|
|
|
|
Thread Tools | Display Modes |
05-10-2003, 01:19 PM | #26 |
Scooby Specialist
Member#: 13095
Join Date: Dec 2001
|
I've read all that before and more and still have more questions than answers.
* Registered users of the site do not see these ads.
|
05-10-2003, 01:48 PM | #27 | |
Scooby Specialist
Member#: 3348
Join Date: Dec 2000
Chapter/Region:
NESIC
Location: Injun Country
Vehicle:2013 Polo TSi Red |
Quote:
|
|
05-10-2003, 02:28 PM | #28 |
Scooby Specialist
Member#: 856
Join Date: Feb 2000
Chapter/Region:
International
Location: Cambridgeshire, England, UK
Vehicle:2123 JDM STi Black |
guys, that writeup is just a laymans explanation of how the centre diff affects the handling, technically it is wrong.
The only way to change a torque split ratio in an AWD system is to change the mechanical gearing of the centre diff, the DCCD doesnt do that. Efectively all the DCCD is doing is varying the amount of permisible slip that can ocur in the centre diff. Fully open means you can get into a situation where all power is going to the rear wheels when you get them spinning up, this is how i can do power slides with full oposite lock aplied, that doesnt mean the torque split isnt a natural 65/35 ratio, just in the same way as an open front diff in a FWD car has a 50/50 split left/right yet when you get stuck in mud all the power goes to one wheel. When you have the diff fully locked, that means no slip is permited front/rear, in a straight line you dont get any wind up with this, but as soon as you start to corner the varying amounts of wheel travel causes the diffs to bind up, then you get judering as the centre diff breaks away from fully locked because it cant clamp that much force and you also get the tyres patering as they try and break traction to eliminate the diff windup. Stick one of these cars in a 15MPH small circle and gradually increase the centre diff lock ratio, you will feel the car binding up and the diff ratio increases to a point where its like aplying the brakes. The diff lock goes from 0-100% locked, that isnt altering the centre diff ratio. The other thing is that description says there are 6 positions, thats not correct either, there are 6 display points on the dash, but the changeover is analogue and completely variable. |
05-10-2003, 04:56 PM | #29 |
Scooby Guru
Member#: 26361
Join Date: Oct 2002
Chapter/Region:
TXIC
Location: Sugar Land (Houston), Tx
Vehicle:My shenanigans are cheeky and fun |
Whoo hoo I was right.
|
05-11-2003, 09:07 PM | #30 | |
Scooby Newbie
Member#: 17903
Join Date: Apr 2002
Location: Melbourne, Australia
Vehicle:2006 |
Quote:
|
|
05-11-2003, 10:04 PM | #31 |
Cowabunga!
Super Moderator Member#: 185
Join Date: Aug 1999
Chapter/Region:
South East
Location: Orlando, Fl
Vehicle:2014 Impreza Sport Ice Silver Metalic |
Thanks John.
I don't know why people argue with ya as you have been using the dam thing for a while now! Cheers, Leo |
05-12-2003, 02:25 AM | #32 |
Scooby Newbie
Member#: 34388
Join Date: Mar 2003
Location: Lehigh Valley, PA
Vehicle:04 WRX STi Black w/gunmetal |
glad someone got the message...
Miss Cleo was drawing a blank with the cards!
|
05-12-2003, 09:18 AM | #33 | |
Scooby Specialist
Member#: 8193
Join Date: Jul 2001
Chapter/Region:
MWSOC
Location: Illinois, USA
Vehicle:2008 WRX STI Blue |
Quote:
|
|
05-12-2003, 04:56 PM | #34 |
Scooby Specialist
Member#: 31948
Join Date: Jan 2003
Location: SoCal
Vehicle:2004 STi Aspen White |
and whats a good "position" on the DCCD button to provoke oversteer?
thx |
05-12-2003, 05:29 PM | #35 | |
Scooby Specialist
Member#: 856
Join Date: Feb 2000
Chapter/Region:
International
Location: Cambridgeshire, England, UK
Vehicle:2123 JDM STi Black |
Quote:
Just imagine if this car had an active front or rear diff, you wouldnt be discussing the diff changing it's torque split Left/Right would you? So whats so diferent about the centre diff that makes this so hard to understand? All you are doing is changing the rate of lock of the centre diff, it's just like taking out a 15NM viscous diff and replacing it with a 25NM viscous diff, you wouldnt expect that to have magically changed the torque split, just the locking load making it a tighter diff. All the DCCD does is stops you from needing to physically change the diff unit to change it's locking rate, it does this by aplying an electromagnetic force to a mechanical diff unit. It's not black magic. Having the DCCD set to open will enable you to break traction easier and provoke oversteer more easily, you can equally have the car oversteering with the diff fully locked, but it takes more effort, power and more weight transfer to get the car into a slip angle where you are oversteering. |
|
05-12-2003, 06:31 PM | #36 | ||
Scooby Specialist
Member#: 8193
Join Date: Jul 2001
Chapter/Region:
MWSOC
Location: Illinois, USA
Vehicle:2008 WRX STI Blue |
Quote:
Quote:
|
||
05-12-2003, 07:00 PM | #37 |
Scooby Specialist
Member#: 856
Join Date: Feb 2000
Chapter/Region:
International
Location: Cambridgeshire, England, UK
Vehicle:2123 JDM STi Black |
Read up on how gearing alters torque distribution is my best advice if you want to understand this properly.
Or better still, go and drive the thing and learn what it does/doesnt do. |
05-12-2003, 07:09 PM | #38 | |
Scooby Specialist
Member#: 856
Join Date: Feb 2000
Chapter/Region:
International
Location: Cambridgeshire, England, UK
Vehicle:2123 JDM STi Black |
Quote:
The gearbox in the DCCD doesnt match that analogy, as the DCCD gearbox has 2 sticks with a gear in the middle of it to give you the torque split change. |
|
05-12-2003, 07:15 PM | #39 | |
Scooby Specialist
Member#: 13095
Join Date: Dec 2001
|
Quote:
It's also funny that you think driving the car will explain how it functions....given that the information in the parent post that you are correcting comes from someone who IS driving the car. I do admire your attempts to explain though....and look forward to further explanation. |
|
05-12-2003, 07:19 PM | #40 | |
Scooby Specialist
Member#: 13095
Join Date: Dec 2001
|
Quote:
|
|
05-12-2003, 07:34 PM | #41 | |
Scooby Specialist
Member#: 856
Join Date: Feb 2000
Chapter/Region:
International
Location: Cambridgeshire, England, UK
Vehicle:2123 JDM STi Black |
Quote:
The WRX has a direct 50/50 torque split, put a variable lock LSD in a WRX and you still have 50/50 torque split. The DCCD setup gives you that 64:36 split irespective of how locked the diff happens to be. Weld the thing solid and you have 64:36, take the Electromagnet away and you still have 64:36. The DCCD is just an LSD, it's not a variable gear kit. As to driving the car, no disrespect but i have been driving DCCD equiped cars for years, i know what i am talking about. Top tip, look at what car i drive every single day (1999 WRX STi5 TypeRA) |
|
05-12-2003, 07:38 PM | #42 | |
Scooby Specialist
Member#: 8193
Join Date: Jul 2001
Chapter/Region:
MWSOC
Location: Illinois, USA
Vehicle:2008 WRX STI Blue |
Quote:
Try to think about my analogy not as a point to beat. Tell me how locked diff can vary torque between front and back? I am sorry but you just refuse to get it. |
|
05-12-2003, 07:43 PM | #43 |
Scooby Guru
Member#: 26361
Join Date: Oct 2002
Chapter/Region:
TXIC
Location: Sugar Land (Houston), Tx
Vehicle:My shenanigans are cheeky and fun |
he said the wrx differential is locked not the sti's. The sti has a variable center diff but it only varies slip in the wheels not torque. The 64-36 split come from the gearing of the 2 driveshafts in the diff and it does not vary.
|
05-12-2003, 07:45 PM | #44 | |
Scooby Specialist
Member#: 856
Join Date: Feb 2000
Chapter/Region:
International
Location: Cambridgeshire, England, UK
Vehicle:2123 JDM STi Black |
Quote:
Just think about this, how would you build a system that gave you 10% torque to the front and 90% torque to the rear. Or for simplicity, 10% torque at one end of a shaft and 90% torque at the other. Simple, you cant do it with a solid shaft, you have to have step off gearing to give you that change in torque and two shafts. Thats all the gearbox in the DCCD cars have in adition to a variable diff. |
|
05-12-2003, 07:57 PM | #45 | |||
Scooby Specialist
Member#: 8193
Join Date: Jul 2001
Chapter/Region:
MWSOC
Location: Illinois, USA
Vehicle:2008 WRX STI Blue |
Quote:
Quote:
BINGO! Quote:
|
|||
05-12-2003, 08:17 PM | #46 |
Scooby Guru
Member#: 26361
Join Date: Oct 2002
Chapter/Region:
TXIC
Location: Sugar Land (Houston), Tx
Vehicle:My shenanigans are cheeky and fun |
torque does not change while the tires have traction the limited slip diff only comes into play when some tires have no traction the diff adjust the speed of the tire to regain traction, but when you are driving down the road with the diff at full lock there is still 64% rear and 36% front torque split.
|
05-12-2003, 08:56 PM | #47 | |
Scooby Specialist
Member#: 13095
Join Date: Dec 2001
|
Quote:
Again, appreciate the effort at explanation, but it is still unsatisfactory. Beginning with the fact that the initial torque split is 35% 65%, not 36% 64%. Adding the fact, that we can not tell or determine exactly when or exactly to what degree the differential is redistributing torque. Certainly it is incorrect to state that it responds only to "NO TRACTION", a situation that seldom exists. I have never heard of any LSD that literally functioned that way. I also know that the point is often made that torsen differentials do NOT respond to wheel sleep per se, they don't know anything about wheel-slip per se, they respond to differences in torque. That is a sticking point of many explanations of torsen diffs. Now add to that that DCCD-A supposidly responds to throttle position, g-force, etc. Hence, still more questions than answers. John: We understand that you have a similar car, but that does not help us understand your explanation. After all you are adamently contradicting even Subaru's own explanation of how DCCD works. If you wish to dispute statements to the effect that DCCD alters the effective torque distribution, then it would seem that you must start by getting Subaru to stop saying that it does. |
|
05-12-2003, 10:04 PM | #48 | |
Scooby Specialist
Member#: 8193
Join Date: Jul 2001
Chapter/Region:
MWSOC
Location: Illinois, USA
Vehicle:2008 WRX STI Blue |
Quote:
This is what Subaru says and it has some logic behind it. John's logic is lacking and I do not care if he owns DCCD or not. Let him improve his logic and I might agree with him but only if it makes some sense. |
|
05-12-2003, 10:20 PM | #49 |
Scooby Guru
Member#: 26361
Join Date: Oct 2002
Chapter/Region:
TXIC
Location: Sugar Land (Houston), Tx
Vehicle:My shenanigans are cheeky and fun |
here is the subaru manual for the dccd it mentions nothing about adjusting torque distribution. http://www.scoobynet.co.uk/bbs/threa...hreadID=143750
better explanation of everything and how the diff is not torque sensing http://forums.nasioc.com/forums/show...hreadid=226610 And THE dccd disscusion thread http://forums.nasioc.com/forums/show...highlight=dccd |
05-12-2003, 10:42 PM | #50 | |
Scooby Specialist
Member#: 13095
Join Date: Dec 2001
|
Quote:
"DIFF FREE: No front and rear LSD (Front to rear power distribution=36:64) DIFF LOCK: The front and rear have an almost direct connection. (Front to rear power distribution=front/rear load distribution)" |
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Come on i-clubbers, what's one thing that you are ashamed of actually liking. | Eric SS | Off-Topic | 72 | 01-02-2009 07:42 PM |
The ONLY thing that will be on the news for the next 4 weeks | tacomaprime | Off-Topic | 11 | 11-14-2007 12:56 PM |
New, 2005 2.5RS or used, 02-03 WRX for a first-time Subie driver? | live- | Newbies & FAQs | 19 | 02-10-2005 02:29 AM |
haha that new Neon...first time ive seen one yet | yzfrone | Mid Atlantic Impreza Club -- MAIC | 33 | 12-19-2003 07:24 PM |
One thing that is wrong with the world (music related) | JGard | Off-Topic | 18 | 03-05-2003 07:19 PM |