Here is the TEST of the more capable DCCD tranny. Tranny is an '04 JDM DCCD STi 6spd running STI driveshaft/axles knuckles/spindles AND BREMBOS. I'll will test the OUTBACK w/ its 5spd tranny tomorrow or so. This DCCD test eliminates the welded center diff RS test because I am able to LOCK the center diff, unless you guys wanna see that in action, I can do that too. SORRY MY CAMERA PHONE SUCKS!!!! Part 1 The rear lifted OFF the ground without DCCD. Then the rear held by the e-brake and it died. I then applied more gas and it moved a little but not like I WISHED it'd do. THEN the DCCD is enaged and the car does MOVE, then DCCD taken off and you see the simple regular open center diff feeding more power to the rear. I Could have done the front and it would have been the same thing. Part 2 This test shows how the AWD is capable of climbing a SINGLE RAMP with DCCD locked. First no DCCD and you notice wheel spin. THEN DCCD engaged and it'll climb up. I took the DCCD off again and it didn't climb. I WANT YOU ALL TO UNDERSTAND that the front tires are STILL ON THE GROUND. If a front wheel was to LIFT OFF, that wheel will spin with the rear that is off the ground and it would have not made it up the ramp. Part 3 This SETUP shows the disadvantage of the locked center diff with inresponsive front/rear LSD. We simulate it being tee-tered on oppisite corners. You can see the wheels spinning front and rear. I held onto the wheels with the DCCD off. I would not have been able to hold the wheels from spinning if the DCCD was locked so I didn't attempt to. The front LSD is not HELICAL like what I said, it is a SURETRAC but I mistakenly said it was a HELICAL, which functions the same. The STi 2way clutch type will only LOCK UP if there is resistance to where the pinion shaft is able to push the pressure rings against the clutch plates. If it was an aftermarket rear LSD, it'd probably have more INITIAL lockup to where it'd be able to move the car and if torque applied it'd probably apply pressure to the clutch packs. e-brake technique with DCCD off This technique is applied in this SAME SITUATION single ramp setup to allow the clutch type LSD to WORK. By applying the e-brake, the wheels are held from spinning. In turn the pinion shaft will be pushing the pressure rings apart from each other from the torque applied from the engine. The ENGINE will overpower the brakes no doubt. We climb up first again without e-brake and no DCCD. Then we apply e-brake and you can see it climbs right up because the clutch LSD is now able to apply lockup because there is RESISTANCE. The second time I applied e-brake, I used less than the first and you can see the wheel now spin a bit more but because there is some resistance the clutch LSD is able to do what it was designed to do. Now this test just SHOWS how the AWD system works with the DCCD or your typical part-time-4WD. In any case, if you wanted ultimate, just have the rear welded or have a locker put in and have the center diff locked. If you want me to test this on slippery surfaces, I can. I will simulate slippery surfaces if you want to see that. .....I know nothing....
haha, your center diff is as primitive as mine....except I have a stronger rear LSD. I bet I could climb one ramp on the rear with the center unlocked. oh yea.....and less gears, weaker gears, and smaller brakes. oh well.....fuji still wins :yumyum: interesting vids though!
Nice Video, I tried to understand the different advantages, but I don't exacltly know how it all works still. The video made alot more sence to me, But what is the best way to go? Asuming you have a set up like mine: 07' wrx 5spd, What would be the best parts to swap? I always thought the best way to go would be a STI 6 spd with DCCD. What is going to allow me to keep the power grounded the best? In terms of Parts?
It Depends what I want to do with the car. If you know your application, you can replace your stock diffs with better units available KAAZ, CUSCO, Quaife, OBX, etc. IF I had your driveline: Tarmac specific and some drifting I'd do Quaife front Helical gear type LSD....CUSCO tarmac center diff, and KAAZ clutch type 1.5way rear LSD. For gravel rally cross type KAAZ 1way front LSD, STi 20kg center diff, and KAAZ 2way rear LSD. For regular steet and some track events Stock front diff, STi 20kg, KAAZ 1.5way rear. Anytime you add an LSD to the car, the character of the car will CHANGE when on/off the throttle. You must relearn to drive it.
SO, with an 05 STI, if you have it in LOCKED mode, is it equal power to the front and back? What about AUTO mode and the other arrows in the dash? I am still confused with the setup. I was told that LOCK would be equal power to all wheels, and best for low traction situations, but not a lot of cornering, since the wheels are all trying to go the same speed, even if they aren't actually doing so.
Yes the DCCD diff is essentially open without any control. Pretty much an auto transfer clutch controlled magnetically instead of using hydraulic pressure.
Yes, with it in LOCKED MODE, it will send power EQUAL to "front and back." There are differentials in the front and back so if a front happens to lift off the ground as well as a rear tire those two will most likely spin when throttle is applied. If your LSD units work very well, they will most likely not spin. Auto mode the ECU uses the ABS sensors to read wheel speed. If your STi was on the ramp test in AUTO DCCD mode, it would most likely engage the DCCD because of wheel slippage. The rear does have an LSD, but for it to work you need resistance so the pressure rings in the diff can push the clutch plates to limit slip from left to right or vise versa. Maybe I should ask my buddie to bring over his STi for a test. lolz With differentials the left to right wheels will always have the option to spin different speeds even though the center diff is locked. When I had a welded center diff, basically locked, I found that the inside rear always chirped when doin turns. This is because the inside rear is the SLOWEST wheel spinning. The differentials up front makeup for the speed difference, but the rear has to as well, and because the inside rear is the one that has the least circumference, it will have to SPIN faster than what it's going to catch up with the front. It will SPIN dispite having LSDs. Remember even with LSDs, you will only get power to ALL WHEELS if they are on the ground. Each wheel get 25% of the power. You lose traction in the front passenger and that wheel will get MORE power to it dispite having an LSD. A LSD only limits the left to right wheel speed, but limited slip depending on lockup strength; like in the e-brake demonstration.
So, LOCKED should be better in snow and all of that then. Does Auto just give power to the wheels that are slipping, rather than a set percentage? When I would go up the tightly circled ramp at work in the parking garage, it seemed like the car didn't like it, its almost like it would make a weird shudder or shifting sounds as if the wheels were being forced to do something they didn't want to. This was in auto mode too.
Locked is better in MOST cases, a lot better than your average AWD Subaru. It's pretty par with the NEW Subarus with the traction control system, applying brake to the slipping wheel, but locked responds faster in some cases because it's locked. You don't have to wait for wheel slippage. If the rears where on ice, and the fronts on dry ground, the rears would NOT slip on a "normal" start. If you where to DUMP the clutch and apply A LOT OF POWER to over power the front tires, yes they will spin. In auto mode, it doesn't really give power. It just applies lockup in the center diff. It'll send a certain percentage depending on wheel slippage and lateral G, acceleration/deceleration, yaw and steering angle. If you where in a SLIDE, the lateral G center would sense some G's, the steering angle would be different, also throttle position. The DCCD control unit would apply an amount of lockup depending on the feedback from the sensors and try to pull you out of the slide. Some cases it make even go FULL LOCK UP if you where in a BIG SLIDE. The rear tire will chirp a little when you apply gas because of the clutch type LSD unit; '04-'05? With the center diff locked it also does this. Your DCCD set in auto probably doesn't lock the diff, but just the rear tires chirping because of the LSD? I may be wrong and the DCCD may even apply limited slip because of wheel speed. I guess the DCCD control unit is only as smart as Subaru engineers design it to be. Subaru DCCD http://www.driveperformance.subaru.com/version1_2/blueprint.asp The Skyline GTR R34 works like this, it also has a rear diff that works VERY MUCH LIKE the Mitsubishi's YAW CONTROL which it'll send power to left or right. I'm not sure on how that rear diff works....does it apply braking??? does it apply LOCK UP in the rear diff????
I have an 05. I have never really used lock. It's a shame I probably won't have the car long enough to test it in more snow---probably selling it. Thanks for all of the info and knowledge...I have always been curious about all of that.
you sure about this? my understanding is that the DCCD center diff in full lockup is extremely strong. a trusted source over on USMB posted a lb/ft number a while back that really surprised me (the site is down now.....once it's back up I'll see if I can find it). speaking from my own experience, which is slightly different as the FT4WD is a bit different. but full lock can really play with the handling characteristics. I find that with my car, it can really amplify the understeer while off the throttle, but a quick flick of the wheel and jab of the happy pedal, and the car comes around wonderfully.
If the rears where on a slippery surface, yes the front will spin if you apply LOTS of power and let go of the clutch, because the rear isn't holding up anymore. Center diff is still locked.
I've spun all four on my car on dry pavement. That is also with 350 lb*ft on crappy Fusion HRi's. I had my Spiider DCCD controler set to full aggressive. When you turn in, the controller will apply less lock to aid with rotation. But when you get back on it, it will apply more lock. This is even more advantageous when you have an '05 or newer 6mt with the helical front differential. The DCCD differential is very much like the transfer clutch on an automatic, except using an electromagnet to apply pressure on the transfer clutches vs. using hydraulic pressure like an automatic transmission does. Also, it defaults to open, where an auto tranny defaults to locked because the the hydraulic pressure that is constantly there, unless the duty C solenoid is diverting it.
I see what you mean. I thought you meant the diff would slip......you were talking about all 4 tires slipping. nice!
When My rear axle broke and I locked the center diff, the only path of torque to be transferred to was the front. When I went WOT the front tires slipped. This broken rear axle simulates the rear on ICE as well because there is no traction in the rear at all. ya? ya?
oh yea, makes perfect sense. I too have run with a locked center and missing/broken rear axle.....(even tried with open center, and missing axle. nothing but the LSD to rely on. it's surprisingly strong!) I Just misunderstood what you were saying.
Here's a bunch of vids of the Forester going in snow stuff. Please ask questions if any!! Wew learn something new everyday, you know! http://www.youtube.com/profile?user=DCA555&view=videos When I start looking at these vids, the more pop up. Here's how capable the NEW AWD system with traction control is. If your rotors are wet the traction control won't be able to help much. If you want fast reacting AWD you have to have high initial limited slip or full lock up. The NEWer Subaru's with traction control is the very next best AWD system available.
This test is a very good test to show the center diffs capability in limiting the front and rear tire's slippage. Also is a good test to show how well a rear LSD works. I can do this test once I get my car running. My DCCD 6spd can be locked and also I can apply some e-brake to give the rear LSD some load so the pressure ring can apply some lock up. No rear LSD makes it a bit hard. Reason I say rear LSD is that since the back is LIGHTEST, it's better to put one back there since it will be the first to lift a tire. Here is the NEW Forester. As you may know, they come with VDC and Traction Control. This new system makes the AWD MUCH more useful since neither front or rear diff runs a VLSD like some models in the previous years. Some models do come with a VLSD still. However in the video he saying the front spun faster because the rears didn't have much traction is not correct. The front spun more because the tire started to come off the ground and losing traction as it came over the little hump there. It doesn't look for traction, it just stops the spinning wheels via traction control system. Non-the-less this is a very good REAL WORLD test.
edited my wording in the last paragraph. The front spun more because the tire started to come off the ground and losing traction as it came over the little hump there. It doesn't look for traction, it just stops the spinning wheels via traction control system. Non-the-less this is a very good REAL WORLD test.
Only real tests I'm concerned about is when a wheel lifts off the ground and how well the traction control system works to slow that wheel down so the diffs can turn the other wheels. This aint STOCK.
LSD test with 3wheels. You can see the driverside rear dig down into the dirt with the rear LSD locking the rear wheels together. If it been an open diff, the pass rear wheel would have spun.
That was a very good test, it's just too bad the concept is just tooooo difficult for the average owner to understand and fully utilize. I'd like to just insert my idiot card and drive away.
now the DCCD is in all subaru correct? but can be adjusted in the sti? I'm i tracking right or am I way off.
You are way off. DCCD Driver controlled center differential. If the driver can't control it I'm sure it would have a different acronym.
I want to say that Subaru uses a similar system if not the same system they use on for the DCCD as they do on the auto trannies; hence the different torque split and the transfer clutch, in a sense, automatic DCCD mode. They just have to change the planetary center diff to what they want for torque and apply the transfer clutch to it. Subaru can make the auto tranny a 35:65 if they wanted to. The DCCD option is what's available on the Impreza STi. The 5spd trannies here in the USA are a viscous "locking" LSD. The auto trannies work like the STi's DCCD, but automatically applies the the transfer clutch whenever there's speed difference front to rear. The STi runs a similar if not the same system as auto trannies but with manual adjustibile center diff locking rate. You can make a switch to LOCK the center diff on the autos, which is a much better AWD from Subaru. SO... the auto tranny has a far better center diff from factory. The 5spd will lose. The DCCD system is the best system IMO that Subaru uses. Being able to LOCK the center diff is a good option for extreme off-road driving
Great video of how DCCD works, but how old is this video anyway and what does it say about the technology Subaru is applying to today's cars? I personally wish they would do just a bit more.
