AWD & 4WD, A Conversation.

[Broadway One]

Hi all...I am aware of the basic difference, however less so on the dividing line between the two.
So much out there centered on intended use, tarmac roads with light off road vs serious off road capabilities....simple.
However it seems there are AWD's offering more off road capability than others, blurring the difference.
I'm well aware that there are many of you with hands on experience of differing terrains.
Hence my query;

In other words how does the RAV AWD perform when pushed off road compared with others? 
Where does the RAV 4 AWD figure in capability wise in the range of manufacturers producing AWD's ?
Are there goodies on the RAV favouring off road experience which most of us will ever need or use ?

Lots pooh pooh AWD's as pretend off roaders including several family members.....HELP !
Barry Wright, Lancashire.

       

[Cyker]

I don't think the RAV4 is really designed for it TBH; It can probably do it in a pinch, but if I was going to do serious off-road stuff it would not be my first pick!

Traditionally if you wanted proper off-roadability you'd want a proper 4x4 with full diff-lockups, usually a Land Cruiser or Land Rover of some sort.

If you needed a mix, but still with good on-road performance, Subaru were the ones to go for.

The thing with AWD is that most vehicles labelled "AWD" are not really AWD, they're FWD with occasional AWD - Those are basically useless for any serious off-roading; It was one of Subaru's main selling points, as they are one of the few manufacturers who only made full-time AWD cars, so they were consistently good on all surfaces.

It's tricky to say tho' as you have funny ones like the Panda Cross which are surprisingly capable off-road. They don't have the ground clearance of a serious 4x4, but they are much lighter and get surprisingly good traction!

 

[TonyHSD]

4x4 , awd, 4wd , 4 matic, Quattro,  and similar are simply trade names and calls between  the different makes and models vehicles.
Similar to diesels for example TDI, CTDI, JTD, or the estate cars like Touring sport, combi, variant, wagon. 
There is no difference in the meaning, however there are always some small or big differences between the cars and their awd system and how they work. 
If we compare a heavy duty vehicle with more than 4 wheels and more than two axles then the difference between awd and 4wd can be significant, for example awd on three axles 6 wheels truck will mean all 6 wheels can deliver torque and push the truck where if the same vehicle is marked with 4wd will mean that 4 wheels out of 6 can deliver torque only and propel the truck. Then if we accept the same truck above can also be rwd or 2wd, again this two are same between but differentiated from the above power train variants. These are the main differences between driven axles and call signs between. 
 

[Roger_N]

2 hours ago, Broadway One said:

Hi all...I am aware of the basic difference, however less so on the dividing line between the two.
So much out there centered on intended use, tarmac roads with light off road vs serious off road capabilities....simple.
However it seems there are AWD's offering more off road capability than others, blurring the difference.
I'm well aware that there are many of you with hands on experience of differing terrains.
Hence my query;

In other words how does the RAV AWD perform when pushed off road compared with others? 
Where does the RAV 4 AWD figure in capability wise in the range of manufacturers producing AWD's ?
Are there goodies on the RAV favouring off road experience which most of us will ever need or use ?

Lots pooh pooh AWD's as pretend off roaders including several family members.....HELP !
Barry Wright, Lancashire.

       

Barry have a look on YouTube there are lots of videos people have made about taking Rav4's off road.

[Cyker]

I think people broadly differentiate AWD and 4x4, although technically they could be considered the same as you say above; Conventionally,

4x4 is usually your traditional 4x4, where you can diff-lock all 3 diffs, and it has selectable drive train modes, usually 2WD, 4WD, 4WD-LOW. Normally you'd only use 2WD mode on the road, and manually set it to 4WD only when you're on terrain that actually warrants it. You'd normally avoid using 4WD on the road, and especially at high speed, in these as it can damage the drivetrain.

AWD is usually used for the 'always on', more road-focused type, where there are no mechanical diff locks (Maybe some electronic LSDs) and it's always in 'AWD' mode (e.g. Subaru), or the car decides whether to switch between 2WD and 4WD, and it's fine to drive in 4WD mode all the time on all road surfaces and at high speed.

The 4x4 types tend to have a lot more rugged drivetrain components and big beefy transfer boxes to handle high torque abuse, while the AWD-type tends to just be a normal drivetrain with some extra bits for the AWD.

There is some blurring of the two, but that's why people often don't use 4x4 and AWD interchangeably, but instead separate the terms.

 

[Broadway One]

Thanks guys for a comprehensive insight into AWD/4WD layouts. So much misinformation out there; another plus tick for this forum & its contributors.
Barry Wright.    

[FROSTYBALLS]

Toyota originally introduced the RAV4 as Toyota 'Recreational Activity Vehicle with 4 wheel drive' ......

[Cyker]

Well don't take it as gospel; As with all my posts it's more strong opinion than solid fact!  

 

[Cyker]

4 minutes ago, FROSTYBALLS said:

Toyota originally introduced the RAV4 as Toyota 'Recreational Activity Vehicle with 4 wheel drive' ......

I always found that funny since you can get it in 2WD-only configurations!  

Legend has it the original one was essentially a Celica GT4 with a mini SUV-body on it! It's put on a lot of weight since then though...  

[Strangely Brown]

5 hours ago, Roger_N said:

Barry have a look on YouTube there are lots of videos people have made about taking Rav4's off road.

Of those - and I have watched probably far too many of them - this one is probably the most informative.

 

[philip42h]

48 minutes ago, Cyker said:

I always found that funny since you can get it in 2WD-only configurations!

You can't ... those are just miss labelled RAV2s ...

[Dippy]

Which RAV4?

there are 30 years worth…

[Broadway One]

3 hours ago, Strangely Brown said:

Of those - and I have watched probably far too many of them - this one is probably the most informative.

 

Ta for that, very impressive, spotlighting what this road car can do away from the tarmac. So much latent ability exposed in the clip. Well done Toyota......Barry.     

[Yugguy1970]

That video is a good one, it shows what the Rav is and isn't.

I wouldn't expect it to rival a proper Landy but it's more capable than people think.

[Strangely Brown]

And if you want to know what it's like in similar conditions but with snow, then they did that too. A treat for all you PHEV owners.
 

 

[philip42h]

I can't find a definitive definition of the terms 4x4, 4WD and AWD - rather, I find that they are defined differently in different places. So, for me, we'd have to compare the capabilities of specific models of vehicle rather that get excited by the marketing terms used.

As said above, the Recreational Activity Vehicle with 4-wheel drive has been around for 30 years and across 5 generation. And over that time it has always been a 'soft roader' rather than an 'off roader" - a car than is capable of being taken off the tarmac into a field or on a track rather than a full blown 'go anywhere' vehicle. The owner's manual for my 4.4 basically said "do not take it off-road - it wasn't designed for that". While the owner's manual for my 4.5 states that "This vehicle belongs to the utility vehicle class, which has higher ground clearance and narrower tread in relation to the height of its center of gravity to make it capable of performing in a wide variety of offroad applications.". And then goes on the list a load of warnings about doing so. As above, there are plenty of videos about showing what the car can and can't do in realistic and less realistic scenarios.

For the past three generations we have had a part-time AWD system. The car starts off from rest with all four wheels being driven and switches to front wheel drive as the speed increases. And that works for me ... at speed I want the economy of a front wheel drive car and do not (in general) need the added traction of a driven rear axle - so I don't want a permanent four-wheel drive system wasting fuel under those circumstances. Meanwhile, under low grip conditions, the intelligent all-wheel drive system does a more than acceptable job of getting the car moving - and I can't, off hand, think of a better system for that.

But then I am not planning to enter my car into the Paris - Dakar rally nor attempt to drive to the North Pole! 😉

[Yugguy1970]

I think 4wd is used to describe cars with permanent mechanical 4wd systems driven by axles and transfer boxes.  They can still go from 2wd.to 4wd but they are physically connected front to rear.

Awd like ours have no physical connection front to rear.

[philip42h]

2 hours ago, Yugguy1970 said:

I think 4wd is used to describe cars with permanent mechanical 4wd systems driven by axles and transfer boxes.  They can still go from 2wd.to 4wd but they are physically connected front to rear.

Awd like ours have no physical connection front to rear.

Well, yes, that covers the basic difference between a RAV4.1 - permanent mechanical 4wd - and the current RAV4.5. But doesn't really cover the system used in the 4.3 and 4.4 where the mechanical connection between front and rear is equipped with an electromechanical clutch that disengages the rear drive above about 15mph. Toyota called it "Intelligent All Wheel Drive" to distinguish it from the dumb systems used by the dinosaurs with mechanical Haldex systems ... 😉

All wheel drive systems have evolved over the years and the naming is mostly about marketing.

Things should all get simpler once we get to proper AWD EVs - they should have a motor per wheel hub and the overall drive system controlled electronically. 👍

[Cyker]

AFAIK there is no 'official' definition, other than AWD=All-Wheel drive, and 4WD=Four Wheel Drive, with 4x4 meaning 4-by-4 as in 4 wheels and all 4 are driven.

So technically they can all be used to describe the same thing.

However, at least in my circles, the terms separated as I described above in my previous post; I think mainly because the hard-locking type 4x4s (The Landys and LCs of the world) were always marketted as 4x4, while the more road-going type were marketted as AWD. I'd forgotten 4WD, but that seems to have had more vague connotations as to which type it references.

This isn't set in stone tho', and this is a topic guaranteed to start an argument among 4wd people  

 

[Rhymes with Paris]

I have spoken to a few deluded people who insist that AWD is 4WD.

And some even more deluded when their car has no selectable 4WD system or AWD thinking that a snow button on a 2WD that reduces torque to the driven wheels to reduce wheelspin equates to the same thing.

I would imagine that most of that delusion stems from a desire to appear as an owner of a go anywhere, ready for any emergency, general purpose hero type.

Especially with cars that would not climb a 4" kerb without ripping it's skirt off.

I was working on the Maldon bypass in 1989 and the client surveyor side (highways) had some kind of 4WD pick ups (hired for them by the contractor of course) to get around the deeply muddy site.

I had my newly purchased Citroen ax diesel which went everywhere on that site and never got stuck once, also up a snow covered hill back home which stopped most cars,or maybe just drivers.

I had looked at the Subaru justy which I think was an actual 4WD specifically for that purpose,ie civil engineering contracts.

But a pushy lying dealer put me off, before I realised that they all are.

Wish I'd bought the Subaru anyway now, but all the armchair experts at the time were saying you can't trust Japanese cars.

Then,as now, they were wrong 😐

 

 

[SUPERIOR MUDFLAP]

I realize that "real 4WD" with locking differentials is superior to computer controlled AWD systems but I don't quite understand why. One would think that a computer controller braking the spinning wheel on an open diff would be able to emulate a locking diff quite well. But why isn't that so? Is it just bad software or is there some actual mechanical reason why the software can't be too aggressive?

[philip42h]

1 hour ago, SUPERIOR MUDFLAP said:

I realize that "real 4WD" with locking differentials is superior to computer controlled AWD systems but I don't quite understand why. One would think that a computer controller braking the spinning wheel on an open diff would be able to emulate a locking diff quite well. But why isn't that so? Is it just bad software or is there some actual mechanical reason why the software can't be too aggressive?

And that's almost entirely the point - "real 4WD" with locking differentials ISN'T necessarily superior to computer-controlled AWD systems, and, in an ideal world the converse would be true.

Mechanical systems are limited by the mechanism used. It is difficult and expensive to build a good mechanical system but early 4x4 systems were mechanical and were made to work very effectively.

Early computer-controlled emulations of these systems were inferior - simply because they were less well developed - but the main clamour against them came from 'luddites' who were opposed to any change from the systems they knew.

The system on the RAV today uses the brakes to limit power transfer to the spinning wheels - which isn't perhaps ideal but works perfectly well. It emulates the behaviour of a limited slip differential but has somewhat different characteristics. But it is simpler, lighter, cheaper and more reliable than fitting an LSD.

Once we get to four independently driven wheels in an EV the computer-controlled system will win hands down ... 🙂

[Yugguy1970]

Exactly, while the awd RAV does have drive to all four wheels, all four wheels are not driven independently.  Trail mode enables independent braking but not drive.

As Philip says, the ideal would be fully computer controlled independent drive and braking on each wheel.  The EV motor could also provide braking analogous to a limited slip diff.

That would let you program it to function as any kind of mechanical diff you liked, for instance you could have an lsd and change the amount of slip allowed instantly as the terrain changed.  

[Cyker]

One of the reasons having a fully-locked up system is beneficial off-road is because you won't get the one-tyre-fire that you often get with full-time AWD systems, and they're also better able to transmit all the power to the wheels with grip, because they're all turning in lock-step.

The big downside is the reason cars have differentials in the first place - When you turn, the outside wheels have to turn more than the inside wheels, but when fully locked up they can't, so you end up skidding wheels or breaking an axle. On rough terrain this isn't a problem since they will slip anyway, but on grippy tarmac it will likely break something!

Full-time AWD systems don't have this problem as they have differentials, but so far there are only a handful of them that are as capable as a fully-locked up system on rough terrain - Turns out it's harder than it looks to send torque to the grippy wheel, even with LSDs and computer-controlled independent braking (aka traction control). I can think of very few AWD systems that can pass the roller test where only 1 wheel has grip, and most of them are Subarus  

 

Theoretically, EVs should be the ultimate off-roaders - Each wheel completely independent, no need for full-width axles so better ground clearance, and as long as each motor is strong enough to move the car on its own, it should never get stuck as long as at least 1 wheel has enough grip. EVs should also have an advantage in descent control, as regen-braking is anti-lock by nature - It relies on the wheel turning to generate a braking force, so if the wheel stops turning the braking force stops, so the wheel can turn again.

However, there aren't many EVs out there set up like this; I only know of the Humvee and high-end Rivians off the top of my head. The vast majority of EVs use 1 motor, maybe 2 if they're being fancy, so they still have all the problems you get with having a differential.

 

[SUPERIOR MUDFLAP]

15 hours ago, Cyker said:

Full-time AWD systems don't have this problem as they have differentials, but so far there are only a handful of them that are as capable as a fully-locked up system on rough terrain - Turns out it's harder than it looks to send torque to the grippy wheel, even with LSDs and computer-controlled independent braking (aka traction control). I can think of very few AWD systems that can pass the roller test where only 1 wheel has grip, and most of them are Subarus

The RAV4.5 AWD-i seems to do quite well compared to most of its competition, I've seen it pass (though barely) the roller test with just 1 wheel having grip. And those videos linked previously in this topic really show how extremely helpful it is to have the instant torque of an electric motor in offroad situations.

15 hours ago, Cyker said:

Theoretically, EVs should be the ultimate off-roaders - Each wheel completely independent, no need for full-width axles so better ground clearance, and as long as each motor is strong enough to move the car on its own, it should never get stuck as long as at least 1 wheel has enough grip. EVs should also have an advantage in descent control, as regen-braking is anti-lock by nature - It relies on the wheel turning to generate a braking force, so if the wheel stops turning the braking force stops, so the wheel can turn again.

Indeed, electric motors should be excellent for this, just look at how precise traction control electric locomotives are capable of: