PHEV propulsion tech vs. Twin motor 4WD lock ==> Peak power?

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maby said:
anko said:
maby said:
At last!!! :D
At last what?

Acceptance that it is a CVT - there was blood on the walls the last time this topic was discussed!
Tried to stay away from that, because I was afraid this would happen. But you had to, didn't you :lol:
You did notice the word "effectively"? Not saying it is or it is not. Just saying it has the effect of a CVT. To my recollection, nobody ever said it did not have the effect of a CVT.
 
Thanks Anko for the above post, fantastically clear explanation of how the power levels and modes work I learnt a lot and I have had my PHEV for 2 years.

The forum should file that post for reference.

One other thing related to 4WD is I can feel a slight difference in vehicle handling enough to be able to tell if its on or off, especially on a country road at some speed. Perhaps some effect of split torque winding up the suspension or some affect on weight transfer but the car just feels a bit tighter handling, of course its a bad idea because SOC seems to disappear at a terrible speed.
 
BobEngineer said:
One other thing related to 4WD is I can feel a slight difference in vehicle handling enough to be able to tell if its on or off, especially on a country road at some speed. Perhaps some effect of split torque winding up the suspension or some affect on weight transfer but the car just feels a bit tighter handling, of course its a bad idea because SOC seems to disappear at a terrible speed.

This keeps to be very interesting here. We've confirmed that rear motor delivers power irrespectively of 4WD activated or not. However I too feel it when 4wd is on on low speeds. If reversing on a bump and 4WD lock is on, i can truly feel the difference of the rear wheels pulling the car up on the bump while moving backwards.

I can only but put it down to this functioning (a probable scenario): if 4WD lock is ON, the rear motor operates on higher power, whereas in 2WD mode, it only gets limited voltage from the controller system - only this to get increased when there's a higher power need (throttle position..). So, if there's no need for power (acceleration or uphill), the rear motor doesn't work as much, but if you switch to 4WD lock, the rear motor's output is increased - even on steady speed. Hence you get to feel all 4 wheels being driven. Please accept this as a theory only though, until confirmed/disapproved by others.
 
mrqz said:
So, if there's no need for power (acceleration or uphill), the rear motor doesn't work as much, but if you switch to 4WD lock, the rear motor's output is increased - even on steady speed. Hence you get to feel all 4 wheels being driven. Please accept this as a theory only though, until confirmed/disapproved by others.
Some of us have tools to monitor Torque Requested and Torque Delivered by each of the E-motors. As long as you are in serial mode and driving on a flat road at a steady pace (demand not to high), selecting or deselecting 4WD appears to have no effect.
 
Tipper said:
I think ECVT is a better terminology...

I think describing the Outlander system as a CVT is somewhat confusing. It is true that the engine/generator/motor combination is fulfilling an analogous role to a CVT, but the term CVT is well understood in engineering to mean a variable ratio mechanical (occasionally hydraulic) linkage.

Calling it an ECVT doesn't help much, because that term already has at least two meanings. Various car makers have used it to mean a conventional belt or chain type CVT with electronic control. And Toyota call the the Prius transmission an eCVT. And while the Prius doesn't contain a conventional belt/chain type CVT, it does contain parts that are doing something close to the same job.

-- Steve
 
Daff said:
Tipper said:
I think ECVT is a better terminology...

I think describing the Outlander system as a CVT is somewhat confusing. It is true that the engine/generator/motor combination is fulfilling an analogous role to a CVT, but the term CVT is well understood in engineering to mean a variable ratio mechanical (occasionally hydraulic) linkage.

Calling it an ECVT doesn't help much, because that term already has at least two meanings. Various car makers have used it to mean a conventional belt or chain type CVT with electronic control. And Toyota call the the Prius transmission an eCVT. And while the Prius doesn't contain a conventional belt/chain type CVT, it does contain parts that are doing something close to the same job.

-- Steve

Agreed :geek:

Our PHEV has no Variable Transmission ... it has just a clutch and a fix gear ratio ...

So, calling this CVT or eCVT is both wrong.

The PHEV is just an EV car, with a clutch for the ICE and a single gear (both for EV motors and ICE when connected to the front wheels)
 
elm70 said:
...
Agreed :geek:

Our PHEV has no Variable Transmission ... it has just a clutch and a fix gear ratio ...

So, calling this CVT or eCVT is both wrong.

The PHEV is just an EV car, with a clutch for the ICE and a single gear (both for EV motors and ICE when connected to the front wheels)
In the interests of avoiding further bloodshed, we'll agree to disagree! :D
 
anko said:
A few observations that may help us understand what / how / why:

I must congratulate Anko on the clearest technical explanation of the transmission of energy around the PHEV in different drive modes and at different speeds. I have taken a copy of it because I know I won’t be able to find my way back to it on the forum.

The previous best explanation for me was a series of diagrams sent to me (and many others) by Mitsubishi in their series of emails titled “A to Z Guide to your Outlander PHEV”. These would be an excellent complement to Anko’s written explanation. Unfortunately I deleted the email. If any member retained a copy or knows where they can be found on the internet I would be pleased to hear.
 
Thanks for the kind words, left and right. I feel encouraged (sorry for that) to try to explain why the car will eat away SOC when using 4WD mode while towing. Although not many will tow or use 4WD or do both at the same time, it might still provide people with some insights that could be helpful elsewhere.

The ICE has, when engaged, a strong preference for working at a relative load of 75% load (so 75% of available torque at given RPMs). I think it is safe to assume this is the sweetspot: the load at which it works most efficiently. Why would a higher load be more efficient? For one thing: higher load at same RPMs => more kW at same RPMs => more kWh per unit of time at same RPMS => more kWh per number of revolutions of the engine => less internal resistance to overcome per kWh => …. In parallel mode, under most circumstances, you will need far less than 75% of the power available with the RPMs associated with your speed. Normal cars deal with this by shifting into a higher gear: same speed, less RPMs, higher relative load.

We cannot shift into a higher gear was we have only one if them. So, instead we artificially increase power demand by bringing into play the generator. Surplus ICE torque (or power, if you like) is fed into the generator which transforms this into electrical energy which is used to recharge the battery. Of course, instantaneous fuel consumption goes up, but the extra ICE output is not wasted. It flows into the battery, to be used later. Of course, some conversion losses are involved, but I am convinced that these losses are outweighed by the increased efficiency of the ICE at higher load. Otherwise, why would they bother? Tada, IMHO this is the advantage of a hybrid car in a nutshell.

Small side step: The amount of power the battery is willing to accept depends on actual SOC: the higher the SOC, the less power the battery will accept. At some point it means we cannot reach the optimal 75% load because at 75% load the generator would be producing more power than the battery is willing to accept. Opinions differ on whether or not driving around with high SOC results in a measurable reduction of overall fuel economy. But that is a different story ;-)

So, the ICE has a preference for 75% load. It will take the load associated with driving and add a load associated to charging to reach this 75% load. When load associated with driving goes down (driving on a down ramp, tail wind, etc), charging load is increased. When load associated with driving goes up (driving on an up ramp, head wind, …) charging load is decreased. We can see this result in a very, very constant instantaneous fuel consumption. Also, our Cruise Control does not play with the throttle to maintain constant speed, it plays with the charge current to achieve this. IMHO, this explains why CC is so very effective, when it comes to maintaining a constant speed.

When the load associated with driving reaches 75% of the power, available at the current RPMs, charging simply stops. Only when the load associated with driving exceeds 75% of available power, the ICE will work harder, still at the same RPMs associated with your speed.

Another small side step: When the load associated with driving exceeds 100% of available power, the battery will send power to the E-motors, so they can support the ICE. When the load associated with driving exceeds 100% of available ICE power + 60 kW from the battery, the car will switch to serial mode, allowing the ICE to produce even more power.

Now, imagine load associated with driving is 50% of available power at current RPMs. In non 4WD mode, the ICE will produce 75% of available power, 50% out of 75% used for driving the front wheels, 25% out of 75% used for recharging. Now you engage 4WD mode. The ICE wil still produce 75% of available power. 25% out of 75% will be sent to the from wheels. Another 25% out of 75% will be sent (via the generator) to the rear E-motor and the last 25% will be sent to the battery. Nothing really changes, apart for some additional conversion losses that have been introduced.

Now, imagine load associated with driving is 75% of available power at current RPMs. In non 4WD mode, the ICE will produce 75% of available power, 75% out of 75% used for driving the front wheels, nothing left for recharging. Now you engage 4WD mode. The ICE wil still produce 75% of available power. 37.5% out of 75% will be sent to the from wheels. Another 37.5% out of 75% will be sent (via the generator) to the rear E-motor and nothing is left for recharging. Again, nothing really changes, apart for some additional conversion losses that have been introduced.

Now, imagine load associated with driving is 90% of available power at current RPMs. In non 4WD mode, the ICE will produce 90% of available power (it will step up), 90% out of 90% used for driving the front wheels, nothing left for recharging. Now you engage 4WD mode. 45% of available power will be sent directly to the front wheels. As, from a pure ICE perspective, the load associated with driving is less than 75%, the ICE will work at 75% relative load, the sweetspot. Now only 30% remain. These 30% are sent to the rear motor, but the rear motor needs 45%. The missing 15% are taken from the battery. The draining has started.

Now, imagine load associated with driving is 100% of available power at current RPMs. In non 4WD mode, the ICE will produce 100% of available power (it will step up), 100% out of 100% used for driving the front wheels, nothing left for recharging. Now you engage 4WD mode. 50% of available power will be sent directly to the front wheels. As, from a pure ICE perspective, the load associated with driving is less than 75%, the ICE will work at 75% relative load, the sweetspot. Now only 25% remain. These 25% are sent to the rear motor, but the rear motor needs 50%. The missing 25% are taken from the battery. The draining goes even faster.
 
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