Little all terrain trip

[pasquinade]

Had a little all terrain experience this weekend (with other vehicles), here are some conclusions.






In the rough terrain you see above the expected hindrances manifest themselves:

1) low clearance - need to be carefull not to hit the bottom or bumpers.

2) low suspension travel (allowing wheels off the ground) + open diffs. Although the electronics do something - in the second photo above I was able to run the car forward even though back wheel was in the air - I did find myself with wheel slippage in several situations. Probably the known cross axled situations.

But it went through, with more or less wheel supports...

My greatest amazement was in deep fine sand (beach like). It went perfectly with the "big boys" and it never got stuck going up and down the dunes (quite surprising to other onlookers). Here I need to say that other SUVs (e.g. Dacia Duster TT) also behaved great, so it might be just me that is easily impressed

 

[maby]

I'm not too surprised that it coped well with sand - the trick on surfaces like that is getting the power down very smoothly and the electric drive should be much better at that than any transmission including a clutch. The PHEV will give you plenty of torque onto the ground right from stationary.

 

[Sailordoc]

When you say wheel spin, was that transient wheel spin for a few seconds before traction control braked the spinning wheel and transferred the power to the wheel with traction, or did wheels continue spinning? On a previous excursion last year when I got into wet mud, traction control just braked each wheel to a standstill, and I had to turn ASC off to get going in an undignified manner with mud sprayed all over the car! What I'm not sure about is how the car handles when (for example) both left side wheels lose traction.

 

[jaapv]

That echoes its excellent performance in deep snow. Mitsubishi does indeed advise the switching off ASC in such conditions. (see the manual)

 

[Sailordoc]

That echoes its excellent performance in deep snow. Mitsubishi does indeed advise the switching off ASC in such conditions. (see the manual)

Yup, knew that, which is why I did it. What I remain unsure of (because I haven't been able to test yet) is how effective the PHEV all wheel drive system is when say front and rear left wheels lose traction. i.e. will it brake the left wheels and transfer the power to the right wheels or not? In most SUVs that lack locking diffs you would expect a few seconds of wheel spin, followed by the traction control and Haldex systems kicking in and power being directed to the wheels with grip. The PHEV cannot transfer power between axles, and cannot sort itself out with a cross axle situation, but will traction control and the electric motors behave appropriately in the situation I've described?

 

[pasquinade]

When you say wheel spin, was that transient wheel spin for a few seconds before traction control braked the spinning wheel and transferred the power to the wheel with traction, or did wheels continue spinning? On a previous excursion last year when I got into wet mud, traction control just braked each wheel to a standstill, and I had to turn ASC off to get going in an undignified manner with mud sprayed all over the car! What I'm not sure about is how the car handles when (for example) both left side wheels lose traction.

Hi Sailordoc,

First I need to say that it is difficult from inside the car to judge what's happening to the weels (with ASC turned on, see below).

I have tried with ASC and without ASC, here are the conclusions:

1) with ASC turned on it seems to "sometimes work". When watching the videos afterwards I saw some places with a rear wheel half a meter off the ground, wheel stopped, and the wheels on the ground were capable of providing forward motion. In these situations, from inside the car I would not even notice the wheel was up. But from inside the car I would sense that sometimes the wheels would just slip and no motion was achieved (sorry, I had to rely on other people for videos so I don't have these situations recorded). In these cases it would be enough for a bit of weight to be applied in particular spots to get the wheel on the floor (e.g. someone would just put his weight on the front) and it would start moving. This leads me to confirm that it is probably cross-axled situations that are troublesome, as seen in other videos online, although I cannot understand why this would be true on an electronically controlled brake system... Perhaps some flawed software design decisions as was mentioned before (related to rear torque being limited by front torque).

2) I sometimes have turned off ASC in these situations but results are not usually better. It usually leads to the wheel above ground to start spinning really fast, burning the tires when they lightly touch the ground (if the ground is hard usually accompanied by a lot of smoke). I have given up on this... perhaps it is useful for mud-like terrains where the wheel spinning faster will actually slightly increase forward force, but not in wheel up situations.

Will have more opportunities to conduct further tests

 

[pasquinade]

That echoes its excellent performance in deep snow. Mitsubishi does indeed advise the switching off ASC in such conditions. (see the manual)

Yup, knew that, which is why I did it. What I remain unsure of (because I haven't been able to test yet) is how effective the PHEV all wheel drive system is when say front and rear left wheels lose traction. i.e. will it brake the left wheels and transfer the power to the right wheels or not? In most SUVs that lack locking diffs you would expect a few seconds of wheel spin, followed by the traction control and Haldex systems kicking in and power being directed to the wheels with grip. The PHEV cannot transfer power between axles, and cannot sort itself out with a cross axle situation, but will traction control and the electric motors behave appropriately in the situation I've described?

I would expect to behave the same as the cross-axled situation, but it is usually not talked about since it does not usually happen. While it is easy to cross-axle a vehicle with wheels up, you cannot get both left wheels in the air and remain in some sort of (unstable) equilibrium. If considering a slippery surface on the left, it should be noted that most slippery surfaces still have some traction, so it would still allow the phev to go forward (with slippage).

Note that this is complete speculation on my part:

 

[pasquinade]

I'm not too surprised that it coped well with sand - the trick on surfaces like that is getting the power down very smoothly and the electric drive should be much better at that than any transmission including a clutch. The PHEV will give you plenty of torque onto the ground right from stationary.

Yes, and that shows very nicely in sand, but don't rely too much on it to get you out of a small hole

1) If both four wheels are capable of digging themselves 9cm down, you're basically stuck with the phev (see here: http://www.myoutlanderphev.com/forum/viewtopic.php?f=10&t=2998&p=34985&hilit=9cm#p34985 ). Note that on sand the wheel is always capable of reshaping the hole around it (make the front wall collapse under it).

2) if you get stuck in a not very large rain-digged ditch (again 9cm for both wheels), you'll need a jack to get it out of there...

With only one wheel you'll probably be a bit better than the theoretical "14cm deep hole-of-hell" due to the suspension.

I think a low gear clutch (lets say 1:5 - that would be able to haul around 3500kg) would be a very interesting all terrain addition

 

[Sailordoc]

I would expect to behave the same as the cross-axled situation, but it is usually not talked about since it does not usually happen. While it is easy to cross-axle a vehicle with wheels up, you cannot get both left wheels in the air and remain in some sort of (unstable) equilibrium. If considering a slippery surface on the left, it should be noted that most slippery surfaces still have some traction, so it would still allow the phev to go forward (with slippage).

Note that this is complete speculation on my part:

Thanks for your observations. Yes, it is the "left wheels in mud" rather than "left wheels up in the air" I am talking about. In such situations my old Freelander 2 would spin the wheels for a few seconds, then brake the spinnng wheel and send power to the wheel with traction without too much slippage. Was just curious as to what the PHEV would do in the same situation. It's all wheel drive system does not seem to be very sophisticated :lol:

 

[Sailordoc]

Hi Sailordoc,

<Snip>

2) I sometimes have turned off ASC in these situations but results are not usually better. It usually leads to the wheel above ground to start spinning really fast, burning the tires when they lightly touch the ground (if the ground is hard usually accompanied by a lot of smoke). I have given up on this... perhaps it is useful for mud-like terrains where the wheel spinning faster will actually slightly increase forward force, but not in wheel up situations.

Will have more opportunities to conduct further tests

Thanks. That is what I suspected would happen with ASC off in that situation. The inability to transfer power between axles may also mean that the car simply doesn't have enough grunt available when it does have a wheel with grip. I'm still confused regarding what the car does with ASC on and a slipping wheel with regards to torque distribution etc.