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  #1  
Old 10th February 2014, 09:28 PM
BeeJ BeeJ is offline
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Default VTD vs MPT

Found this video on foz.org and thought it was worth sharing:

https://www.youtube.com/watch?v=2uu_mN062M8

Shows the difference between the auto with VTD, auto with MPT and dual range manual.
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Old 10th February 2014, 09:44 PM
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Except the first foz was an na 2.0L driven reasonably conservatively and the second was a 2.5 turbo and they gave it some beans too.

VTD isnt bad but I don't think the difference would have been that profound in a equal test on that sort of surface.
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Old 10th February 2014, 10:16 PM
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Gidday BJ & David

I have to agree with you, David.

1) The vehicles were driven in a manner that deliberately accentuated the differences - i.e. not driven in anything like the same manner.

2) The tests were specifically designed to show the differences - i.e. the ramps set up at exactly the Forester's wheel base apart; and the drivers specifically stopped at the worst possible point (in a couple of cases reversing back to that point ... ), rather than maintaining some momentum that would have carried the vehicle over with ease.

3) If they were trying to demonstrate the benefits to a completely incompetent driver driving in conditions that they should have avoided like the plague to begin with, perhaps they have a point.
However, one simply doesn't rev the rings off the car in those situations the way they obviously did ...
If one gets a bit stuck, allow the car to roll backwards a little bit and regain grip, then gently power on allowing the momentum to carry one over the 'hump'.
If you power on when you have lost momentum and grip, you will spin the wheels like crazy, while travelling backwards (as they did), you are almost guaranteed to lose traction (as they did ... ).

I am sure that there are positives to all this, but if there are (specially in the ramp test), why does Subaru recommend turning the VDC OFF when off road?

Personally, I find that my SG with 5MT/DR without VDC is more stable than SWMBO's SH 4EAT with VDC, in all the conditions I have been in, specially on road where I have driven the SH more miles. I have never driven the SH on anything approximating a dirt road. One must also bear in mind that the SH is higher, longer, wider and heavier than the SG II.

IMO, the SH is a far better family type car than my SG; but I far prefer the SG for my driving, precisely because it is lower, shorter, narrower and (slightly) lighter than the SH. I also far prefer the MT to the AT, regardless that the 4EAT with SportShift is better than any other auto box I've driven.
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Old 11th February 2014, 01:49 AM
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yeah not a very fair test but VDC does seem pretty good!

I liked the manual on the ramps, just shows how limited open diffs are!
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Old 11th February 2014, 02:31 AM
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Gidday NL

Only the front diff is open on the MY06/07 SG. Centre is vLSD and so is the rear.

Really shows what a "stunt driver" can make a car do, more than anything else, IMNSHO.

Any experiment without controls on the non-random variables isn't worth a bumper statistically, or otherwise ... .

I have got myself into that kind of position. The solution was to roll back to where I could get good grip, and use a different line with a bit more power while I had grip so that the momentum took me over the hump, back off the power as I hit the loose stuff just before the hump, then power on again when the front wheels had something to grip on. Venom pointed me to a better line. It worked.
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Old 11th February 2014, 04:33 AM
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It's important to distinguish between the two systems -

VTD: a centre differential with an electronically controlled lockup feature which is used on some higher-end automatic models in place of the simpler MPT system used on cheaper models

VDC: a stability and traction control system that can cut engine power and apply the brakes to the individual wheels in cases of oversteer, understeer or wheelspin

Quote:
Originally Posted by Ratbag View Post

Why does Subaru recommend turning the VDC OFF when off road?
Turning it 'off' (with the button on the dashboard) only disables the ability of the VDC to cut engine power - it still leaves active the facility whereby individual wheels are automatically braked in the case of wheelspin. This is handy for offroading as you still have full engine power (and at low offroad speeds, this represents less of a safety risk) but still have enabled the brake traction control that curtails cross-axle wheelspin.
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Old 11th February 2014, 05:57 AM
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Thanks for the detailed explanation, Simon.

What I was rather perplexed by is that only VDC was available on the models being "tested", AFAIK. Just checked in the OM for our MY06. Mine does not have VDC. It states "If Equipped", so was an option somewhere in the world ... .

If one stripped out all the items marked "If Equipped" out of my car, I am not sure how much would be left! . The OM would be about half the thickness it is .
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Old 11th February 2014, 06:37 AM
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seriously RB
VTD isnt VDC
why are you talking about SH foresters? The test was SG foresters.

1) This doesnt make the results less true, and I disagree
2) whats your point? Its a test, arent you supposed to create a scenario to highlight the differences
3) Thats your opinion but I dont think the test pits in competent drivers against each other, think its a great illustration of diagonal situation and the centre manual diff, vs auto MPT vs VTD

vLSD is sh!thouse! almost everyone agrees its almost a sh!t as a open diff!

This isnt a thread about how you think your DR manual 5 speed with vLSD is completely adequate and no one should modify or challenge standard subaru, I see a comment like this on almost any thread that someone talks about modding a foz, inadequate diffs, inadequate LR

Thanks for adding a VDC discussion
Thanks for adding a discussion for the millionth time on auto vs manual
Thanks for adding sportshift vs standard auto

It was supposed to be a thread to show a centre VTD vs a MPT

/rant
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Old 11th February 2014, 06:47 AM
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^ ??
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Old 11th February 2014, 07:31 AM
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Hahahaha, oh you guys.
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