What about Limited Slip Differentials?

[atr_hugo]

Track? That's a public road in Europe. There a lot like it (public roads) in the US. Ever hear of the Berthoud Pass? Trail Ridge road in Rocky Mountain Nat'l park? US 50 to the Continental Divide in CO? How about the 'Million Dollar' road out of Ouray, CO? Tail of the Dragon? Black Road connecting CA-17 to Skyline Drive south of San Fran? They go on and on. Grip/traction exiting a corner is essential to enjoy spirited driving on roads like these and a good LSD is essential. We don't know yet how good or bad the E-Diff will be in the 135i - but if it is (at best) a poor compromise then a number of us will get LSDs because we seek roads like these to drive.

[BimmerBoi2100]

I've lived in Germany for many years. I know all about those twisting and turning roads without street lights. That's why I asked is that track in America.

Ok you got me. I don't go seeking seeking out these roads because my ball and chain aka the wifey aka the warden won't let me......She always gives me the "we have kids" speech.

[atr_hugo]

That's too bad, those kinda roads are extremely fun (and oftentimes humbling). My wife goes along - very reluctantly though. And my wife's name is "She Who Must Be Obeyed" ; -)

[BimmerBoi2100]

She brainwashed me. She doesn't like to drive as much as I do. We drove on the Alaska Highway once and that killed her love for driving.

So anyway good luck guys....

[ducati]

Originally Posted by atr_hugo

We don't know yet how good or bad the E-Diff will be in the 135i - but if it is (at best) a poor compromise then a number of us will get LSDs because we seek roads like these to drive.

+1.

There are two types of "e-diffs", and sometimes folks use the term to describe both. I suppose it makes sense to clarify what we're talking about. BMW uses an electronically controlled limited slip diff in the M cars--this is a mechanical device in which the torque split is controlled by a computer. It functions like a clutch-pack LSD, simply has a bit of a "brain."

This is similar to Subaru's "DCCD" center diff in the STIs, although Subaru also give the driver the ability to override the diff's computer-controlled settings, and choose their own preload.

The "e diff" in the 135 is completely different. It is mechanically EXACTLY the same as an open differential. BMW is using the ABS braking system to sense when a wheel spins up, and then uses the braking system (Traction Control), to brake the wheel that has spun up. Due to the operation characteristics of an open diff, this then sends torque to the other side of the axle.

Sounds cool, right? Not at all. When you were a kid and racing your bigwheel, did you drag your shoes on the ground to go faster, or slow down? What BMW is doing is using an essentially "free" system (ABS, TC) with some extra software programming to "act" like an LSD... But in the end wastes engine power by turning it into heat.

Not to mention traction control systems are notoriously interruptive. When cornering at or near the limit, any odd inputs by the driver (or now, the car), can very much upset the fine balance the chassis has attained. You now need further electronic intervention to prevent a spin. I'm sure BMW is working hard on this one, which is why we haven't yet seen this on a 335... But personally I'd rather have a good old Torsen.

No computers.

No burning brakes.

No wasting torque for traction.

Just traction, when and where you need it. (as long as you don't lift a wheel)...

[atr_hugo]

Originally Posted by ducati

+1.
But personally I'd rather have a good old Torsen.

No computers.

No burning brakes.

No wasting torque for traction.

Just traction, when and where you need it. (as long as you don't lift a wheel)...

Yup the stinking Torsen (Torque Sensing) gives up when it has one wheel 'freewheeling'. I stopped my Miata eqp'd/w Torsen purposefully with one rear tire on ice uphill and tried to take off - it sat and spun.

[ducati]

Originally Posted by atr_hugo

Yup the stinking Torsen (Torque Sensing) gives up when it has one wheel 'freewheeling'. I stopped my Miata eqp'd/w Torsen purposefully with one rear tire on ice uphill and tried to take off - it sat and spun.

Yup, or if you up roll stiffness too much that you start lifting a wheel... Bad juju, Torsen gets angry.

You can in that case use the parking brake just a smidge (Miata does use rear drums as a brake, and not on the driveshaft, right?), and pretend you're BMW.

[atr_hugo]

Yup - I think they have 'hats in back' as opposed to 'cats in hats'. Speaking of driveshaft e-Brakes, a buddy of mine builds Cobras and here's an illustration of a driveshaft E-Brake:

[BMWeber]

Originally Posted by grant

Anyone who thinks the 135i doesn't need a real LSD shouldn't be buying a BMW :-)

[Advevo]

ok but the 10 mil question is.

The E diff will work when traction control is all set on off.
So what will happen when mounting LSD.

[atr_hugo]

That is the question indeed!! Will the E-DIFF beat the LSD to the punch?

I had a nice long talk, before the 2001 Indy 500, with a Delphi engineer about the rev limiter the Indy Racing League had. It was a 'hard' limiter that cut spark to all cylinders and just plain made the engine go 'flat'. Delphi had built a rev limiter that some teams used that cut spark to a single cylinder randomly about 5 to 10 RPM below the 'hard' rev limiter. That was a much better, more forgiving, solution.

If the E-Diff is a 'hard' or abrupt LSD we'd better hope that the true LSD kicks in before it does or that we can disable the code.

[Advevo]

yes otherwise i be waiting for an M1 and leave the 135i at the dealer.

[BMWeber]

Originally Posted by Advevo

ok but the 10 mil question is.

The E diff will work when traction control is all set on off.
So what will happen when mounting LSD.

There are chips out there that disable such things as specific OBD2 systems and the EWS security codes in the computers I'm sure shutting off the E-LSD will not be impossible or even that difficult for the software engineers

[R32]

FWIW, i ran across this quote from the quaif website, referring to the 335i:

"Birds have now slide a Quaife differential into place and left the standard DSC settings alone. This sounds like a recipe for a large shunt, but actually translates into one of the most pleasant-handling BMWs I've driven for years."

here's the whole page:
http://www.quaife.co.uk/AUTOCAR-Why-...s-shouldnt-die

might not have to fiddle with the electronic nannies that much after all.

[inTgr8r]

Originally Posted by R32

FWIW, i ran across this quote from the quaif website, referring to the 335i:

"Birds have now slide a Quaife differential into place and left the standard DSC settings alone. This sounds like a recipe for a large shunt, but actually translates into one of the most pleasant-handling BMWs I've driven for years."

here's the whole page:
http://www.quaife.co.uk/AUTOCAR-Why-...s-shouldnt-die

might not have to fiddle with the electronic nannies that much after all.

Except, the 335 doesn't have the E-dif.

[wrh3]

Originally Posted by BimmerBoi2100

Ok you got me. I don't go seeking seeking out these roads because my ball and chain aka the wifey aka the warden won't let me......She always gives me the "we have kids" speech.

That's funny, it's just the opposite for me, we have made some family outings to Tail of the Dragon/Hellbender/Cherohala Skyway in my R32 and I have family member rotation when I take the Lotus.......with the Elise, Lotus recommends an open diff since that is what the handling characteristics of the car were designed around for the track (although they did give in by offering the limited slip diff after the first year, autocrossers complained that the limited slip diff was essential for tight corner exit)

[R32]

Originally Posted by inTgr8r

Except, the 335 doesn't have the E-dif.

i thought the presumption was that the 135 will have the same rear torque management as the 335, i.e. open diff with braking of a slipping wheel.

[inTgr8r]

Originally Posted by R32

i thought the presumption was that the 135 will have the same rear torque management as the 335, i.e. open diff with braking of a slipping wheel.

The 335 has no electronic LS torque management, only the 135.

[R32]

Originally Posted by inTgr8r

The 335 has no electronic LS torque management, only the 135.

ah.

if it is a matter of software, one wonders why they wouldn't give the 335i a similar feature.

seems like stability control would brake a spinning wheel, even if its intent isn't for torque distribution... perhaps it is a matter of degree of intervention?

[ducati]

Originally Posted by inTgr8r

The 335 has no electronic LS torque management, only the 135.

Not entirely true.

The 335 does indeed have electronic traction control, which will brake one wheel to move torque to the other side of the axle.

The thing that's different about the 135 is the programming, which is supposed to "imitate" a LSD. What kind of LSD, we don't know. How this will be accomplished, we don't know other than it will still use DTC to accomplish the task.

My educated guess is the brake will be applied in a smooth fashion, rather than pulsed, and less brake will be applied that standard DTC. Additionally, I surmise no ignition cut, to continue to allow power being put down. (unless the g-sensors determine the yaw rate is above a certain threshold, when it will again become aggressive).

Why they didn't just stick in a LSD, I'll never know. Leave it to the Germans to try to find an unnecessary technical solution to a physical problem.

Elise: much less torque than the 335. Probably more similar to my old '86 Toyota MR2, which could still get along quite nicely without LSD. That said, I would have preferred the TRD LSD to the open diff, to help make sideways driving more manageable. I drove that car sideways more than a Tokyo Drifter

[CDR_UK]

It sounds like the same e-diff mechanism as on the cayman S.... rather just have the real thing!

[kurichan]

Originally Posted by ducati

Probably more similar to my old '86 Toyota MR2, which could still get along quite nicely without LSD. That said, I would have preferred the TRD LSD to the open diff, to help make sideways driving more manageable. I drove that car sideways more than a Tokyo Drifter

The old "Mister Two" was given to snap spins... Ever get hairy?