Continously Variable Transmission

[KRISKARRERA 2 1 Cars]

I've been reading this: HOWSTUFFWORKS: TRANSMISSION!

 

Imagine if rather than the revs rising in each gear and having to change up, the revs were held dead at peak power and the gear ratios simply increased all on their own. Man you could have a lower powered car but have a s*it-hot accelerate time because there'd never be any gear changes or work done outside the power band.

 

As that site says, "Ideally, the transmission would be so flexible in its ratios that the engine could always run at its single, best-performance rpm value. That is the idea behind the continuously variable transmission (CVT). A CVT has a nearly infinite range of gear ratios. In the past, CVTs could not compete with four-speed and five-speed transmissions in terms of cost, size and reliability, so you didn't see them in production automobiles. These days, improvements in design have made CVTs more common. The Toyota Prius is a hybrid car that uses a CVT. "

[Doof 11]

Yea but think how crap it would sound.

 

vroooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo

ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo

oooooooooooooooooooooooooooooooooooooom

[danGTI 0]

yeah, it'd sound like the constant drone of a moped engine...it'd be great at the lights though!

[C_W 3 1 Cars]

A regular automatic holds the revs a bit like that but not anywhere near the same sort of range, there is a degree of slip with them.

 

The CVT 1.1 Metro was actually quicker than the manual 1.1 Metro for the reasons quoted above, but I don't think it sat at 6000rpm doing this!!! lol

[Guest Dave]

CVT is nothing new, back in the good ol` days my dad had a booger-green colour Volvo 345GL. It was a W reg, so that must be early 80`s.

It had beige velour seats.

It also had CVT transmission.

it was only a 1.4 iirc so it wasnt exactly a flying machine, but the CVT worked pretty well.

Drive was transmitted to the rear wheels via two big "rubber band" things that needed replacing every now and then.

It sounded guff though, it just made a constant whining noise.

[Simes 248 2 Cars]

Yep drone' scooter sound, but effective at lights and up hills.

The Daf 33 was the first popular CVT car...ugly isn't it?

 

[jackherer 543]

I went in a Fiat Punto with this the other day. Was very odd, it was at about 4k ALL the time, unless you switched the gearbox from E to S then it sat at about 6k all the time. It also had a tiptronic mode where it simulated six gears.

[jackherer 543]

http://www.carkeys.co.uk/launch/LA000038.htm

 

This is an effect which takes some getting used to, of course. To begin with, your brain may refuse to accept the evidence of your eyes that the car is actually accelerating, because your ears don't hear a rising engine note. First-time CVT drivers sometimes pull back from an overtaking manoeuvre which is actually going all right.

[Guest justin85]

Williams developed and tested a Van Doorne Transmission (CVT) in a Forumla One car (FW16 Chassis) I think and it was tested by David Coulthard at Silverstone. Bloody wierd seeing an F1 car leave the pits and accelerate normally but sounding like a 1.4 CVT Metro!

 

Justin.

[Doof 11]

So they wouldn't be deaf doing 20,000 rpm constantly

[DrSeuss 0]

Only problem is getting them to handle serious power. But its not such a bad idea really. In terms of performance at the very least.

[Guest johno_78]

my missus had a 1.1 fiesta with a cvt, and it was nippy of the line, even beating a kevin in a nova sr once. however, they are notorious for breaking a lot earlier than you would expect from a standard gearbox. we were lucky to get 120,000 miles out of ours.

[NickR 10]

Sounds like that CVT would suit a derv engine.

 

To make a car accelerate well, you can make the engine rev AND/OR use various ratios.

 

With CVT there would be No need for a revvy engine. Peak power would be of little value (eg vtec engine), but a grunty not very revvy td would be fantastic.

[jackherer 543]

Sounds like that CVT would suit a derv engine.

 

To make a car accelerate well, you can make the engine rev AND/OR use various ratios.

 

With CVT there would be No need for a revvy engine. Peak power would be of little value (eg vtec engine), but a grunty not very revvy td would be fantastic.

also diesel engines (unlike petrols) are at their most efficient when held at a certain RPM. This is illustrated well by Intercity trains that have a diesel engine that is held at its most efficient RPM to drive an electrical generator that powers the traisn electric motor.

[Guest jeremy]

however, they are notorious for breaking a lot earlier than you would expect from a standard gearbox. we were lucky to get 120,000 miles out of ours.

That sounds better than most Pug boxes I've experienced in 205's

[CJ_2_0_5 0]

Williams developed and tested a Van Doorne Transmission (CVT) in a Forumla One car (FW16 Chassis) I think and it was tested by David Coulthard at Silverstone. Bloody wierd seeing an F1 car leave the pits and accelerate normally but sounding like a 1.4 CVT Metro!

 

Justin.

I believe the CVT box was a full 2 seconds quicker per lap straight out of the box, and was instantly banned by the FIA!!

 

The best CVT out there at the moment is found in Audi's (made by LuK) which uses a chain rather than the Van Doorne style belt. It can handle a reasonable amount of power and is as efficient as the manual despite still having a torque converter.

 

The early DAF ones used a reinforced rubber belt!

 

The ultimate evolution of CVT is IVT (infinitely variable transmission) where you effectively get a geared neutral. If Torotrack manange to make it work successfully and reliably you'll want to own shares in them!

 

CJ

[KRISKARRERA 2 1 Cars]

I only took an interest in the CVT thing when I read that it enabled the engine to always be at peak power if you wanted that. People are always trying to get their gear box ratios as close as possible but the problem is that you'll kill acceleration because you'll spend so much bloody time changing gear. Can't we have an engine that is 160 bhp from 2000-7000 rpm, then we could have a nice longer diesel box,:-)

[C_W 3 1 Cars]

Sounds like that CVT would suit a derv engine.

 

To make a car accelerate well, you can make the engine rev AND/OR use various ratios.

 

With CVT there would be No need for a revvy engine. Peak power would be of little value (eg vtec engine), but a grunty not very revvy td would be fantastic.

But if the CVT can maintain the revs around peak power then no set of gear ratios can better that.

 

A regular automatic suits a diesel engine nicely as it's strongest around 2000-2500rpm which under moderate driving it will always sit around there, but if you start wanting to open it up then the gears "lock" and it's not as a good as a manual.

[NickR 10]

Chris.... a vtec at 7000rpm vs a td at 2500rpm ALL THE TIME...

 

Which would you rather have.

 

Im sure the vtec would also get hot and wear out faster, high rpm would also cause problems on the clutch system.