How Does VTM Work? - Honda Pilot - Honda Pilot Forums
 
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post #1 of 8 (permalink) Old 01-05-2009, 12:50 AM Thread Starter
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How Does VTM Work?

As stated in the subject header, How does VTM work exactly? I have a 2004 Pilot EX with Navi and I am fascinated about what VTM does and how it contributes to the pilot being a great light-off-roading vehicle. Also I am not too sure how the 4WD works.

From my understanding, pilot primarily front wheel drive until it detects slippage on the front tires. When it detects slippage on the front tires, the transmission then diverts torque to the rear tires.

Please, clarify how VTM operates in relation to the 4WD system of a 2004 Pilot.

2004 Honda Pilot 4WD EX-L w/ Navigation
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post #2 of 8 (permalink) Old 01-05-2009, 12:58 AM
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The VTM system is the 4wd system.

<------------ click here first, n0oB!!!
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post #3 of 8 (permalink) Old 01-05-2009, 01:54 AM
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Re: How Does VTM Work?

Quote:
Originally posted by Alpo714

How does VTM work exactly?

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.
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post #4 of 8 (permalink) Old 01-05-2009, 02:44 AM Thread Starter
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Re: Re: How Does VTM Work?

Quote:
Originally posted by xGS


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.
Wow. That is an incredibly detailed response. Thanks xGS!

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post #5 of 8 (permalink) Old 01-05-2009, 08:50 PM
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Question

In the second engagement mode, I have noticed a slight, momentary drag. Is the ABS engaging to help correct the slippage?

I ask because during some recent storms in the Northeast, on a slippery hill, I can feel one or more wheels slipping, then a mometary drag, like someone is touching the brakes and then the vehicle surges with what feels like four wheel drive. It then powers forward, starts to slip, slight drag and the takes off again. This will continue if I'm too aggressive for the driving conditions.


And by the way, I have new Michellin M+S tires.

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04 Audi A4 3.0 6MT
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post #6 of 8 (permalink) Old 01-05-2009, 10:44 PM
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Quote:
Originally posted by mriley
In the second engagement mode, I have noticed a slight, momentary drag. Is the ABS engaging to help correct the slippage?
i believe that's the VSA (traction control) kicking in. i've experienced the same drag or hesitation upon hard acceleration on icy/wet pavement, accompanied by the flashing VSA symbol in the instrument cluster.

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post #7 of 8 (permalink) Old 01-06-2009, 06:17 PM
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Re: Re: How Does VTM Work?

Quote:
Originally posted by xGS


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.

What does ECU stand for?

"This is going to be a very expensive war, and Victory is not guaranteed -- for anyone, and certainly not for anyone as baffled as George W. Bush. All he knows is that his father started the war a long time ago, and that he, the goofy child-President, has been chosen by Fate and the global Oil industry to finish it Now."

Dr. Gonzo
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post #8 of 8 (permalink) Old 01-06-2009, 06:27 PM
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ECU/ECM=the BRAINS of the operation=electronic control unit/module

http://en.wikipedia.org/wiki/Engine_Control_Module

http://en.wikipedia.org/wiki/Electronic_control_unit

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