Differentials

[Red_Bean_Bun]

Saw this on e90post - excellent explanation about how differentials work.

Makes you think about changing the rear diff oil for maintenance when looking at all that cog gnashing .....

FYI - BMW now use e-diffs (feature of the dsc function) and they said it negates the use of an LSD. Anyone with an LSD can comment ?

[video=youtube;K4JhruinbWc]http://www.youtube.com/watch?v=K4JhruinbWc&desktop_uri=%2Fwatch%3Fv%3DK4JhruinbWc[/video]

 

[kenntona]

Re: Differentials

I have installed a torque-biased Quaife LSD in my previous 335 to smoothen out the torque delivery between the two rear wheels around corners. I was running in excess of 600 NM on the wheels and I had wheel spins on straights and slips around corners. I needed traction. The LSD took the torque and divides it between the 2 wheels and increases the bias ratio - a 2.5 : 1 ratio will multiply the torque that is going to the slipping wheel by 2.5 and transfer it to the wheel that has grip. Installation wise, gotta verify if the differential in your ride is bolted (pre-2007) or welded. Bolted version enjoys a direct swap against Quaife. Welded version gotta exchange the entire axle, if I am not wrong.

Your e-diff is still a differential lock (plus a computerised LSD), using chassis sensors such as speed sensors, ABS sensors and microcomputers to electronically monitor wheel slip and vehicle motion. When a wheel slips, the computer applies the brakes to that wheel instead of sending more torque to the slower wheel like the mechanical LSD.

So what's the difference?

The feel, especially if you abuse your car.

Both targets traction. But the positive driving feedback, confidence and control are different. The e-diff has it's limits. Once traction loss is too great, you will face a sudden loss in traction than what a mechanical LSD - you might spin more suddenly than with a mechanical LSD. This is mostly evident exiting corners under heavy throttle. This is where the mechanical LSD shines. Because the e-diff uses brakes to aid traction, excessive heat and wear may be generated on your rear brakes during track driving.

When would you feel the differences? Normal street driving? No. Spirited driving? No. Track and drifting? Yes, but only if you do.

 

[het]

Re: Differentials

I have installed a torque-biased Quaife LSD in my previous 335 to smoothen out the torque delivery between the two rear wheels around corners. I was running in excess of 600 NM on the wheels and I had wheel spins on straights and slips around corners. I needed traction. The LSD took the torque and divides it between the 2 wheels and increases the bias ratio - a 2.5 : 1 ratio will multiply the torque that is going to the slipping wheel by 2.5 and transfer it to the wheel that has grip. Installation wise, gotta verify if the differential in your ride is bolted (pre-2007) or welded. Bolted version enjoys a direct swap against Quaife. Welded version gotta exchange the entire axle, if I am not wrong.

Your e-diff is still a differential lock (plus a computerised LSD), using chassis sensors such as speed sensors, ABS sensors and microcomputers to electronically monitor wheel slip and vehicle motion. When a wheel slips, the computer applies the brakes to that wheel instead of sending more torque to the slower wheel like the mechanical LSD.

So what's the difference?

The feel, especially if you abuse your car.

Both targets traction. But the positive driving feedback, confidence and control are different. The e-diff has it's limits. Once traction loss is too great, you will face a sudden loss in traction than what a mechanical LSD - you might spin more suddenly than with a mechanical LSD. This is mostly evident exiting corners under heavy throttle. This is where the mechanical LSD shines. Because the e-diff uses brakes to aid traction, excessive heat and wear may be generated on your rear brakes during track driving.

When would you feel the differences? Normal street driving? No. Spirited driving? No. Track and drifting? Yes, but only if you do.

sibei chim.....

 

[davidtch]

Re: Differentials

In simple term, if u drive Chris Harris, u will feel the diff.

 

[SUPAN]

Re: Differentials

I have installed a torque-biased Quaife LSD in my previous 335 to smoothen out the torque delivery between the two rear wheels around corners. I was running in excess of 600 NM on the wheels and I had wheel spins on straights and slips around corners. I needed traction. The LSD took the torque and divides it between the 2 wheels and increases the bias ratio - a 2.5 : 1 ratio will multiply the torque that is going to the slipping wheel by 2.5 and transfer it to the wheel that has grip. Installation wise, gotta verify if the differential in your ride is bolted (pre-2007) or welded. Bolted version enjoys a direct swap against Quaife. Welded version gotta exchange the entire axle, if I am not wrong.

Your e-diff is still a differential lock (plus a computerised LSD), using chassis sensors such as speed sensors, ABS sensors and microcomputers to electronically monitor wheel slip and vehicle motion. When a wheel slips, the computer applies the brakes to that wheel instead of sending more torque to the slower wheel like the mechanical LSD.

So what's the difference?

The feel, especially if you abuse your car.

Both targets traction. But the positive driving feedback, confidence and control are different. The e-diff has it's limits. Once traction loss is too great, you will face a sudden loss in traction than what a mechanical LSD - you might spin more suddenly than with a mechanical LSD. This is mostly evident exiting corners under heavy throttle. This is where the mechanical LSD shines. Because the e-diff uses brakes to aid traction, excessive heat and wear may be generated on your rear brakes during track driving.

When would you feel the differences? Normal street driving? No. Spirited driving? No. Track and drifting? Yes, but only if you do.

Senior ...

So during rain meaning heavy downpour ... is it easy to skid on normal road driving ... ?

 

[sandman369]

Re: Differentials

Senior ...

So during rain meaning heavy downpour ... is it easy to skid on normal road driving ... ?

I think the limitation of tires against physics applies in heavy downpour

 

[SUPAN]

Re: Differentials

Until I find out the limitation I m likely not to go for it. As I dun like me or my car to be a hazard

 

[aloysiuschia]

Re: Differentials

since we are at this topic, anyone knows where to find recon rear differential?

 

[lf37]

Re: Differentials

Water plane-ing happen around 55 mph or 90 kph. Hard to overcome so drive slowly in rain lor!

 

[Red_Bean_Bun]

Re: Differentials

Especially for those with wide tires ......

Water plane-ing happen around 55 mph or 90 kph. Hard to overcome so drive slowly in rain lor!

 

[wt_know]

Re: Differentials

after so many years ... this problem is not resolved
the shaft is merely "covered" with awesome armrest & controls in front but huge center piece in the rear
the center seat for rear is practically useless ...

 

[Red_Bean_Bun]

Re: Differentials

SUV types resolved .......

after so many years ... this problem is not resolved
the shaft is merely "covered" with awesome armrest & controls in front but huge center piece in the rear
the center seat for rear is practically useless ...