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I've read many horror stories about people "burning up" Dual Clutch Automatic Transmissions by sitting on a slight grade and holding the vehicle from rolling back with the throttle INSTEAD of the brakes or from "Creeping Along" at very slow speeds such as in Stop & Go rush hour traffic. Effectively, it's like doing the same thing with a manual transmission by sitting there slipping the clutch, thus overheating it and burning up the clutch face. This of course is not an issue with a traditional automatic transmission which uses a fluid torque converter and can sit there all day slipping with no degradation.

So my question is this. When the Gas Engine is NOT running and the Electric Motor is providing the energy required to just Creep Along or hold position on a hill, is that Clutch in use and slipping the same as it would be with an ICE vehicle with a DCT transmission, OR is the Electric Motor providing slight torque DIRECTLY to the transmission without using the clutch? Since an electric motor provides maximum torque from a dead stop it would appear to me that the clutch would be unnecessary in such instances.

My mind would rest easier IF the latter were true. I'm not concerned about myself because I understand that a DCT is in fact a manual transmission, which just happens to shift automatically, and I will use the brakes as intended. However, my wife is, shall we say, non technically inclined so I'm hoping she doesn't burn up the clutches in the DCT unexpectedly.

Thanks to anyone who KNOWS for CERTAIN how creeping/hill holding is accomplished in the Niro. Clutch in use or not?
 

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Creeping on flat, clutch is fully engaged and EV is motive force (even if engine is running). Creeping on a hill, depends. So far in 14,000 miles, creeping on a hill with more torque than motor can provide has not happened once. Non-problem. Less of a problem for sure than all the ICE cars with a DCT and no traction motor.
 

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I've read many horror stories about people "burning up" Dual Clutch Automatic Transmissions by sitting on a slight grade and holding the vehicle from rolling back with the throttle INSTEAD of the brakes or from "Creeping Along" at very slow speeds such as in Stop & Go rush hour traffic. Effectively, it's like doing the same thing with a manual transmission by sitting there slipping the clutch, thus overheating it and burning up the clutch face. This of course is not an issue with a traditional automatic transmission which uses a fluid torque converter and can sit there all day slipping with no degradation.

So my question is this. When the Gas Engine is NOT running and the Electric Motor is providing the energy required to just Creep Along or hold position on a hill, is that Clutch in use and slipping the same as it would be with an ICE vehicle with a DCT transmission, OR is the Electric Motor providing slight torque DIRECTLY to the transmission without using the clutch? Since an electric motor provides maximum torque from a dead stop it would appear to me that the clutch would be unnecessary in such instances.

My mind would rest easier IF the latter were true. I'm not concerned about myself because I understand that a DCT is in fact a manual transmission, which just happens to shift automatically, and I will use the brakes as intended. However, my wife is, shall we say, non technically inclined so I'm hoping she doesn't burn up the clutches in the DCT unexpectedly.

Thanks to anyone who KNOWS for CERTAIN how creeping/hill holding is accomplished in the Niro. Clutch in use or not?
DCT and motor is a match made in heaven.

Rated at 125 ft lb at 0-1800 rpm, a 14:1 final gear ratio and a wheel radius of ~1ft, the motor alone provides 125*14=1750 lb of motive force at the wheels. That's enough to pull a 3500 lb niro up a 30% grade.

Starting above a 30 % grade I presume the ICE is needed and a clutch is slipped.
 

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DCT and motor is a match made in heaven.

Rated at 125 ft lb at 0-1800 rpm, a 14:1 final gear ratio and a wheel radius of ~1ft, the motor alone provides 125*14=1750 lb of motive force at the wheels. That's enough to pull a 3500 lb niro up a 30% grade.

Starting above a 30 % grade I presume the ICE is needed and a clutch is slipped.
final gear ratio may be 17:1 thus 125x17=2125lb thus 35+% grade
 

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Yes, the traction motor does pull you ahead on an incline. If you don't accelerate for too long, it will roll backwards, depending on the grade. But by that time you would accelerate, or at least put your foot on the brake. One nice thing is the DCT is part of the drivetrain, so is warrantied for 10 yrs./100k miles. That should cover most driver abuse.
 

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Latter. If you think about the purpose of a transmission, it is gear reduction. A gasoline engine at idle is turning 800 RPM or so and at full throttle something like 6000-ish. The vehicle engine RPM has to somehow end up at the desired wheel RPM so it has to be reduced which typically happens in two stages. 1 the transmission gearing and 2. the differential. At 'creep' you are maybe wanting the wheels to turn 10 rpm (just made that up) and the combination of 1st gear and the differential simply does not step down the 800 rpm idle enough to get to that desired ratio so you end up with the in/out/riding of the clutch to engage/disengage.

So when the gas engine isn't running you are just using the electric motor this problem is completely eliminated. Pure BEVs have a single gear..period. That's because the electric motor has no 'idle' speed necessary to stay running. It turns at whatever RPM is needed. Thus it can adjust perfectly.

Short answer....no your clutch/transmission isn't burning out. The EV motor is actually reducing wear/tear by applying the necessary direct force. Yes the transmission is engaged but the clutch is not getting slipped like the situation of gas engine only.
 

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So when the gas engine isn't running you are just using the electric motor this problem is completely eliminated. Pure BEVs have a single gear..period. That's because the electric motor has no 'idle' speed necessary to stay running. It turns at whatever RPM is needed. Thus it can adjust perfectly.

This sadly is not true as the electric motor also has a minimum stall speed. It is far slower than a gas motor, but still there. We are lucky as the car has a DC motor and not an AC. I have multiple DC motors inside my shop and the lowest I have ever gotten a motor to turn without stalling under and load is about 100 rpm. So you will still need to have some form of clutch in a car that can slip to allow for a motor that can't drop below a certain speed.


Short answer....no your clutch/transmission isn't burning out. The EV motor is actually reducing wear/tear by applying the necessary direct force. Yes the transmission is engaged but the clutch is not getting slipped like the situation of gas engine only.

Actually the Niro has a dual clutch transmission. WHY? because you need to be able to slip the motor between if it's engaged with the gear box to drive the wheels, or the electric motor that is used to regenerate the battery. Sitting on an incline and just using the motor to hold you is simply just being lazy and heating up the oil in the clutch plates needlessly that causes wear depending on what state the motor is in.
 

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I can tool around parking lots at a couple mph just as easily as an ICE car and same method, light pressure on brake pedal. Stall speed? I don't see it.

The Niro has a dry clutch, no oil.
 

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This sadly is not true as the electric motor also has a minimum stall speed. It is far slower than a gas motor, but still there. We are lucky as the car has a DC motor and not an AC. I have multiple DC motors inside my shop and the lowest I have ever gotten a motor to turn without stalling under and load is about 100 rpm. So you will still need to have some form of clutch in a car that can slip to allow for a motor that can't drop below a certain speed.





Actually the Niro has a dual clutch transmission. WHY? because you need to be able to slip the motor between if it's engaged with the gear box to drive the wheels, or the electric motor that is used to regenerate the battery. Sitting on an incline and just using the motor to hold you is simply just being lazy and heating up the oil in the clutch plates needlessly that causes wear depending on what state the motor is in.

The motor is rated 125 ft lb 0-1800 or 2500 rpm. Full torque at 0 rpm. There is no (100rpm) stall speed.
 

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The motor is rated 125 ft lb 0-1800 or 2500 rpm. Full torque at 0 rpm. There is no (100rpm) stall speed.

And no doubt that a marketing company wrote that spec and not a PEng who knew that they were talking about
 

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And no doubt that a marketing company wrote that spec and not a PEng who knew that they were talking about
Are you an engineer?

Links to references?





The graph above shows a torque/speed curve of a typical D.C. motor. Note that torque is inversely proportioal to the speed of the output shaft. In other words, there is a tradeoff between how much torque a motor delivers, and how fast the output shaft spins. Motor characteristics are frequently given as two points on this graph:

The stall torque,[Ts], represents the point on the graph at which the torque is a maximum, but the shaft is not rotating.

The no load speed,[Wn], is the maximum output speed of the motor (when no torque is applied to the output shaft).

D.C. Motor Torque/Speed Curve Tutorial:::Understanding Motor Characteristics
 

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Are you an engineer?

Links to references?





The graph above shows a torque/speed curve of a typical D.C. motor. Note that torque is inversely proportioal to the speed of the output shaft. In other words, there is a tradeoff between how much torque a motor delivers, and how fast the output shaft spins. Motor characteristics are frequently given as two points on this graph:

The stall torque,[Ts], represents the point on the graph at which the torque is a maximum, but the shaft is not rotating.

The no load speed,[Wn], is the maximum output speed of the motor (when no torque is applied to the output shaft).

D.C. Motor Torque/Speed Curve Tutorial:::Understanding Motor Characteristics
Graph attatched
 

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I am definitely not an engineer and I don’t play one on tv. I see the term stall speed being used and, based on the chart shown, I am wondering if it is being misapplied here. My interpretation is that the stall speed of the electric motor used in the chart just means that the shaft is not turning. To get it turning, the motor is going to apply 100% torque to it and then the torque is reduced as the shaft spins up to max rpm. There is no “stall” in the ICE transmission sense since the electric motor will just stop applying torque if you let your foot totally off the pedal and will go again instantly if you press the pedal again.

I know this doesn’t help the original debate, but am I even close to understanding what is being discussed here?
 

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I am definitely not an engineer and I don’t play one on tv. I see the term stall speed being used and, based on the chart shown, I am wondering if it is being misapplied here. My interpretation is that the stall speed of the electric motor used in the chart just means that the shaft is not turning. To get it turning, the motor is going to apply 100% torque to it and then the torque is reduced as the shaft spins up to max rpm. There is no “stall” in the ICE transmission sense since the electric motor will just stop applying torque if you let your foot totally off the pedal and will go again instantly if you press the pedal again.

I know this doesn’t help the original debate, but am I even close to understanding what is being discussed here?
I think you got it about right. Despite the nerd competition, I think the general consensus is that the EV motor helps at very low speeds if the gas engine isn't on. I also used to have a DCT in a 2009 Audi A3 which by the way I keep pointing out the reason Kia is using a DCT is they hired the design dude away from Audi. But I digress. That engine/transmission was a masterpiece (unlike the shoddy electronics) but at slow creeping speeds it tended to remind you of all that fanciness under the hood. But that led to rather lively take offs if you punched it. Between the DCT (DSG in German) and the turbo you never quite knew if you were going to get thrown back in your seat or it was going to take it more leisurely. Way less boring than a regular car. Felt like you spurred a horse of something and its reaction might vary. With the Kia if the gas engine is off, the transmission is going to be in gear but not 'riding the clutch' at all...or perhaps only a tiny fraction of....and the electric motor will drive it forward until it decides the engine is called for....which depends on numerous things of course. Oh and there's a hill assist that if you take your foot off the brake to move to the gas it holds. I think that is actually using the mechanical brakes. It has a 2 second 'fuse'.
 

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I am definitely not an engineer and I don’t play one on tv. I see the term stall speed being used and, based on the chart shown, I am wondering if it is being misapplied here. My interpretation is that the stall speed of the electric motor used in the chart just means that the shaft is not turning. To get it turning, the motor is going to apply 100% torque to it and then the torque is reduced as the shaft spins up to max rpm. There is no “stall” in the ICE transmission sense since the electric motor will just stop applying torque if you let your foot totally off the pedal and will go again instantly if you press the pedal again.

I know this doesn’t help the original debate, but am I even close to understanding what is being discussed here?
Correct. Motor not turning, DCT clutches closed, car not moving, max torque available to get the car moving.
 

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Discussion Starter #17
Sorry for taking so long to get back to you all. Thank you for all the input on this subject. It's pretty much what I thought and I feel more at ease now.
 

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I didn’t read the article, but the electric motors used in cars, torque is essentially constant from 0-100% rpm whereas power is linear.
 
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