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Old 07-26-2003, 03:09 AM   #1
SportyBry
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Wink Handling (DCCD? tire press?) problems with new STi? Please help...

ok guys- this is my last post this evening- I promise


I am experiencing some handling irregularities with my new STi.

Mainly I notice the car really "tucks in" when letting off the throttle in a corner. This seems to happen both when turning left and right. I mainly drive in DCCD auto mode. If you are in even a light turn and go back on the throttle you can feel the car push again.

At the speeds and cornering loads I am feeling this at (relatively low) I didn't think this would be the cars 'understeering tendancy' showing through. After all, I am still breaking the car in (~900KM=600miles since Monday pickup). Any idea what's going on? It almost feels as if the DCCD is doing things it shouldn't be.

I checked pressures the other day and they were 42psi all around. I'm not sure if this was a cold/warm/hot measure -- I am kinda brain dead right now. I did see the other posts about 36/30 and was thinking about trying these. The car just sticks so well where they're at now. I can't imagine the sidewalls being as stiff at the lower pressure, PLUS I'd think lowering the rear pressures would make the rear end step out worsening the problem.

The car feels light it wants to track to the left slightly on most roads I've driven on so the alignment could be an issue. The edges of both front tires show some scuffy which could be 'feathering' but it's hard to tell with so little mileage on it. A very knowledgeable owner of a performance shop I went to looked and said he thinks there is nothing abnormal about the wear.

Also a question about DCCD operation. The manual is useless in it's explanation -- I think it's a very bad translation from japanese to english! Ipresume that as you scroll the DCCD wheel back towards you and the arrows go DOWN in the display you are shifting torque rear-ward- correct? I tried driving in the last 2 positions for some time but ended up getting the cracking and banging noises when turning a little sharp. Why ? I presumed that the more rearward the drive the less 'locking' is going on so it should not be an issue like it is driving it in 50:50 lock (something I know enough NOT to do on dry pavement)


Feedback? Thoughts ?


..../Sporty

Kitchener, Ontario.
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Old 07-26-2003, 09:28 AM   #2
happasaiyan
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Default Re: Handling (DCCD? tire press?) problems with new STi? Please help...

Quote:
Originally posted by SportyBry
Mainly I notice the car really "tucks in" when letting off the throttle in a corner. This seems to happen both when turning left and right. I mainly drive in DCCD auto mode. If you are in even a light turn and go back on the throttle you can feel the car push again.
this is the premise behind a good handling car that has the natural tendancy to "understeer". in an integra type r, or any other excellent handling fwd car, when you release the throttle in a corner, the back end will rotate around since all the weight is then lifted off the back wheels, which allows it to slip...

HOWEVER, if you were to go against your natural instincts, you will find that when the STi is starting to understeer, and you MASH the throttle mid turn, the car just squats, and the dccd really starts doing its job and rockets the car out of the corner...REALLY FAST.

i do not recommend that a newbie driver (not saying you are...) just start to floor it in the turns, because that is how cars get wrecked...but if you ease into it, and start learning your cars limits first, then you can start to gauge what the car can and cant do. drive safe.
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Old 07-26-2003, 10:30 AM   #3
mike of pa
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I noticed similar behavior while shifting up in a corner.
Solution appears to be to hold your throttle in corner, or
get to know the corners and work up your speed where
you will progressively be applying more throttle, and
going through the corner more quickly.

You may also wish to try going through a corner (or series
of corners) you know well doing similarly, but with the dccd
in manual. Start off modestly in either case so you will
be prepared to handle to consequences.

Key is learning the characteristics of the car (as above)
and gradually extending your abilities while keeping
the car (and your pride) in original condition.

Untidy results tend to mar both the car and your pride.

On motorcycle we call it going slow to go fast. You'll
find yourself going through much more smoothly, effortlessly,
and (I'm sure not interested in this part) quickly.

Mike
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Old 07-26-2003, 10:30 AM   #4
TurboPhoon
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I have 40 all around in mine. I have noticed some understeer at times, but I have used the dccd to get rid of most of it. I'm probably going to drop the pressure a little bit all around. The tires always loose grip when i'm moderately hard on the brakes.

If you put the dccd into the bottom green position you should have no binding noises when going around a turn. With it in this position and the other green one, the back of the car can and will come out, sometimes significantly so be sure to test these settings out on empty roads.

happasaiyan,

I think i have noticed what you are talking about. It happens when there is some slippage around a turn and feels like the front diff just pulls you through it and closer to your line.
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Old 07-26-2003, 10:36 AM   #5
shirokuma
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I'm generalizing through because I'm sleepy, -

DCCD-a, or even in manual setting, cannot do much at all when you don't have your foot on the gas. You need to be routing power to the DCCD for it to route power to the wheels. This also goes for regular Subaru's, btw. It's one of the reasons that it's important to have some power going to the wheels when cornering, otherwise the AWD system doesn't do much, and you are stuck in a vehicle with a lot of weight on the front.

Another thing to really remember is that the STi has a front differential. Love it or hate it, it's there, and it certainly does affect handling. Off-throttle even, for it's likely to have some sort of drag effect on the front wheels. One of the reasons I save off-throttle for straight line braking.

Cheers,

Paul Hansen
www.apexjapan.com
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Old 07-26-2003, 11:05 AM   #6
SportyBry
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Hi again guys,

First off, many thanks for the responses....

You know, I never thought of this before, but the problem is arising because I am still breaking the car in -- and with a 4K rpm artificial redline that means shifting in the corner alot of times when accelerating through them, hence the off throttle rear-end tuck in is apparent. I think about how I've driven everything I've owned in the past, and I don't think I've ever regularly lifted in corners. It is thoughts of Porsche 911/MR2 turbo-like drop throttle oversteer that sent a chill up my spine (especially given the possibility I will drive the car in the winter). Maybe it is something I will just have to get used to, although my highly modified AWD 323GTX never exhibited this behaviour (and it could put up some serious numbers!).

I was more concerned thinking that something was wrong with the DCCD, and that this was abnormal behaviour I was experiencing. Maybe I will play with tire pressures to see if that affects the situation at all.

Cheers,


Sporty.
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Old 07-26-2003, 01:06 PM   #7
WRX 2002
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I had the same situation during the run in period,even had the back out on a mild off ramp once. Once the run in period is over and you start to use the whole RPM band this trait seems to go away.

At the track at full speed I have never notice the problem.

N
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Old 07-26-2003, 01:12 PM   #8
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Just wait till you are willing to use the whole RPM band before trying to learn the handling.

Then go slow, this car does NOT react like any other car out there. Its very strange, but very very very good once you have it down.
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Old 07-26-2003, 05:26 PM   #9
happasaiyan
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Quote:
Originally posted by XT6Wagon
this car does NOT react like any other car out there. Its very strange, but very very very good once you have it down.
i remember shirokuma wrote something very similar to this before...and i didnt really understand what he meant at the time...but slowly im learning he was absolutely correct.
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Old 07-26-2003, 06:04 PM   #10
ANZAC_1915
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The behaviour you describe is not the DCCD. I believe it is the Suretrac front diff.

It is very "non-linear" and also seems to have some hysteresis.

That said, it is better than an open diff or a clutch type (for a front diff).

Glenn
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Old 07-26-2003, 06:36 PM   #11
happasaiyan
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yeah i realize that most of what i was describing was specifically the front lsd...but to me, its all part of the dccd system, and im sure the torque shift has something to do with it.
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Old 07-26-2003, 11:03 PM   #12
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At the throttle inputs you describe, I'd expect the DCCD is twiddling its thumbs. The DCCD is Center Diff and doesn't control the front diff.
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Old 07-27-2003, 06:23 PM   #13
fastwrx
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Although I can't explain the mechanics of all the differentials, I can say this "tucking in" on throttle lift is normal. In fact, it is advantageous on the track. I was on the track yesterday for the first time with my STi. As I went through turns on the car starts to "push" (understeer), all I had to do was lift momentarily on the throttle... car tucks in and gets pointed in the right direction down track, and then squeeze back into the throttle. Very controllable. Very cool! My instructor who had a LOT of track experience knew exactly (and expected) how this works. He coached me through the turns:

1. Straight line braking.

2. Turn in. (squeeze throttle)

3. Lift on throttle (car rotates - almost magically!)

4. Once car is stable and pointed in the right direction... back on throttle and GO! GO! GO!

This car ROCKS on the track. See the thread I started in which I reviewed my experience.

Mike
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Old 07-27-2003, 10:54 PM   #14
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You should be able to skip step 3 with the Suretrac.
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Old 07-27-2003, 11:23 PM   #15
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Hi Glenn,

Can you explain more? I dunno, but step 3 worked like magic for me. As the car pushed (understeered) to the outside of the turn, I just momentarily lifted, and the car tucks right in pointing down the track. Then back on the gas. Mind you, I didn't have to do this for every turn. But, when the car pushed, the throttle-lift corrected very nicely.

Thanks for chiming in. I keep an eye out for your posts, as it seems you really know your stuff!

Mike
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Old 07-28-2003, 01:32 AM   #16
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Depends on the corner what will be appropriate. On long sweepers I prefer the "turn in... then stand on the loud pedal" method. The front WILL shoot wide briefly as the front unloads and the rear pushes the car in a straight line. Once the front diff winds up and gets with it though the front will swing right back to the inside and possibly even start to take a much tighter line than origionaly intended. So you just wind off a little lock and enjoy the insane exit speeds.
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Old 07-28-2003, 01:56 AM   #17
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I am told by people whose opinion I trust that with the STi you don't need to lift to get the car set up, that you can go in quite hard. Obviously some caution should be exercised on the track but with the WRX you do it to correct the attitude and end up pointing in a direction where you won't push coming out.

With the STi (up to a point) the more gas the more it pulls in.

Again, all that said, I think really using the diffs on this car requires a different driving style... and not everyone is going to master it. Certainly there's no harm in driving it like a WRX, just you can go faster into corners if you so choose.

Anyway, I'd suggest working up to this approach, and of course, my advice comes with the usual disclaimers about killing yourself etc.

Glenn
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Old 07-28-2003, 09:43 AM   #18
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Every technique has it's place in cornering. What seperates the JP Montoya's from the rest of us is the ability to figure them out quickly.

The tuck in is quite pronounced, but doesn't really make the car twitchy in my opinion (my other car is a 911)... just gives me more options for placement.

I have had the STi a bit sideways by dropping throttle suddenly with a good bit of steering lock dialed in. The first reaction is opposite lock, of course, but applying the loud pedal aggressively seems to work better.

One thing I've noticed in both the merely mortal WRX and even moreso in the STi is that when you get understeer, you need to apply more power... when you get oversteer, you need to apply more power.

The only thing that more power doesn't seem to help is braking!

Driving this thing feels a bit weird at first, young Skywalker, but if you trust the force.... YEEEEHAAAAAA
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Old 08-02-2003, 06:03 AM   #19
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I agree, this car isn't as forgiving as some in turns as far as throttle/braking is concerned.

One thing I noticed is that if I adjust the torque bias on the DCCD more to the rear, the car seems a lot more solid in turns (i.e. cloverleafs, etc.).

FWIW,

Zen
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Old 08-02-2003, 07:30 AM   #20
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Lifting off the throttle abruptly with the wheels cocked induces drift at too high of a speed (be careful). Glenn & Paul made good points about the DccD and the front diff action. It's true that only lifting during braking in a straight line is the better way to keep the speed and handling safe. Staying constant on the throttle thru curves, or even adding power seems to be the way to maintain control.
This has been the easiest car for me to have fun w/o fear.
...but drive defensively cause there's an idiot around every corner.
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Old 08-02-2003, 12:20 PM   #21
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Quote:
torque bias on the DCCD more to the rear
This has been covered to death but fyi with the knob rearward it "opens" the center diff and with it forward it "locks" the diff.
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Old 08-02-2003, 12:22 PM   #22
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Quote:
One thing I've noticed in both the merely mortal WRX and even moreso in the STi is that when you get understeer, you need to apply more power... when you get oversteer, you need to apply more power.
Disagree -- with the WRX you need to lift when you get understeer, tuck and hit the gas. WIth the STi the difference is that more gas seems to reduce the understeer, lifting doesn't seem to buy you anything.
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Old 08-02-2003, 12:25 PM   #23
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Quote:
Originally posted by Glenn Wallace


This has been covered to death but fyi with the knob rearward it "opens" the center diff and with it forward it "locks" the diff.
Really? I honestly didn't know that - my understanding was that it just adjusted the torque bias to something like 30/70 f/r or something like that. So that really has nothing to do with it?

Feeling like a noob here....

Zen
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Old 08-02-2003, 12:33 PM   #24
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Quote:
Originally posted by Glenn Wallace


Disagree -- with the WRX you need to lift when you get understeer, tuck and hit the gas. WIth the STi the difference is that more gas seems to reduce the understeer, lifting doesn't seem to buy you anything.
I was going to be smart and say nothing about this question that has been bugging me, but I' m feeling dense so.......

I have heard it said that the STI -

a) understeers on lift
b) does nothing on lift
c) oversteers on lift

I have never known of any car that provides so much conflicting data about its handling from people who drive it.

I'm assuming this can be attributed to a combination of inconsistent front differential, divergent driving styles, and different expectations. ???
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Old 08-02-2003, 12:41 PM   #25
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Quote:
Originally posted by strangerq

I have heard it said that the STI -

a) understeers on lift
b) does nothing on lift
c) oversteers on lift
I'll take c) for $1000, Alex.

It oversteers - the tail wants to come around. There seems to be something going on with the center diff that magnifies this phenomenon, but at least in part it's because as with braking, when you lift off the throttle the weight transfers forward, effectively "lightening" the rear wheels.

Drive one and you'll see!

Zen
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