Open Diff & 11's....Special German Magic?

[shah269]

Open Diff & 11's....Special German Magic?

Stand back ladies and germs…I am the great Shah…zini?
Im in a stock 2009 135 which according to the documents has an open differential.

But with a wave of my hand and a hard launch….behold…

She lays down two perfectly symmetrical patches of rubber on the road…….how no one knows!

Ok this may sound silly but I don’t do burn outs….yeah I’m a total square!
But I mentor a number of great kids and they were saying that the 135 can’t do a burn out….and let me tell you high school students are nothing but enablers.
Long story short….i gave it a shot last night as I was leaving the schoo…..FYI doing burnouts in the local high school parking lot is a lot cooler than you think it is. Mature? No…safe…Hell no…cool? My inner Fanz was like “eeeeyyyy!”

But I digress…help out this mechanical engineer…how the hell does an open differential car lay down to perfect tracks?
What kind of special German Magic is this!

[brusk]

With the right circumstances an open diff has always had a small chance of laying rubber if you get both wheels spinning immediately, I've had a few cars that I thought had LSD on the test drive to find out later I got lucky on a burnout. But the BMW's do have an electrical LSD. The electrics will apply a little brake force on the wheel that is moving faster than the other. It is very quick and precise about it you won't even notice in most situations other than trying to drift.

[shah269]

Oh poop forgot to mentin i turned off the DTC. pressed it and held it for a solid 10 seconds to make sure that the electric nanny was 100% off....or is it?

[NYHoustonman]

Originally Posted by shah269

Oh poop forgot to mentin i turned off the DTC. pressed it and held it for a solid 10 seconds to make sure that the electric nanny was 100% off....or is it?

I've read that this system is on at all times, regardless of traction/stability control setting, and from experience this certainly seems to be the case .

[3002 tii]

Originally Posted by NYHoustonman

I've read that this system is on at all times, regardless of traction/stability control setting, and from experience this certainly seems to be the case .

You're telling me that you can't turn off traction 100%? I don't buy that as I've taken my other car to the limit with and without traction and when it's off, you know it's off. And that car has the same traction system of ours: ON, DTC, and DSC OFF. In fact the other day I hit a patch of gravel by construction and I forgot DTC was on and I was caught off guard and had to counter steer when I made the turn, fun commute home.

[shah269]

Many good crash stories start off with...
"So i turned off the DTC....." and end with "The car is now in a tree!"

[JeffyD]

Turning DCT off is my sure fire method of not lagging on low gear shift while warming up. It also makes me feel good to know that the warning triangle will always be on so I don't know if a real problem shows up. Ignorance and bliss, y'know?

[slampig]

DTC and the E-diff are not necisarily the same system.

[NYHoustonman]

Originally Posted by 3002 tii

You're telling me that you can't turn off traction 100%? I don't buy that as I've taken my other car to the limit with and without traction and when it's off, you know it's off. And that car has the same traction system of ours: ON, DTC, and DSC OFF. In fact the other day I hit a patch of gravel by construction and I forgot DTC was on and I was caught off guard and had to counter steer when I made the turn, fun commute home.

Originally Posted by slampig

DTC and the E-diff are not necisarily the same system.

See above. E-diff is much better than nothing, and I want that on all the time! It makes for some good sideways action in DSC OFF mode, and a good bit of throttle adjustability even with DTC on - at least in my road driving .

[JeffyD]

I drive like a stupid ape with learning disabilities who just got his permit an hour beforehand. So everything needs to be as off as possible so that, when I screw up, I have nothing to blame but my own ineptitude.

[3002 tii]

Originally Posted by NYHoustonman

See above. E-diff is much better than nothing, and I want that on all the time! It makes for some good sideways action in DSC OFF mode, and a good bit of throttle adjustability even with DTC on - at least in my road driving .

Gotcha, didn't realize you were referring to E-Diff being on all the time, you are correct.

[2tonik]

The first thing I do after lighting the engine is turn off all the electronic stability controls. I let the Quaife do its job and rely on 38 years of driving to keep the car positioned where I want.
I've never spun a rear wheel drive car - I've owned at least 7 of them - though I have snap spun two FWD cars:
a '78 Civic CVCC and and '90 Civic Si.

[Andrewcoja]

You can turn the throttle cut off and the traction control all the way off. The E-diff will never turn off.

[Nugget]

Originally Posted by Andrewcoja

You can turn the throttle cut off and the traction control all the way off. The E-diff will never turn off.

Correct.
You can't turn off electronic brake-force distribution either.

[JeffyD]

No one is saying they turn their e-diff off. They're talking about disabling, at least as far as allowed, the nanny that controls cutting power to balance output based on readings of traction loss - not the e-diff that applies braking pressure in an attempt to balance power being put down to the ground effectively and avoid horrendous slippage.

In other words, Hitting the nanny button once (Turning on/off DTC) allows the wheels to spin without power being cut, and turning off DSC (holding nanny button down) basically just raises the threshold of when the sensors indicate rear braking is to be applied to attempt better distribution of traction.

As far as I'm aware, while DTC and the e diff use the same sensors to monitor power output to the rear, they aren't truly tied together. They just accomplish a goal in a similar manner, but are controlled separately. DSC, using the same sensors, attempts to just limit power to the wheels in order to control wheel spin.

I only typed that because I'm confused why the fact the E-diff isn't deactivated keeps popping up. Correct me if I'm mistaken, though, please.

[shah269]

so why does it hurt my head? I'm a mech E....an open diff should not lay down two perfect lines like that! What the hell gives?

[Xaoc]

An open diff can lay down lines, its just that most of the time, 1 of the wheels grips while the other spins. If both wheels have equal traction slip, they will both lay down lines.

[Stohlen]

Originally Posted by shah269

so why does it hurt my head? I'm a mech E....an open diff should not lay down two perfect lines like that! What the hell gives?

If the coefficient of friction is the same on both wheels, both wheels will spin. If you were in a clean parking lot, chances are that was the case since both wheels were on the same, clean type of pavement.

Go put one wheel on gravel and one on pavement and see what happens.

The real issue comes when turning, as you put more load on one tire than the other which causes more traction in that tire, and results in the inside wheel spinning.

[Eyeman]

We used to call the DTC button the TIM YOYO button on this site. For sure you want to at least push the button and preferably hold it down a few seconds if you plan an aggressive takeoff. If not if you spin one tire really bad braking will kick in and you'll barely move.

I think a few have tried to "code out" the E-diff but I don't remember if they were successful or not. Any excess braking on the track will just heat up your brakes worse.

Btw, TIM YOYO stands for "that's it m..........r, your on your own".

[ShocknAwe]

Damn! Been a while since someone mentioned TIMYOYO...