Ninj

Hi all,

Been reading with interest the Type R diff threads, I do have a couple of questions though.

Firstly, in a normal Impreza the use of the handbrake on Snow etc is not a good idea (many of us I know have tried it having dipped the clutch, but Im sure its not far from causing damage). Is the TypeR any different, ie how much damage is likely if the handbrake is used to aid turning on snow or gravel? Surely if it transfers the split to the rear wheels locking them with the handbrake would be a tad pointless, does the use of clutch make any difference?

Secondly, with the switch wound fully forward am I right in thinking the car is as close to a standard Impreza as the control allows, and in the rearward position its as close to the "fully rear wheel drive" position (though I appreciate its not actually rear wheel drive).

Tying both questions together, does applying the hadbrake have the same effect as moving the switch fully rearward? ie it biases the torque split to the rear wheels.

Cheers for any advice

Rgds

N|nj

[Edited by Ninj - 12/5/2003 12:54:42 PM]

Stuart Knight

iTrader: (2)

AFAIK when you pull the handbrake on in a car with DCCD it "opens" the centre diff to stop it damaging anything. When you lety go of the handbrake, it returns the centre dif to what it was set at before.

greasemonkey

You can still handbrake a viscous Impreza on these surfaces if you provoke it, but the transmission isn't really conducive to doing it, no.

Yeah, completely, but possibly not for the reasons you're thinkng. The DCCD has an inherently rear-biased torque split, and doesn't have the permanent viscous coupling (which is the bit that causes problems when trying to handbrake a "normal" Impreza). Instead of the VC, it has an electromagnetically controlled system that, in as simple terms as possible, creates driver adjustable amounts of friction between the front and rear axles, basically "sticking" them together. Because this system is electrical and non-permanent, it can be switched off when necessary - for example when you want to handbrake the car.

There's little risk of damage on a DCCD car, as long as you're not doing it all the time of course.

Are you asking whether or not you have to dip it if you want to perform a "proper" handbrake turn? If so, of course the answer's yes.

Obviously you've got to dip the clutch if you want the (relatively weak) handbrake to be in with a chance of locking the rear axle. This is fundamentally different to, for example, an FWD car, where it's theoretically possible to lock the rear wheels at any time, provided the handbrake is strong enough to do it.

No. It is not possible to exactly replicate the behaviour of a standard Impreza's centre diff on a DCCD car, the setup is fundamentally different. However, I find the setting that mimics a viscous car most closely on tarmac is around the area where the middle of the five LED's is lit.

On Lock, and just below it, the car is much more understeery than a viscous car.

Yeah. In this condition, the car has an inherent 33:66 rearward torque bias, and only a small amount of preload on the centre diff.

Yes, as there's a switch built into the handbrake lever that temporarily overrides the thumbwheel setting.

So, on a DCCD car, if you dip the clutch and yank the handbrake, the rear axle will lock, but because the centre diff preload has been released, the front axle should be free to rotate, allowing the car to pivot around the front wheels which will still be gripping, provided of course you get a bit of sideways momentup into the car first!

[Edited by greasemonkey - 12/5/2003 4:54:16 PM]

Ninj

Thanks Greasemonkey, exactly what I was asking, much appreciated.

Sounds like the DCCD is most useful little toy if thats your driving style.

Thanks again, rgds

N|nj

ps Im off to look for one now, I've got the Type R bug

DanTheMan

so to summarise.....the TypeR/RA/C's with DCCD are excellent at handbrake turns, you can make them dance on ice

TonyBurns

iTrader: (3)

Who needs to use a handbrake on snow/ice all you need to do is give a little flick of the steering wheel and hey presto

Tony

andypugh2000

is there anything the greasemonkey doesn't know about imprezas?? the guy is amazing!!

greasemonkey

Whew, few things to add here. Ninj, the DCCD equipped cars do feel considerably better than the viscous ones, but the difference in "handbrakeability" isn't a big factor TBH, simply because there are precious few occasions when it's either necessary or safe to do this on the public road. You can feel the difference in the car's traction and handling balance pretty much all the time.

It's also worth remembering that it isn't just the centre diff that's different. DCCD cars also normally come with better front and rear diffs than the more "standard" cars, which is a big factor in their different feel.

Dan, as Tony says, you neither need nor want to use the handbrake on real (or suspected) ice as trying it could easily get you into a heap of trouble.

All Imprezas (unless they're running genuine ice tyres) are crap on this surface, and the addition of the DCCD doesn't perform any miracles. Same goes for snow, unless you're running a tread pattern that's really designed for it. In fact these cars' biggest problem is the unrealistic levels of confidence they can sometimes inspire in their drivers!

Andy, like the saying goes, the more I learn, the more I realise I've yet to learn. Still, there are some very good people to learn from round these parts.

But as a minor aside, what makes you so sure I'm a bloke???

sg72

Yep Don't get too cocky with these cars in snow and ice.

Unless you do it regular.

My car still bears the scars from trying to overtake someone who I thought was going too slow for the conditions.

These cars loose grip on ice just like any other.

I think many can make this mistake.

It's traction we have more of .When grip is available.

Andy.F

Because in your profile it says your interests are "Mrs Monkey"
Or is that your mum

Andy

zhastaph

Sorry to hijack this thread, but it does relate.

Greasemonkey, or anyone for that fact;

I'm looking at changing my MY00 5 door to a not 5 door. I've been looking at 4's but I've become really attracted to the Type-R's. I think the 2 door styling coupled with an STi spoiler looks totally spot on

Anyways, for the babble;

• Is a DCCD standard fitment on a Type R?
• My one gripe about the Impreza's handling is the severe understeer under power out of a corner, if the DCCD gives a 33:66 power split, does this then alleviate the understeer?
• If these DCCD are some form of clutch so as they can slip, do they wear out and need replacing?

Fanx

DanTheMan

DCCD is standard on the TypeR's and yes it does get rid of the understeer, infact it promotes HUGE oversteer powerslides.

As for fun in the snow, I have had a little practice

but you guys are so right that these cars get you into trouble faster than you can get out of it, Ive had a nasty "off" in the snow thinking I was the greatest snow driver.....


edited cos I got my diffs confused !

[Edited by DanTheMan - 12/8/2003 12:41:31 AM]

johnfelstead

No DCCD isnt standard on all TypeR's, it is found on the STi versions, the WRX version doesnt have DCCD normally.

The DCCD doesnt wear out in my experience, it is recomended you change the gearbox oil more regularly than a UK turbo though, very few people know this. You should replace the gearbox oil every 12,500 miles when it is equiped with DCCD.

The DCCD in fully open mode, gives you a fully open centre diff, so you can have the rear wheels locked and the fronts rotating without any force being applied to the rear diff/driveshafts etc. This also means that if you get the car spinning the rear wheels, all torque goes to the rear, so in a power slide or doing donuts with an open DCCD, the car is 100% RWD. As soon as the rear wheels start to grip the centre diff starts to apply torque back to the front wheels, so you have to be comitted in your driving style to truly generate a RWD power slide.

Moving the centre diff control forward increases the locking ratio of the centre diff, it doesnt alter the torque split, that is fixed at 65:35 by the gearing in the centre diff unit.

RayC

not meaning to intrude!

does my WRX Type R V. limited (which doesn't have a thumb wheel adjusty thing) have permenant 33/66 split?

if i boot it mid bend it tends to throw the back out then pull its self straight

Andy.F

Oooh, not sure I'm with you on that one JF What you say is only true until you start to get slip (which actually happens at a very low level as soon as you apply any power whatsoever) increasing the locking action of the diff only serves to distribute more torque to the end of the car with most grip.

Andy

greasemonkey

Isn't there a very subtle distinction between what you and John are saying Andy?

It seems to me that the fundamental torque split of the diff unit itself is determined by the gearing and therefore fixed, as John says. From there on in the only point of conjecture is exactly how the electromagnets do their work.

If they are in effect acting like a plated diff with variable preload, by creating friction between the front and rear outputs, it seems that the torque bias of the unit as a whole will vary according to the thumbwheel setting that is selected.

Has anyone got a broken DCCD? I know a few good pictures would be worth a thousand words to me.

BTW Ray, your car will have come with the normal 50/50 viscous coupled centre diff as standard, and the handling behaviour you describe certainly backs that up.

[Edited by greasemonkey - 12/8/2003 4:22:13 PM]

RayC

No interesting rear biased split then?

thought it would handle like a fake 4x4 like VW/Audi if it was 50/50 i.e understeer

Gridlock Mikey

More

Good thread

Mikey

greasemonkey

It will ultimately understeer if you push it beyond the limit under power, whereas a DCCD car running fully open will tend to break traction at the back first.

If you're asking why it doesn't understeer anywhere near as badly as a typical VAG 4WD car, that's a combination of the specific transmission design and suspension setup. Don't forget that many of these modern so-called 4WD systems have a front axle torque bias, and some include devices that only engage the rear wheels if the fronts start to slip, and thus they're less 4WD systems than "rear wheel assist".

Speaking of which, Zastaph, if your car is understeering "severely", have you had the suspension set up properly and/or had the bump-steer mod carried out?

[Edited by greasemonkey - 12/8/2003 8:01:20 PM]

zhastaph

Cheers Greasemonkey, no I haven't. I have been looking at the bumpsteer mod, but I've been looking round recently at MY99/00 type R's, I'm pretty much convinced I'm gonna change if I can get a decent enough trade in

As for 'Severly', ok that was a tad of an over exageration, but you know what I mean, your certainly cant put the power down quite as early or quite as much as you'd like coming out of a 'long' corner.

On the whole the Impreza's handling is superb and that's my only gripe

StickyMicky

hmmm
ive watched sumbody handbrake a scooby, really quite severly, it didnt seam to have a problem flying around, although i cringed as i know its pretty bad for the 4wd system

this was on slightly damp tarmac
from memory it was a 4 door car as well so no type r gubbins

johnfelstead

my car is a 4 door and has the DCCD, its called an STi5 TypeRA.

I only use the handbrake to get the **** out when i need to make it more unstable to start a full power slide on grippy surfaces, or when i fancy doing a donut, or of course parking up.

It's quite easy to get a UK turbo into a donut too, if you just start it with a little weight transfer assisted by a dab on the handbrake. P1's do great donuts, but you have all four wheels spinning rather than just the rears with an open DCCD, so the syle is diferent.

StickyMicky

i have managed to et my 4 door wrx doing sum pretty good doughnuts on sum wet grass

i didnt use the handbrake tho
i pulsed the throttle and slipped the clutch a few times, to keep forcing the power towards the rear wheels

once it was settled and moving round pretty fast it was easy enough to hold the power down and hold the full lock on for as long as i wanted/got bored

i set the steering wheel straight, and kept the power on, and it was good how the circles became bigger and bigger untill it pulled itself out forwards

i was scared to go anywhere near the handbrake due to advice i was taught regards it blowing up

johnfelstead

slipping the clutch doesnt force the power to the rear, it just burns your clutch out.

sg72

LOL!

Whoops! I'm a F*nny.

greasemonkey

Being a bit hard on yourself aren't ya?

sg72

Cheeky monkey! LOL!

I can't help it.

Phrase like a German.

Drive like a Penguin.

Steve.

StickyMicky

john wouldnt this make the car initialy send the power biased slighty towards the front, spin the wheels and then send the power to the back of the car thereby pushed the back end round, from what i understand of the 4wd system this would then pull the power back to the front and vice versa??

seamed to work fine for me

i tried just messing about with full lock and planting my foot and it just understeerd and then started swinging the bac around but this was a much bigger arc then i really needed and i would have ended up hitting sumthing about 2 miles from where i stated

StickyMicky

typos

also this was on wet grass so the clutch shouldnt have been under that much grief should it?

i probably would have fell over had i got out the ground was so slippy

if i drive my car round a greasy corner and stick my foot down, the car will understeer @ first and then the power seams to go towards the rear wheels which pushes the back round, is this not correct??

StickyMicky