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View Full Version : It is possible to manually turn OFF RT-4WD!


MPovoa
04-15-2009, 02:57 PM
I purchased a 2008 CR-V EX-L, and about 2 months ago I posted a thread at hondasuv.com asking:

- If it was possible to manually turn on/off RT-4WD
- If there is an inter-relation in between VSA and RT-4WD

Well, I got plenty of answers, but none of it seems to have answered 100% correctly.

I was told that:


It is not possible to manually turn ON RT-4WD (correct)
It is not possible to manually turn OFF RT-4WD (wrong!)
VSA and RT-4WD are not inter-related systems (wrong!).
So, last week I finally got to experience the car on an unpaved, slippery road. After observing and researching I found that:

The Honda CR-V manual clearly states that if VSA is turned OFF, the traction control is also deactivated. Therefore:


There is a way to manually turn off RT-4WD
You can’t have VSA activated without RT-4WD and vice-versa.
The 2 systems are indeed inter-related.
Any comments?

liquidfuel88
04-15-2009, 03:04 PM
No, RT4WD will still work with everything else off.

Only real way to turn off RT4WD is to remove the propeller shaft to the rear wheels.

:roll:

MPovoa
04-15-2009, 03:09 PM
This is not what the honda CR-V manual says. The manual clearly states that if VSA is turned OFF, the traction control is also deactivated.

liquidfuel88
04-15-2009, 03:10 PM
Ok, but traction control is not the 4WD system. ;)

liquidfuel88
04-15-2009, 03:12 PM
Your VSA IS the traction control system. ;)

MPovoa
04-15-2009, 03:12 PM
I can not see how traction control is not related to 4WD.

liquidfuel88
04-15-2009, 03:15 PM
VSA only controls wheel slip. A 4WD system powers the wheels.

In other words, the 4WD makes the wheel spin, and VSA stops the spin if there is no grip.

Racoon
04-15-2009, 03:19 PM
I think we have some terminology confusion. If your CR-V has RT4WD then there are three systems worth discussing...

VSA - Vechicle Stability Assist
TPMS - Tire Pressure Monitoring System
RT4WD - Real Time 4 Wheel Drive

You can manually turn VSA off using the switch. The 2008 CR-V Owners Manual on page 256 says this about turning off VSA:

Without VSA, your vehicle will have normal braking and cornering ability, but it will not have VSA traction and stability enhancement.

So VSA is the terminology Honda uses for their traction control system.

If the TPMS system is showing a fault (the light is on) then VSA is automatically turned ON, even if you have turned it off (page 259).

There are two sections that mention the "4-wheel drive" system. Page 244 and 270. Neither mentions either VSA or TPMS, although Page 270 does mention overheating and possible damage to the system if you spin the tires excessively.


So, VSA and TPMS have nothing to do with the RT4WD system.
:)

MPovoa
04-15-2009, 03:19 PM
Yes, but what the 2 systems do is not the point. The issue is that if you turn off VSA, the traction control is deactivated. Thus, the 4WD can not work anymore.

MPovoa
04-15-2009, 03:24 PM
well, we are looking at 2 different manuals ( though they shouldn't be ). Mine is in Portuguese ( Brazil ), so I can't check the page numbers you are suggesting -- though I would love to. Do you have a digital version of the english manual you can send me, or I can check online?

liquidfuel88
04-15-2009, 03:25 PM
Yes, but what the 2 systems do is not the point. The issue is that if you turn off VSA, the traction control is deactivated. Thus, the 4WD can not work anymore.

Why not? The RT4WD system is 100% mechanical, nothing electronic about it.

My CR-V does NOT have any VSA or other control system crap. Just RT4WD. So according to what you are saying, mine wouldn't work at all?

:roll:

Racoon
04-15-2009, 03:28 PM
Yes, but what the 2 systems do is not the point. The issue is that if you turn off VSA, the traction control is deactivated. Thus, the 4WD can not work anymore.

VSA is an electronic system which uses sensors on the wheels to help it control wheel spin. VSA _is_ the traction control system.

You misunderstand how the RT4WD system works. RT4WD is an hydraulic system with no electronic components. Turning off other electronic systems can not affect the RT4WD system.

There are two hydraulic pumps in the rear differential. One is turned by the rear axles, and one is turned by the propeller shaft that's connected to the transmission. When the front and rear wheels are rotating at the same speed, each pump is putting out the same fluid pressure and RT4WD is disengaged. When the front and rear wheels spin at different speeds, as when you spin the front wheels, the two pumps put out different fluid pressures, which causes the clutch packs inside the rear differential to engage, transferring some power to the rear wheels. Once the front and rear wheels are spinning at the same speed again, the pressure equalizes, and the clutch packs disengage.

There is no way to turn the RT4WD on, except by intentionally spinning the front wheels.
There is no way to turn the RT4WD off, except by removing the propeller shaft.

:)

dgoff07
04-15-2009, 03:28 PM
Yes, but what the 2 systems do is not the point. The issue is that if you turn off VSA, the traction control is deactivated. Thus, the 4WD can not work anymore.

The traction control has no effect on the RT4WD system. The 4-wheel-drive system is a completely isolated hydraulic system. It functions with or without the VSA (traction control) enabled.

The RT4WD system CANNOT be "turned off."

Racoon
04-15-2009, 03:28 PM
US 2008 Owners Manuals:

https://techinfo.honda.com/rjanisis/RJAAI001_OMANUAL.ASP?YEAR=2008

liquidfuel88
04-15-2009, 03:32 PM
^^^

I could not have said it better myself. :lol:

MPovoa
04-15-2009, 03:46 PM
I did check the US version Manual, thanks for sending the link.
The translation is actually correct ( page 257 ):
"When the VSA system is off, the traction control system is also off".

So, I assumed that traction control was what activated the 4WD.
If not, what exactly the traction control does?

p.s: My manual does not have the part about TPMS on page 256. So I assume my model doesn't have it.

Racoon
04-15-2009, 04:04 PM
Page 256 of the US 2008 CR-V Owners Manual:

The vehicle stability assist (VSA) system helps to stabilize the vehicle during cornering if the vehicle turns more or less than desired. It also assists you in maintaining traction while accelerating on loose or slippery road surfaces. It does this by regulating the engine’s output and by selectively applying the brakes.

ASLGuy
04-15-2009, 04:06 PM
VSA = Traction Control and can be turned off/on (unless TPMS issue--then it's always on).

VSA is NOT the same as RT4WD. You cannot turn the RT4WD system off.

VSA (traction control) monitors wheel spin and the direction of the vehicle to make sure you're on your intended path. It can apply brakes to individual wheels should you start to go out of control and off your intended path.

MPovoa
04-15-2009, 04:29 PM
It is clear now. There was a semanthics issue, but also now I undestand much better how both systems work. Thanks much.

so, as a "grand" conclusion to my driving issue:

I can turn off VSA and 4WD will still work, it is a completely independent system. :-P

ASLGuy
04-15-2009, 04:34 PM
I can turn off VSA and 4WD will still work, it is a completely independent system. :-P

¡Exactamente! Bienvenido a Honda SUV Foros.

liquidfuel88
04-15-2009, 04:37 PM
Glad to help clear things up for you. :)

06whtcrv
04-15-2009, 05:26 PM
Glad to help clear things up for you. :)
thank goodness! I was afraid he was going to have to jack up all four wheels, turn off the VSA and put it in gear to see for himself!:mrgreen:

chiph
04-15-2009, 06:33 PM
Agree with everyone above saying that RT-4WD is an entirely different system and technology from VSA & traction control.


Technically, VSA isn't the traction control. But they are related systems.

VSA has yaw and steering-angle sensors, plus uses the ABS sensors to determine if the car is understeering or oversteering, and then applies the brakes (using the ABS pump) to attempt to bring the car back into the line chosen by the driver. Works great on snowy roads & other slippery surfaces -- but if you see the light turn on, you should really slow down as you're exceeding the available grip on the road surface (ask me how I know this!)

Traction control limits wheel-slip (as others have said) and uses the ABS sensors to detect when one or more wheels are slipping (there's a software profile for this in the computer). To reduce the slippage, it will use the drive-by-wire system to reduce the throttle, and optionally apply the brake to the slipping wheel (using the ABS pump). Since the CR-V has open differentials, this has the effect of transferring torque from other wheels to the wheel that is slipping.

Note that both systems cannot violate the laws of physics, and there are combinations of conditions which will cause them not to function. So neither are a substitute for common-sense behind the wheel.

Chip H.

blizzard797
04-16-2009, 08:29 AM
I actually went off the main streets in the snow to play with this. It is much more fun with the VSA turned off. And yes I can get all 4 wheels spinning. With the VSA on. It tries to compensate and the car acts way different.

dlynch
06-05-2009, 08:26 PM
I learned a lot reading this post. My '03 didn't have traction control. My '09 will.
But the most important lesson?
The quality of responses from participants and moderators.
This is a happy forum, and I'm glad I'm here!
Regards,
DaveL