Honda/Acura (English, Русский)

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CR-V, HR-V 1996-...

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 hrv
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Figure: Honda's rear differential with dual pump system and multi-plate clutch
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Figure: Honda's dual pump system
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Figure: Honda CR-V rear differential
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Figure: Honda CR-V
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Figure: Honda HR-V
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How Honda's Dual Pump 4WD works

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.

Source: www.theaa.com

Legend 2004-...

Super Handling All-Wheel-Drive system (SH-AWD) - torque-Vectoring full-time all wheel drive.

Honda's SH-AWD all wheel drive system

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:

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:

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:

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.

Figure: Honda Legend SH-AWD rear differential.
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Figure: honda legend sh awd
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Figure: honda sh awd x
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Figure: honda sh awd xx
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Figure: honda sh awd xxx
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Figure: Acura RDX SH-AWD rear differential
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Source: http://world.honda.com/news/2004/4040401.html

Watch Honda's video about SH-AWD: http://world.honda.com/HDTV/news/2004-4040401a/

About SH-AWD (in German): http://www.hondaoldies.de/Korbmacher-Archiv/Technik/sh4wd.htm

This is a Wiki, so feel free to correct any factual or grammatical error. Test here before posting.

1-15 of 19 Comments
Jim
January 12, 2024 - 18:27

I think the 2012 data is severely lacking. I own a 2012 Honda CR-V AWD and it seems to work by activating the ABS system on the front wheels which forces power to the back wheels. If you turn off traction control, you essentially disable the AWD unless you're revving the heck out of it.. but that's only from driver experience. (I used to work for Adesa, so I've driven every car out there.. might help you decide whether my input is worthwhile)

If it was electrically operated clutch in the rear differential, you'd think I'd actually get some AWD action with TC off and foot mashed but it'll one-wheel-peel on a front tire every time. Some of that is of course no locking differential, but you have to wonder..

AWD system was way better in the older machines; capable of 2x the torque/HP it was designed for (somebody built an AWD civic with 450 HP using CR-V parts out of the square-bodied-years; I think Jay Leno drove it on his YouTube channel).

Neil Taylor
February 17, 2019 - 02:19

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.

Reply to Neil Taylor
Anonymous
December 01, 2019 - 05:25

AWD is not a god send for traction. Your tires are what's actually putting the power down, so if they're worn or not able to cope with multiple surfaces, you're done. That gen of CRV is also known for the AWD being ineffective.

Frank
March 27, 2018 - 17:45

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.

Reply to Frank
Fred Neal
July 14, 2019 - 02:25

I very much agree. The current Pilot/Ridgeline does have torque vectoring. The main difference is software and how it is a more subdued version. Especially on loose surfaces. They do however do over drive the outside rear wheel in turns on dry pavement.

Abrumada
June 22, 2015 - 22:20

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!!

Andri
January 19, 2015 - 13:33

What the different of Honda HR-V and Honda Vezel?

Don Scarbrough
December 14, 2014 - 06:33

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
George
February 07, 2015 - 00:06

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
Frank
July 24, 2017 - 08:07

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.

mpx14
October 26, 2014 - 00:39

I guess the 2012 onwards version of the CR-V is not very keen of driving the rear wheels www.youtube.com

san
August 18, 2014 - 20:59

Horacio Botella
March 16, 2014 - 18:51

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
andres
February 28, 2015 - 05:37

Lograste solucionar esto? me acaba de pasar lo mismo y pienso que el problema es el diferencial delantero. Me gustaria saber como resolviste

kim shepherd
September 28, 2013 - 20:07

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!

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