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  #421  
Unread 8th June 2019, 01:05 AM
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Certainly not the line to take if you want to get to the other side, but a great comparison for a thread like this!


As soon as the SG gets out flexed the only thing giving power to the wheels with traction is the 4kg vLSD, which usually doesn't give enough torque if trying to get up and over something, like getting out of that hole. So it doesn't matter how grippy the tyres in the air are and the wheels on the ground aren't receiving enough torque to climb out of the hole, so doesn't matter how grippy those tyres are either. The SH on the other hand has the electronic traction aids that help trasnfer that extra bit of torque to the wheels with weight on them, which allows it to drive out of the hole. As soon as a car is getting out flexed, the driveline becomes more important then tyres.
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  #422  
Unread 8th June 2019, 01:18 AM
Beachworm Beachworm is offline
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I tend to agree. As the driver of the SH, and observing the video I now realise that only the right rear wheel had any significant contact with the ground yet the VDC was able to put enough torque to that wheel to keep the car in its wheelstanding pose. When I took my foot completely off the accelerator and gently on the brake it rolled back into the hole. It required only a small change in line for me to then drive out without further trouble.

This situation raises an issue that can be very important when off roading. The three cars chose an inappropriate line because the drivers all felt that it was safer to err on that side of the best line than on the other. If we had gone too far to the left, the left wheels would have fallen into a very deep wheel track resulting in likely water entry on the side where the ECU resides in the Foz. Overcompensating in managing risk has its own problems. The fact is we couldn't see where our wheels were meant to go and relied on the directions of the spotter who didn't indicate the best line until we had all committed to the wrong one.

Last edited by Kevin; 8th June 2019 at 04:17 AM. Reason: Unnecessary use of Quote
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  #423  
Unread 10th June 2019, 07:41 PM
ABFoz ABFoz is offline
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Quote:
Originally Posted by Red XS View Post
As soon as the SG gets out flexed the only thing giving power to the wheels with traction is the 4kg vLSD, which usually doesn't give enough torque if trying to get up and over something, like getting out of that hole.
This is the 4kg centre diff, right? It has its limits and if used hard, usually they will need replacement. Subaru still manufactures genuine ones for older models. The 20kg, one for me is the way to go if it's a manual. Even the brand new ones from Japan are surprisingly decently priced.

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Originally Posted by Beachworm View Post
I tend to agree. As the driver of the SH, and observing the video I now realise that only the right rear wheel had any significant contact with the ground yet the VDC was able to put enough torque to that wheel to keep the car in its wheelstanding pose. When I took my foot completely off the accelerator and gently on the brake it rolled back into the hole. It required only a small change in line for me to then drive out without further trouble.
During diagonals like this one, traction systems like the VDC excel a lot. Your 4EAT gives decent torque supply to both axles and if coupled with the VDC, the drivetrain will do wonders.
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  #424  
Unread 10th June 2019, 07:53 PM
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The SG is an auto so the centre diff is a clutch pack, not a viscous coupling. He may have benefited from a centre diff lock switch.
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  #425  
Unread 11th June 2019, 02:03 AM
ABFoz ABFoz is offline
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Oh OK. In that case, the difference is the VDC which performs really well in those diagonals. It gives the car traction to the front, as well. In the rear, it is much more effective in giving power to the correct wheel that the vLSD.

The front diff on the SG is open when stock.The rear vLSD could have helped but it would require a lot of rpm first before engaging the other wheel. Also, with that incline the vLSD may struggle, although I've seen ones that were able to go out of much deeper ones but, again, with a lot of rpm and wheel spin. Cheers.
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  #426  
Unread 11th June 2019, 09:38 AM
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I meant the rear vlsd in my above post. It takes a fair bit of wheel spin for it to transfer enough torque to the wheel with traction to get out of a hole like that. The VDC does those diagonals more effectively.



Which 20kg centre diffs are you talking about? Genuine? And where from?
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  #427  
Unread 11th June 2019, 01:55 PM
MiddleAgeSubie MiddleAgeSubie is offline
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Re: VDC


Since it is not optimized as offroad traction control (X-mode hopefully is), VDC does not always do well. There are situations where it will leave an Outback like the one I had hopelessly spin certain wheels or, conversely, as on the Tribeca, allow zero wheelspin in other situations.


One weakness, and this I have heard from others as well, is generally when the front wheels are sideways and the vehicle is going uphill. I even vaguely recall someone on youtube exploiting this weakness to argue for a different AwD system as being superior.


Another scenario where I have found VDC above its pay grade is a very slippery hill, like big gravel mixed with dirt. VDC totally loses its mind in such conditions and thinks you are asking for a tire burnout
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  #428  
Unread 11th June 2019, 07:31 PM
Beachworm Beachworm is offline
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Quote:
Originally Posted by MiddleAgeSubie View Post
Re: VDC


Since it is not optimized as offroad traction control (X-mode hopefully is), VDC does not always do well. There are situations where it will leave an Outback like the one I had hopelessly spin certain wheels or, conversely, as on the Tribeca, allow zero wheelspin in other situations.


One weakness, and this I have heard from others as well, is generally when the front wheels are sideways and the vehicle is going uphill. I even vaguely recall someone on youtube exploiting this weakness to argue for a different AwD system as being superior.


Another scenario where I have found VDC above its pay grade is a very slippery hill, like big gravel mixed with dirt. VDC totally loses its mind in such conditions and thinks you are asking for a tire burnout
Perhaps it would help to know that I have had the ECU software modified to perform better off road. This affects the front/rear split and the responsiveness of the VDC. In effect it has given me X Mode without the hill descent control. I have not experienced the problems you mentioned and I have climbed some impressive hills on rock/gravel/clay mixed surfaces. As long as traction control is switched off, my tweaked VDC performs above expectations.
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  #429  
Unread 11th June 2019, 07:34 PM
Beachworm Beachworm is offline
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Quote:
Originally Posted by Red XS View Post
I meant the rear vlsd in my above post. It takes a fair bit of wheel spin for it to transfer enough torque to the wheel with traction to get out of a hole like that. The VDC does those diagonals more effectively.



Which 20kg centre diffs are you talking about? Genuine? And where from?
Try alldrivesubaroo
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  #430  
Unread 12th June 2019, 04:46 AM
ABFoz ABFoz is offline
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Quote:
Originally Posted by Red XS View Post
I meant the rear vlsd in my above post. It takes a fair bit of wheel spin for it to transfer enough torque to the wheel with traction to get out of a hole like that. The VDC does those diagonals more effectively.

Which 20kg centre diffs are you talking about? Genuine? And where from?
Yes, it will need some decent wheelspin for the vLSD to work. It also takes some practice to get used to.

Regarding 20kg centre diffs, Subaru lists them as maintenance parts so, according to one of our local dealership, all Subaru parts people should be able to procure brand new 4kg and 20kg ones. They said all parts from 1990, or 1989 in JDMs, should be available for procurement. If they are in stock in Japan, it will take 3 weeks to arrive here and if it’s not the dealership said they can request one from the factory but it may take up to 4 months, if manufacturing is approved.

They said that some dealerships wouldn’t bother because of the hassle, just like another one closest to us. They won’t really car whereas the one a bit further away will happily procure the products for their clients. It’s pretty hard to get a good parts person because most don’t want to be bothered with older models.

You can try searching for a good dealership that does this because if they are happy to do it, they will give a decent price. For reference, my sister’s partner fell in love with his GH8 S-GT so he asked how much a brand new EJ205 is and they gave a price of NZD 2,700 shipped. This is for a 2008 model. Some parts people are happy to do it for you.

UAE Subaru in Dubai is also very enthusiastic although their shipping quotes cover Japan to Dubai only. They cover supply in Central and South East Asia, as well as Europe and Africa.

All Drive Subaroo may be able to help. Some Subaru garages are able to help.

Quote:
Originally Posted by MiddleAgeSubie View Post
One weakness, and this I have heard from others as well, is generally when the front wheels are sideways and the vehicle is going uphill. I even vaguely recall someone on youtube exploiting this weakness to argue for a different AwD system as being superior.

Another scenario where I have found VDC above its pay grade is a very slippery hill, like big gravel mixed with dirt. VDC totally loses its mind in such conditions and thinks you are asking for a tire burnout
I think I remember that video. Mazda salespeople or marketers would exploit a scenario where they say their computer would react a bit more quickly when a stopped CX-5 is on the top of the hill and the wheel is turned. Somehow, it reached Japan so the car companies had to hire an independent tester to prove/disprove a couple of things off-road. They used the SG where VDC was first implemented and, as usual, the Subaru won in all scenarios. The X-trail was the next. The other ones including the Mazdas struggled with the courses including what’s supposed to be their weakness because the uphill was muddy whereas in the US, they only used dry but loose surfaces.

There are some clips of that test popping up on YT but they are sometimes hard to find because they are in Japanese. I will see if I can find a clip shared by my brother who is living in Japan but that was from a chat a long time ago.

For mud and rocks on an uphill, I think my right foot does a better job!

Quote:
Originally Posted by Beachworm View Post
Perhaps it would help to know that I have had the ECU software modified to perform better off road. This affects the front/rear split and the responsiveness of the VDC. In effect it has given me X Mode without the hill descent control. I have not experienced the problems you mentioned and I have climbed some impressive hills on rock/gravel/clay mixed surfaces. As long as traction control is switched off, my tweaked VDC performs above expectations.
I think it may have helped, @Beachworm. My brother said that in Japan, it’s not unusual for a Subaru owner to drop by a garage to get a technician to use SSM to adjust the dynamics according to the owners’ driving styles. Cheers
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