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-   -   VTM vs SH-AWD (http://www.piloteers.org/forums/70-2009-2011-pilot/22448-vtm-vs-sh-awd.html)

wenhlin 09-20-2008 05:54 PM

VTM vs SH-AWD
 
Is the VTM system on Pilot mechanically and functionally identical to SH-AWD on MDX?

bdac2k 09-20-2008 06:06 PM

Quoted from vtec.net

There are quite a few difference actually...
VTM-4:
-Front wheel drive under normal driving
-Can transfer power to rear differential when needed, but power distribution is limited to front to rear and not side to side.
-Sends power to rear when needed (ie limited traction)
-Sends power to rear when accelerating at low speeds up to 18mph.
-Sends power to rear when in reverse
-Sends power to rear when diff lock is on and tranny is in D1 or D2 up to 18mph.

In short, the VTM-4 system is basically a traction enhancement system.

SH-AWD: Based on VTM-4
-Full time all wheel drive with front drive bias
-Can send up to 70% of torque to rear diff
-Can distribute up to 100% of the rear torque to one axle; to the outside rear to help rotate the vehicle when cornering and to the inside rear to offset an overstear situation.

Unlike VTM-4, SH-AWD is more than just a traction enhancement, it is capable of enhancing handling/cornering in addition to improving traction in low grip situations. Additionally, it acts as a traction control system by actively controlling the torque distribution to counteract undesirable vehicle dynamics/movement without the intrusiveness and power sapping of ABS based VSA/traction control.

rlapid 09-20-2008 06:08 PM

nope. SH-AWD can distribute torque left and right, as well as front and rear. VTM4 can only send torque to the rear wheels upon detection of wheel slippage. there's probably more to it, but that's the main idea.

rlapid 09-20-2008 06:09 PM

ah, bdac2k beat me to it. there's your more detailed description.

N_Jay 09-20-2008 06:58 PM

SH says it can accelerate the outer rear wheel to enhance traction, but VTM is incapable of turning one wheel faster then the other (and at the same speed as the average of the fronts.
That would point to a significant mechanical difference.

wenhlin 09-20-2008 07:54 PM

If VTM system is only a part-time all wheel drive and not full-time like SH-AWD then why is the MPG on AWD Pilot yields only 16/22 mpg versus the FWD's 17/23 mpg? I know the AWD weights about 200 lbs more but I doubt the weight alone will make that much of a difference? Especially if the system disengages over 18 mph then it really shouldn't effect the hwy MPG, right?

N_Jay 09-20-2008 10:35 PM

Quote:

Originally posted by wenhlin
If VTM system is only a part-time all wheel drive and not full-time like SH-AWD then why is the MPG on AWD Pilot yields only 16/22 mpg versus the FWD's 17/23 mpg? I know the AWD weights about 200 lbs more but I doubt the weight alone will make that much of a difference? Especially if the system disengages over 18 mph then it really shouldn't effect the hwy MPG, right?
Maybe it is just the extra drag of spinning the drive shaft and input to the VTM unit.

Plus it turn on with every start from a stop, so there is added drag then also.

vtec95 09-24-2008 08:52 PM

Give it 5 years..they will make the pilot with an awd system..i guarantee it. How do people like the vtm-4? I just got this pilot and curious to see how it handles in the snow.

N_Jay 09-24-2008 09:15 PM

Quote:

Originally posted by vtec95
Give it 5 years..they will make the pilot with an awd system..i guarantee it. How do people like the vtm-4? I just got this pilot and curious to see how it handles in the snow.
Works well, does the job.

Full time AWD is mostly overrated.

rlapid 09-25-2008 12:38 AM

yeah, when you think about it, full-time AWD isn't necessary when the weather is clear and you're just driving around town running errands or cruising on the freeway. its just wasting precious MPG. VTM-4 works just like its supposed to -- AWD kicks in when you need it (hard acceleration or driving on wet/slippery surfaces) -- and it does a very good job.

jonaz 10-02-2008 01:11 AM

VTM is not a true locking differential. Both rear tires do not turn at the same speed in VTM mode in first or 2nd gear. Ive watched it work in the snow, and it is not a locking differential like you see on Chevys or Toyotas.

Rocky 10-02-2008 03:12 AM

Quote:

Originally posted by N_Jay
SH says it can accelerate the outer rear wheel to enhance traction, but VTM is incapable of turning one wheel faster then the other (and at the same speed as the average of the fronts.
That would point to a significant mechanical difference.

A normal open diff will always turn the outer wheel faster than the inner wheel.

Where did you get this info? Be interested to read it.

N_Jay 10-02-2008 06:57 AM

Quote:

Originally posted by rocky


A normal open diff will always turn the outer wheel faster than the inner wheel.

Where did you get this info? Be interested to read it.

I recalled it from my memory of the original SHAWD announcement.

Remember, the VTM unit does not have a differential at all.
I don't know what is inside the SHAWD unit

deparson 10-02-2008 09:07 AM

VTM-4 (and SH) uses a clutch pack on each rear wheel. Thus, it can perform LIKE a LSD if it needs to.

It is NOT an open diff in the normal use of that term as it can direct 100% of the rear power to either the left or right wheel as needed.

Quote:

Originally posted by jonaz
VTM is not a true locking differential. Both rear tires do not turn at the same speed in VTM mode in first or 2nd gear. Ive watched it work in the snow, and it is not a locking differential like you see on Chevys or Toyotas.

N_Jay 10-02-2008 10:02 AM

Quote:

Originally posted by deparson
VTM-4 (and SH) uses a clutch pack on each rear wheel. Thus, it can perform LIKE a LSD if it needs to.

It is NOT an open diff in the normal use of that term as it can direct 100% of the rear power to either the left or right wheel as needed.


If that is the case, then it can not turn either wheel faster than the average of the front (drive-line speed)


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