CVT does it stop the car from rolling back?

[guest4291]

Hi there,

I have notice the car do roll back when i am in "D" gear in the automatic?

Is this normal?

Thanks
Ming

[Pine]

Yes it is normal. If you drive the car with the lever in position D and come to a halt and keep the foot brake applied the gearbox puts itself into neutral, when you release the brake it takes about 1 second to re-engage the drive. If you are stopped on a hill it can roll in this short interval, I usually use the handbrake if I am stopped on a hill . If you drive in the sport mode it does not go into neutral so the drive is continually engaged for a quicker get away, it does not roll in sport mode.

[Ozzie]

If you squeeze the footbrake a bit more before moving off on a hill, it will hold you a bit longer and there will be no rollback.

[Pine]

Ozzie,

Thanks for the tip but I thought that hybrids did not rollback because they had Hill Assist and petrol models don't have it.

[Ozzie]

I didn't think it would roll back either, I am assuming that the car sits in a form of "neutral", as giving it a bit of gas when using the handbrake also stops the car from rolling, but I prefer the use of firm pressure on the footbrake when teaching pupils.

[culzean]

http://www.honda.co.nz/technology/driving/cvt/#How

from what i can see of earlier Honda CVT it used a hydraulic torque converter in conjunction with CVT to act as a clutch and allow the gearbox to creep - don't know what they use nowadays.  My wifes old Punto Selecta used a magnetic powder clutch,  where an increasing current was applied to a magnetic powder to cause it to 'stick together' in a controlled way,  moving it from a viscous 'fluid' to a solid mass,  this worked well (in hindsight it was probably the best part of the car ).

all automatic transmissions still need a clutch or torque converter of some sort to disconnect engine drive from the wheels and then take up the drive in a controlled manner.  Fully electric car motor drive is different, as you can just remove power from an electric motor and it stops rotating, and can ramp up the power to the motor in an easily controlled manner to take up the drive from standstill and accelerate the car, electric motors also have a huge speed range,  so a gearbox may be dispensed with.  Also electric motors have maximum torque when they are not rotating (which is why electric power is a good idea for trains, and even diesel trains were actually diesel-electric,  where a diesel engine did not drive wheels directly, but drove a generator which supplied electric power to electric motors to drive the wheels)

[Jazzmeister]

Yes it is normal. If you drive the car with the lever in position D and come to a halt and keep the foot brake applied the gearbox puts itself into neutral, when you release the brake it takes about 1 second to re-engage the drive. If you are stopped on a hill it can roll in this short interval, I usually use the handbrake if I am stopped on a hill . If you drive in the sport mode it does not go into neutral so the drive is continually engaged for a quicker get away, it does not roll in sport mode.

Interesting, I got a GD Cvt recently, coming from a GE Cvt(hydraulic torque converter) which never displayed this behaviour and I have noticed this 1sec delay sometimes before drive is engaged after being stopped at a traffic light.

It got me a bit worried because it doesn't happen all the time and I couldn't find a way to replicate it but it's supposed to be normal for these GD Cvt's?

How long do you need to have the foot on the brake for neutral to be engaged and I'm assuming it does this to save wear on the clutchpack's friction discs?

[UKjim]

Does it really go into neutral when holding the brake pedal at rest, where is this documented?

[Jazzmeister]

Does it really go into neutral when holding the brake pedal at rest, where is this documented?

I was also wondering that, I haven't seen it mentioned in the owners manual because if I would have assumed if it was going into neutral with extended braking there would be a warning about the potential to roll back before drive was re-engaged.

[Jazzmeister]

I just found this link on the AA website:
https://www.theaa.com/cars/news/ask-edmund/automatic-roll-back-on-incline

"Should my automatic Honda Jazz roll back when in drive on a slight incline? Is there any adjustment that can be made to the carburettor to stop this?"

    Asked by Mary Hyland

Answered by Edmund King AA President

This is normal operation with CVT transmission and no adjustment is possible.

Unlike traditional torque converter automatics a CVT transmission will go into neutral if held on the foot brake and there will be a short delay between lifting your foot off the brake and drive being selected again.

Using the parking brake will overcome the problem.

[UKjim]

.........

Unlike traditional torque converter automatics a CVT transmission will go into neutral if held on the foot brake and there will be a short delay between lifting your foot off the brake and drive being selected again.

Using the parking brake will overcome the problem.

Thanks for the information.

As the car is already in drive I assume they mean when you take your foot off the brake and depress the accelerator.

[Jazzmeister]

Thanks for the information.

As the car is already in drive I assume they mean when you take your foot off the brake and depress the accelerator.

No just after you take your foot off the brake.
It appears the gearbox puts itself into neutral after you hold the brake for a certain amount of time and then once you release the brake it needs to switch back into drive and re-engage the clutch, both of which causes the delay you experience, then the car will creep forward as it would normally do when in Drive with the brake off and not facing up an incline.

[Jocko]

I assume this is why they replaced the earlier CVT (with a start clutch) with the later model with a Torque Converter.

[Jazzmeister]

I assume this is why they replaced the earlier CVT (with a start clutch) with the later model with a Torque Converter.

The delay and also the fact that a friction clutchpack can wear out but a hydraulic torque converter can't.
It seems the cluthpacks are designed to last for the life of the gearbox, it'd not a service item but if you don't replace the oil regularly the build-up of contamination can prematurely wear the clutch.