[tilt]

Here you go, a starting point: https://gprivate.com/67g28

Cheers

[dhanushs]

See.. I think we have to start from basics here..

What is a 4WD or an AWD?..

In a four wheeled car/van/truck/SUV.. Usually for on-tarmac use, two driving wheels are enough for all practical purposes.. But, when you venture out to areas with less traction(grip) what do you do? First you try and increase your grip levels from the driven two wheels by reducing air or using traction aids etc, but if its still not enough?.. You will wish that if only the other two wheels could also be driven and give you more grip..

Well..thats exactly what the engineers have done in a 4WD/AWD, develop a mechanism where all four wheels are driven.

Why the low ratio?.

Now that you have all four wheels being driven, you can do better gradients than before.. but you want to do more.. You also drive through very bad broken terrain that you have to be very slow and controlled. Doing this in your regular gear ratios is demanding for the driver and the system.. Hence the engineers have installed a low ratio gearbox which makes the vehicle go even slower and helps tackle even better gradients.

Why AWD on tarmac?

Now you have four wheels driven for areas where there is very less grip. But, this configuration of 4 wheel drive cannot be driven in areas where you have good traction (grip).. So you switch to 2WD.. But what about hilly snowy areas where you have freequent intervals of good grip and bad grip coming and going.. It'll be a pain to always switch between gears. Worse, you might also miss switching to 4WD and end up spining your wheels and car.. So engineers have come up with the AWD mechanism, where you can drive on good grip (tarmac) as well as bad grip areas with no capability compromise...

What about all the traction aids?

Well, now you have all four wheels driven.. but something called as the differentials which help you so much on road, cause problems offroad and make one or two wheels not be driven. So engineers have developed tech like diff-lockers, Brake Locking, Limited Slip Diffs etc.. to ensure all four wheels remain driven as required.

Now, coming to the question.. The answer will depend on what you want your vehicle to do?

- If you want capability of driving on slippery surface as well as surface with good grip simentaneously, then AWD is more capable for that.

- If you want gradeability then choose a vehicle with a low ratio gearbox.

- If you want both of the above then get something like the Fortuner, which has a low ratio gearbox and a center diff which allows it to be AWD and also has an intelligent braking system to give all traction aid, and also a switchable locker..

a 4x4 without MLD is useless.

Going by that logic.. All the Gypsys and MM540/550, Major, CJ500, Classic, CL340, Old jeeps are all useless..

[Mr.Fawlty]

Originally Posted by tilt

Here you go, a starting point

Thank you!

Originally Posted by dhanushs

Going by that logic.. All the Gypsys and MM540/550, Major, CJ500, Classic, CL340, Old jeeps are all useless..

There's so much (mis)info out there, so much of subjective opinion without context or explanation to confuse and mislead. I read that somewhere in the comments section of a YT video. Wasn't convinced and wanted to validate.

Originally Posted by dhanushs

You will wish that if only the other two wheels could also be driven and give you more grip..

You also drive through very bad broken terrain that you have to be very slow and controlled. Doing this in your regular gear ratios is demanding for the driver and the system

It'll be a pain to always switch between gears. Worse, you might also miss switching to 4WD

@dhanushs, thank you so much for taking the time to summarize and addressing the 'whys'. Would it be safe to say then the key takeaway would then be, the different mechanisms expect different levels of driver intervention - AWD systems being the least demanding whilst 4WD systems offer more fine grained manual controls, the perceived advantages of which can easily be nullified in the hands of an uninformed/unengaged driver?

At the expense of oversimplification, borrowing parallels from the world of photography for self explanation, 4x4 appears to be akin to shooting 'pro'/manual modes and AWD more or less like using the in camera presets, the latter often producing more usable image because you've been fumbling all along getting the exposure right in manual!

[Tejas@perioimpl]

You also need to understand that most new gen AWDs are not designed for continuous hard usage. I'm talking about cars with clutch based or similar systems and not the ones with a proper centre differential.

These cars with clutch packs / similar would disengage the AWD capability as soon as you push it to prevent the clutch from burning out. These are just good enough for minor outings.

I've seen numerous cases where suddenly in the middle of a climb, the over heated system would move the car into a 2wd mode leaving you unable to make a climb.

[Mr.Fawlty]

Originally Posted by Tejas@perioimpl

You also need to understand that most new gen AWDs are not designed for continuous hard usage.

I consider this an honor that you responded to something that must be so trivial for you, Sir. Hope to learn from you someday, but I'm so way off from even the basic theories of things at the moment.

And that brings me to one more doubt.

This is about ESP and traction control.

ESC is composed of the following safety features:-
Traction Control:

Source: ruzbehxyz on page 1 of this thread

Stability control is just traction control with more vehicular education (computer programming) and better tools (a more powerful processor and more electronic sensors).

Source

Also, if your car does have ECS, traction control is an automatic part of the same, so it's not as if you can choose whether you want one or both.

Source

Conversations here (Traction control explained) and here (Electronic Stability Control In Indian Cars?) helped in getting some insight on how the systems work.

But, I wonder, in general, if there could be incentives for manufacturers for not offering TC along with ESP in one variant while the higher variant of the same model is sold with the full suite?

Specifically, I'm looking at the Scorpio-N (one of its 4x4 options) as a potential next purchase and I'm unable to decipher this: TC is a separate line item, so is HH/HDC, yet the latter two are stated to be components of ESC, but not TC. As on their website...



The brochure doesn't make any mention of TC, the user manual mentions it in passing and only in reference to the 4Xplor system on Z8/L. (The Thar user manual on the other hand elaborates "TCS function is part of Electronic Stability Program (ESP)")

So the z4 4x4, even with ESC as optional extra, misses out on traction control? Or, am missing something?