumps "), which are connected to one another via a hydraulic circuit. One of the pumps is connected to the front axle via the cardan shaft, the other to the rear axle. These pumps generate a pressure proportional to the number of revolutions of the respective axis. In normal operation (front wheels are driven), the front and rear wheels rotate at approximately the same speed. As a result, both pumps work with the same pumping power and the hydraulic oil circulates between them without pressure.

If for any reason the front wheels have a higher speed than the rear wheels, the pump connected to the front axle works with a higher pumping capacity than that connected to the rear axle. Because this pump pumps away less hydraulic oil than is supplied to it by the other pump, pressure builds up in the hydraulic system. This pressure acts via a pressure cylinder on a multi-plate clutch (later versions: claw clutch ) and closes it. As a result, torque is now applied to the rear wheels. The greater the speed difference between the front and rear axles, the greater the drive force transmitted to the rear wheels.

The Real Time 4WD system is designed (through the use of valves) to work even when driving backwards. An overpressure and an overtemperature valve protect the system from damage in extreme situations.

The “dual pump” system was supplemented in 2005 by a mechanical clutch that is activated immediately if one of the front wheels spins. With this improvement, Honda has been able to improve driving performance when starting off, on inclines and when accelerating.

INTRAC

INTRAC stands for IN novative TRA ction C (control traction dt .: Innovative) ontrol and was developed by Honda, as used for power transmission disk clutch of the Real Time 4WD prevented the effect of the ABS. For this reason, a differential was developed to remedy this problem. In the housing of the differential there are two viscous clutches (for power transmission to the wheels) and an electrical claw clutch controlled by the ABS . The dog clutch ensures that the rear-wheel drive is decoupled when the braked wheels are blocked. This allows the ABS to do its job (preventing the wheel from locking). Each rear wheel has its own viscous coupling, which drives the wheel.

Occurrence

Real Time 4WD is available in the following models:

Trivia

  • Vehicles equipped with Real Time 4WD systems should not be parked sideways using the handbrake (popular driving trick e.g. on snow). Because the rear wheels lock, the all-wheel drive system is automatically activated and works against the braking force of the handbrake. The subsequent closing of the multi-plate clutch can lead to the front axle also locking, which leads to the complete loss of the vehicle's steerability.
  • If a car with Real Time 4WD is raised so that all wheels hang freely, the all-wheel drive comes into effect and turns all wheels.
  • The housing of the differential has a vent. This venting process can cause the oil in the differential to mix with the water in the air. If the Real Time 4WD is not used for a longer period (4–5 months), the oil may already have so much water that when the four-wheel drive is switched on, a so-called "seal yelp" can be heard for about a second. If the oil has mixed with too much water, the hydraulic oil in the rear axle differential should be changed to avoid possible damage. Only the special “Dual Pump Fluid” should be used.