Team-BHP - Active traction control vs Locking differential in offroad conditions

I've heard people say that Toyota Atrac is as good as a locker. But doesn't the Atrac, and other similar active traction solutions, suffer from a disadvantage that engine has to work against vehicle’s brakes, when traction control is activated, to overcome a low-traction situation? All that energy is lost as heat, which could’ve all been directed, with a locking differential, to the wheel, which still had traction.

Of course, with a locking differential, you’ll need stronger axle shafts, hubs, wheels that can carry all that torque alone, and also tires with stiffer sidewalls and grippier tread that can hold on the surface to be able to convert that power into motion. What the traction control solutions do is provide half the power (because half is lost overcoming braking force) that would’ve possible in a normal circumstance of both wheels of an axle having traction, rather than providing no usable power at all (as with open diff). A locker is still superior, in the sense that it channels all power to one axle shaft, hub and wheel. It is just that the components downstream of locker should be able to bear that torque.

Other advantage of Atrac would be that it does all of this without needing upgradation of driveline components.

Traction control in offroad situations chews brakes, for full on offroad I reckon locking diffs are still the way to go.

Also, if it is a sedan with a generic 'program' the program may not be suited to the surface you are on gravel, sand, mud, ice etc.

Locking diffs are hard on the drivetrain/clutch and if you lock the front wheels the turning radius becomes very wide.

LSD is the current compromise.

In the near future, with EVs having motors at all ends I guess all these technologies will become redundant.

Quote:

Originally Posted by black_rider (Post 4648386)

My guess is that the amount of force applied to brakes used by Toyota's Atrac system exists but is not all that great. You are going to creep out of a stuck situation at very low speed, maybe 5 km per hour tops, not 40-90km per hour. I would guess that Atrac turns off altogether at higher than crawling speeds, after all, at higher speeds you ain't stuck. Hence, not so much strain to brakes.

Similarly, you are going to use lockers at crawling speeds. You are not going to use a locker to blast thru a bog at any great speed. That would be a recipe for loss of control and disaster. Lockers and Atrac are for crawling slowly out of trouble, e.g. being stuck in the mud. Once they have done that, they serve no purpose. They are not meant for high speed use. Hence strain on hardware exists but is minimal.

In the new age 4x4 SUVs, active traction control the norm. I have seen systems tuned to perfection like the Toyota’s A-Trac, mediocre systems like on Renault Duster and Isuzu V-Cross(2.5 high variant), slightly worse than Mediocre systems like on Ford Endeavour.

Having spent a lot of time experimenting with these systems, I can confidently say, Differential locks are superior to traction control, if the driver knows what he is doing. But also there are risks involving damage to drivetrain system sometimes topples in offroading scenarios. Advanced driving skills will be required to efficiently utilise front locker.

A well-tuned TC system however is more user friendly for beginners and regular users. It’s cheaper for manufacturers to fit because it utilises the existing ESP/ABS hardware. TC systems are good for crawling but at places where some speed is to be carried like in rutted sandy climbs it just can’t match the Diff locks, same for places like Mud where a lot of wheel spin and continuous uninterrupted power is to be put down.

The best combo however for me would be a factory fitted rear diff lock with a well-tuned Traction control system. But almost all such combos I have seen TCS is switched off as soon as you turn on the diff lock. But if you are stuck in a scenario where only one front wheel has grip, just turn off the diff lock, used the active TC mode to get the car moving.

As an end-user, electronic gizmos like the traction control works better than diff-locks, because of convenience. If you focus on only getting out of an obstacle, maybe diff-locks are better, but, if you take the whole picture..

Like why would you attempt that obstacle? Usually, in cars with traction control, it is to reach a specific destination and not to have fun tackling that obstacle. In that case, I'd choose traction control, since it does all the work for me even before getting stuck. I dont need to engage diff-locks when I sense a loss in traction and no need to be careful enough to disengage it as to not damage the drivetrain.

That said, what's better in tackling obstacles? Diff-Locks. However, in a road use (luxury) cars, traction control makes more sense, since diff-locks need educated user input.

We offroad a lot with SUVs as well. There are a few guys with the Toyotas and few with the endys. The Toyota has ATRAC and the Ford has the Diff Locks.

The Toyota guys are always at an advantage because they don't need to remember to switch on the Diff Locks. As soon as the they are struggling, the ATRAC kicks in and they are out. The Endy guys on the other hand keep paging me if a certain obstacle requires them to engage the DL or not.

And I agree with Dan the Dirty one that the hardware damage is negligible.

For a newbie to average off-roader, the ATRAC is the best option out there in my opinion.

EDIT:

@anshuman Traction control and ATRAC in the Toyota SUVS are slightly different. I can switch off TC but not ATRAC. And as always, in offroad I prefer TC off!