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.
Figure: Honda's rear differential with dual pump system and multi-plate clutch (23KB)
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.
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.
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
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.
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.
torque-Vectoringfull-time all wheel drive. Version 2 is similar to Version 1 but with the system but lacked the "Acceleration Device" of the former. This limited the rear wheel overdrive ratio from 5.7% to 1.7%, decreasing the effectiveness of SH-AWD in tight turns. However V2 still is a full-time system with torque vectoring actuated via electro-mechanical clutches, which in turn holds 2 planetary gearsets (one for each rear wheel) in which power can be transferred.
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torque-Vectoringfull-time all wheel drive. Version 3 was introduced in the 2015+ TLX 3.5L & 2016+ MDX, but its design is closer to VTM-4 than SH-AWD V2. Like VTM-4 the 2 planetary gearsets & electro-mechanical clutches are gone, replaced by 2 independent hydraulic clutches. Rear axle overdrive ratio is increased from 1.7% to 2.7%, allowing greater torque vectoring ability & range of SH-AWD operation in tighter turns. Like V2 there is no longer an "Acceleration Device". Unlike VTM-4 however SH-AWD V3 continues to be a full-time AWD and operates up to any speed. Thanks to reduction in complexity, the size & weight of V3 is less than that of SH-AWD V2 & V1.
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torque-Vectoringfull-time all wheel drive. Version 4 is the newest member of SH-AWD and operates significantly more different than any SH-AWD to date, as the system is built on a 3 electric motor Hybrid system with the rear axles lacking any mechanical means of connecting to the petrol/gas engine at the front.
Employed first on the 2014+ RLX Sport Hybrid & later on the 2017+ MDX Sport Hybrid, the front axle is driven by a gas engine (3.5L on RLX, 3.0L on MDX) aided by a 47hp & 109lb/ft electric motor. The rear axle is driven by a Twin Motor Unit (TMU) fed by a 1.3kWh battery driving 2 separate motors each pushing out 36hp & 54lb/ft (total 72hp & 108lb/ft). Each rear motor can be controlled independently: propelling the car in EV mode alone (up to 78 MPH to prevent damage from overspeeding), providing regenerative braking together to slow the car and lastly, independent regenerative braking via the inside wheel and powering the outside wheel to enable torque vectoring in corners.
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Last changed: 2018/12/31 22:00
1-15 of 16 Comments
February 17, 2019 - 00:19
On a grassy slope today and was left stranded as front wheels spinning and back not engaging. Went under car to ensure it was AWD. Saw the driveshafts going to the wheels. This is why I bought the Honda CRV 2014 for traction on grassy slopes. Why does it not work in this real world situation.
March 27, 2018 - 14:45
I would just like to point out an inaccuracy about the AWD system of the new generation Pilot ( 2016 ) and the 2nd Generation Ridgeline ( Introduced in 2017, there were no 2015 or 2016 Ridgeline’s ) The 2nd Generation Ridgeline most definitely DOES HAVE TORQUE VECTORING CAPABILITY. I don’t why someone would say It doesn’t. In every review on YouTube, the Honda rep accompanying the reviewer usually makes a point of stressing this. The main difference between the Torque vectoring capability Honda put in the new Ridgeline and what they put in certain ( not all ) high end Acura’s is the amount of rear outer wheel overdrive the system will allow when cornering. The Ridgeline’s is fixed at around 2% maximum, whereas some of the more sporty Acura’s can overdrive the outside rear wheel by upwards of 5% to enhance performance.
The Ridgeline is a full time AWD system and power is almost never exclusively delivered to just the front wheels. It would be more appropriate to say that this AWD system is front wheel drive “biased” in that most of the time the majority of power is sent to the front wheels. However, when conditions require it, the Ridgeline is capable of sending up to 70% of the power to the rear wheels and it can send up 100% of that 70% to one side and that is classic torque vectoring.
I purchased a 2017 Ridgeline in May 2017 in RTL trim and zi did extensive research on it and every other truck in the segment and I am convinced there is no truck, full size or midsize, that offers a system as competent to deal with inclement weather conditions on paved surfaces thAn the Ridgeline. For instance the Ridgeline is incredible in the rain, a dangerous condition where traditional 4WD cannot be engaged without risk of damage.
Click on this YouTube link youtu.be/Zb92baNEu9o and fast forward to the 17 minute mark to listen to a very detailed explanation of the Ridgeline’s AWD system and it’s capability.
June 22, 2015 - 19:20
Hola! Si alguien me pudiera ayudar, lo agradezco. Tengo un Honda CRV-1999, con problemas de "clutcH"/aceleración??!!! Explico: camina bien, acelera bien, y de repente, no puedo "compresionar", cambio de marchas y acelero "pero el vehículo No se mueve", la aguja de potencia al máximo, pedal de "gas" al máximo, pero "no Camina". ¡Auxilio!!
January 19, 2015 - 11:33
What the different of Honda HR-V and Honda Vezel?
December 14, 2014 - 04:33
I bought a 2014 Crosstour EX-L 6cyl that shows "4WD" on the hatchback, and has drive axles to all wheels. There is no apparent control to engage the 4WD. After reading all 568 pages of the owner manual, I find not a single word about the drive system, and still don't know if this is a full time all wheel drive or a part time that drives the front wheels only until slippage is detected. The dealer is no help.
Can someone enlighten me?
Reply to Don Scarbrough
February 06, 2015 - 22:06
There is no such thing as 'all wheel drive', no part-time/full-time nonsense.
Your car does not have a center differential-so it is not four wheel drive.
It is more sophisticated than a Jeep Wranger-which uses a very simplistic on/off connection to bring the front axle into play.
Your car is a front drive Power Take Off system. Mechanically 100% of the power goes to the front differential, minus how much is take off to the rear differential.
The CrossTour is Honda's last use of their updated dual pump system.
Reply to Don Scarbrough
July 24, 2017 - 05:07
Even without center differential, it is still a 4WD. 2WD TO starT WITH, then engages rear wheels when needed. That by definition is 4WD. There is more than one 4WD system out there.
October 25, 2014 - 21:39
I guess the 2012 onwards version of the CR-V is not very keen of driving the rear wheels www.youtube.com
August 18, 2014 - 17:59
March 16, 2014 - 16:51
Hola , alguien si me puede ayudar, tengo un problema con mi crv 2001, se calienta mucbleepedel diferencial trasero y empieza a chillar. al rato se desacopla todo el vehiculo , queda como desembragado. gracias
Reply to Horacio Botella
February 28, 2015 - 03:37
Lograste solucionar esto? me acaba de pasar lo mismo y pienso que el problema es el diferencial delantero. Me gustaria saber como resolviste
September 28, 2013 - 17:07
Hi,dose the 4x4 system come in when making sharp slow turns? I seem to feel the tyres scuffing even when turning in to the drive!
January 19, 2012 - 18:53
The newest Honda CR-V adopts a modernized computer controlled clutch pack system (+ front & rear differentials)
January 11, 2011 - 11:35
Honda HRV Transfer Box
Hi, I'm trying to replace the transfer box from a 2000 Honda HRV 1.6 CVT Automatic 4 wheel drive, have filled out a lot of forms on line but haven't found one yet. Can anyone advise me please?
January 11, 2010 - 00:23
Don't forget Honda's 'VTM-4' system: eliminates this dual pump nonsense, eliminates the rear differential. Each 'half-shaft' [axleshaft] is now independently coupled to the front via an electro-magnetically controlled wet clutch pack. www.ridgelineownersclub.com mypage.siu.edu
and the Acura 'SH-awd' system. How do you get a front wheel drive car to drive like a rear drive car? Easy, shunt as much power to the outer rear wheel during cornering, while not powering the inner rear-3 wheel drive. world.honda.com
Synthetic Handling would be a better name.