Possible 4WD fault?

[jaapv]

To a car pumping out 332 Nm, pulling 1500 kg up a short incline should be child's play. As a comparison, the Diesel only brings 190 Nm to the party. That clonk is strange and suggests something is wrong with the car. ""In fact, it should be better than an ICE car as you don't have to rev to get maximum torque and there is no clutch to burn out.

 

[anko]

Jaapv,

You are comparing torque at the engine 'cranckshaft', not force at the wheels (which is what is important). For this, you have to take into account gear reductions and tire sizes. Compared to the higher gears of a diesel car, our car has the advantage, as our motors spin faster than the diesel engine would. But whether this is still the case when the diesel is in first gear? I wonder. Plus, imho the 190 Nm applies to the petrol version. The diesel should be at least 350 or so.

Yet, I agree that it should be well capable...

 

[jaapv]

Yes, you are right, that is the petrol one. Blame Mitsubishi's inept website . And yes, gears do matter, but so does my argument that you need to have the engine at the optimum revolutions to get the torque, which will strain the clutch.

 

[anko]

When it comes to not breaking stuff, yes. But when it comes to being able to tow a boat up a ramp, having to rev is not a disadvantage perse. Especially when the diesel is equipped with a conventional automatic with torque converter. Such a combination will most likely outperform the PHEV. Until the transmission oil starts boiling, that is :mrgreen: .

 

[Steepndeep]

I am quite interested myself as I would like to tow a boat which is fairly heavy. I just compared gear ratios on the Mitsu and regardless of Diesel or Petrol version the difference between 1st and 5th gear is about 5 times. Assuming that 5th gear is roughly the same as the single gear in the PHEV for the ICE. I also assume that this is roughly equivalent to the gear for the electrical engines. I know it is a big assumption and anyone having the correct gear ratio please comment. Now the diesel has maximum torgue at app 2500 rpm which I guess is around 20 km/h in first gear. Then comparing the Diesel in first gear with the PHEV at slow speed the diesel would be 5 times more "powerful". The PHEV having max torque even from 0 rpm. So I am really suspicious over the Mitsu claim on PHEV being able to pull roughly the same weight up a steep hill at slow speed as the Diesel.

Second question is then how you actually even get to start the towing from standing still on say a boat ramp. The PHEV would in theory have an advantage as the max torque is from RPM zero, but here is when the clutch or torque converter comes in. Also bear in mind that the stand still friction is higher than rolling friction so you really need to "jerk" the boat to start. Revving the Diesel to max torque and then realease the clutch and applying full throttle simultaneously would give you an instant "jerk" and then you are off. Doing it wrong burns the clutch but why would you do it wrong This I have tested several times on other cars.

With the PHEV there is no clutch and hence no jerk. The only way I would think this would work is as follows, note I have not tested this!!

1 Put a log or rock under the trailer wheels to stop it from rolling backwards. Do this whilst the trailer is hooked to the PHEV
2 Put PHEV in reverse and back into the trailer the few centimeters that are possible to take ANY pulling force out of the hitch-trailer connection and maybe role the trailer wheels into the logs a little bit.
3 Apply charge so the ICE is running
4 Traction control OFF
5 S-AWC ON
6 Floor it and hope for the best. The idea is to get the PHEV to build momentum in the, say 5 centimeters, it can before the trailer connection kicks in. Or maybe even apply full brake, floor it, wait a short time (maybe less than a second but long enough so you start building power but less than damage or shutdown will happen, have not tried this either) and remove foot from brake.
7 If it moves, do NOT stop until you are on level ground.

 

[anko]

Quick answer:

You cannot compare diesel / petrol 5th gear with the PHEV single gear as the max rpm for the e-motors is much higher than it is for the ICEs. At 20 km/h, the front motor will spin at roughly 1450 RPM (9.663 : 1 total ratio), the rear motor at roughly 1060 RPM (7.065 : 1 total ratio). So, it is not nearly 1:5.

And even then: how useful is 'max torque at 2500 rpm' when towing away? Other than when you want to burn clutches or rubber?

IMHO, the 'jerk' in conventional cars is not so much needed for overcoming stand-still friction. Instead, it is needed for bridging the RPM gap between wheels and engine, a gap that does not exist with the PHEV. So, there is no need for a jerk. Think diesel-electric locomotives. They use a generator and e-motor to provide the optimal torque converter and have no problem starting up very heavy trains.

 

[Steepndeep]

Thank's Anko. I just took a wild guess on the electric gear ratio. In that case the torque at the wheels would be very similar between a diesel and the PHEV at 20 km/h. At lower speed the PHEV would have an advantage. So we are good with the PHEV to able to match or even surpass the Diesel when towing heavy loads. But you will obviously have the ICE at high revs on the incline but as you point out, that's how the PHEV works

On the "jerk" issue I partly agree. There will be a jerk when you try to match the speed between engine and wheels with the clutch. All I am saying is that if there is any high starting friction (like the trailer being on the bottom of the ramp where there may be mud or other debris) then the jerk will actually help you. Or you burn the clutch

Train comparison is not really useful. The biggest problem with starting a train is that the friction between steel wheels and steel tracks is comparatively much lower than for a car with rubber wheels on tarmac. So gear ratio is really low to be able to pull away without spinning. A little bit as starting a car on snow.

Anyhow, looking at the gear ratios for the PHEV it should be possible to start quite heavy trailers so it clearly looks like a fault in the thread starters car.

A question is then if you do have a PHEV without fault what happens if the trailer really is stuck. On an ICE with manual gear you either stall the engine or burns the clutch. On an automatic you will cook the transmission oil (and then the transmission). So supposing excellent traction on the car and stuck trailer. What happens? Burnt electrical engines or are there safety controls switching of the power?

 

[jaapv]

Anyway, doing the calculations - Anko can start his holiday combination - 1950 kg of car , 4 persons 300 kg, assumed luggage 150 kg and 1500 kg of caravan - making 3900 kg total- up a 17% incline.

It certainly suggests something is wrong with the poster's car.

BTW, 3800 kg is more than the basic Dutch driving license B - the limit is 3500 kg, (the license B+ is 4250 and the old B-E unlimited.)

 

[anko]

But you will obviously have the ICE at high revs on the incline but as you point out, that's how the PHEV works

Not that obvious. Below 28 km/h, the total output of the e-motors is limited to approx. 60 kW. So, in theory there would hardly be a need to start the engine just to master the ramp (setting aside losses).

Train comparison is not really useful. The biggest problem with starting a train is that the friction between steel wheels and steel tracks is comparatively much lower than for a car with rubber wheels on tarmac. So gear ratio is really low to be able to pull away without spinning. A little bit as starting a car on snow.

So, there is no way to use a 'jerk' to get going, as it would only cause the traction wheels to spin .... Apparently, it can get going without a 'jerk'. Exactly my point

 

[Steepndeep]

Hi Anko

I was not aware of the e-motor power limitation at low speeds. Are you sure? Because then you actually may hamper the e-motor advantage of max torque at 0 RPM. Or maybe not if it really as a power limitation, what you want is max torque and at "0" RPM there is not much power

But having the ICE running or not still puzzles me. Maybe you can help explaining the following situation? My driveway to my house is very steep, maybe 15-20 % incline and I always back the car up. This after driving up and opening the trunk from within the cabin and almost everything fell out. Including some wine bottles. Now the street where I live is very narrow (single lane) and you have to turn very sharp in reverse and then into the incline. When the car is empty to half loaded you can do this without the ICE starting but at fully loaded car the ICE ALWAYS STARTS. Extremely annoying. And I am VERY delicate with the accelerator and the Power meter on the dashboard never goes beyond 1/3 into the green area. Sometimes the ICE starts even when the powermeter hardly moves at all. The way to not get the ICE to start seems to be to never let the car come to a halt at all during the crawl up the incline. But again with a fully loaded car the ICE always starts. An I am talking crawling speeds between 1-5 kph.

Driving in the alps this summer the car behaved as expected and even in steep inclines the ICE came on when the powermeter came into white, as expected. But not so at crawl speed. Why?? Anyone having a good explanation?

 

[anko]

I did really mean a power limitation . Power is torque * RPM * some factor. Without exceeding max torque on the E-motors, you need at least 28 km/h to reach 60 kW.

I am familiar with the effect you describe, although I have experienced it only once: I had to pull my caravan out of a little ditch and the engine fired up, even before the car started rolling. Didn't make sense to me at that time, because of the above. And still doesn't make much sense to me now. This is why I wrote 'in theory' .....

My guess now is this:

My statement applies when the E-motors are 100% efficient. Although not 100%, E-motors are very efficient, so maybe it would be 25 km/h instead of 28 km/h. But they are only very efficient once they are spinning. As long as they are not spinning they are extremely inefficient (RPM is 0 => power output is 0 kW => loss is 100%). In order to 'brake loose' they need a lot of electrical power. In some cases more than the battery can provide.

Come to think of it, could this explain the issue with the boat trailer?

 

[Steepndeep]

Yes it could possibly explain the boat on trailer issue.

What you need when you start is massive Force in order to get moving with the boat trailer, not power. Torque at 0 RPM is Force. And force from an e-motor not spinning equals massive current. Now going back to my illustrious train example, if you need massive force to get going you need massive cables and a big engine which will not overheat. Not a problem with an engine (locomotive) as you want a very heavy engine to have enough friction through the wheel/rail interface. Not so on a car.


So speculating here, with smaller but highly efficient e-motors you have two problems starting with heavy load uphill.
1 Make sure you have enough current rapidly at hand to get moving
2 Limit current so as not to fry cables and engine if you do not move

I do not know which safety functions Mitsu have deployed but it may look like this
1 If you really crawl slowly with the car under heavy load let's start the ICE so we can get enough current. That would also suggest that the cables from the battery to the e-motors are not heavy enough IMHO.
2 If you do not get moving after a short time, limit current so as not to fry the e-motor

So if these speculations are correct we should go back to my suggestion of starting up the ramp with a jerk :lol:

And it would also mean that driving slowly (crawl) in steep hills offroad would most likely not work. Now the car is not rally meant to go offroad (the marketing says otherwise though) but having to drive at 25 kph or above to have maximum power is not really doing the electrical cars justice. I wonder how Tesla Model X does this. If you have ludicrous power mode at least it suggests that their cabling is sufficient to handle enormous current.

 

[anko]

Don't worry about the cables. Max current is not dictated by demand (the e-motors) but by supply (60 kW from battery + 60 kW from generator). 120 kW at 320 volt is 375 amps. That should not be a problem, should it? As it occurs every time you max out the power meter during a fast acceleration.

 

[Steepndeep]

You are probably right on the cable gauges. They should be well sized. But why on earth does the ICE start at crawl speed and low power output?? In wintertime this will be extremely annoying. I am reversing the car up the driveway 8 meters. Outside temp. -20 C, ICE starts and runs for 2 seconds, then I am up and switches the car off. This is the worst polluting and mechnical wear sceanrio for any ICE. Clearly this must be a huge misengineering from Mitsu.

On the boatramp issue again. On a diesel car when you want to pull a heavy load there are 2 "safety mechanisms" if you are really stuck and the wheels do not spin. You either cook the clutch or the engine stalls. What happens on the e-motor? If you run 300+ Amps through the engines at 300+ Volts there will be heat build-up quickly. So are there safety mechanisms built in to prohibit overload? And if so, can those safety mechanisms malfunction and lower power to engine prematurely?

 

[anko]

You are probably right on the cable gauges. They should be well sized. But why on earth does the ICE start at crawl speed and low power output?? In wintertime this will be extremely annoying. I am reversing the car up the driveway 8 meters. Outside temp. -20 C, ICE starts and runs for 2 seconds, then I am up and switches the car off. This is the worst polluting and mechnical wear sceanrio for any ICE. Clearly this must be a huge misengineering from Mitsu.

Sure, it is very polluting and annoying. But what if 190 amps (60 kW from battery / voltage) is simply not enough to transition the E-motors from a stopped state into a spinning state under high load (backing up your driveway loaded, or pulling a caravan out of a ditch)? Than it is either that or walk.

 

[Steepndeep]

Yes, if it is not enough with battery power then I need the ICE obviously. Problem is that I do not floor the pedal at all, rather gently presses it to 25% level. And the powermeter on the dashboard hardly moves at all. Still the ICE starts.

 

[sas1]

You are correct that the battery and ICE generator cannot provide enough power to pull a heavy load over a slope of 12 degrees. The ICE will only engage round 80 kmh or above as it is a direct drive. This means that the ICE is useless for motive power from zero to about 80 kmh.

I have had the same problem pulling a 1400Kg camper trailer up a steep slope. The PHEV goes into turtle mode about as fast as one foot in front of the other walking very slowly. Frustrating but I get through. There is also the problem of how the internal computer works out the power output at any given stage. If the battery is low the car will not move as the computer calculates that there is not a sustainable charge to keep the vehicle moving. A full battery possibly, the quick charge to 80% might give enough for the computer to give power to the wheels.

The other problem is that awd setup in the outlander is not up to the pajero standards and cannot brake slipping wheels. Open diffs and no locking do not make an off road or boat ramp capable car.

 

[jaapv]

For full power the ICE goes into series mode at any speed under 120 kph, doubling the power supplied to the motors. With a full battery you will not go into turtle mode. And no, you are right. An SUV is not a full-blown off-road vehicle like a Landrover or Pajero.

 

[jaapv]

Yes, if it is not enough with battery power then I need the ICE obviously. Problem is that I do not floor the pedal at all, rather gently presses it to 25% level. And the powermeter on the dashboard hardly moves at all. Still the ICE starts.

You say -20. Aren't you confusing the power demand with the ICE starting up for heating purposes?

 

[anko]

You are correct that the battery and ICE generator cannot provide enough power to pull a heavy load over a slope of 12 degrees.

This is not true for my PHEV. My caravan is 1500 kg and with 4 adults in the car, the car has proven well capable of pulling away on 16 and even 17% slopes. And it managed to do so several times in just a few minutes.

The ICE will only engage round 80 kmh or above as it is a direct drive. This means that the ICE is useless for motive power from zero to about 80 kmh

It seems to me as if you are not to familiar with the architecture of the car. The ICE propels the generator, so how is the ICE useless at speeds below 80 km/h? Which should be more like 65 km/h anyway ....

I have had the same problem pulling a 1400Kg camper trailer up a steep slope. The PHEV goes into turtle mode about as fast as one foot in front of the other walking very slowly. Frustrating but I get through. There is also the problem of how the internal computer works out the power output at any given stage. If the battery is low the car will not move as the computer calculates that there is not a sustainable charge to keep the vehicle moving. A full battery possibly, the quick charge to 80% might give enough for the computer to give power to the wheels.

Why would you try to attack a steep slope with a car that is already in Turtle mode? And how do you manage to do so? Anyway, I've see a handful of Turtle warnings and even experienced a few Turtle modes, while driving north on the A75 in the South of France, this summer. Battery has been as low as 18%, very close to a full stop (which should happen at 13%). But I have never experienced power dropping to less than 60 kW. This 60 kW should be sufficient to produce max Torque up to a speed of approx. 28 km/h. I don't understand ...