Awd System

[Rollers 6]

As an instructor in 4x4 driving I was interested in an answer to the following. I have the use of two rollers which are placed underneath trhe wheels of mainly Land Rovers to explain what 4x4 actually means. The opportunity occured to place a two RAV 4 vehicles and a Skoda Octavia 4x4 on the rollers to see the systems in these cars working. Both rollers were placed under the front wheels of all three cars in turn. Both Rav 4 vehicles failed to drive off there was little or no transfer of power to the rear axle, no matter how much throttel was used, these were 2005 vehicles. The Skoda Octavia drove straight off after a quick transfer of power to the rear. This was 61 plate vehicle with a Haldex diff. It would suggest that although there are no bad AWD vehicles, some are better than others. A similar result can be seen on the link. It doe make you wonder.

[anchorman]

It doesn't compare apples with apples. The systems on the RAV and the CRV are working as designed. By the way, the CRV has a Haldex rear axle in it. These systems are designed to put emphasis on maintaining dynamic control rather than true off roading. In both cases, when the front wheel slips drive is correctly distributed to the rear axle but then the diff transfers the drive to the other side. Dynamically that provides a certain level of safety for mum with kids in the back. Now in later versions of the RAV you can shut off the VSC to stop the engine falling back to idle and that would allow the traction control to work. Even then you have to remember that the only real way is to have all round limited slip diffs or lock up diffs and that is why you will never beat a LR off road.

The test is flawed because a/ they are using zero friction when often a snowy or muddy road allows some and b/ that you cannot see if anything has been pressed in the subaru - it might be independant premises but it is a subaru advert after all. Maybe it has LSDs.

[DjRav]

In the heaviest snow we had I drove my Discovery and my Rav on the exact same roads. I can categorically state the Rav never put a foot wrong anywhere, whereas the LR lost traction a few times- especially in the bends. Rolling roads etc may have their place, but the only true test is out in the real world.

NB not all LR have diff lock (mine doesn't) and you give far too much credit by saying you'll never beat a LR! I did have a 12 seater V8 Defender before that that too (with Diff lock) used to slide sideways in the mud! The Rav system is far more sophisticated than many rivals IMO.

Dave

[anchorman]

Aye but going up a field or proper off road Dave? Never seen an army RAV!

I agree, the RAV is very capable but these marketing guys will concoct a situation to demonstrate anything they want if they put their mind to it.

[DjRav]

Exactly. You can demonstrate any point by constructing the test to suit your need.

Granted, if its bumping over large rocks or wading through a stream you want, LR's are great (if it actually makes it without breaking down). But in the "real" day to day world of 90% of us, we're more likely to meet ice, mud or snow.

And for driving round a slippery bend (maybe going a bit fast) I'd take my Rav over my LR every time!

"AWD" sounds a bit timid compared to "permanent 4x4" but it works!

Dave

[silly sausage]

I've never had an issue with the Ravs capability in snow, in the winter of 2010 with four bags of sand in the boot and keeping the diesel tank full I drove through everything thrown at us without issue. I must add, I drove a diesel Forrester when they were introduced, it was agricultural compared to the Toyota, the ride was awful .

[Guest]

As an instructor in 4x4 driving I was interested in an answer to the following. I have the use of two rollers which are placed underneath trhe wheels of mainly Land Rovers to explain what 4x4 actually means. The opportunity occured to place a two RAV 4 vehicles and a Skoda Octavia 4x4 on the rollers to see the systems in these cars working. Both rollers were placed under the front wheels of all three cars in turn. Both Rav 4 vehicles failed to drive off there was little or no transfer of power to the rear axle, no matter how much throttel was used, these were 2005 vehicles. The Skoda Octavia drove straight off after a quick transfer of power to the rear. This was 61 plate vehicle with a Haldex diff. It would suggest that although there are no bad AWD vehicles, some are better than others. A similar result can be seen on the link. It doe make you wonder.

Dear Rollers, you compare a 1 year old car (lets call it new) with two 7 year old cars and put up a advert from an unknown organisation to illustrate what exactly?

I know what car I would want to drive in the mud and snow and Skoda Octavia it ain't (Yeti maybe)

Gus

[Plutus]

To me the 2005 Rav was a 4.3? I understood the 4.3 to always have 4wd upon setting off until a certain speed is reached. Is this the case in the USA version?

My 4.2 with a different system has never put a foot wrong in the snow.

Where was the Freelander? Would it have embarrassed the Subaru?

[Timelord]

I would expect the Subaru to do well in this test as it has a permanent AWD system.However like Plutus I thought the 4.3 RAV always set off in 4WD before reverting to 2WD.All I can say is that in the real world I have found my 4.3 RAV's (T180 and XTR) to be very competent in snow and mud.

[CharlieFarlie]

I would expect the Subaru to do well in this test as it has a permanent AWD system.However like Plutus I thought the 4.3 RAV always set off in 4WD before reverting to 2WD.All I can say is that in the real world I have found my 4.3 RAV's (T180 and XTR) to be very competent in snow and mud.

My understanding is that the 4.3 sets of in 4WD if the lock button on the dash is selected.. Other than that it remains front wheel drive unless a wheel starts to loose traction at which point the cars electronics take over and engage 4WD... Well thats what I thought..

Surely the biggest variable factor in a cars capability is the driver ??

When travelling from the midlands to Cambridge two winters ago I saw a Disco stuck in a ditch which if the driver had been just that bit more clued up would surely never have ended up in the ditch in the first place ?

[Big Kev]

I would expect the Subaru to do well in this test as it has a permanent AWD system.However like Plutus I thought the 4.3 RAV always set off in 4WD before reverting to 2WD.All I can say is that in the real world I have found my 4.3 RAV's (T180 and XTR) to be very competent in snow and mud.

My understanding is that the 4.3 sets of in 4WD if the lock button on the dash is selected.. Other than that it remains front wheel drive unless a wheel starts to loose traction at which point the cars electronics take over and engage 4WD... Well thats what I thought..

Surely the biggest variable factor in a cars capability is the driver ??

When travelling from the midlands to Cambridge two winters ago I saw a Disco stuck in a ditch which if the driver had been just that bit more clued up would surely never have ended up in the ditch in the first place ?

No need to press the lock button, Charlie....from zero speed it always takes away in 4WD, and when the system detects it is not required, it reverts seamlessly to 2WD. Also when locked up, it reverts to 2WD at around 26mph if it detects no wheel slip. So I am telt anyway.

Avatarred Kev......

[Davrav]

I would expect the Subaru to do well in this test as it has a permanent AWD system.However like Plutus I thought the 4.3 RAV always set off in 4WD before reverting to 2WD.All I can say is that in the real world I have found my 4.3 RAV's (T180 and XTR) to be very competent in snow and mud.

My understanding is that the 4.3 sets of in 4WD if the lock button on the dash is selected.. Other than that it remains front wheel drive unless a wheel starts to loose traction at which point the cars electronics take over and engage 4WD... Well thats what I thought..

Surely the biggest variable factor in a cars capability is the driver ??

When travelling from the midlands to Cambridge two winters ago I saw a Disco stuck in a ditch which if the driver had been just that bit more clued up would surely never have ended up in the ditch in the first place ?

The 4.3 always starts off in 4WD Charlie.

It then reverts to front wheel drive unless conditions merit continued 4WD. The system continuously monitors and adjusts according to conditions.

[Timelord]

Agreed Charlie neither AWD or 4WD override the laws of physics!

[Rollers 6]

Thanks for all the replies, I include Gust in this as well. I fogot to mention that there was an equally old Octavia there as well which coped with the rollers. It would appear that the RAV in question had a viscous coupling set up without the ability to to lock the centre diff as the first edition was able to do, and it would suggest that the system was not working as well as it should have been. I had no wish to denegrate any AWD system in any vehicle I was just pointing out that not all systems are as good as the literature sometime suggests. I am sure that the Freelander would also have coped with the rollers as it has a Haldex set up the same as the Skoda. This is a very interesting link, anything wrong with it, write to them not me. The spelling is so much better on this site than on some Land Rover forums

Landcruiser 80 series

http://www.awdwiki.com/en/home/

[DjRav]

I would expect the Subaru to do well in this test as it has a permanent AWD system.However like Plutus I thought the 4.3 RAV always set off in 4WD before reverting to 2WD.All I can say is that in the real world I have found my 4.3 RAV's (T180 and XTR) to be very competent in snow and mud.

My understanding is that the 4.3 sets of in 4WD if the lock button on the dash is selected.. Other than that it remains front wheel drive unless a wheel starts to loose traction at which point the cars electronics take over and engage 4WD... Well thats what I thought..

Surely the biggest variable factor in a cars capability is the driver ??

When travelling from the midlands to Cambridge two winters ago I saw a Disco stuck in a ditch which if the driver had been just that bit more clued up would surely never have ended up in the ditch in the first place ?

Re the Disco, you could well be right as in that was driver error, but talking from experience- the earlier Disco (D1, D2) has its plus points but there is very little stopping it from sliding sideways. The later ones (D3, D4) are more sophisticated (so I hear) but are even worse for reliability than the early version. And a lot less DIY mechanicable!

At least the Rav has the VSC.

Dave

[anchorman]

Rollers.

Don't worry we are not easily upset but the debates can get heated at times - we love a good chunner. We can spell reasonably well because we are all old farts who don't know how and have no wish to learn text speak!!!

Not wishing to be pedantic but the RAV doesn't have a viscous coupling it has an oil immersed multi plate clutch. The former works on viscous drag where the latter gets physically engaged (although never quite fully to prevent inter axle drag). I referred to the CRV in the first response as having a Haldex drive system. My point there was that the Skoda must have something different because if you put 2 axles on zero friction rollers then without dout both diffs will spin. If it doesn't on the Skoda then there is definitely something different like a limited slip diff'. Its why we have to be dead careful when making comparisons as you have to know just what these things are built with. Additionally, there is nothing wrong with the RAVs torque control. If it sits on zero friction rollers then it will back off the power all the way to idle rather than allow the power to pull the car out of alignment. Drivers of BMW and Merc saloons will tell you that on an icy surface you canot get the car to come off idle - it simply remains motionless.

Notice in this test, the blanked off rollers are at the back where it would be more expected to find a limited slip diff'. I would like to see those blanking plates swapped to the front and then see how well scooby doo fairs. And another thing! That gal who is driving the Ford with the torque steer wants an oscar for over acting.

Not wishing to be peda

[Rollers 6]

Anchorman

Thanks for that. The only reason I mentioned that the RAV might have had a viscous arragement is because that what the link suggested for vehicles built between 2001 - 2005. We only put the front axles on the rollers not both, which is why I was surprised that the RAV did not drive off. I do not have a RAV myself this was a customers vehicle as were the two others, they wanted see what would happen, I drive a Landcruiser 80 series and a Skoda Octavia with Haldex4. I do not do text speak either, lol, whatever that means. Off to-morrow to have an hour in the new Range Rover, Euro Millions will be required.

Rollers

[anchorman]

We must add those words to the swear filter - Land Rover and Range Rover........

Have a good day!

[Tech01]

A couple of winters ago I boobed seriously and took a wrong turning out of a local village, and ended heading up a riverbed - no problem usually out here, as many riverbeds are used as rural roads (in the dry months).

OK, but shallow mud turned to deeper mud, and, after 400m or so - and with no possibility of turning around - I found myself driving through 35cm deep thick mud! Amazingly, the RAV just kept on going - even on its H/T Bridgestone Dueler 687's.

So back through the half km of mud again, and eventually free of the riverbed, after a few km of tarmac road, I pulled on to a motorway. At just 50km/h the wheel shudder was unbelievable. A quick look underneath revealed that the inside rims of the alloys were cms thick in mud, putting everything out of balance.

A HP hose-off at a garage put everything right again, but it wasn't until a few weeks later that I discovered that the chassis members underneath had also scooped up shovelfuls of mud, which had now solidified. So out came the Karcher...

But, I just couldn't fault the 4WD, even with the underside working as a snowplough.

Chris

[mystic]

In real world situation i cant fault my little RAV, even with worn tyres i've yet to have any problems and i use it for a lot of muddy track, field and woodland driving. With a decent set of tyres i can imagine it being a good competitor. Maybe not a amazing offroader (i dont like the exhaust being under the rear axle, poor thing takes a beating) but its not out of it's depth either.

[CharlieFarlie]

Coming back to this thing about the car always setting off in 4WD mode...

Is this each and every time the car comes to a standstill IE will it do it just once as we pull away from the house in the morning or does it do it all the time like say in traffic or every time the vehicle comes to a stop ??

I really had no idea it did this !!

When on a wet slipway I used to push the button on the dash but it seems there was no need ??

Cheers !

[anchorman]

Each and every time even in traffic. As the car speed increases and the torque reduces on the transmission it starts to back off. If you take your foot off the accelerator it compltely disengages. If you squeeze it again it will bring in the rear axle proportionately. Think of it being connected to your accelerator. The harder you squeeze the more it will engage and if you floor it it will be fully engaged until at some point (might be 80 mph accelerating hard on the motorway) it backs off. It is stepllessly variable.

There are odd exceptions which I will explain but got to go out now.

[anchorman]

Where was I?

The main exception to it always setting off in 4WD is when the steering lock is turned. The tighter you turn the lock the more it backs off to a point where it is perhaps 10% engaged. The reason is to stop the front and rear axle diff's binding up on each other. So if you set off by doing a U turn on full lock it won't fully engage until you straighten the lock after completing the turn. By having a large amount of slip it frees the 2 axles.

On my old FWD company cars, I could easily get wheel spin when leaving a junction uphill in the wet. This never hapens on a RAV because it sets off in 4WD. It still has traction control because that would counter a single wheel slipping. It simply applies the brake on the spinning wheel and transfers the drive to the other wheel on the same axle.

Going back to the rear axle backing off, remember it does so according to throttle position and load. If you were to turn into a downhill street and just feather the throttle it may well revert to FWD by the time you are doing say 15-20mph. All the axle lock up button does is to hold the 4WD fully engaged up to 25mph where it drops out to protect the transmission.

On later models you can turn off the TRC and the VSC (the latter is done by pressing and holding the TRC OFF button).

The forthcoming 4.4 has taken this system one step further. When the "sport" button is pressed, it will also use the 4WD system to supplement cornering and braking which should radically improve the handling. At the moment it only intervenes if the VSC detects difficulties in maintaing control.

[Big Kev]

Good wan sir...blissfully unaware of a lot of this, and even more impressed.

Big Kev

[CharlieFarlie]

Good wan sir...blissfully unaware of a lot of this, and even more impressed.

Big Kev

Ditto...........