Thread: AWD intelligent diesel or non-intelligent petrol?

Originally Posted by 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

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.

Originally Posted by one_iota

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

Originally Posted by DavidLew

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.

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.

Originally Posted by one_iota

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

Originally Posted by DavidLew

..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

Originally Posted by one_iota

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"

Originally Posted by DavidLew

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!