AWD intelligent diesel or non-intelligent petrol?

[DavidLew]

Hi All,
Newbie here
Read a thread here talking about intelligent AWD for LR diesels some time ago. Was wondering if someone could kindly explain what exactly intelligent iAWD means and how it differs from the petrol standard AWD system.

I am wanting to but a Defender for towing boat and/or caravan, mainly sealed surfaces, slippery boat ramps, and some off-road, so a D300MHEV seems like a no brainer. I would prefer a real full time AWD for this, even if intelligently variable, so long as it doesn't default to 2WD at say 30kph or something.

The other question is whether you can manually override or customize the "intelligent" system in settings or by choice of drive mode?

If P400MHEV is a genuine AWD (with at least some front wheel torque) then maybe its a better choice?

Cheers
David

[one_iota]

Hi All,
Newbie here
Read a thread here talking about intelligent AWD for LR diesels some time ago. Was wondering if someone could kindly explain what exactly intelligent iAWD means and how it differs from the petrol standard AWD system.

I am wanting to but a Defender for towing boat and/or caravan, mainly sealed surfaces, slippery boat ramps, and some off-road, so a D300MHEV seems like a no brainer. I would prefer a real full time AWD for this, even if intelligently variable, so long as it doesn't default to 2WD at say 30kph or something.

The other question is whether you can manually override or customize the "intelligent" system in settings or by choice of drive mode?

If P400MHEV is a genuine AWD (with at least some front wheel torque) then maybe its a better choice?

Cheers
David

Welcome to AULRO David.

To my knowledge both petrol and diesel engined Defenders now have the same driveline which Land Rover calls AWD (All Wheel Drive).

This system distributes torque in varying amounts to the front axles according to demand and the drive mode settings chosen by the driver.

In my experience observing the information screen showing the driveline operation even in "comfort mode", the centre differential (and the rear diff in my vehicle) operates occasionally on sealed roads.

Also being an owner of the traditional 4wd Defender I'm mightily impressed with the D300's performance on and off road.

[DavidLew]

Welcome to AULRO David.

To my knowledge both petrol and diesel engined Defenders now have the same driveline which Land Rover calls AWD (All Wheel Drive).

This system distributes torque in varying amounts to the front axles according to demand and the drive mode settings chosen by the driver.

In my experience observing the information screen showing the driveline operation even in "comfort mode", the centre differential (and the rear diff in my vehicle) operates occasionally on sealed roads.

Also being an owner of the traditional 4wd Defender I'm mightily impressed with the D300's performance on and off road.

Ah ok thanks for that. If both AWD systems are the same then it is no longer a criterion that differentiates the models.

I thought only the diesel got the 'special' (intelligent) treatment and my speculation was that it was a compromise to produce lower emissions. There was also mention of the diesel not having a true center dif.

Does your diesel have a display that shows the distribution of torque to front and back wheels and does it go into 2WD when driving?

Thanks again
David

[one_iota]

Ah ok thanks for that. If both AWD systems are the same then it is no longer a criterion that differentiates the models.

I thought only the diesel got the 'special' (intelligent) treatment and my speculation was that it was a compromise to produce lower emissions. There was also mention of the diesel not having a true center dif.

Does your diesel have a display that shows the distribution of torque to front and back wheels and does it go into 2WD when driving?

Thanks again
David

Apart from the engine mechanically there is little to differentiate the models. The engine choice is more important in the real world because it should suit your predominant driving requirements: city or country, off-road or towing. No longer does the sales documentation mention constant 4wd. AWD is what you get.

Once upon a time there was a difference between petrol and diesel versions. Diesel engines emit more pollutants so reducing those to meet European standards was and still is important in the market place. Having a vehicle that only drives all the axles when needed achieves these standards regardless of whether it is diesel or petrol.

There is no longer a geared centre differential. Differential action that happens in the transfer case between the front and rear axles is achieved through clutch plates that allow limited slip controlled by sensors. A maximum of 50% of torque can be sent to the front if it is required. Traction control takes care of the rest.

The display tells me whether the centre differential is partially or fully engaged. The sensitivity depends on the driving mode selected. If I don't need any drive to the front wheels then it isn't applied and the Defender is rear wheel drive. In an instant it can be 4wd.

We've moved on from the "good old days". The system that Land Rover has developed is IMHO remarkable. Let's not mourn the passing of the manual lockable 4wd centre differential.

[Eric SDV6SE]

In auto mode you can watch the centre and rear e diff lock and unlock at varying times depending on throttle, speed and road conditions. TR2 is thr best thing since, well, TR. Just love it. I opted for the P400 over the diesel due to ever increasing emission regs that will eventually strangle all diesel engines off the road. 550Nm and 400 bhp is enough to tow our single axle van, you have to pack smart and travel as light as possible.

[DavidLew]

There is no longer a geared centre differential. Differential action that happens in the transfer case between the front and rear axles is achieved through clutch plates that allow limited slip controlled by sensors. A maximum of 50% of torque can be sent to the front if it is required.

Thanks, it looks like the D300 is the one for me.....there still remains some academic curiosity...

IF I am correct, the centre limited slip control suggests to me that the centre 'mechanism' is a limited slip differential but not a locking (no slip) differential. "Fully engaged" may not be fully locked? Full locking diff (no slip) would allow for 0 to 100% torque split, not just up to 50%. 100% torque, and resultant power (torque x rpm), sent to rear or front wheels would be desirable in some circumstances.

I wonder if the rear "electronically active dif" fully locks (0 -100% torque/power split) and is otherwise supplemented by "torque vectoring by braking".

On a more practical note, I guess I would prefer some degree of full time 4wd when towing ie all four wheels engaged, Does this happen in any kind of "Towing mode" or setting?

Cheers

[one_iota]

..there still remains some academic curiosity...

Indeed! Having reached the limits of my understanding my brain hurts. Given that we are dealing with a system when factoring in the traction control system, it hurts even more

[DavidLew]

Indeed! Having reached the limits of my understanding my brain hurts. Given that we are dealing with a system when factoring in the traction control system, it hurts even more

haha yes I too feel your pain!

That said, the physics and engineering shouldn't be that difficult to explain if LR (and other manufacturers) were inclined to do so. I think they focus a lot on marketing hype a bit too much, "trust us this works great"

[one_iota]

haha yes I too feel your pain!

That said, the physics and engineering shouldn't be that difficult to explain if LR (and other manufacturers) were inclined to do so. I think they focus a lot on marketing hype a bit too much, "trust us this works great"

An animated diagram would suit me.....but that doesn't sell vehicles.

I even wonder whether anyone outside JLR's engineering department knows. JLR head office doesn't, dealers' sales don't and their service department seem not to.

Whatever is going on it seems to work very well!

[DavidLew]

An animated diagram would suit me.....but that doesn't sell vehicles.

Explaining how and why it works would help me make an informed choice.It's frustrating that we are left with deciding between my "special sauce" works better than their "special sauce"


I even wonder whether anyone outside JLR's engineering department knows. JLR head office doesn't, dealers' sales don't and their service department seem not to.

Oh, almost certainly not


Whatever is going on it seems to work very well!

There is that! Maybe

I once had a snow ski instructor who told me how to do parallel turns. When I asked "how does that work" , he replied "who gives a f*ck".
.......The problem is he was wrong.

That said, if it works for you, that's all that matters.The universe doesn't owe us answers but I expect a little more from car manufacturers (and ski instructors) lol

[DiscoDB]

This diagram below explains how there are now 2 clutch packs to control the split of torque from rear to front, and to also fully disconnect the front drive.

The transfer box clutch pack acts “like a differential” and can go from fully open with no drive to the front and 100% to the rear, to fully locked with 50/50 split front and rear.

The 2nd clutch pack on the front axle allows the front prop shaft and crown wheel to come to a full stop when in rear wheel drive mode to save fuel.

https://uploads.tapatalk-cdn.com/20230509/d157a7b16e1aae686c33eb2ccf88b842.jpg

This diagram was prior to both systems being fully adopted across all models.

The difference with the technology today is how quickly it can respond to open and close when needed, and how it works in conjunction with the individual wheel braking for traction control.

[one_iota]

The 2022 workshop manual describes its operation (as copied and pasted):


The twin speed transfer case is full time, permanent all wheel drive unit, with 50/50
torque distribution to the front and rear driveshafts. The transfer case is identical for all
engine derivatives and supports the following features:

Permanent all wheel drive with a bevel gear center differential, providing a 50:50
torque split

Selectable high and low range for optimum on-road and off-road performance

A pre-loading function, increasing locking torque with increased driving torque

A slip controller to increase locking torque under off-road conditions and decrease
locking torque for optimum comfort, for example during parking.

The twin speed transfer case is located under the vehicle and is mounted on the cross
member, behind the automatic transmission.

The input torque is equally distributed via a bevel gear center differential. In order to
provide an optimal torque distribution to each wheel in all driving conditions, the twin
speed transfer case is equipped with an electronically controlled locking and torque-
biasing device. This device detects wheel slip via various vehicle system inputs to the
Transfer Case Control Module (TCCM) and locks the differential accordingly. The locking
torque is applied through a multiplate clutch assembly.

A planetary gear set, located in the differential assembly, allows the driver to select
high or low range. In low range, the planetary gear set provides a ratio of 2.93:1,
which gives the vehicle an extremely low crawl speed for off-road driving and trailer
towing. High range is a direct drive from the transmission output shaft and provides a
1:1 ratio.

[DiscoDB]

The 2022 workshop manual describes its operation (as copied and pasted):

That description is just the same as what the D3/D4 has. In fact the wording is almost identical to the D3 workshop manual description for the transfer box.

Does not explain how iAWD is different.

When iAWD was first marketed they definitely described it as being different to the normal permanent all wheel drive - even pointing out that it was different between the petrol and diesel model Defenders.

This is how it is described for the new Range Rover:

https://uploads.tapatalk-cdn.com/20230510/de3e3a11a4a9e33969645011c28c274c.jpg

For the new RRS, similar description but they also note the use of a clutch pack to disconnect the front driveline.

My guess - the documentation for the Defender has not caught up but they are now fitting the same system used in the new Range Rover and RRS, which is a different set up to what the new Defender (and its predecessor the D3/D4) originally came with.

[one_iota]

That description is just the same as what the D3/D4 has. In fact the wording is almost identical to the D3 workshop manual description for the transfer box. ....



The documentation I copied is suspiciously out of date. Whilst it refers to the 22 Defenders most of the illustrations are those of the D3/D4.

So?

[DiscoDB]

The documentation I copied is suspiciously out of date. Whilst it refers to the 22 Defenders most of the illustrations are those of the D3/D4.

So?

I guess we always knew the new Defender was the replacement for the D3/D4 that we should have always had. [emoji41]

That manual sounds dodgy to me.

[one_iota]

I guess we always knew the new Defender was the replacement for the D3/D4 that we should have always had. [emoji41]

That manual sounds dodgy to me.

The classic Defender was an evolutionary dead end! As much as it is revered it is an anachronism.

We need to find someone with a my23.5 Defender workshop manual!

[Eric SDV6SE]

The classic Defender was an evolutionary dead end! As much as it is revered it is an anachronism.

We need to find someone with a my23.5 Defender workshop manual!

Will check mine when I have time...and post the extract here.

[DavidLew]

This diagram below explains how there are now 2 clutch packs to control the split of torque from rear to front, and to also fully disconnect the front drive.

The transfer box clutch pack acts “like a differential” and can go from fully open with no drive to the front and 100% to the rear, to fully locked with 50/50 split front and rear.

The 2nd clutch pack on the front axle allows the front prop shaft and crown wheel to come to a full stop when in rear wheel drive mode to save fuel.



This diagram was prior to both systems being fully adopted across all models.

The difference with the technology today is how quickly it can respond to open and close when needed, and how it works in conjunction with the individual wheel braking for traction control.


Hi Thanks for that.

I must say the diagrams and explanations are confusing to me.

"Acts like a differential....fully open clutch with no drive to the front wheels". However, In an open traditional differential there remains torque to the front and rear wheels and indeed split exactly 50:50. Power or "drive" goes to wheels of least resistance ie no traction

" A completely closed clutch with equal torque to the front and rear as with a locked differential" . However, you always get 50:50 torque with an open diff (torque not power/drive - you cannot interchange the terms Power = torque x rpm. No rpm= no power despite infinite torque).

With a locked diff with wheels locked to the same speed (rpm) there exists anywhere between 0 to 100% torque between front and rear. It will only be 50:50 when the the traction on all wheels are the same.

Locked Diff means axles (wheels) spin at same speed and allows for uneven torque split from 0% to 100% between axles and with both torque and power in the same percentage (eg 15% torque will yield 15% power for equal rpm) sent to wheel with most resistance, where it is most needed. Power and drive will result provided the surface allows adequate traction


This video explains open vs closed difs and torque and Power transfer How 4WD Works Part 2 - Open vs. Locked Differentials - Power and Torque Transfer - YouTube (https://www.youtube.com/watch?v=zrNYVp227Zk&ab_channel=NJSInstructional)
185314
(https://www.youtube.com/watch?v=UAGg_WsFB_o&ab_channel=NJSInstructional)So however the system works it is not "like a differential". It may work fantastically well by sending or "vectoring" (torque is a vector) torque to different wheels by whatever mechanism, cluthes.It is theoretically disappointing that only 50% can be maximally sent to the front wheels and if true, the front wheels automatically receive no torque as a priority especially if it cannot be overridden in drive mode selections

[RANDLOVER]

That description is just the same as what the D3/D4 has. In fact the wording is almost identical to the D3 workshop manual description for the transfer box.

Does not explain how iAWD is different.

When iAWD was first marketed they definitely described it as being different to the normal permanent all wheel drive - even pointing out that it was different between the petrol and diesel model Defenders.

This is how it is described for the new Range Rover:

https://uploads.tapatalk-cdn.com/20230510/de3e3a11a4a9e33969645011c28c274c.jpg
..................

The drag reduction part (3rd para.) doesn't make sense, unless they mean mechanical drag and not aerodynamic drag.

[one_iota]

I confess to being party to this shemozzle!

As nice intellectually as it would be to know what is going on in the real world does it matter?

I used to drive a Mini Moke. It had winter tread tyres and got me to places that on paper couldn't be gotten to.

[DiscoDB]

The drag reduction part (3rd para.) doesn't make sense, unless they mean mechanical drag and not aerodynamic drag.

Yes - they mean mechanical drag. The entire front drive shaft and front carrier in the diff stops spinning with the front axle free wheeling. They are chasing micro fuel efficiencies.

[DavidLew]

I confess to being party to this shemozzle!

As nice intellectually as it would be to know what is going on in the real world does it matter?

I used to drive a Mini Moke. It had winter tread tyres and got me to places that on paper couldn't be gotten to.

According to Kant Experience without theory is blind, but theory without experience is mere intellectual play. ideally, best to have both, experience backed by explanatory theory ( and vice versa).

We do not live in an ideal world so I guess you often have to make compromises. I don't see this as one of those situations ie the answers are knowable.

[DiscoDB]

Hi Thanks for that.

I must say the diagrams and explanations are confusing to me.

"Acts like a differential....fully open clutch with no drive to the front wheels". However, In an open traditional differential there remains torque to the front and rear wheels and indeed split exactly 50:50. Power or "drive" goes to wheels of least resistance ie no traction

" A completely closed clutch with equal torque to the front and rear as with a locked differential" . However, you always get 50:50 torque with an open diff (torque not power/drive - you cannot interchange the terms Power = torque x rpm. No rpm= no power despite infinite torque).

With a locked diff with wheels locked to the same speed (rpm) there exists anywhere between 0 to 100% torque between front and rear. It will only be 50:50 when the the traction on all wheels are the same.

Locked Diff means axles (wheels) spin at same speed and allows for uneven torque split from 0% to 100% between axles and with both torque and power in the same percentage (eg 15% torque will yield 15% power for equal rpm) sent to wheel with most resistance, where it is most needed. Power and drive will result provided the surface allows adequate traction


This video explains open vs closed difs and torque and Power transfer How 4WD Works Part 2 - Open vs. Locked Differentials - Power and Torque Transfer - YouTube (https://www.youtube.com/watch?v=zrNYVp227Zk&ab_channel=NJSInstructional)
185314
(https://www.youtube.com/watch?v=UAGg_WsFB_o&ab_channel=NJSInstructional)So however the system works it is not "like a differential". It may work fantastically well by sending or "vectoring" (torque is a vector) torque to different wheels by whatever mechanism, cluthes.It is theoretically disappointing that only 50% can be maximally sent to the front wheels and if true, the front wheels automatically receive no torque as a priority especially if it cannot be overridden in drive mode selections

I would suggest it is confusing because JLR are intentionally being vague about the technology.

But it sounds very much like the BorgWarner Torque on Demand system which eliminates the centre differential and replaces it with a clutch pack to drive the front axle.

BorgWarner TOD[emoji768] Transfer Case - YouTube (https://youtu.be/QWiFl9K3WqI)

It acts like a “differential” because it can vary the speeds between the front and rear, but it is not a traditional differential.

It is old technology that was fitted to the Ford Territory with a single speed transfer case, and then to the F-150 with a dual speed transfer case.

BorgWarner Electro-Mechanical On-Demand (EMOD) Transfer Case - YouTube (https://youtu.be/m1xtGKl41Pw)

BorgWarner also have a front axle mounted drive disconnect unit to completely disconnect the front axle.

[DiscoDB]

By the way- it is also possible that JLR are just using marketing BS here to put a new spin on what the Transfer Case Control Module does.

iAWD has a very specific explanation for what it is on the Range Rover and involves new hardware and software, but has no explanation on what it is on the Defender.

Maybe the Defender just gets the “enhanced” software to manage the clutch pack on the centre diff and there has been no change to the mechanical side.

Very strange marketing.

[DavidLew]

I would suggest it is confusing because JLR are intentionally being vague about the technology.

But it sounds very much like the BorgWarner Torque on Demand system which eliminates the centre differential and replaces it with a clutch pack to drive the front axle.

BorgWarner TOD[emoji768] Transfer Case - YouTube (https://youtu.be/QWiFl9K3WqI)

It acts like a “differential” because it can vary the speeds between the front and rear, but it is not a traditional differential.

It is old technology that was fitted to the Ford Territory with a single speed transfer case, and then to the F-150 with a dual speed transfer case.

BorgWarner Electro-Mechanical On-Demand (EMOD) Transfer Case - YouTube (https://youtu.be/m1xtGKl41Pw)

BorgWarner also have a front axle mounted drive disconnect unit to completely disconnect the front axle.


By the way- it is also possible that JLR are just using marketing BS here to put a new spin on what the Transfer Case Control Module does.

iAWD has a very specific explanation for what it is on the Range Rover and involves new hardware and software, but has no explanation on what it is on the Defender.

Maybe the Defender just gets the “enhanced” software to manage the clutch pack on the centre diff and there has been no change to the mechanical side.

Very strange marketing.

I would wager you are correct on the marketing spin aspect. A cloud of mystery works well if there has not been genuine innovation.

That Borg-Warner system, now around for many years, does indeed seem clever, "intelligent" even. One of the videos suggested the front wheel spilt is not typically below 20% torque and it senses turning wheels to apportion torque. I think my porsche Macan's "torque vectoring" does something similar and shows a graphical display of torque to front and rear

Anyways, I will try to explore a little further if there is still a difference in the AWD systems between diesel and petrol Defender as this may influence my purchase choice.I'm sure either works well but, a bit like colour, it may come down to little things.

Not sure what the Range rover AWD is or if it carries over to Defender

[DiscoDB]

So found this press release from 2017 which confirms the Range Rover does get the BorgWarner Torque on Demand system.

Enhanced Traction - BorgWarner Transfer Case for Range Rover Velar (https://www.prnewswire.com/news-releases/enhanced-traction---borgwarner-transfer-case-for-range-rover-velar-300531652.html)

The unknown is are they now fitting this to the Defender.

[DavidLew]

So found this press release from 2017 which confirms the Range Rover does get the BorgWarner Torque on Demand system.

Enhanced Traction - BorgWarner Transfer Case for Range Rover Velar (https://www.prnewswire.com/news-releases/enhanced-traction---borgwarner-transfer-case-for-range-rover-velar-300531652.html)

The unknown is are they now fitting this to the Defender.

Ah very interesting! Like the videos you linked this article also talks about the "pre-emptive" aspects as well as responding to wheel angles. Not sure if JLR uses this now or some further adaptation that frequently sees front wheel torque at 0% ie RWD.

I found online user and service manuals that refer to workshop manual and with the latter said to explain the AWD system. problem is unable to actually get the said workshop manual.