What's this CVT I keep hearing about?
- Thread starter geno
- Start date
CVT really hit the mainstream when Honda released the Civic HX. Other have tried but never really got it to sell. A CVT transmission does not use gears to transfer engine power to the wheels. Instead it uses a belt to do that. In theory there are an infinite number of ratios possible that allow optimium power level to drive the vehicle more efficiently. In the Civic, it offers an automatic that is economical like a manual.
Windogg
Windogg
It's a transmission that doesn't use fixed ratios - like 1st, 2nd, 3rd, etc.
Basically, the engine can run at any speed, irrespective of the speed of the car, within limits.
It gives the ease of use of automatic transmission, with a smoother ride as there are so sudden shift. By allowing the engine to develop maximum power irrespective of road speed, acceleration is maximized - modern CVTs can out accelerate the same car with manual transmission. Conversely when cruising, the engine speed can drop to just above tick-over when little power is needed - providing fuel economy unmatched by conventional automatic or manual transmissions.
It also removes some of the bad features of conventional autos - for example, there is no sudden 'kickdown', instead power is gradually applied, reducing the risk of losing control in a corner
Basically, the engine can run at any speed, irrespective of the speed of the car, within limits.
It gives the ease of use of automatic transmission, with a smoother ride as there are so sudden shift. By allowing the engine to develop maximum power irrespective of road speed, acceleration is maximized - modern CVTs can out accelerate the same car with manual transmission. Conversely when cruising, the engine speed can drop to just above tick-over when little power is needed - providing fuel economy unmatched by conventional automatic or manual transmissions.
It also removes some of the bad features of conventional autos - for example, there is no sudden 'kickdown', instead power is gradually applied, reducing the risk of losing control in a corner
Its a gearbox, where instaed of having all these planetary gears & cogs & stuff, it has a belt, & on either end of the belt are cranks that contract & expand. consequently there's an infinit amount of gear-ratios between low 'n high.
Driving on can be strange, but they are setup to match the revs in which your engine is most efficient at so when you put you foot down to rev up the cranks will keep expanding/contracting, to keep you in that rev band of maximum efficiency. When brakeing the opposite occures - say your car has a efficient rev band of 1.7k to 3k then as you slow down & as your engine cuts back to 1.7k the gearbox drops accordinally & keeps dropping back so you don't get under that 1.7K unless you are virtually stationary.
It also means there's a loss less where 'n tear on the engine a it virtually always stays in the relativelly narrow band. It also means great efficiency as the car can be tuned (cam grind, etc) perfectly to that rev band, rather than having a compomise tune covering everything from 700 revs to 7000 revs.
It works a bit like a Aeroplane, where the revs stay relative static, but as you speed up & slow down the pitch of your propellor changes.
Driving on can be strange, but they are setup to match the revs in which your engine is most efficient at so when you put you foot down to rev up the cranks will keep expanding/contracting, to keep you in that rev band of maximum efficiency. When brakeing the opposite occures - say your car has a efficient rev band of 1.7k to 3k then as you slow down & as your engine cuts back to 1.7k the gearbox drops accordinally & keeps dropping back so you don't get under that 1.7K unless you are virtually stationary.
It also means there's a loss less where 'n tear on the engine a it virtually always stays in the relativelly narrow band. It also means great efficiency as the car can be tuned (cam grind, etc) perfectly to that rev band, rather than having a compomise tune covering everything from 700 revs to 7000 revs.
It works a bit like a Aeroplane, where the revs stay relative static, but as you speed up & slow down the pitch of your propellor changes.
Nissan uses this in some of their cars that are sold in Japan. It is rumoured that CVT will be included in the Infiniti XVL and other models.
How come sport cars don't come with CVT, it would be more efficient and powerful.
How come sport cars don't come with CVT, it would be more efficient and powerful.
StageLeft
No Lifer
- Sep 29, 2000
- 70,150
- 5
- 0
MarkR is right, I read that some audi with cvt does 0-60 .1 faster than the standard.
My mother used to own a Subaru Justy (early 90's model) and it had "ECVT". OH MY GOD was it ever a pile of junk. About 60,000 km in the transmission died on it - but most of that is because my brothers and I were ALWAYS flooring the car because of it's lack of power. It's peak was about 3500 RPM and I found its lack of gear-changing to be quite annoying (as NFS4 apparently would too).
Its a shame about CVT really, I always used an auto vs. manual as a mark between "real men" and panzies who can't drive a standard - the only exception being that many old muscle cars had autos, and in that case it is ok.
My mother used to own a Subaru Justy (early 90's model) and it had "ECVT". OH MY GOD was it ever a pile of junk. About 60,000 km in the transmission died on it - but most of that is because my brothers and I were ALWAYS flooring the car because of it's lack of power. It's peak was about 3500 RPM and I found its lack of gear-changing to be quite annoying (as NFS4 apparently would too).
Its a shame about CVT really, I always used an auto vs. manual as a mark between "real men" and panzies who can't drive a standard - the only exception being that many old muscle cars had autos, and in that case it is ok.
The biggest advantage, if done properly, is to allow the engine to run a a set rpm. This simplifies emission control and problems incured by a variable fuel delivery system since the engine runs at a set rpm no matter the load.
"Its a shame about CVT really, I always used an auto vs. manual as a mark between "real men" and panzies who can't drive a standard - the only exception being that many old muscle cars had autos, and in that case it is ok. "
Current trends show that CVT is going to be the way of the future. I read somewhere about Japanese manufacturer building CVT transmissions for future models (can't remember who), and one/two european manufacturer as well.
Current trends show that CVT is going to be the way of the future. I read somewhere about Japanese manufacturer building CVT transmissions for future models (can't remember who), and one/two european manufacturer as well.
Saturn is releasing an SUV on Oct. 6th that "has a transmission never before used in an SUV". Could it be a CVT?
On the other end of the spectrum, I had a Toyota Corolla with a two-speed "Toyoglide" automatic. The thing would wind up to 5 grand and then dump WAY down almost to stall. What a POS that was!
On the other end of the spectrum, I had a Toyota Corolla with a two-speed "Toyoglide" automatic. The thing would wind up to 5 grand and then dump WAY down almost to stall. What a POS that was!
NFS4
No Lifer
- Oct 9, 1999
- 72,636
- 46
- 91
Speaking of the Saturn, they've been showing brief clips of it during the Olympics. They also have a small clippet of a picture of it on Saturn's website. Here's the artist's rendition of the sport-ute also found on Saturn's site:
Saturn SUV Rendering
Saturn SUV Rendering
Blech...
That *thing* has the looks of the BMW X5 and the ugliness of the Pontiac @SStec.:disgust:
That *thing* has the looks of the BMW X5 and the ugliness of the Pontiac @SStec.:disgust:
Actually Tom's, right, the CVT 'gearbox' was invented by the Dutch automaker DAF about 50 years ago.
But it didn't help them much, as DAF Cars were bought out by Volvo (actually a Volvo 360 is basically a badge engineered DAF), while DAF Trucks became a branch of Leyland Trucks.
But it didn't help them much, as DAF Cars were bought out by Volvo (actually a Volvo 360 is basically a badge engineered DAF), while DAF Trucks became a branch of Leyland Trucks.
Audi is starting to use an newly developed CVT Transmission right now, called "Multitronic", it´s supposed to be optimised for an better feeling...it does accelerate better than any manual and it is more economic too...Audi`s version is also able to "emulate" an 6-gear semi-automatic (you just have to press up and down) if you ´dislike the CVT´s feel.
Currently only avaible in the Audi A6 2.8 multitronic, but it will be avaible really soon with the 2.4 liter engine too, and is planned to debut in the Audi A4 early next year.
If Audi manages to release the "Multitronic" in the A4 together with VW`s new FSI engines (Fuel Stratified Injection) early-middle of next year I will be really tempted to give it a try...
edit:
DAF looks like it used to be fun, I remember seeing an DAF race on TV...those little cars could go just as fast backwards as forwards, and some guys tried racing backwards with them...
Currently only avaible in the Audi A6 2.8 multitronic, but it will be avaible really soon with the 2.4 liter engine too, and is planned to debut in the Audi A4 early next year.
If Audi manages to release the "Multitronic" in the A4 together with VW`s new FSI engines (Fuel Stratified Injection) early-middle of next year I will be really tempted to give it a try...
edit:
DAF looks like it used to be fun, I remember seeing an DAF race on TV...those little cars could go just as fast backwards as forwards, and some guys tried racing backwards with them...
NFS4
No Lifer
- Oct 9, 1999
- 72,636
- 46
- 91
<< Saturn is releasing an SUV on Oct. 6th that "has a transmission never before used in an SUV". Could it be a CVT? >>
Yep, you were right
Go to Saturn's website as they have announced the new SUV. It has a CVT transmission available with the 4-clyinder engine.TRENDING THREADS
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