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Discussion Starter #1
So far so good on our Pilot...but I ned to be educated on this 4WD system... We have a 1/2 mile driveway up a mountain and yes, I understand how the locking switch works and the how the system works under 18 mph. But I never see anything written that explains how it works OVER 18 mph. What happens if your driving on a snowy road at about 30-35 mph and it's a lilttle slippy? Does the system still engage as needed? Has anyone tested this feature?

On some rainy days, I have noticed the system engage coming off of a stop... Since I used to drive the 4Runner everyday, I was used to the security of locking in 4WD on those questionable driving days, sometimes at higher speeds...

What I need is an education on this system. Can anyone help?

Thanks.

Cindy:2:
 

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The Beauty of VTM-4

For those of us used to driving a more traditional 4WD system, the VTM-4 takes some getting used to.

The computer system monitors the wheels and somehow (according to HONDA) the computer is able to detect any possible slippage before the wheels even do it. So, the computer system kicks the VTM-4 into gear and off you go.

Yesterday (10/29/02), the Denver area was hit with snow and very icy conditions and the only way I know the VTM-4 was working, was that everyone else was sliding all over the place and I was just chuggin' right through it without a problem.

The VTM-4 (at least on my PILOT) engages and disengages withgout me even feeling or knowing about it. So far, it's worked incredibly!
 

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The VTM-4 system does not work over 18 mph. Any speeds over that and the system won't engage. As far as start & stop traffic, the VTM-4 system engages on accelleration, even without wheel slippage being detected so you should be fine there. They do not recommend that you put the VTM-4 lock button on for this. In fact, I don't think the manual lock will engage with the transmission in drive. I think it needs to be in 1,2, or reverse for the button to work.

Chris
 

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Here you go...

Variable Torque Management 4-wheel-drive (VTM-4)
The Pilot's innovative VTM-4 four-wheel drive system was designed to deliver outstanding traction, stability and control in all weather conditions as well as good medium-duty off-road performance. It was also designed to minimize the weight and packaging penalties associated with conventional four-wheel drive systems.

The VTM-4 system is unique in its operation. Unlike many competitive systems that use an engagement strategy triggered by wheel slippage, VTM-4 anticipates the need for all-wheel drive and engages the rear wheels whenever the vehicle is accelerating. Additional torque is applied to the rear wheels when wheel slip is detected, up to an approximate maximum of 50-percent in low gear. Another unique feature of the system is the VTM-4 Lock function.

Activated by a button on the instrument panel, the VTM-4 Lock mode delivers maximum torque transfer to the rear wheels to aid extraction from extremely slippery or "stuck" conditions. The feature works only when the vehicle is in first, second or reverse gears, and automatically disengages at speeds above 18 miles per hour.

When cruising under normal conditions, the Pilot provides front-wheel drive power for improved efficiency. Torque is proactively distributed to the rear wheels when the vehicle is accelerating or wheel slip is detected. The level of torque delivery, front to rear, is determined by the amount of acceleration (rate of change in velocity) and wheel slip (difference in rotational speed) and is controlled by a dedicated CPU with sensors in the braking, engine and transmission systems.

To avoid the weight and bulk of a conventional transfer case, VTM-4's torque transfer unit is a compact cast-aluminum housing bolted directly to transaxle. The transfer case is a single-speed, permanently engaged device without a low-range, reducing weight and space penalties while maintaining excellent on- and off-road capabilities. Attached to the front wheel differential's ring gear is a helical gear that provides input torque to the transfer unit. A short horizontal shaft and a hypoid gear set within the case turn the drive ninety degrees, move it to the vehicle center line and lower its axis by approximately 3.75-inches.

VTM-4 Engagement Modes
There are three distinct modes of VTM-4 engagement:

(1) The first mode, called Acceleration Torque Control (ATC), works whenever the vehicle's throttle is depressed, even on dry pavement - a feature unique to the VTM-4 system. Sensors in the engine and transmission monitor vehicle speed and acceleration. The amount of torque applied, as directed by the system's ECU, is determined according to vehicle speed, the amount of acceleration and transmission status (gear setting). This benefits not only the Pilot's ability to gain traction from a standing start, before wheel slip occurs, but also its overall dynamic stability on both dry and slippery roads. Reducing the propulsive force carried by the front tires under acceleration reduced torque steer and cornering adhesion. Rear wheel torque rises smoothly from zero to a preset maximum in proportion to vehicle acceleration (both forward and reverse). During constant-speed driving, all power is driven to the front wheels for improved fuel efficiency.

(2) The second engagement mode occurs when wheel slip is detected. Differences in rotational speed between front and rear wheels are measured by sensors in the ABS system and monitored by the ECU. In response, the ECU commands an increase in torque delivery to the rear wheels. Torque application is adjusted according to the amount and the rate of change in wheel slip. As slip increase, more power is delivered to the rear wheels for improved traction.

(3) The third mode of engagement is VTM-4 Lock. Lock mode occurs when the driver shifts into first, second or reverse gears and depresses the VTM-Lock button on the instrument panel. When lock mode is selected at vehicle speeds below 18-mph, the system ECU commands a preset maximum amount of rear-drive torque to be delivered to the rear wheels for improved traction in very low-speed, low-traction, conditions. As control is regained and vehicle speed increases, the system gradually reduces rear axle torque until it is completely disengaged.

The maximum torque delivered to the rear wheels is sufficient to climb the steepest grade observed on any public road in America - 31-degrees (60 percent slope) - with a two-passenger load on board. The Pilot will also move from rest up a 28-degree (53 percent slope) dirt grade. On a split-friction grade (different amounts of traction at each wheel), VTM-4 automatically provides sufficient rear-wheel torque to help the vehicle climb a steep, slippery driveway to enter a garage.
 

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Discussion Starter #5
4WD

WOW....that was awe inspiring.... Do you work for Honda? I know there was info. about the system in the brocure, but not to this degree. Where did you get this?

So basically, I have nothing to worry about under normal and snowy conditions? I was wondering since we actually received some sleet and snow yesterday in Harrisburg (very early). Had me worried, especially since I drop my kids off at daycare in the moring at 6:30. Don't want to get stuck or anything...

Thanks a Bunch!

Cindy

:2:
 

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It is a great system.

It absolutely works great over 18mph as well. I think it also handles slippage on either side by applying more torque on the opposite site.

MY big complaint is there should be an indicator light(other than the VTM-4 lock) that indicates when it gets engaged. I prefer to know as soon as 4WD kicks in(other than not skidding off the road)

If they can notify the wheels of slippage, the Honda engineers could have notified the driver. This is especially an issue with my wife.
 

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what??

You want a light that blinks unexpectedly, distracting you with no actionable information, just when you should be paying attention to your driving, prompting you to alter your control of the vehicle thereby reducing the systems ability to compensate for a loss of traction?????
 

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smitman said:
It is a great system.

It absolutely works great over 18mph as well.
Ah yes, you are correct. The 18 mph limit is only when the lock is used. My mistake.

Chris
 

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Re: what??

N_Jay said:
You want a light that blinks unexpectedly, distracting you with no actionable information, just when you should be paying attention to your driving, prompting you to alter your control of the vehicle thereby reducing the systems ability to compensate for a loss of traction?????
Yep,

I pd 43K Cdn for a 4wd system that I don't know when it is running. At least they did include lft and rgt flashers for the turn signals, hi beam indicator, cruise indicator, ABS indicator, but no 4WD indicator?

Anyway, I would like the extra indicator. I put that on all our Honda surveys.
 

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No you don't

smitman said:


Yep,

I pd 43K Cdn for a 4wd system that I don't know when it is running. At least they did include lft and rgt flashers for the turn signals, hi beam indicator, cruise indicator, ABS indicator, but no 4WD indicator?

Anyway, I would like the extra indicator. I put that on all our Honda surveys.
You ABS light does not light up when the ABS is active, it tell you when it fails,
and your cruise indicator tell you when you have engaged it, but does not change state when you are under or over the set speed.
 

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Re: No you don't

N_Jay said:


You ABS light does not light up when the ABS is active, it tell you when it fails,
and your cruise indicator tell you when you have engaged it, but does not change state when you are under or over the set speed.
Thank you all for being so exact. MY opinion is that I would like a 4WD indicator.

By the way, BMW's stability control system notifys you when it activates to control traction:

In the event of ASC+T being activated, the driver is notified by means of a flashing control lamp in the instrument cluster

Automatiske Stabilitets-Control
 

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Lots of theories on UI design

The one I subscribe to says to minimize or eliminate non-actionable information.
 

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ui design

notification that wheel slip is occuring and the 4wd system is engaged because your car is starting to slide - I would call that actionable info.

My main reason is that my wife is not a confident winter weather driver, if there was an indicator, it would prompt her to slow down(shes a german-used to autobahn!)

Any way thanks for your opinion, and happy piloting.
 

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The problem here is that the pilot is constantly reapplying torque to the rear wheels especially in ice and snow conditions. So if the light went on every time it sensed slippage and sent more transfer case messages if you will to the rear wheels, that light would blink constantly, and probably just confuse the hell out of people.
 

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My point exactly

I think a much better feature would be a cruise control light that started flashing when your downhill speed exceeded the set speed!

Or maybe a "Low Traction" warning light, that used input from the ABS, and VTM systems to warn you when your speed or driving style is taking the vehicle near the limits of traction on one or more wheels.

Seems some realy cheap GM cars had these in teh early days of traction control.
 

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I've seen "how to" articles on the Internet on making a VTEC light for the dash that lights up when you make the cutover. I thought it was interesting, but would probably lose it's cool factor pretty quick.

Chris
 

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on the fence

You guys all have good points, I certainly would not want it flashing on and off, especially if it engages and disengages frequently.

I'll bet there were lots of arguments on the honda design team on this one.
 

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Don't know about Honda, But;

I avoid the UI discussions at work.
We have experts in that area.
They are good at what they do.
They never agree.
The arguments get bloody.
What comes out is usually good enough. :D
 
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