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      04-12-2009, 08:27 AM   #1
ozigreg
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DSC & DTC

Hi Guys, I am curious on the forum thoughts in regard to DSC & DTC. I have read the manuals and also spent a wet rainy weekend morning in a deserted industrial area experimenting with the three options of DSC fully on, DTC on and then everything off (I know the E diff is still on).

When reading the manual many months ago, I mistakingly thought DTC was a higher level of traction control as "it is intended for special circumstances such as deep snow". I think the manual should have just said:

DSC = Safe
DTC = Fun
Off = Scary

Apart from your thoughts my main question is, when the car is understeering (pushing) into a corner does DSC apply braking to the front wheels and not just power retardation to the rear wheels. To me if definatly felt this was the case. The manual says braking will be applied to the indiviual wheels in DSC mode, so does this apply to the front wheels as well and does the braking also apply when in DTC mode. (the car pushed much more in DTC mode)

Appreciate your thoughts.
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      04-12-2009, 09:44 AM   #2
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Don't know if I answer your question, but the only way the front wheel can contribute in traction control in any kind is to apply brakes . You are driving a RWD after all.

Each brake can grab individually in traction control situation, but in minimal slip of the rear wheel. The fuel is simply cut off the keep the car in check.

Hope this helps.
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      04-12-2009, 10:37 AM   #3
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Quote:
Originally Posted by ozigreg View Post
Hi Guys, I am curious on the forum thoughts in regard to DSC & DTC. I have read the manuals and also spent a wet rainy weekend morning in a deserted industrial area experimenting with the three options of DSC fully on, DTC on and then everything off (I know the E diff is still on).

When reading the manual many months ago, I mistakingly thought DTC was a higher level of traction control as "it is intended for special circumstances such as deep snow". I think the manual should have just said:

DSC = Safe
DTC = Fun
Off = Scary

Apart from your thoughts my main question is, when the car is understeering (pushing) into a corner does DSC apply braking to the front wheels and not just power retardation to the rear wheels. To me if definatly felt this was the case. The manual says braking will be applied to the indiviual wheels in DSC mode, so does this apply to the front wheels as well and does the braking also apply when in DTC mode. (the car pushed much more in DTC mode)

Appreciate your thoughts.
The default mode is DSC (Dynamic Stability Control). In this mode, the computer will temporarily reduce power to the engine, and/or apply brakes at individual wheels if it detects the car is about to swerve or go out of control. This is how most drivers should be driving their 135i. This feature can definitely be felt when it kicks in, and you will see the indicator light come on.

One quick press turns ON DTC mode (dynamic traction control) or DSC light. This mode reduces stability control, and adds increased traction. This is used in heavy snow, rain or loose gravel or any environment where you need extra traction but you don't want the stability control intervening because it always thinks your skidding. Some wheel slipping is allowed under DTC.

Hold the button down for 5 seconds turns off both DSC (dynamic stability control) and DTC (dynamic traction control) but the e-diff is activated. This puts the car in 'TIM YOYO' mode. (That's It Motherf***er You’re On Your Own). In this mode, power to the engine is not controlled. The only action the computer will take is to apply braking to the rear wheel that is spinning the most.

When DSC (dynamic stability control) is on, the goal isn't just to stop the rear wheels from spinning. The goal is to prevent the car from going out of control. The computer will use engine cut out, and individual brakes to slow the car down and bring it back in line. That works opposite from the E-Diff, which tries to slow down the wheel that's spinning, to shift power to the one that is not.


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      04-12-2009, 11:43 AM   #4
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Nice explanation Lester. Like your T-shirt. "Tim Yoyo"

I haven been game enough to drive my 135i with any verve with DSC/DTC off. Have compared quick standing starts with DSC and DTC. You can do real nice launches with DTC on. With DSC, the car just bogs down.
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      04-12-2009, 09:55 PM   #5
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Yeh I was out at eastern ck last week and did some experimentation with the different modes. The car is quite manageable with everything switched off in the dry...I thought it might be a bit scary but in my experience the oversteer was quite controllable and predictable. It also allowed me to get the power down out of the corners better. I think turning everything off on the track teaches you a lot more about car control so I will endeavour to do this every time i get out there now.

I don't see any real need to have everything off on the street though - even during spirited driving just having DTC on is more than enough fun and allows cleaner launches as d3Syd said. ANd in the wet I always just leave DSC on.
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      04-13-2009, 07:17 PM   #6
ozigreg
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I think I was able to induce quite a bit of understeer at low speed as the road was quite wet.

I love the TIM YOYO concept,
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      04-13-2009, 07:31 PM   #7
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I have the DTC off at the track as it interferes too much to enjoy a lap. And mainly completely on when driving on normal roads. I only ever turn it off if I want to step the back out, but to be honest don't think it's a great look on the street.
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      04-14-2009, 06:06 AM   #8
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Maybe its just me but I was hoping there was a way to program the car so 'everything off' was the default =)
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      04-14-2009, 07:00 AM   #9
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Quote:
Originally Posted by spdrcr View Post
Maybe its just me but I was hoping there was a way to program the car so 'everything off' was the default =)
BMW Legal department would never allow that to happen. Too much liability.
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      04-15-2009, 12:13 AM   #10
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Quote:
Originally Posted by spdrcr View Post
Maybe its just me but I was hoping there was a way to program the car so 'everything off' was the default =)
No Jeff, it's just you
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      04-20-2009, 09:42 PM   #11
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"Hold the button down for 5 seconds turns off both DSC (dynamic stability control) and DTC (dynamic traction control) but the e-diff is activated. This puts the car in 'TIM YOYO' mode. (That's It Motherf***er You’re On Your Own). In this mode, power to the engine is not controlled. The only action the computer will take is to apply braking to the rear wheel that is spinning the most.

When DSC (dynamic stability control) is on, the goal isn't just to stop the rear wheels from spinning. The goal is to prevent the car from going out of control. The computer will use engine cut out, and individual brakes to slow the car down and bring it back in line. That works opposite from the E-Diff, which tries to slow down the wheel that's spinning, to shift power to the one that is not.
"
Sorry to keep this going, so the E-Diff will only work in TIM YOYO mode?

I've made a few hard starts recently in DTC mode. The acceleration difference in in first gear was astonishing. Not that I'd ever try such a thing..., but if I was to race somebody at the lights I'd definitely put it in this mode first.
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      04-20-2009, 10:35 PM   #12
ozigreg
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Tim, i could be wrong here, but my understanding was that the E diff was part of the DSC package and therefore engaged at all times.

When the DSC is turned off it is only the E Diff that remains operational.

When I was conducting my experiment I could certainly feel the inside wheel spinning hard with DSC turned off.
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      04-21-2009, 02:03 AM   #13
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What is an E-Diff? It is really nothing more than the rear brake attempting to control a spinning wheel. It has nothing to do with the differential at all. There is nothing in the differntial being controlled.

So - once we get over the teminology, the car has three modes:

Full Dynamic Stability Control - default mode DSC.
In this mode the brakes are appllied at any wheel, and the engine power is contolled (ie shut off) in order to bring the car back into line. If the car senses a spin is about to happen, the engine power is cut momentarily and the brakes are applied any any individual wheel to cause an offset force to straighten the car out and bring it back under control.

Dynamic Traction Control DTC - Press the button momentarily.
This mode is DSC 'light'. It can still reduce power or apply brakes to any wheel, however it will allow some wheel slippage and assumes it is due to road conditions (gravel, snow, mud, ice or rain). This is simply a software program change to DSC, with some of the stability parameters modified from the default.

DSC/DTC Off (hold the button for 5 seconds).
This is 'E-Diff' mode. The computer is reduced to only attempting to limit a spinning rear wheel by applying the brake to that wheel. In this mode, the engine is not controlled, nor are the front brakes activated. It is not really an E-Diff at all. It is just called that, to sound special. If the car is about to flip over, in this mode it will not try and save the car by cutting engine power. If it is about to do a 360 - it doesn't care - the computer is only monitoring rear wheel spin. This is our TIM YOYO mode.

The same computer, controlling the same parameters, with three different settings. It would have been nicer if BMW had used a rotary knob, with three indents for the three current modes, with an 'off' indent on the far right. This would have allowed for much more granular control, and allow one to turn off the computer completely. The knob could have included led's with Green for DSC, Amber for DTC and Red for 'E-Diff' only. I guess they don't trust their customers. I bet they have a secret way to turn off everything back at the lab in Germany though - some kind of a {Cntrl} {Alt} {Del} function.
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      04-21-2009, 03:33 AM   #14
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Thanks guys.

Yeah I understand how the "E-Diff"works. What I'm wondering is, with respect to the first two DSC modes only, if I have wheelspin on one wheel only but the car is not losing control in any other way (eg, still going in a straight line where the front wheels are pointing etc), will the spinning wheel be braked or does the computer just cut power to get things back under control.

Lester, I thought you were implying that "the e-diff is activated" in the 3rd mode only in your original post when I thought it may have worked in all modes to some extent as per ozigreg's first two lines above. Greg's last line seems to contradict things though - why doesn't the E-Diff stop the inside wheel spinning?

Cheers, Tim.
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      04-21-2009, 04:18 PM   #15
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Because the E-diff is not a proper LSD at all. It just brakes the slipping inside wheel. If you're really worried about this you'll need a proper LSD.
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      04-21-2009, 09:18 PM   #16
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Quote:
Originally Posted by Guran View Post
Because the E-diff is not a proper LSD at all. It just brakes the slipping inside wheel. If you're really worried about this you'll need a proper LSD.
Yeah we know that Guran. There's no debate about the difference betweeen a proper LSD & our E-Diff, but if the wheel is braked as it reads it should be then there should be no "inside wheel spinning hard with DSC turned off" as Greg got. The car should be driving harder off the outside wheel with the grip (as torque is transfered by braking the spinning wheel), or both wheels should be spinning. In essence it should behave the same way as a proper LSD would - except we're heating up our rear brakes whereas the LSD will be heating up it's clutch pack.
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      04-22-2009, 01:20 AM   #17
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With the e-diff it must just be a case of brakes being applied to the slipping wheel, but not enough to stop it from spinning. I also assume there must be some level of slip on one rear wheel before the e-diff is activated.
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      04-22-2009, 02:18 AM   #18
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Quote:
Originally Posted by Guran View Post
With the e-diff it must just be a case of brakes being applied to the slipping wheel, but not enough to stop it from spinning. I also assume there must be some level of slip on one rear wheel before the e-diff is activated.
Sounds fair Guran. I may have to save up for a proper LSD one day...
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      06-08-2009, 02:52 PM   #19
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So where can I buy the T-Shirt from?
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      06-10-2009, 02:48 AM   #20
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That's one of my 'wish-list' items for the E82, a true LSD. That and a larger fuel tank for better range...

Yes, I know. BMW reserves real LSD's for their 'M' cars.
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      07-08-2009, 03:16 PM   #21
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      07-08-2009, 09:35 PM   #22
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Quote:
Originally Posted by TimMc View Post
Thanks guys.

Yeah I understand how the "E-Diff"works. What I'm wondering is, with respect to the first two DSC modes only, if I have wheelspin on one wheel only but the car is not losing control in any other way (eg, still going in a straight line where the front wheels are pointing etc), will the spinning wheel be braked or does the computer just cut power to get things back under control.

Lester, I thought you were implying that "the e-diff is activated" in the 3rd mode only in your original post when I thought it may have worked in all modes to some extent as per ozigreg's first two lines above. Greg's last line seems to contradict things though - why doesn't the E-Diff stop the inside wheel spinning?

Cheers, Tim.
They call it an E-Diff. It is actually just a rear brake being actuated. It is still the same computer, but now it limits itself to applying the brake to one rear wheel at a time. In the other modes, it can apply brakes to all or any wheels, and cut the fuel to the engine. It is simply the narrowest version of the computer control program. There is nothing magical about it at all. There is a tendancy on this forum to over think this mode.
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