Press 4WD under HEAVY load, or not needed?

[MartinH]

I use my car as a Ardenner(Google and you understand), working in the forrest with sometime Heavy load on the trailer + soft ground=need alot of torque.
Therefore i use to press "charge", the ICE starts and charges the battery + press 4WD, My impression is that the torque is then devided between the both electrical Engines, but my question is if the both Engines is used without the 4WD pressed, and without the Wheels spinning when the torque is needed?
Or does someone has beter ideas how to pull very Heavy load?

 

[anko]

In both EV mode and serial hybrid mode, the car is always 4WD. No need to press a button. Whether having pressed or not having pressed the button makes a difference once you loose traction on a wheel or axle, I don't know for sure. But I do know what the effect is of pressing 4WD Lock in parallel hybrid mode.

As long as you haven't pressed 4WD Lock, just enough electric power is fed into the front E-motor to eliminate electromagnetic draft and make it spin truly 'idle'. A little bit more electric power is fed into the rear motor, causing it to actually produce a little torque (like 15 Nm or so). Because of this, the rear wheels are pushing the car, rather than being pulled by the car. According to Mitsubishi this is done to maintain the 4WD characteristics of the car.

Once you have pushed the 4WD Lock button, half of the driving force is delivered by the engine and the other half is delivered by the rear E-motor. Just what you would want. But ....

Imagine that at the chosen speed (and associated RPMs) a maximum of 40 kW of engine power is available. Also imagine that the full 40 kW of power is needed to maintain speed. Then the engine load will be 100%. When you hit 4WD Lock, only 20 kW will be delivered from the engine to the front wheels and the other 20 kW will be delivered by the rear E-motor to the rear wheels. In theory, in addition to driving the front wheels, the engine should have enough power reserves to produce the 20 kW of electrical power consumed by the rear E-motor (ignoring losses). In practice, the engine will settle at a load of 75% (or 30 kW). Next to delivering 20 kW directly to the front wheels, it will produce only 10 kW of electrical power, meaning the other 10 kW needed by the rear E-motor will be drawn from the battery. As a result, you will deplete your battery within the hour, even though you are driving in parallel hybrid mode.

The graphics on the dashboard will show an orange arrow from engine to wheels, a blue arrow from engine to battery and a blue arrow battery to wheels. So, no clear indication something is 'wrong'.

 

[gwatpe]

This is a valid reason for having the 4WD lock function NOT sticky.

 

[Neverfuel]

I use my car as a Ardenner(Google and you understand), working in the forrest with sometime Heavy load on the trailer + soft ground=need alot of torque.
Therefore i use to press "charge", the ICE starts and charges the battery + press 4WD, My impression is that the torque is then devided between the both electrical Engines, but my question is if the both Engines is used without the 4WD pressed, and without the Wheels spinning when the torque is needed?
Or does someone has beter ideas how to pull very Heavy load?

And I guess it can get really slippery in the mud - I don't know what the acronym is in Sweden, so in plain language - also turn off anti skid, stability control, yaw control (in the UK they are all controlled from one button), as anything that detects a single wheel spinning will enforce the safety systems to take action. By turning off the systems that prevent you from crashing your car at high speed, when you are in low speed 4wd conditions, the car will distribute power to the appropriate wheel to get you out of most sticky situations - including wheel off ground etc.

 

[jaapv]

This is a valid reason for having the 4WD lock function NOT sticky.

It does not matter because 4WD Lock only functions at low speed.

 

[anko]

This is a valid reason for having the 4WD lock function NOT sticky.

Totally agree

 

[anko]

This is a valid reason for having the 4WD lock function NOT sticky.

It does not matter because 4WD Lock only functions at low speed.

Have you perhaps skipped my post on the effect of 4WD Lock on parallel mode speeds?

 

[Fragge]

A Swedish car magazine tested the MY16 PHEV (along with other SUV:s). They placed the cars on a slight incline with rollers under the left set of wheels to test the diff locking capabilities. The PHEV failed the test and only spun the left wheels getting nowhere. The "4WD Lock" function made no difference. All the other SUV:s passed the test.
That makes me doubt that the the 4WD Lock button actually does anything at all.

 

[Yorks2000]

We recently had a couple of inches of snow - I tried a test whilst travelling up a steep hill.

First, normal settings with no adjustment - got about 20% up the hill

2nd - applied 4WD lock only - got 50% up the hill

Finally - 4WD+turn off ASC - got all the way up without problem

Not scientific but it certainly made a difference for me

 

[Ballycfc]

We recently had a couple of inches of snow - I tried a test whilst travelling up a steep hill.

First, normal settings with no adjustment - got about 20% up the hill

2nd - applied 4WD lock only - got 50% up the hill

Finally - 4WD+turn off ASC - got all the way up without problem

Not scientific but it certainly made a difference for me

That seems really strange (and to prove I know nothing about cars) I would always have thought the ASC would help, but obviously not.

 

[maby]

A Swedish car magazine tested the MY16 PHEV (along with other SUV:s). They placed the cars on a slight incline with rollers under the left set of wheels to test the diff locking capabilities. The PHEV failed the test and only spun the left wheels getting nowhere. The "4WD Lock" function made no difference. All the other SUV:s passed the test.
That makes me doubt that the the 4WD Lock button actually does anything at all.

There is no diff lock in the axles. The 4WD lock simulates the centre diff lock that you get on a conventional 4WD. Cars like Landrover Defenders and Toyota Landcruisers have three differentials - one in each axle and one in the centre of the car to split the drive between the front and rear axles. Our Landcruiser and the Defenders that preceded it have locks on all three diffs and would have passed the test you describe above. The PHEV only has a lock on the (virtual) centre diff - if at least one wheel on each axle loses grip, the 4WD lock will have no effect.

 

[anko]

That makes me doubt that the the 4WD Lock button actually does anything at all.

Have you perhaps skipped my post on the effect of 4WD Lock on parallel mode speeds? :lol:

 

[jaapv]

A Swedish car magazine tested the MY16 PHEV (along with other SUV:s). They placed the cars on a slight incline with rollers under the left set of wheels to test the diff locking capabilities. The PHEV failed the test and only spun the left wheels getting nowhere. The "4WD Lock" function made no difference. All the other SUV:s passed the test.
That makes me doubt that the the 4WD Lock button actually does anything at all.

There is no diff lock in the axles. The 4WD lock simulates the centre diff lock that you get on a conventional 4WD. Cars like Landrover Defenders and Toyota Landcruisers have three differentials - one in each axle and one in the centre of the car to split the drive between the front and rear axles. Our Landcruiser and the Defenders that preceded it have locks on all three diffs and would have passed the test you describe above. The PHEV only has a lock on the (virtual) centre diff - if at least one wheel on each axle loses grip, the 4WD lock will have no effect.

Just driving back from very slippery and mountainous conditions. I can testify that this does not describe the real life use. In reality the car outperforms " real" off-roaders in these conditions. It will only lose out in serous off-roading which is which thisSwedish test simulates.

 

[maby]

A Swedish car magazine tested the MY16 PHEV (along with other SUV:s). They placed the cars on a slight incline with rollers under the left set of wheels to test the diff locking capabilities. The PHEV failed the test and only spun the left wheels getting nowhere. The "4WD Lock" function made no difference. All the other SUV:s passed the test.
That makes me doubt that the the 4WD Lock button actually does anything at all.

There is no diff lock in the axles. The 4WD lock simulates the centre diff lock that you get on a conventional 4WD. Cars like Landrover Defenders and Toyota Landcruisers have three differentials - one in each axle and one in the centre of the car to split the drive between the front and rear axles. Our Landcruiser and the Defenders that preceded it have locks on all three diffs and would have passed the test you describe above. The PHEV only has a lock on the (virtual) centre diff - if at least one wheel on each axle loses grip, the 4WD lock will have no effect.

Just driving back from very slippery and mountainous conditions. I can testify that this does not describe the real life use. In reality the car outperforms " real" off-roaders in these conditions. It will only lose out in serous off-roading which is which thisSwedish test simulates.

Quite true - Mitsubishi do not claim that it is a serious off-roader...

 

[Claymore]

...Just driving back from very slippery and mountainous conditions. I can testify that this does not describe the real life use. In reality the car outperforms " real" off-roaders in these conditions. It will only lose out in serous off-roading which is which thisSwedish test simulates.

Do you disable ASC in those conditions?

JimB

 

[Kristian]

Here in snowy Norway I think the PHEV does quite well as 4WD. But since it has an open differential, how does it distribute energy/torque between the left and right side of each axel?

 

[jaapv]

...Just driving back from very slippery and mountainous conditions. I can testify that this does not describe the real life use. In reality the car outperforms " real" off-roaders in these conditions. It will only lose out in serous off-roading which is which thisSwedish test simulates.

Do you disable ASC in those conditions?

JimB

Of course.

 

[jaapv]

Here in snowy Norway I think the PHEV does quite well as 4WD. But since it has an open differential, how does it distribute energy/torque between the left and right side of each axel?

Well, you must take car not to cross-axle the vehicle. That will get you stuck.

 

[anko]

Here in snowy Norway I think the PHEV does quite well as 4WD. But since it has an open differential, how does it distribute energy/torque between the left and right side of each axel?

Well, you must take car not to cross-axle the vehicle. That will get you stuck.

I must say, I have no personal experience with such situations. But how hard would it be for the car to lock the free spinning wheels using the friction brakes, making sure all power is directed to the wheels that do have grip?

I do realise that the amount of torque available at the wheels would be reduced by 50%, but there might still be enough left.

- edit

In another thread you wrote:

Well, next time switch 4WD lock on and Traction Control off, the car will be transformed into a very good performer.
The point about traction control is that it will slow a spinning wheel down by applying the brake. If it does that on several wheels in succession when on a slippery uphill slope, you'll find that the car will brake itself to a standstill in the end.

If the car is capable of slowing down wheels one by one, would Traction Control be able to get you out of a cross-axle (is that an official term?) situation?

 

[maby]

Here in snowy Norway I think the PHEV does quite well as 4WD. But since it has an open differential, how does it distribute energy/torque between the left and right side of each axel?

Well, you must take car not to cross-axle the vehicle. That will get you stuck.

I must say, I have no personal experience with such situations. But how hard would it be for the car to lock the free spinning wheels using the friction brakes, making sure all power is directed to the wheels that do have grip?

I do realise that the amount of torque available at the wheels would be reduced by 50%, but there might still be enough left.

- edit

In another thread you wrote:

Well, next time switch 4WD lock on and Traction Control off, the car will be transformed into a very good performer.
The point about traction control is that it will slow a spinning wheel down by applying the brake. If it does that on several wheels in succession when on a slippery uphill slope, you'll find that the car will brake itself to a standstill in the end.

If the car is capable of slowing down wheels one by one, would Traction Control be able to get you out of a cross-axle (is that an official term?) situation?

The problem with this approach is that the cross-axle loss of traction in serious off-road conditions is a rather transient thing. You lose traction on one wheel, the electronics recognises it and locks the brakes on it - the car moves forwards and both wheels gain traction, but the previously spinning wheel now has the brakes engaged - how does the car recognise that it has gained traction again? The locked wheel is now in contact with the ground and not turning - it's fighting the wheel that is driving the car (which probably does not have very good traction itself) - and there is no easy way to detect that it is now time to release the brake...

There is no good alternative to a limited slip diff in the middle. I do seem to remember that the Lexus 4WD hybrid actually has two electric motors on the rear - one for each wheel - that can simulate a limited slip diff perfectly well, but presumably adds quite a lot to the build cost.