snow/slushy conditions - DSC on or off?

[tranquility]

I've always been confused about the *DSC off* button on the centre console: when exactly do you use it to switch it off? Today we had a snowstorm and I was wagging my tail ever so slightly even though I was light on the gas from the stoplight as my car struggled to gain traction from rest position: would switching DSC off help in that case? When do you switch it off? Do you switch it back on after the 'event' you switch it off or do you leave it off?

The only time I heard about switching it off is when you're actually stuck in the snow and spinning your tires, in order to get traction. Otherwise, not sure about other applications for the *off* mode. Thx in advance.

[SchweiZ4]

Found this:

"According to Thecarmarket.com, traction control helps to "limit tire slip in acceleration on slippery surfaces." The main purpose of traction control is to potentially eliminate situations like spin-outs or hydroplaning through sensors that monitor wheel-spin. If slippage is detected, engine power will be cut down and/or brake pressure applied without driver interaction.

Snow
Tires spin a bit when trying to gain traction from a stand still in the snow.
The vehicle sensors act on this loss of traction by reducing engine power to the wheels.
Turn off the traction control to maintain power in start off situations.

Burnouts
Although burnouts are not necessary for driving, they are popular at a car show or short race.
Vehicles will not burn out to their maximum potential while the traction control limits the amount of tire spin.

Submerged Wheels
Any vehicle that is stuck in mud, snow or ice must have the traction control shut off to spin the wheels and gain momentum.
To get out of this situation, the wheels have to spin to find traction or to allow the driver to "rock" the vehicle back and forth to roll out of the area that the wheels are stuck in.

Racing
For racing, speed and gear shifting go hand in hand.
It will not be necessary to keep the traction control on because any instance of reduced engine power to the wheels will defeat the purpose of racing.

Drifting
Drifting is a vehicle activity that gains more popularity every year. In order to drift (or slide) around a turn, the traction control has to be off.
Traction control will reduce engine power and apply outside brake pressure to eliminate sliding, which is necessary for drifting."

Links:
http://www.answerbag.com/q_view/1930083
http://www.bimmerfest.com/forums/arc.../t-646563.html

[juhap]

Originally Posted by tranquility

I've always been confused about the *DSC off* button on the centre console: when exactly do you use it to switch it off?

Pressing that button once activates DTC, which allows some wheel slip, and may help when driving in deep snow/slush or when you're stuck in snow. It will still keep you out of trouble by for example preventing too much oversteer.

Holding that button down for couple of seconds (3 or 5, don't remember which) will switch DSC off completely, and there's no invisible hand to keep you out of trouble.

[Asbjorn]

In my opinion there are 4 modes of the DSC available with the Z4. What you should use is the one called DTC / Traction if you drive in snow. DSC=on is for normal use. Sport+ is for fun on dry roads and DSC=off is for burn-outs, donuts and drifting.

Here is the list as I experience it. Unfortunately the user manual does not provide very detailed information.

DSC=on: This is the normal mode which is active when you turn the car on. The rear wheels are not allowed to move much faster than the front wheels and engine power is reduced if needed. To some extend individual rear brakes are also applied to prevent either wheel from moving significantly faster than the other at city speeds (this is the so-called e-diff btw). Whether the parameters of the e-diff change with each mode is un-documented. It may be that brakes can applied to a higher degree in for instance sport+ and traction modes, wheras in DSC=on mode, engine power is just reduced instead. Anyhow, not only is wheelspin restricted. If the car starts to over or understeer, brakes are also applied to individual rear and front wheels in order to correct the unwanted rotation (or lack of rotation in case of understeer).

DTC / Traction enabled (short press on "DSC off"-button). In this mode the rear wheels are allowed to move a bit faster than the front wheels, perhaps only at lower speeds and while stationary. It allows the wheels to find traction while setting off by simply "spinning" the upper layers of "loose" snow away. This would not be possible to the same extend with DSC fully on. Over- and understeer is still very much prevented according to my experience EDIT: Nah, I was wrong it is possible to over-steer in this mode as well.

Sport+ mode (selected with the dynamic driving mode switch just behind the "DSC off"-button). Similar to DTC / Traction but with some degrees of oversteer and more wheel-spin allowed at high speeds (probably its around 8-10% wheel-spin at any speed). Its probably exactly the same as the MDM mode found with the 1M (minus the e-diff), and especially in the wet, you could possibly spin the car 180 degrees if you REALLY wanted to.
I am not entirely sure if under-steer is corrected to the same extend as with DTC/DSC=on however. But this mode was made for fun on dry roads and I think this mode will give you the fastest possible lap times in most cases. With the DCT transmission this is also the only mode where launch control and the fastest gear shifts become available.

DSC=off (very long press on "DSC off" button). As with DTC, this mode is only available with normal/comfort mode (So if you plan to use this mode alot, probably you shouldn't get the adaptive suspension (or DCT gearbox in a 35i)). The rear wheels are allowed to spin alot (how much I dont know, perhaps 100%). The e-diff is probably still active up to a certain speed, but again, its hard to find the documentation for this. I know for sure that ABS is still active, but neither under- nor oversteer is corrected to any degree. As documented on youtube, with DSC off, you can finally pull drifts and donuts with a stock Z4.

In conclusion, what you need in the snow is the DTC which (tries to) keep you from any under and oversteer while allowing wheel-spin in order to find traction if needed. You would not want any wheelspin or oversteer at higher speeds, because then things could quickly get out of control. That is why DTC/traction mode is better than sport+ and DSC=off while driving in snow.

[SchweiZ4]

Nice reply Asbjorn. Lots of details and explanation. Thanks!

On snow, nothing better than snow tires or/and chains!
With no snow tires, DTC didn't help me to get out snow, when chains in my trunk did.. (living in mountain)

[nicknaz]

In your case, I would keep it on for sure. If the traction is so bad you are starting to get sideways just for a light start, it is good to have all the electronic assistance possible.

The only time I go to DTC mode or OFF mode on the street in the snow is when I am really stuck and the DSC won't let me even turn the tires.

[tranquility]

Thx all for your replies. Really useful info and I learned a lot.

Originally Posted by nicknaz

In your case, I would keep it on for sure. If the traction is so bad you are starting to get sideways just for a light start, it is good to have all the electronic assistance possible.

It seems that I'm still confused about driving in snow and which is better: using DSC or DTC? According to Asbjorn's very thorough post, DTC seems better than DSC in snow conditions because it still tries to prevent oversteer but gives more traction whenever the wheel slips (so it still has the ftn of DSC+giving traction whenever the wheel spins?). Reading SchweiZ4's excerpt on snow, it seems DTC is good for when the car is starting from rest position, but what mode should I be when the car is moving, still in DTC or go to DSC?

As an aside, I always found that our 'DSC off' button is confusing: they should have 2 lights for that button, 1 for DSC, 1 for DTC and both off when everything is off. The way it is now, it seems that there is only a choice of DSC on or off (in which case 'traction' confusingly appears on the dashscreen), which is part of the reason for my confusion.

[nicknaz]

when you see "traction" or "sport+" that is dtc mode.

No lights or words is full on / dsc mode

Dtc only better form stop in snow if you are stuck and need wheelspin to get the car moving.

If you are in DTC mode you will need to counter steer etc. because intervention of nannies comes when you have some slip angle already.

As an aside you should drive in sport + and slide the car at all possible times. I hear this is the best way to drive in snow.

[Asbjorn]

Originally Posted by nicknaz

when you see "traction" or "sport+" that is dtc mode.

No lights or words is full on / dsc mode

Dtc only better form stop in snow if you are stuck and need wheelspin to get the car moving.

If you are in DTC mode you will need to counter steer etc. because intervention of nannies comes when you have some slip angle already.

I am 90% sure DTC/traction and sport+ are NOT the same modes. Have you tried pushing the car into oversteer with DTC/traction vs Sport+? I feel it is much harder with DTC/traction. I was surprised to find this as I originally also thought they were the same modes.

I agree with your other statement that DTC is only really needed when indeed the car is not moving in snow. But if my butt feeling is not totally off, then there is no harm in leaving it on, because of clever German engineering.

[tranquility]

Originally Posted by Asbjorn

I am 90% sure DTC/traction and sport+ are NOT the same modes. Have you tried pushing the car into oversteer with DTC/traction vs Sport+? I feel it is much harder with DTC/traction. I was surprised to find this as I originally also thought they were the same modes.

I agree with your other statement that DTC is only really needed when indeed the car is not moving in snow. But if my butt feeling is not totally off, then there is no harm in leaving it on, because of clever German engineering.

Can't you do DTC/traction in normal and sport mode as well? What happens if you are in sport+ and press the 'DSC off' button?

[Asbjorn]

Originally Posted by tranquility

Can't you do DTC/traction in normal and sport mode as well? What happens if you are in sport+ and press the 'DSC off' button?

In mine, if I press the DSC button (no matter short or long press) the dynamic driving mode reverts to the normal/comfort position. When you hit the dynamic driving selector again, it enter the DSC mode which belongs to the driving mode selected no matter what is was before.

Only M cars allow you to select each setting independently. . This is one reason you would want the non-adaptive M sport suspension if you want to track your Z4 with DSC=off.

[nicknaz]

Originally Posted by Asbjorn

I am 90% sure DTC/traction and sport+ are NOT the same modes. Have you tried pushing the car into oversteer with DTC/traction vs Sport+? I feel it is much harder with DTC/traction. I was surprised to find this as I originally also thought they were the same modes.

That huge pdf file that another member posted suggested that sport+ mode and DTC/traction are the same stability program.

I don't really have any way to verify when the electronics will intervene. It seems similar to me?

[Incipio]

Originally Posted by tranquility

I've always been confused about the *DSC off* button on the centre console: when exactly do you use it to switch it off? Today we had a snowstorm and I was wagging my tail ever so slightly even though I was light on the gas from the stoplight as my car struggled to gain traction from rest position: would switching DSC off help in that case? When do you switch it off? Do you switch it back on after the 'event' you switch it off or do you leave it off?

The only time I heard about switching it off is when you're actually stuck in the snow and spinning your tires, in order to get traction. Otherwise, not sure about other applications for the *off* mode. Thx in advance.

Hey, I know the feeling I live in Montreal we got the same crap.. The tech manuals and 'Modes" don't mean anything when it comes to real world driving. The cars tail will fish tail regardless, thats when panic sets in and you take the foot off the pedal to correct it. But you have to stick thru it and it will correct it self at any of those modes. I find DTC/Traction works best when you know you are stopped in slush or ice and to get moving it will help, DSC will put ur car in limp mode, this will make the tires spin slowly and create friction and you are stuck. When driving In ice nothing will help you, she will be all over the place regardless of any mode, only option is to pull your gut in, engage your core, pray and go extremely easy on the gas.

Best way is to take your car to an empty parking lot with snow, ice what have you and let her rip, try all the scenarios till you know how she handles and you are comfortable with what she's capable of. Hope it helps.

-s

[tranquility]

Originally Posted by Asbjorn

In mine, if I press the DSC button (no matter short or long press) the dynamic driving mode reverts to the normal/comfort position. When you hit the dynamic driving selector again, it enter the DSC mode which belongs to the driving mode selected no matter what is was before.

Only M cars allow you to select each setting independently. . This is one reason you would want the non-adaptive M sport suspension if you want to track your Z4 with DSC=off.

You're right, I thought that I could get DTC in sport/sport+ but it goes back to normal/DTC.

Originally Posted by Vert335i

Hey, I know the feeling I live in Montreal we got the same crap.. The tech manuals and 'Modes" don't mean anything when it comes to real world driving. The cars tail will fish tail regardless, thats when panic sets in and you take the foot off the pedal to correct it. But you have to stick thru it and it will correct it self at any of those modes. I find DTC/Traction works best when you know you are stopped in slush or ice and to get moving it will help, DSC will put ur car in limp mode, this will make the tires spin slowly and create friction and you are stuck. When driving In ice nothing will help you, she will be all over the place regardless of any mode, only option is to pull your gut in, engage your core, pray and go extremely easy on the gas.

Best way is to take your car to an empty parking lot with snow, ice what have you and let her rip, try all the scenarios till you know how she handles and you are comfortable with what she's capable of. Hope it helps.

-s

Thx. Ya, I fooled around a little bit in empty parking lots. Actually, the car is quite predictable and one should be ok in snow unless they go crazy on the gas. It's still a very capable good car for winter (save for the lower grd clearance).

[Hoa]

i was stuck in a snow storm two years ago. i was going up hill and there were so much snow that the traction control kept kicking in because i was getting wheel spin. when it kicked in, i couldn't go anywhere. i actually started slipping back down as traction control tries to bog down my throttle. i ended up turning off the DSC and the car started rolling up the hill. my tail was kicking out a little here and there but at least i was able to make it home

[ZheHbKa]

snow => Z4 in the garage

[nicknaz]

Originally Posted by ZheHbKa

snow => Z4 in the garage

Doesn't have to be though. As others have said it is fine in the snow with good snow tires

[tranquility]

Originally Posted by nicknaz

Doesn't have to be though. As others have said it is fine in the snow with good snow tires

Exactly. The other poster makes it sound like the Z4 is useless in snow, when it is actually very capable and surefooted.