Continuously Variable Transmission

[Talus1]

Originally Posted by jsimon7777

The bad part of CVT is the delay. You floor it from idle, wait, and then accelerate. It's like having a car that's always in the wrong gear. The throttle delay on our Forester is maddening.

That true of ANY transmission! If I'm cruising along 6th at 1600 rpm saving gas, it takes a couple of seconds for me to downshift to 3rd to accelerate in my manual. It just isn't as frustrating because I'm in control. I'd be interested in trying a cvt that had a mode that let me control the ratio or at least the target engine rpm. That would be like being able to make a preemptive downshift in a manual, like I would do while waiting for an opportunity to pass someone on a 2 lane road.

[EAGLE5]

I can downshift in the manual or a manumatic, as you said. Can't do that in a CVT. I've tired shifting to L, but it doesn't accelerate any faster, and it doesn't raise the revs much.

[KoolBRZ]

How about dual CVT's beside each other with a clutch between them. When accelerating the other CVT is set to a taller ratio you could shift to just like a next gear. When decelerating the other CVT could be set to a lower ratio, just like shifting to a lower gear. There would only be a slight delay when switching from acceleration to deceleration. Because each CVT only needs to handle torque for the length of a gear change, they wouldn't have to be built as strong. The key would be that the CVT's wouldn't change ratios while they are being powered, but instead changing only when their clutch is disengaged between shifts. If only CVT's could be created which could lock into a particular ratio under power, but unlock as soon as it was unpowered. Control it all with a Android-based controller and voila! The perfect transmission.

[serialk11r]

Originally Posted by KoolBRZ

How about dual CVT's beside each other with a clutch between them.

That's not necessary, all you need is a button that tells it to rev higher.

Normally the CVT responds to your foot, giving you the rpm the engine needs to produce however much power. This creates a little bit of lag since it needs to "shift" and rev the engine.

The Sentra CVT I drove had a button on the shifter that disengaged "overdrive", which I am pretty sure just made it "shift down". You could easily design this so that the CVT operates the engine at a higher rpm at any given throttle input so that you have reserve power if you want to floor it.

[stugray]

Originally Posted by jsimon7777

I can downshift in the manual or a manumatic, as you said. Can't do that in a CVT. I've tired shifting to L, but it doesn't accelerate any faster, and it doesn't raise the revs much.

The loaner subaru imprezza-thing they gave me while the car was in the shop had a CVT.
It also had paddle shifters.

You can "shift" and it feels sort of like a normal AT, but it is just a trick to make it feel more like a traditional trans.
with a CVT, you can have a continuum of points of Engine-RPM vs CVT-ratio for any given wheel speed.
So if the trans ECU jumps abruptly between two or more points it feels just like shifting an AT.
For gas mileage you want the ratio so that the engine stays in the efficiency range of RPM/load but when you want acceleration it shifts the engine into the power band.
The concept is sound and a really good CVT should actually be faster in a racecar. They just never caught on and got the high tech treatment that the other options have.

[DohcTor]

Cvt is the future of all cars. Period.

The manual tranny has about 5 years left... At most. Say goodbye fanboys

[Tcoat]

Originally Posted by DohcTor

Cvt is the future of all cars. Period.

The manual tranny has about 5 years left... At most. Say goodbye fanboys

I have heard the "MT has 5 years left" song annually since about 1976.

[DohcTor]

Originally Posted by Tcoat

I have heard the "MT has 5 years left" song annually since about 1976.

Cool Story.

Anyways, back on topic. With Cvt, DSG and dual clutch autos in general becoming more efficient, reliable and cheap.... We may never have to shift our cars again!

Thank god, I know we are all getting tired of the 1% (manual tranny owners) saying how they drive a Racecar because they have a third pedal :


LMFAOOOO!!!

[yanfoo]

Originally Posted by DohcTor

Cool Story.

Anyways, back on topic. With Cvt, DSG and dual clutch autos in general becoming more efficient, reliable and cheap.... We may never have to shift our cars again!

Thank god, I know we are all getting tired of the 1% (manual tranny owners) saying how they drive a Racecar because they have a third pedal :


LMFAOOOO!!!

lol are you real??

[themadscientist]

Here a year and THAT was your third post? Are YOU real?

[yanfoo]

Originally Posted by themadscientist

Here a year and THAT was your third post? Are YOU real?

actually no, I'm just an automated program that tracks very stupid replies...


3rd hit in a year, this is such a good forum!

[gramicci101]

Originally Posted by themadscientist

Here a year and THAT was your third post? Are YOU real?

Are any of us real, or are we just some celestial being's fever dream?


I don't know, man. But it keeps me up at night.

[EAGLE5]

Originally Posted by gramicci101

Are any of us real, or are we just some celestial being's fever dream?


I don't know, man. But it keeps me up at night.

Kegel exercises help keep me up.

[wparsons]

Originally Posted by KoolBRZ

How about dual CVT's beside each other with a clutch between them. When accelerating the other CVT is set to a taller ratio you could shift to just like a next gear. When decelerating the other CVT could be set to a lower ratio, just like shifting to a lower gear. There would only be a slight delay when switching from acceleration to deceleration. Because each CVT only needs to handle torque for the length of a gear change, they wouldn't have to be built as strong. The key would be that the CVT's wouldn't change ratios while they are being powered, but instead changing only when their clutch is disengaged between shifts. If only CVT's could be created which could lock into a particular ratio under power, but unlock as soon as it was unpowered. Control it all with a Android-based controller and voila! The perfect transmission.

This defeats the entire purpose of a CVT, so why even bother?

The benefit to a CVT is that it can keep the engine at the best RPM for the scenario (based on load and throttle input) instead of constantly revving up and down, and changing gears.

Almost all CVT's have had a "manual" mode which lets you pick 5 or 6 pre-selected ratios and shift between them, it's nothing new at all. It's also worse on gas and much slower to use that compared to letting the CVT work as designed.