electronic locking differential

[xlover]

So i have not really seen mention of an electronic locking diff in any of the discussions on the SVT, what are the thoughts around SVT developing one of these vs the mechanical setup they used on the previous GT500.

In my opinion if the gt with PP can out do a boss 302 in order to get the GT350 an order of magnitude better this might be a direction ford needs to go with this car. Also its something we would have no way of noticing in spy shots....

Maybe an insider can weigh in on whether this is a direction ford is planning on going. I think it would be a very beneficial upgrade as part of stepping up to the SVT car.

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[NDSP]

No need for an electronic locking diff. the T2R is more than adequate. An electronic locking diff would really only benefit the drag racers and the GT350 will be track oriented from all appearances.

 

[xlover]

No need for an electronic locking diff. the T2R is more than adequate. An electronic locking diff would really only benefit the drag racers and the GT350 will be track oriented from all appearances.

This is incorrect. i think you are thinking of a diff that is only 100% on or off.

I was thinking more in the manner of the new BMW M or audi S/RS cars where the electronic diff can vary the % of lock based on the driving situation. Less locking at the beginning of a corner to help agility and more lock as the corner is exited and power needs to be put down. The electronic function allows the amount of lockup to be variable based on the dynamic situation. My audi has one and it is great. The system will actually push more torque to the outside rear wheel to enable better cornering. This would absolutely be a benefit to an SVT car if its going to be a rival for the M4 on the track.

 

[NDSP]

TR2 does this in a mechanical way, and I can't see Ford putting money and thus increase in price towards a electronic diff that functions nominally better than what already exists. They want to compete with the M3/4 is performance not price. JMHO

 

[Pablo GT350]

TR2 does this in a mechanical way, and I can't see Ford putting money and thus increase in price towards a electronic diff that functions nominally better than what already exists. They want to compete with the M3/4 is performance not price. JMHO

OP's question is valid. Corvette and M4 have this feature. It has yet to be determined if it would provide more than a "nominal" increase in performance on the GT350. TBD on the price increase as well.

 

[Trackaholic]

The c7 diff can vary the locking % electronically but does not actively proportion torque side to side. Not sure how much better that is than a purely mechanical one that varies the locking based on applied torque (such as a traditional Torsen or Quaiffe). The electronic version in the c7 seems to be highly regarded, but I am typically a fan of the simpler, mechanical approach.

-T

 

[Not_sure]

I could see potential for a drag and drift mode considering how versatile a electronic diff could be.

Neat stuff, it would be nice to see it as an option, or developed from the aftermarket community.

 

[Norm Peterson]

The c7 diff can vary the locking % electronically but does not actively proportion torque side to side. Not sure how much better that is than a purely mechanical one that varies the locking based on applied torque (such as a traditional Torsen or Quaiffe). The electronic version in the c7 seems to be highly regarded, but I am typically a fan of the simpler, mechanical approach.

-T

Same here. I'm not a fan of electronic interference (read: other peoples' preferences, with conservatism piled on top of that for good measure).

Never mind the likelihood of any electronic control system being more heavily biased toward understeer under some (many?) situations so that it hopefully won't ever be trying to work at cross-purposes to the stability control.

What really bothers me is that electronic crutches could become substitutes for proper vehicle suspension and handling, or band-aids for known deficiencies. If they aren't being used that way already (2010 Lexus GX460, anyone?).


Norm

 

[EXP Jawa]

While some active systems do have means of driving torque to one side and forcing the differential to overrun in a direction it ordinarily wouldn't, the hardware to do this is very expensive, its heavy and it is only marginally beneficial. Honda's SH-AWD system did exactly this for a while, before they backed off for cost reasons and simplified it. The system basically had a planetary gearset on either side of the differential that could be engaged and force the axle shaft to speed up. The PCM could command that one wheel run unnaturally fast and use that to induce yaw. This worked, but as I said, was hugely complicated.

I should point out that for all intents and purposes, simply varying the % locking (AKA torque bias ratio) does essentially the same thing. If the locking effect is increased, the differential can support a greater torque imbalance from side to side without slip. This allows more torque to be applied to whichever side that can use it without slippage on the low traction side. The net affect is that more torque is proportioned to where it needs to be.

Mechanical differentials like the Torsen T-2R, the Quaife, or even the clutch plate Traction-Lok are operating on this basic principle. The diff generates internal friction, friction supports the left to right imbalance without slip. The more friction you can generate, the greater the imbalance that's allowed. Helical gear units like the Torsen or Quaife build that friction in proportion to input torque. If the car is coasting with the clutch in, the unit differentiates very freely. If you're standing on it, it provides maximum (within its TBR limits) resistance to differentiation.

The advantage of the eLSD like the Corvette has is that this can be varied on the fly, as the vehicle or driver requires. It can be programmed to have different locking behavior depending on drive mode (sport/eco/off-road etc depending on vehicle), it can operate at different levels if you're autocrossing versus driving VIR or the Glen, it can be harnessed into the chassis controls to cooperate with stability and traction controls, etc.

The mechanical diffs have just one set point for their TBR level and it doesn't have the ability to change with conditions. The OEM has to make sure that they've tuned it right for the vehicle's intended use. OTOH, it requires no further calibration and will always behave predictably and is a very simple integration into the drivetrain. They may be more cost effective than eLSD systems, especially compared to what Honda was using. This is why Ford used the Torsen in the Boss and is continuing to with S550, and GM used one in the Z/28.

Finally, to the point of this thread, the SVT car could potentially use an eLSD in the new car. It all depends on cost of the system, ease of integration and what the car will be intended to do. If its another high-powered boulevard cruiser with a lot tech features, they might want exactly that. If it does turn out to be a Boss successor, though, I'd put my $$$ on them using a tuned mechanical device.

 

[Trackaholic]

Just got back from the Ron Fellows Driving School, where I was able to drive the C7 quite aggressively for three days.

In addition to experiencing the eLSD, I was able to see a x-sectioned assembly that was left over from the C7 dealer introduction that GM held at the school.

I wish I had taken pictures, because the design was definitely pretty cool. But it did increase the space required for packaging the components, it increased weight, and it increased complexity.

I could definitely feel it working on the track, and it seemed a little more seamless than the aftermarket Quaife unit on my 350Z, but I wasn't able to notice a significant difference between the two when throttle steering or during turn-in. But maybe that's part of the advantage of the eLSD - that it can be tuned to be very well integrated.

In any event, I'm a bit of a Luddite on these topics and still prefer the mechanical LSD due to the consistency and simplicity.

The C7 is a damn good car BTW.

-T

 

[Devon]

While some active systems do have means of driving torque to one side and forcing the differential to overrun in a direction it ordinarily wouldn't, the hardware to do this is very expensive, its heavy and it is only marginally beneficial....

Thanks for the great description of LSD types and their effects, it's posts like these that keep me coming back here....

Your description makes it clear how the M Performance LSD (a dealer/port install option for the 3 series and the M235i) does its variable lockup magic--it's purely mechanical, but it's been tuned to give a low degree of lock on corner entry and about 3X the lock on power-on after corner exit (although nowhere near 100%). Impressive engineering voodoo!

 

[Devon]

Just got back from the Ron Fellows Driving School, where I was able to drive the C7 quite aggressively for three days....
The C7 is a damn good car BTW.

-T

So, so tempting. I assume your drive had the Z51 package, adaptive suspension etc.

The one thing that left me cold about this car when sitting in it was the awful rearward visibility. Not sure I'd want to be negotiating city traffic in that bad boy. (Of course compared to a 370Z it's a greenhouse.) But what a value for money proposition. The C7, the M2, the GT 350... making a decision next year is going to be tough.

 

[Trackaholic]

So, so tempting. I assume your drive had the Z51 package, adaptive suspension etc.

The one thing that left me cold about this car when sitting in it was the awful rearward visibility. Not sure I'd want to be negotiating city traffic in that bad boy. (Of course compared to a 370Z it's a greenhouse.) But what a value for money proposition. The C7, the M2, the GT 350... making a decision next year is going to be tough.

Yes, it was the Z51 with the mag shocks. Rearward visibility wasn't that bad, but I have a 350Z which isn't great either so maybe I'm used to it. You just needed to set the side mirrors to be aimed out a bit to cover the blind spots.

Definitely a lots of nice cars showing up these days.

-T

 

[Norm Peterson]

it can be harnessed into the chassis controls to cooperate with stability and traction controls, etc.

This is the part about an e-diff that I don't like, as it would tend to teach a certain amount of sloppiness - that by its intervention you can get away with being less "smooth" with the throttle than you should be. Somehow, I just can't make that sound like a good thing.


Norm

 

[Shredicus]

This is the part about an e-diff that I don't like, as it would tend to teach a certain amount of sloppiness - that by its intervention you can get away with being less "smooth" with the throttle than you should be. Somehow, I just can't make that sound like a good thing.


Norm

Same concept as ABS which has made its way into every car on the street. You can brake more quickly and effectively without the system, but very few average drivers today would know what to do if they didn't have the system in place.

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