The GKN Multimode E-Transmission

[STS134]

I seriously can't decide if I like the thing or hate it. It's more a combination of the two, depending on what's happening. At low speeds, I like the thing. At high speeds when I'm trying to accelerate, and the clutch is transmitting mechanical power directly to the wheels, I'm indifferent to it. At lower speeds (45-60 mph) when going uphill and I call for more power to accelerate, I get annoyed with it. Typically, the fixed gear ratio means that the engine can't generate enough torque to accelerate the car up the hill. But instead of just downshifting like a traditional tranny would, to allow the ICE to power the car up the hill, it sometimes starts drawing power from the battery to supplement the ICE power, which is...well, really dumb, and just wears out my battery for no reason.

Heck, even Toyota's HSD system can do a partial mechanical power path between ICE and wheels at variable ratios. Of course, the problem with that system is apparently at higher power levels (above 100-150 HP output), it starts pushing 25% power losses in the gearbox. At medium speeds (30-50 mph), when the GTK transmission is operating in series mode, it seems wasteful to turn mechanical power into electrical power only to turn it back into mechanical power, just because there's no tranny to allow the ICE to turn at a reasonable speed and directly power the wheels. It seems to lose about 15% in the mechanical-electrical-mechanical conversion (70 kW in and 60 kW out). But then again, this is probably in line with the power losses in a traditional gearbox, so in that sense, maybe it's not so bad. Then there's the Porsche Cayenne e-Hybrid's solution of engine -> motor <--> transmission <--> wheels which allows both motor and ICE to operate in their ideal power bands at all times. I'd love that thing when climbing hills at varying speeds. But then again, there's a reason why the Cayenne only goes 14 miles on 10.8 kWh and the Outlander goes 22-28 miles on 12 kWh, and a lot of it probably has to do with pushing power through that transmission.

I did find one shift shock issue with the GKN transmission though. I merged onto the freeway with the accelerator floored, and kept it floored at the speed reached and exceeded 78 mph (125 km/h). The transmission actually stayed in series mode all the way until around 88 mph (141 km/h) at which point the clutch engaged suddenly. You could immediately feel the difference between losing around 10 kW in the mechanical-electrical-mechanical conversion and having a direct mechanical path to transmit all 70 kW from the ICE to the wheels as the car suddenly lurched forward.

But finally, there's the fact that any failures in the GKN transmission would probably consist of replacing a single motor or clutch. Sometimes, simplicity is good. So yeah, I really can't decide if I like this thing or hate it, and it's a combination of both.

 

[Woodman411]

At lower speeds (45-60 mph) when going uphill and I call for more power to accelerate, I get annoyed with it. Typically, the fixed gear ratio means that the engine can't generate enough torque to accelerate the car up the hill. But instead of just downshifting like a traditional tranny would, to allow the ICE to power the car up the hill, it sometimes starts drawing power from the battery to supplement the ICE power, which is...well, really dumb, and just wears out my battery for no reason.

FWIW, Wired UK also noticed eTransmission un-refinement when going uphill. An excerpt from their review:

It's only the engine/gearbox combo that spoils the peace and tranquillity from inside, with the “Multimode eTransmission” occasionally holding on to gears for far too long and allowing a jarring, monotonous engine note to leak into the cabin. We only experienced this when the engine was under particularly heavy loads, such as climbing steep hills or attempting to perform a quick overtraining manoeuvre, but it was unpleasant nonetheless.

https://www.wired.co.uk/article/mitsubishi-outlander-phev-2019-review

 

[anko]

... the “Multimode eTransmission” occasionally holding on to gears for far too long and allowing a jarring, monotonous engine note to leak into the cabin.

And with this they have totally disqualified themselves. Wouldn't you say?

 

[anko]

Typically, the fixed gear ratio means that the engine can't generate enough torque to accelerate the car up the hill. But instead of just downshifting like a traditional tranny would, to allow the ICE to power the car up the hill, it sometimes starts drawing power from the battery to supplement the ICE power, which is...well, really dumb, and just wears out my battery for no reason.

Make up your mind about what you want / don't want. The alternative would be switching serial mode, which again introduces losses you don't like either. You have three options:
- accept that the battery is drained
- accept the noise and losses associated with serial mode
- pay extra money for a gearbox with multiple gears

BTW: the engine is lacking power, not torque in these situations ;-)

 

[Trex]

I cannot believe someone is complaining about using the battery in a hybrid. :roll:

All the hybrids I have owned have used the drive battery for adding power for abnormal loads.

I thought it was the whole idea behind having a smallish petrol motor running efficiently for average loads being backed up with electric motors for those abnormal loads.

 

[ThudnBlundr]

^^ Couldn't agree more

 

[elm70]

...

But finally, there's the fact that any failures in the GKN transmission would probably consist of replacing a single motor or clutch. Sometimes, simplicity is good. So yeah, I really can't decide if I like this thing or hate it, and it's a combination of both.

Mitsubishi could have "copy" the Prius or Volt Hybrid approach, with an eCVT, and have somehow the ICE connected to the front wheels at any speed, and without the need to use any battery

Still I think the Mitsubishi opted for have a more simple and reliable design (or maybe was more easy for them to buy this ready made system from GKN)

From efficiency point of view, I guess Prius and Volt have better fuel efficiency compared to our Outlander
From reliability point of view ... I don't have data from Prius or Volt ... but I did not find anybody with an issue on the Outlander powertrain ... only weak area in our PHEV is the battery degradation , which appear to be relative bad compared to other EV batteries

PS: The fact that the battery is used sometime for support the ICE in parallel mode, I think this is a plus in the Outlander PHEV design. It is the serial mode which is bad from efficiency point of view, and it is not even a nice sound to hear too while driving.

PPS: I believe that 75% of battery degradation is due to the number of times that the car get fully charged, and the hours spent with the battery at 100% SOC .. the charge and discharge that happen in our PHEV in hybrid mode (at around 30% SOC), are not particularly damaging the life of the battery ... the second wearing issue for the battery is the high current charge in regen braking

 

[Woodman411]

... the “Multimode eTransmission” occasionally holding on to gears for far too long and allowing a jarring, monotonous engine note to leak into the cabin.

And with this they have totally disqualified themselves. Wouldn't you say?

Going past the seeming technical inaccuracy, there is the feeling here, the driving experience, of uphill unrefinement.

 

[mellobob]

... the “Multimode eTransmission” occasionally holding on to gears for far too long and allowing a jarring, monotonous engine note to leak into the cabin.

And with this they have totally disqualified themselves. Wouldn't you say?

Can't really hold on to things you don't have ... unless ... maybe our car is running on magic gears

 

[STS134]

FWIW, Wired UK also noticed eTransmission un-refinement when going uphill. An excerpt from their review:

It's only the engine/gearbox combo that spoils the peace and tranquillity from inside, with the “Multimode eTransmission” occasionally holding on to gears for far too long and allowing a jarring, monotonous engine note to leak into the cabin. We only experienced this when the engine was under particularly heavy loads, such as climbing steep hills or attempting to perform a quick overtraining manoeuvre, but it was unpleasant nonetheless.

https://www.wired.co.uk/article/mitsubishi-outlander-phev-2019-review

LOL, holds on to "gears" for too long? What gears? I think the author of that article doesn't know what in the heck he's talking about. I do notice that the engine revs up a bit when climbing hills in serial mode, but that doesn't bother me too much. I mean, that's what you expect to hear, isn't it?

Make up your mind about what you want / don't want. The alternative would be switching serial mode, which again introduces losses you don't like either. You have three options:
- accept that the battery is drained
- accept the noise and losses associated with serial mode
- pay extra money for a gearbox with multiple gears

BTW: the engine is lacking power, not torque in these situations ;-)

Battery drained? Hardly ever. If I'm climbing a hill, I'm in Save mode, because I don't want to discharge my battery at 3-5C, which is bad for it. What happens is that the clutch is engaged (parallel mode) and the engine, due to the low RPM (say I'm climbing a hill at around 50 mph) can't generate enough power/torque to climb and accelerate. So, it will kick in the motors to assist. On the dash display, if you have the power flow selected, it will show an orange arrow from engine to wheels, and a blue arrow from battery to wheels. And the entire time, I'm thinking "JUST DOWNSHIFT, THE ICE HAS PLENTY OF SPARE CAPACITY LEFT!!!". Except it can't downshift because it has no gears.

The other problem with this transmission is that it overrevs the engine, particularly at speeds of 80-105 mph, when not accelerating quickly. At a sustained speed of 90 mph/145 km/h, the engine RPMs are steady at around 3700. Which would be great if I were accelerating slowly, but when simply cruising along on a flat and level road without acceleration, this ICE could probably propel the car at around 2800-3400 RPM. All of those extra RPMs are also due to the fixed ratio, and are a huge drag on fuel economy at high speed. I get that they want to have the engine in the optimal power band, just in case you actually need the power, but doing it all the time is, well, not efficient at all. I'm just not sure how this compares to actually having to push power through a mechanical transmission, which also has its own losses (typically 10-20%). At least the GKN transmission doesn't do this.

I cannot believe someone is complaining about using the battery in a hybrid. :roll:

All the hybrids I have owned have used the drive battery for adding power for abnormal loads.

I thought it was the whole idea behind having a smallish petrol motor running efficiently for average loads being backed up with electric motors for those abnormal loads.

Well, the German PHEVs have plenty of ICE power and therefore have a full mechanical transmission between the engine/motor and the wheels. So they'll do a better job at keeping the ICE at its optimal RPM over the entire speed range, at the cost of power losses through the transmission itself. The Cayenne S E-Hybrid will do 90 mph up a 6% grade at 2000 RPM, and does not use the motors to assist. It will use motors to assist when it enters Boost mode, which it will only do if you completely mash the accelerator to the floor. But that's pretty rare because its 333 PS ICE is generally more than enough even for climbing the steepest hills at high speed. And it really makes sure that the ICE has nothing left to give before it resorts to using the battery.

...

But finally, there's the fact that any failures in the GKN transmission would probably consist of replacing a single motor or clutch. Sometimes, simplicity is good. So yeah, I really can't decide if I like this thing or hate it, and it's a combination of both.

Mitsubishi could have "copy" the Prius or Volt Hybrid approach, with an eCVT, and have somehow the ICE connected to the front wheels at any speed, and without the need to use any battery

Still I think the Mitsubishi opted for have a more simple and reliable design (or maybe was more easy for them to buy this ready made system from GKN)

From efficiency point of view, I guess Prius and Volt have better fuel efficiency compared to our Outlander
From reliability point of view ... I don't have data from Prius or Volt ... but I did not find anybody with an issue on the Outlander powertrain ... only weak area in our PHEV is the battery degradation , which appear to be relative bad compared to other EV batteries

PS: The fact that the battery is used sometime for support the ICE in parallel mode, I think this is a plus in the Outlander PHEV design. It is the serial mode which is bad from efficiency point of view, and it is not even a nice sound to hear too while driving.

Parallel mode is also bad for efficiency at high speed (see previous comment above). The engine seems WAY overreved. Serial mode seems like it loses around 15% in the mechanical-electrical-mechanical path, which I guess isn't that bad considering the losses in a traditional gearbox.

Toyota's HSD also actually only has ONE ratio at which it can transmit ICE power directly to the wheels without some electrical path being involved. It can make the engine spin faster than the wheels (for low speed driving) by drawing power from MG1 and shunting it to MG2, and it can also make the engine spin slower than the wheels (for high speed driving) by drawing power from MG2 and shunting it to MG1. Both of these processes obviously create losses in the whole mechanical-electrical-mechanical conversion process. The greater the difference in engine/wheel speeds required from the optimal "direct drive" (MG1 and MG2 both locked) ratio, the higher the power losses. The difference here of course is that if the ICE must turn at a SLIGHTLY different speed from the wheels, the power losses aren't too great, whereas in the GKN, it just goes into serial mode and incurs the full amount of losses at all times. But, the downside of the HSD system is that they push 25% gearbox losses at higher power levels (probably due to all of the gearing and motors involved), which I don't think the GKN ever does.

PPS: I believe that 75% of battery degradation is due to the number of times that the car get fully charged, and the hours spent with the battery at 100% SOC .. the charge and discharge that happen in our PHEV in hybrid mode (at around 30% SOC), are not particularly damaging the life of the battery ... the second wearing issue for the battery is the high current charge in regen braking

We'll see. I hardly ever fully charge, maybe 2 times per month, and when I do, it's 30-60 minutes before I drive it, so the dwell time at 100% SoC is extremely low.

By the way, does the GKN multimode transmission have something similar to "B" mode on a HSD car? If the battery's charge is already at the max, the HSD system will draw power from MG2, then use MG1 to spin the ICE with the throttle closed (basically using the power to push the engine, and using the engine as a sort of "resistor" into which power can be dumped, with the resulting heat going out through the cooling system). In the GKN, this would mean doing regenerative braking, but using the power to actually drive the motor/generator connected to the ICE, and keeping the ICE throttle closed. I've never hit max charge on a long enough downhill stretch to see what it does.

 

[anko]

LOL, holds on to "gears" for too long? What gears? I think the author of that article doesn't know what in the heck he's talking about. I do notice that the engine revs up a bit when climbing hills in serial mode, but that doesn't bother me too much. I mean, that's what you expect to hear, isn't it?

There is so much one would expect, but so little one seems to be willing to accept :lol:

Altogether, sometimes you want it to shift up, so the engine does not rev that much. At other times, you want it to shift down, so the battery does not have to jump in. What made you decide to buy a car without a gear box? Really, I think you should have bought a German Plugin Hybrid.

We'll see. I hardly ever fully charge, maybe 2 times per month

Or even better, a German Hybrid.

 

[STS134]

LOL, holds on to "gears" for too long? What gears? I think the author of that article doesn't know what in the heck he's talking about. I do notice that the engine revs up a bit when climbing hills in serial mode, but that doesn't bother me too much. I mean, that's what you expect to hear, isn't it?

There is so much one would expect, but so little one seems to be willing to accept :lol:

Altogether, sometimes you want it to shift up, so the engine does not rev that much. At other times, you want it to shift down, so the battery does not have to jump in. What made you decide to buy a car without a gear box? Really, I think you should have bought a German Plugin Hybrid.

We'll see. I hardly ever fully charge, maybe 2 times per month

Or even better, a German Hybrid.

Well...you don't see many German cars on this list that are SUV/Crossover types, do you? https://ww2.arb.ca.gov/eligible-carpool-sticker-list The Cayenne doesn't qualify because it pollutes too much. And the 14 miles of pure EV range is a real turn off, even if you use the ICE most of the time on the freeway. The Kia Niro is too small and doesn't even have AWD, the Tesla Model X has a decent range but isn't suitable for roadtrips, and the Volvo XC90 T8 is...well, almost the same cost as the Cayenne, but isn't a Porsche, and its pure EV range sucks too.

So why'd I buy it? Because some moron who wasn't paying attention hit my other car from behind and totaled it. Otherwise I'd still be driving that thing around. I had thought of replacing my previous car on and off again for over 10 years, but the entire market seemed like a bunch of bad tradeoffs one way or another that I didn't want to make, and so I had no intention of ever giving it up until something came out that didn't make a bad tradeoff. But I was eventually forced to pick a poison because I didn't have a car anymore.

 

[Trex]

I cannot believe someone is complaining about using the battery in a hybrid. :roll:

All the hybrids I have owned have used the drive battery for adding power for abnormal loads.

I thought it was the whole idea behind having a smallish petrol motor running efficiently for average loads being backed up with electric motors for those abnormal loads.

Well, the German PHEVs have plenty of ICE power and therefore have a full mechanical transmission between the engine/motor and the wheels. So they'll do a better job at keeping the ICE at its optimal RPM over the entire speed range, at the cost of power losses through the transmission itself. The Cayenne S E-Hybrid will do 90 mph up a 6% grade at 2000 RPM, and does not use the motors to assist. It will use motors to assist when it enters Boost mode, which it will only do if you completely mash the accelerator to the floor. But that's pretty rare because its 333 PS ICE is generally more than enough even for climbing the steepest hills at high speed. And it really makes sure that the ICE has nothing left to give before it resorts to using the battery.

Oh so now we are comparing a Porsche to the Mitsi PHEV. A car that is well over double the price over here and it still uses its battery to drive in EV mode and for performance (abnormal loads) so it will still degrade.

For that money that is a lot of drive batteries I can replace in my PHEV as they degrade.

Oh and its heavier and not as efficient as our PHEV. Bugger, I think I will stick with Mitsubishi. :lol:

 

[Trex]

By the way, does the GKN multimode transmission have something similar to "B" mode on a HSD car? If the battery's charge is already at the max, the HSD system will draw power from MG2, then use MG1 to spin the ICE with the throttle closed (basically using the power to push the engine, and using the engine as a sort of "resistor" into which power can be dumped, with the resulting heat going out through the cooling system). In the GKN, this would mean doing regenerative braking, but using the power to actually drive the motor/generator connected to the ICE, and keeping the ICE throttle closed. I've never hit max charge on a long enough downhill stretch to see what it does.

No "B" mode on the PHEV from what I have seen as it has a far bigger battery than the standard Prius or Camry Hybrid.

I remember coming down the Great Dividing Range in my Prius or Camry Hybrid and them screaming their heads off as it used B mode. :lol:

With the PHEV if it has a low SOC on top of the GDR it will add about 1/3 back into the battery after taking about 1/2 climbing it.

 

[STS134]

By the way, does the GKN multimode transmission have something similar to "B" mode on a HSD car? If the battery's charge is already at the max, the HSD system will draw power from MG2, then use MG1 to spin the ICE with the throttle closed (basically using the power to push the engine, and using the engine as a sort of "resistor" into which power can be dumped, with the resulting heat going out through the cooling system). In the GKN, this would mean doing regenerative braking, but using the power to actually drive the motor/generator connected to the ICE, and keeping the ICE throttle closed. I've never hit max charge on a long enough downhill stretch to see what it does.

No "B" mode on the PHEV from what I have seen as it has a far bigger battery than the standard Prius.

I remember coming down the Great Dividing Range in my Prius and it screaming its head off as it used B mode. :lol:

With the PHEV if it has a low SOC on top of the GDR it will add about 1/3 back into the battery after taking about 1/2 climbing it.

You're sure about this, or you haven't tried it? I'm just wondering what would happen if I charged to 100% at the top of Tioga Pass, then drove down to Mono Lake, for example. No, I have no idea why I would ever want to do this, just wondering what would happen. I guess one possible scenario is if I rent a house in the mountains (I'm not paying for electricity), and charge to full before leaving for home. So I wouldn't really care about leaving enough "headroom" in the battery because I already paid for electricity in the rental price.

 

[Trex]

You're sure about this, or you haven't tried it?

Yep pretty sure. No mention in the technical training manuals as far as I can see.

Why would I try it as I want some of my charge back that I lost climbing the bloody big "hills". :lol:

 

[STS134]

You're sure about this, or you haven't tried it?

Yep pretty sure. No mention in the technical training manuals as far as I can see.

Why would I try it as I want some of my charge back that I lost climbing the bloody big "hills". :lol:

Yeah...I guess a real world scenario where this could happen is if you live in the mountains, and you are planning on starting your trip by going uphill over the summit. You charged to 100%. Then some emergency comes up and you have to go down the mountain instead. Mitsubishi better have designed this thing so that it doesn't destroy the brakes on the way down. The simplest way to do this is to make the regenerative braking settings (B1-B5) first charge the battery, and then dump power into the ICE if the battery can't take any more charge.

 

[greendwarf]

Surely no need to go mountaineering - we know already that if the battery is full, regen has no effect and you have to use the mechanical brakes to slow down. Happens to me every morning in the Sarf Lundun Alps. :roll:

 

[STS134]

Surely no need to go mountaineering - we know already that if the battery is full, regen has no effect and you have to use the mechanical brakes to slow down. Happens to me every morning in the Sarf Lundun Alps. :roll:

What is the temperature of your brake rotors after doing that? You can determine this if you have an infrared thermometer. This isn't necessarily unsafe, but it can be if the rotors are undersized for the weight of the vehicle. From an engineering perspective, you EITHER have enough heat dissipation capacity in the rotors to be able to use them continuously on a downhill slope OR you give the car the ability to dissipate kinetic energy using the ICE, OR you do both. What you do not EVER want to do is neither.

 

[Woodman411]

Surely no need to go mountaineering - we know already that if the battery is full, regen has no effect and you have to use the mechanical brakes to slow down. Happens to me every morning in the Sarf Lundun Alps. :roll:

What is the temperature of your brake rotors after doing that? You can determine this if you have an infrared thermometer. This isn't necessarily unsafe, but it can be if the rotors are undersized for the weight of the vehicle. From an engineering perspective, you EITHER have enough heat dissipation capacity in the rotors to be able to use them continuously on a downhill slope OR you give the car the ability to dissipate kinetic energy using the ICE, OR you do both. What you do not EVER want to do is neither.

Not sure if it's undersized, but Mitsubishi did enlarge the front rotors by a noticeable 1 inch/25mm for MY2019: from 11.6 inches/295mm to 12.6 inches/320mm (also the rear increased too, though strangely the press release did not mention this. Rear rotor goes from 11.9 inches/302mm to 12.6 inches/295mm). For comparison, a 2019 Toyota Highlander with almost identical weight has 12.9 inches/328mm front and 12.2 inches/310mm rear.