Automatic all wheel drive. Honda’s Real Time Four Wheel Drive System. Normally front wheel drive vehicle. Torque transfer to rear axle via multi-plate clutch. Dual pump system is used to apply pressure to the clutch. It also disengages the clutch when braking to allow ABS work smoothly.
How Honda’s Dual Pump 4WD worksNext
For most of the time, only the HR-V s front wheels are driven; it s only when they begin to lose grip that the Dual Pump system starts to send power to the rear wheels. This is achieved by a hydraulic torque-split system, consisting of a conventional front-wheel drive arrangement, complete with transfer case, a propeller shaft running the length of the vehicle and a Dual Pump system integrated with the rear differential. This is the heart of the system and comprises two hydraulic pumps, one driven by the front wheels via the prop shaft, the other by the rear wheels via the rear differential.
During normal levels of grip the front and rear wheels, and their respective pumps, turn at the same speed; hydraulic pressure circulates between the two pumps, but no pressure is generated. If the front wheels begin to lose traction and start to spin faster than those at the rear, the two pumps turn at different rates; hydraulic pressure proportional to the difference in their speeds is generated, which in turn opens a valve body and activates a mechanical, multi-plate clutch.
This clutch then connects the front prop shaft to the rear diff, which feeds precisely the correct amount of torque to the rear wheels to re-establish overall traction. The more the front wheels slip, the greater the torque fed to the rear wheels.
The Dual Pump arrangement weighs less than a conventional four-wheel drive system and demands little maintenance just a fluid change at 72,000 miles and thereafter every 36,000 miles. Further advantage of this design is that it automatically disengages under braking, thereby allowing the ABS to operate.
CR-V (2012-. )Next
Automatic all wheel drive. Normally front wheel drive with torque transfer to the rear axle via electronically-controlled multiplate clutch.
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Part-time all wheel drive VTM-4 used in the 2003-2008 Pilot (1st-gen) and 2009-2015 Pilot (2nd-gen) as well as the 2006-2014 Ridgeline. It is a greatly simplified version of SH-AWD Version 2, but lacks any planetary gearsets or electro-mechanical clutches, instead replacing them with single wet-plate clutch pack a single electro-mechanical coil that actuates it. So VTM-4 cannot independently torque vector its clutches must mechanically transfer all of the engine’s torque to the rear axle. Clutch stresses and heat limits VTM-4 to a maximum operation up to 18 MPH.
Version 1. Employed on 2005-2012 Acura RL/Honda Legend
Version 2. Employed on 2007-2012 Acura RDX, 2007-2013 MDX (2nd-gen), 2014-2015 MDX (3rd-gen), 2010-2013 ZDX, and 2009-2014 TL (equipped with 3.7L V6)
Version 3. Employed on the 2015+ Acura TLX and the 2016+ MDX and also the i-VTM4 used on 2016+ Honda Pilot
Version 4. Employed on the 2014+ Acura RLX Sport Hybrid 2017+ Acura MDX Sport Hybrid
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Legend/Acura RL 2004-2012 (Version 1)Next
Honda’s SH-AWD all wheel drive systemNext
By monitoring driver input and driving conditions, the SH-AWD system determines the optimum front-rear and lateral (left-right) torque distribution. This information is then conveyed to the rear differential, where direct electromagnetic clutches continuously regulate and vary front-rear torque distribution between ratios of 30:70 and 70:30, and lateral torque distribution in the rear wheels between ratios of 100:0 and 0:100. Torque is used not only for propulsion, but for cornering as well, resulting in a significant enhancement in vehicle maneuverability. SH-AWD system monitors vehicle speed, wheel speed, gear position, steering angle, yaw rate, lateral G forces and other inputs, while automatically adding torque to the outside rear wheel in corners to make the car turn quicker
How front-to-rear torque is distributed:Next
Straight-line driving front-rear torque distribution is regulated for optimum performance in accordance with the amount of torque produced. During rapid acceleration the load on the front wheels is reduced; conversely, rear-wheel load is reduced during cruising. The result is stable driving at all times.
How left-to-right torque is distributed on the rear wheels:Next
During cornering, torque to the rear wheels is continuously varied to supply up to 100% to the outside wheel and 0% to the inside wheel. This creates an inward yaw moment, significantly improving vehicle handling. Yaw moment is turning torque relative to the vertical axis running through the vehicle s center of gravity.
When decelerating during cornering (throttle closed), torque to the outside rear wheel is freely varied to change from an inward to an outward yaw moment, ensuring vehicle stability at all times.
How does acceleration device works:Next
The rear differential is also equipped with a built-in acceleration device. During cornering, the track of the outside rear wheel normally falls outside the average of the tracks of the front wheels. The outside rear wheel does not rotate fast enough to keep up with the front wheels, preventing efficient transmission of torque. To counteract this problem, the SH-AWD acceleration device alters the gearing to speed up the outside rear wheel s rotation relative to the front wheels. This reduces torque transmission losses and significantly improves vehicle maneuverability. During straight-ahead driving, the twin-pinion planetary carrier spins in synchronization with the propeller shaft, causing the front and rear wheels to turn at the same speed. When the vehicle enters a curve, however, the� planetary carrier is locked to the case, releasing the device from synchronization with the propeller shaft and accelerating the rotation speed of the rear wheels. A hydraulic actuator which turns the clutches on and off, and a one-way clutch are included in this compact configuration.