Welcome to the North American Subaru Impreza Owners Club Friday January 30, 2015
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Subaru Models > Impreza Forum

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 01-23-2013, 10:06 PM   #76
Commander Keen
Scooby Specialist
 
Member#: 319157
Join Date: May 2012
Chapter/Region: MAIC
Vehicle:
2012 Impreza 4DR 5MT

Default

Quote:
It's a completely different car, as I understand it, but is the VDC really that different? I never bothered to look it up.
I can't tell you how different it is because I haven't driven the 2011.

Quote:
And he doesn't park there because he knows how bad his VCU is based on my experience parking there in those conditions with my 5MT Leggy, his ownership of an 09 5MT 2.5i, and my incessant rants about how bad the VCU is.
It seems like it would be better to install a set of winter tires on his 2012, and see how good or bad it is himself.
* Registered users of the site do not see these ads.
Commander Keen is online now   Reply With Quote
Old 01-23-2013, 10:09 PM   #77
sti2010rl
Scooby Newbie
 
Member#: 237008
Join Date: Jan 2010
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2010 WRX STI
Satin White Pearl

Default

Quote:
Originally Posted by Commander Keen View Post
Superior for what purpose?

For driving around in low power, low speed, poor traction situations that most people buy AWD for, the benefit is likely slim to none.
I agree that the marginal return between the multiplate clutch AWD systems and the STI's DCCD is very small for putzing around town in the snow. For spirited winter driving in untracked pow, they're night and day. Absolutely-no-question. Between the VCU and DCCD center diffs? Night and day under all conditions.
sti2010rl is offline   Reply With Quote
Old 01-23-2013, 10:10 PM   #78
sti2010rl
Scooby Newbie
 
Member#: 237008
Join Date: Jan 2010
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2010 WRX STI
Satin White Pearl

Default

Quote:
Originally Posted by Commander Keen View Post

It seems like it would be better to install a set of winter tires on his 2012, and see how good or bad it is himself.
He has to have winters in Montreal by law (December 15 through March??).
sti2010rl is offline   Reply With Quote
Old 01-23-2013, 10:12 PM   #79
Commander Keen
Scooby Specialist
 
Member#: 319157
Join Date: May 2012
Chapter/Region: MAIC
Vehicle:
2012 Impreza 4DR 5MT

Default

Quote:
Commander, if you go back and read the rest of my previous post that you were quoting from, you will see that you and I are saying the same thing.
I know, I'm saying it mostly for sti2010rl who's judging these systems in a vacuum.
Commander Keen is online now   Reply With Quote
Old 01-23-2013, 10:13 PM   #80
sti2010rl
Scooby Newbie
 
Member#: 237008
Join Date: Jan 2010
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2010 WRX STI
Satin White Pearl

Default

Quote:
Originally Posted by Dirt Bringer View Post
I don't want to say you are wrong or right, but you shouldn't call him names or start a flame war if you disagree with him. There is a better way to prove him wrong if he is indeed wrong.
I didn't like the sarcastic tone of his response, so I counter-trolled. It's not because he disagreed. Hell most, if not all of you are disagreeing with me, and yet I only went Ad-hominem on him.
sti2010rl is offline   Reply With Quote
Old 01-23-2013, 10:15 PM   #81
Commander Keen
Scooby Specialist
 
Member#: 319157
Join Date: May 2012
Chapter/Region: MAIC
Vehicle:
2012 Impreza 4DR 5MT

Default

Quote:
He has to have winters in Montreal by law (December 15 through March??).
Fair enough...

It seems like it would be better to install a set of winter tires on his 2012, and see how good or bad it is himself.
Commander Keen is online now   Reply With Quote
Old 01-23-2013, 10:18 PM   #82
sti2010rl
Scooby Newbie
 
Member#: 237008
Join Date: Jan 2010
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2010 WRX STI
Satin White Pearl

Default

Commander, did you read my response to your points regarding the functioning of the VCU (3rd page)? What's your take?
sti2010rl is offline   Reply With Quote
Old 01-23-2013, 10:20 PM   #83
Commander Keen
Scooby Specialist
 
Member#: 319157
Join Date: May 2012
Chapter/Region: MAIC
Vehicle:
2012 Impreza 4DR 5MT

Default

I live in a hilly area and haven't been in a situation where the VC left me helpless.

If it comes down to it, 5MT owners can pull the handbrake to send power forward, or left foot brake to send it to the rear.
Commander Keen is online now   Reply With Quote
Old 01-23-2013, 10:22 PM   #84
Dirt Bringer
Scooby Newbie
 
Member#: 340297
Join Date: Dec 2012
Chapter/Region: MWSOC
Location: Cincinnati
Vehicle:
2013 Impreza 5sp Prm
Ice Silver

Default

Quote:
Originally Posted by sti2010rl View Post
AAAAARGH. It is not a logical comparison of an AWD system because you're comparing an AWD car to a FWD car. Who cares if they're in the same segment? If i lived in Miami, I'd prefer a FWD car, even if it were in the same price and class of an AWD counterpart. Why? Less parasitic drivetrain loss? Not as fugly? (subjective) The list goes on. What does you raping winter with AWD have anything to do with a Civic struggling in the snow? You still haven't shown me how a VCU is an better than a center open diff.

I didn't brag. I used fitness as an analogy the first time. You took it as bragging. I'll admit the second time came off as real douche territory. Do I come across as pompous? I'm sorry if I do. Maybe it's because it comes across differently in writing? Either way apologies.

P.S. I'm not a powerlifter, but I still use the big 3 to train for Strongman. And I'm really a big teddy bear; I don't kick people's asses, except on the internetz.
Well...there is the argument that AWD is more fun to drive and (in theory) doesn't suffer from as much understeer or torque steer as fwd. Not really relevant as we are talking about AWD systems, but if a car is sold in the same area, I consider a comparison valid. Of course if you give me RWD this conversation would not be happening. Because I'd be out driving.
Dirt Bringer is offline   Reply With Quote
Old 01-23-2013, 10:27 PM   #85
nels0300
Scooby Newbie
 
Member#: 331332
Join Date: Sep 2012
Chapter/Region: MWSOC
Location: Minneapolis
Vehicle:
2014 Camry SE V6
Silver

Default

Quote:
Originally Posted by sti2010rl View Post
AAAAARGH. It is not a logical comparison of an AWD system because you're comparing an AWD car to a FWD car. Who cares if they're in the same segment? If i lived in Miami, I'd prefer a FWD car, even if it were in the same price and class of an AWD counterpart. Why? Less parasitic drivetrain loss? Not as fugly? (subjective) The list goes on. What does you raping winter with AWD have anything to do with a Civic struggling in the snow? You still haven't shown me how a VCU is an better than a center open diff.
I'm not saying a VCU is better than a center open diff, sure, the 5sp could have a open center diff and you probably wouldn't know the difference. I'm saying so what. Would most people detect a difference between the Suzuki and Mistu system vs. Subaru VCU system? NO! On top of that, Suzuki is dead in the US, Mitsu is almost dead, there is no comparable Mitsu HATCHBACK, AND the Subaru 5sp works very well in most low traction situations with the exception of 90 degree driveways on Tuesdays in January in Quebec.
nels0300 is offline   Reply With Quote
Old 01-23-2013, 10:29 PM   #86
Commander Keen
Scooby Specialist
 
Member#: 319157
Join Date: May 2012
Chapter/Region: MAIC
Vehicle:
2012 Impreza 4DR 5MT

Default

Quote:
The way I understood it was the the VCU warms up at different rotational speeds of the front and rear axles thus increasing its viscousity, after which it transfers torque at a rate of 4kg X M per 100 rpm. I'm not a VCU expert, so you may need to educate me.
4 Kg/m is about 29 lb/ft, which turns into around 120 lb/ft at the axles.

100 RPM at the VCU is ~24 RPM at the wheel, which is a very slow slip.

I believe with any VC, torque transfer increases exponentially with speed, but I haven't seen data on Subaru's VC.
Commander Keen is online now   Reply With Quote
Old 01-24-2013, 01:48 PM   #87
Commander Keen
Scooby Specialist
 
Member#: 319157
Join Date: May 2012
Chapter/Region: MAIC
Vehicle:
2012 Impreza 4DR 5MT

Default

On my 5MT, taking tight turns in wet parking lots will cause the inner tires to skip like a 4WD vehicle. This shows that the VC is transferring significant torque.

Have you guys noticed this on your 5MT?
Commander Keen is online now   Reply With Quote
Old 01-24-2013, 02:12 PM   #88
John451
Scooby Newbie
 
Member#: 321966
Join Date: Jun 2012
Location: Sydneys South, Australia
Vehicle:
2012 Impreza 2.0i H
Black Pearl

Default

Quote:
Originally Posted by Commander Keen View Post
On my 5MT, taking tight turns in wet parking lots will cause the inner tires to skip like a 4WD vehicle. This shows that the VC is transferring significant torque.

Have you guys noticed this on your 5MT?
I've noticed similar on my CVT, was confused what was going on at first.
John451 is offline   Reply With Quote
Old 01-24-2013, 02:13 PM   #89
sti2010rl
Scooby Newbie
 
Member#: 237008
Join Date: Jan 2010
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2010 WRX STI
Satin White Pearl

Default

Quote:
Originally Posted by Commander Keen View Post
On my 5MT, taking tight turns in wet parking lots will cause the inner tires to skip like a 4WD vehicle. This shows that the VC is transferring significant torque.

Have you guys noticed this on your 5MT?
I have never noticed this. And that shouldn't happen, unless you're doing doughnuts. What I do know for sure it that for the VCU to transfer torque, there needs to be at least significant rotational speed differences (you need some wheel spin) between the front and rear axles before the VCU even starts to heat up--that's the only way the unit can cause lockup. Even if your front wheels rotate slightly faster than your rears in a parking lot scenario, it would not even come close to generating the heat necessarily to lock up the VCU.
sti2010rl is offline   Reply With Quote
Old 01-24-2013, 02:15 PM   #90
sti2010rl
Scooby Newbie
 
Member#: 237008
Join Date: Jan 2010
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2010 WRX STI
Satin White Pearl

Default

Quote:
Originally Posted by John451 View Post
I've noticed similar on my CVT, was confused what was going on at first.
I think you're both experiencing VDC intervention. I have never experienced that with either of the AWD systems.
sti2010rl is offline   Reply With Quote
Old 01-24-2013, 02:18 PM   #91
sti2010rl
Scooby Newbie
 
Member#: 237008
Join Date: Jan 2010
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2010 WRX STI
Satin White Pearl

Default

I definitely have experienced this with the DCCD in lock and pretty much any other manual setting in the parking lot.
sti2010rl is offline   Reply With Quote
Old 01-24-2013, 02:19 PM   #92
Commander Keen
Scooby Specialist
 
Member#: 319157
Join Date: May 2012
Chapter/Region: MAIC
Vehicle:
2012 Impreza 4DR 5MT

Default

Quote:
I think you're both experiencing VDC intervention. I have never experienced that with either of the AWD systems.
No, it wasn't the pulsing/grinding sound VDC makes through the brakes. This was a scrubbing and chirping noise from the tires, easier to hear with the windows down.

This is not something an open center differential system would do.
Commander Keen is online now   Reply With Quote
Old 01-24-2013, 02:28 PM   #93
Commander Keen
Scooby Specialist
 
Member#: 319157
Join Date: May 2012
Chapter/Region: MAIC
Vehicle:
2012 Impreza 4DR 5MT

Default

Quote:
Even if your front wheels rotate slightly faster than your rears in a parking lot scenario, it would not even come close to generating the heat necessarily to lock up the VCU.
The VCU is not an on/off device like a clutch. It transfers significant torque even when cold. Heating the fluid aids torque transfer, but it's not necessary.
Commander Keen is online now   Reply With Quote
Old 01-24-2013, 02:32 PM   #94
sti2010rl
Scooby Newbie
 
Member#: 237008
Join Date: Jan 2010
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2010 WRX STI
Satin White Pearl

Default

Quote:
Originally Posted by Commander Keen View Post
No, it wasn't the pulsing/grinding sound VDC makes through the brakes. This was a scrubbing and chirping noise from the tires, easier to hear with the windows down.

This is not something an open center differential system would do.
Well, the VCU does work. When sajohnson jacked up his rear wheels, the car moved forward easily in a flat surface and barely on an incline. When he jacked up the front, his car barely moved forward in a flat surface, and couldn't make it up the incline. So it does something, and I never really disputed that small something. It's just that that small something doesn't translate into anything meaningful in terms of AWD performance; it doesn't do enough to say that it's completely different from an open diff setup.

Before the 5MT's had VDC, they were really abysmal on the ice. I'm sure VDC has made the 5MTs more useable in such conditions, but I've never had the...pleasure...of testing them after the updates. I mean if the clamping force of the VDC is as strong as you claim it is, then perhaps the VCU is not even needed for what everyone here expects from their car. It would essentially be a 4-Matic in that case.

Regardless, I've never had your experience with my Legacy in a parking lot.
sti2010rl is offline   Reply With Quote
Old 01-24-2013, 02:36 PM   #95
sti2010rl
Scooby Newbie
 
Member#: 237008
Join Date: Jan 2010
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2010 WRX STI
Satin White Pearl

Default

Quote:
Originally Posted by Commander Keen View Post
The VCU is not an on/off device like a clutch. It transfers significant torque even when cold. Heating the fluid aids torque transfer, but it's not necessary.
I'm fairly sure that the viscous fluid needs to be heated (not saying it would take long) for binding to occur. In fact, clutches react faster than VCUs, usually taking about 1/7th of a wheel rotation before locking.
sti2010rl is offline   Reply With Quote
Old 01-24-2013, 02:39 PM   #96
sti2010rl
Scooby Newbie
 
Member#: 237008
Join Date: Jan 2010
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2010 WRX STI
Satin White Pearl

Default

Quote:
Originally Posted by Commander Keen View Post
The VCU is not an on/off device like a clutch. It transfers significant torque even when cold. Heating the fluid aids torque transfer, but it's not necessary.
From http://auto.howstuffworks.com/differential5.htm

Quote:
Under normal conditions, both sets of plates and the viscous fluid spin at the same speed. When one set of wheels tries to spin faster, perhaps because it is slipping, the set of plates corresponding to those wheels spins faster than the other. The viscous fluid, stuck between the plates, tries to catch up with the faster disks, dragging the slower disks along. This transfers more torque to the slower moving wheels -- the wheels that are not slipping.When a car is turning, the difference in speed between the wheels is not as large as when one wheel is slipping. The faster the plates are spinning relative to each other, the more torque the viscous coupling transfers. The coupling does not interfere with turns because the amount of torque transferred during a turn is so small. However, this also highlights a disadvantage of the viscous coupling: No torque transfer will occur until a wheel actually starts slipping.
sti2010rl is offline   Reply With Quote
Old 01-24-2013, 02:46 PM   #97
Commander Keen
Scooby Specialist
 
Member#: 319157
Join Date: May 2012
Chapter/Region: MAIC
Vehicle:
2012 Impreza 4DR 5MT

Default

Quote:
However, this also highlights a disadvantage of the viscous coupling: No torque transfer will occur until a wheel actually starts slipping.
I don't see this as a disadvantage at all. No torque transfer is necessary until a wheel starts slipping. You should not read this as "No torque transfer will occur until the fluid heats up". 4WD transfers plenty of torque with no slip, which is why it's unusable on dry pavement.

Quote:
I'm fairly sure that the viscous fluid needs to be heated (not saying it would take long) for binding to occur. In fact, clutches react faster than VCUs, usually taking about 1/7th of a wheel rotation before locking.
You can't compare them because they're different machines. Some torque is transferred by the VCU the exact instant a wheel begins to slip, and this torque is increased further with time.

If you want a complete picture of the VCU's behavior, it would be a 3D graph showing torque transfer with RPM delta on one axis and internal temperature on the other.

Last edited by Commander Keen; 01-24-2013 at 02:52 PM.
Commander Keen is online now   Reply With Quote
Old 01-24-2013, 03:13 PM   #98
sti2010rl
Scooby Newbie
 
Member#: 237008
Join Date: Jan 2010
Chapter/Region: E. Canada
Location: Montreal
Vehicle:
2010 WRX STI
Satin White Pearl

Default

Quote:
Originally Posted by Commander Keen View Post
I don't see this as a disadvantage at all. No torque transfer is necessary until a wheel starts slipping. You should not read this as "No torque transfer will occur until the fluid heats up". 4WD transfers plenty of torque with no slip, which is why it's unusable on dry pavement.
Fair enough.

Quote:
Originally Posted by Commander Keen View Post
You can't compare them because they're different machines. Some torque is transferred by the VCU the exact instant a wheel begins to slip, and this torque is increased further with time.
I was just just trying to point out (in response to your claim that the VCU is not on or off like a clutchpack) that the onset significant torque transfer of a VCU is gradual, and not abrupt like a clutchpack, and furthermore, because of the behavior of the VCU, you should not have experienced binding when turning in a wet parking lot. Maybe there would be some instant torque transfer as you claim, but as per the source that I posted, it would be so insignificant that it would not interfere with a turn.

Quote:
Originally Posted by Commander Keen View Post
If you want a complete picture of the VCU's behavior, it would be a 3D graph showing torque transfer with RPM delta on one axis and internal temperature on the other.
Sounds good.
sti2010rl is offline   Reply With Quote
Old 01-24-2013, 03:15 PM   #99
Commander Keen
Scooby Specialist
 
Member#: 319157
Join Date: May 2012
Chapter/Region: MAIC
Vehicle:
2012 Impreza 4DR 5MT

Default

Also, the VCU will never lock. It's not supposed to.

If you're in a situation where one axle is spinning and the other is stopped, you're probably better off punching the throttle to quickly get the stopped axle moving. Feathering the throttle over time will just cook the VCU without getting the stopped axle enough torque to move.

You can also direct torque using left foot braking and the handbrake, though I've never found this to be necessary.

None of this applies to the CVT.

Last edited by Commander Keen; 01-24-2013 at 04:06 PM.
Commander Keen is online now   Reply With Quote
Old 01-24-2013, 03:21 PM   #100
Zeeper
Scooby Specialist
 
Member#: 299286
Join Date: Oct 2011
Chapter/Region: NESIC
Location: Upstate NY
Vehicle:
2015 WRX CVT
White

Default

All I know is it works very well, and I don't need a dedicated 4wd rock crawler, I need a fuel efficient car that is safe to drive in the winter in the hilltowns where I live.

This car is great handling these conditions.

If there is an ice storm, I am staying home unless there is a damn good reason. Since I work for myself, and most of my clients will cancel in snow storms, it really isn't an issue for me. If I was worried about ice, studded tires would be on my car.

The subaru in the video on rollers? likely either did not have abs or it was not integrated with vdc.

The video of a Crosstrek (CVT) on a Land Rover course was already posted, wheels off the ground completely stopped, and less wheel slip than the 4WD Land Rover.

If I could get to england, I would gladly drive my car on the same course (5speed). If you really want to see that send me lots of money so I can make the trip, I'll drink a pint in your name after shooting the video.

Last edited by Zeeper; 01-24-2013 at 03:27 PM.
Zeeper is online now   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -4. The time now is 03:49 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2015 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.