DCT Concern Regarding CREEPING in a Niro - Kia Niro Forum
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post #1 of 18 (permalink) Old 08-02-2018, 11:13 AM Thread Starter
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DCT Concern Regarding CREEPING in a Niro

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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post #2 of 18 (permalink) Old 10-07-2018, 05:14 PM
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post #3 of 18 (permalink) Old 10-07-2018, 06:57 PM
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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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post #4 of 18 (permalink) Old 10-07-2018, 09:31 PM
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Originally Posted by achr View Post
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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Last edited by charlesH; 10-07-2018 at 09:35 PM.
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post #5 of 18 (permalink) Old 10-08-2018, 12:32 AM
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Originally Posted by charlesH View Post
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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post #6 of 18 (permalink) Old 10-08-2018, 09:32 AM
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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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post #7 of 18 (permalink) Old 10-08-2018, 11:18 AM
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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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post #8 of 18 (permalink) Old 10-08-2018, 11:51 AM
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Originally Posted by brandent View Post
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.


Quote:
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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post #9 of 18 (permalink) Old 10-08-2018, 12:29 PM
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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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post #10 of 18 (permalink) Old 10-08-2018, 01:55 PM
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Originally Posted by Roadkill401 View Post
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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