continuously variable transmission

its a trim level on the new Honda Insight. What does it mean? is it a auto? manual? triptronic? what?

thanx for any help here:)

Paging Resident Tech Guru... :D

It's an "or what". The CVT transmission idea forgoes a set number of gear ratios (like 4 or 5 speed trannies) and instead is cleverly designed to create a continously variable ratio, meaning it never shifts from one distinct ratio to another like all other transmission designs. I could go on trying to explain it here, but there's already a great page that does so right here (http://www.fortunecity.com/silverstone/lancia/58/technical_school/gearbox/tech_gear.htm#CVT). Hope this helps, peace.

Dude that's weird, what are you psychic??

wow, that's cool. So its like a super-auto transmission, but only for less torquey cars. like the Insight, lol! So am I correct in saying that there is no clutch pedal, and shifting is not required? If so, then I just might get one of those Insights.

btw- thanx much, resident tech guru, that helped alot.:)

I believe all CVTs drive as automatic transmissions. I don't think the Insight has its CVT out yet, because they make such a big deal out of the recommended shift points that are indicated on the gauges.

Originally posted by texan
Dude that's weird, what are you psychic??

Nope. Just your run-of-the-mill stalker.

Yep, its basically just an automatic transmission that always keeps a perfect gear ratio. It's awesome, but they haven't been able to implement it in anything with a decent amount of torque. So right now it's really just in economy cars.

I didn't know the insight had it...but I do know the toyota echo has it.

Posted by IntegraR0064
...but I do know the toyota echo has it.
My wife has a 2001 ECHO, and it doesn't have a CVT. Do you mean in America, Asia or Europe?

The American Echo is not offered with a CVT. The only modern CVTs sold in the US have been in the Insight, Prius, and Subaru Justy.

Newer CVT designs allow for more torquey engines. They will be arriving in just a couple of years.

Originally posted by Hudson
The American Echo is not offered with a CVT. The only modern CVTs sold in the US have been in the Insight, Prius, and Subaru Justy.

Newer CVT designs allow for more torquey engines. They will be arriving in just a couple of years.

Prius! You're right, that's what I meant, I was thinking of the prius when I put echo. The echo doesn't have it.

Sorry...slight mixup

Originally posted by Hudson
The American Echo is not offered with a CVT. The only modern CVTs sold in the US have been in the Insight, Prius, and Subaru Justy.

Newer CVT designs allow for more torquey engines. They will be arriving in just a couple of years.

Don't forget the Honda HX CVT... they've been around quite a while longer than the Insights. I'm sure the Insight looked back to the HX CVT when in the design stages.

My question is that if torque is the problem, why don't they just build a motor with an incredibly short stroke, and a bulletproof valvetrain, and rev it out to 15k rpm... then equip it with a CVT. Sure it won't take a lot of torque, but you don't need torque when you can rev to 15 grand.

Originally posted by F=ma


Don't forget the Honda HX CVT... they've been around quite a while longer than the Insights. I'm sure the Insight looked back to the HX CVT when in the design stages.

My question is that if torque is the problem, why don't they just build a motor with an incredibly short stroke, and a bulletproof valvetrain, and rev it out to 15k rpm... then equip it with a CVT. Sure it won't take a lot of torque, but you don't need torque when you can rev to 15 grand. \

Lots of reasons....

A) They don't have internals that are built for steady driving at 15000 rps...nothing can withstand that. Not to mention that it'd be loud as hell. Think about it...you'd be cruising on the highway at 15000 rpms.

B) It'd be waaaaay too expensive even if things like that existed.

C) Again, it'd be soo loud.

D) That many rpms would kill fuel mileage...you know how much gas you'd need for all that air?

And there are your reasons..

Originally posted by IntegraR0064
\


:shrug: Then how about where race applications?

Where fuel, noise, and cost don't mean jack. (well fuel sort of)

Well.....that'd be a good idea, but they still can't do it, since they don't have stuff that can spin at 15k rpm constantly.

Anyway I'd be willing to bet if it can't handle torque very well, it wouldn't be able to handle high horsepower levels very well either...its probably just not as big of a problem. I don't know though, I haven't really looked into cvts in too much detail yet.

Either way though...

Originally posted by IntegraR0064
Well.....that'd be a good idea, but they still can't do it, since they don't have stuff that can spin at 15k rpm constantly.

Anyway I'd be willing to bet if it can't handle torque very well, it wouldn't be able to handle high horsepower levels very well either...its probably just not as big of a problem. I don't know though, I haven't really looked into cvts in too much detail yet.

Either way though...

Don't Indy Cars and F1's rev to 14-15k? And rotaries as well?

And motorcycles.

If there's any engine manufacturer who can design a production 15K rpm powerplant, it's Honda. With a firm background in the motorcyle industry and Formula 1 (and other racing series), it should be quite doable--but not easy.

I have to agree with IntegraR0064 that it will probably be expensive, and that single drawback leaves far too many good ideas at the drawing board. However, I don't think that a higher rpm engine with a shorter stroke requires much more air/fuel than the standard design. In some cases, they burn cleaner than the norm since high rpm engines are required to be more efficient in combustion, as in the S2000. As for audible noise, it probably wouldn't be the sound that would get frowned upon (high rpm engines have an IMO nice high pitched banshee-like scream, which can be eliminated if necessary through good resonators and mufflers), but it would most likely be the vibration echoing through the cabin at high rev that would get thumbs down.

Another problem to add would be lubrication. If this engine were to be used on the road in an automobile, the driver would need to get a hell of a lot of oil changes, something that's not a problem on the track for two hour races.

God, imagine the bragging rights one would have with a tachometer that DOUBLES the average car. Heck, even the Autometer tachs wouldn't work with it. Of course, if it were to be used with a CVT, there wouldn't be a tach in sight. ;)

Couldn't the gearing between the engine and the cvt allow normal engine operation and ultra high rpm(therefore low torque) on the CVT itself? Same problems with making the CVT work at these rpms, but no significant modification to the engine.

like 13k...

And that's redline, not what you're constantly running at.

Plus you have to consider that they rebuild their engines every race or so....

And again, even if they can do that, that's not the main reason. I very much doubt that cvts can handle much power, since they can't handle torque.

Originally posted by F=ma


Don't Indy Cars and F1's rev to 14-15k? And rotaries as well?

Actually, F1 cars rev to 18K:) Doesn't Audi have a CVT in the A6?

yep, Audi has a CVT in their A6. dont rotaries only get up to 9Kish???

The CVT was pioneered by DKW. In the 60's their cars were equipped with a crude CVT. The engine output shaft was connected to a set of pulleys transverse with the chassis. Connected to the drive wheels were a special set of pulleys where the diameter of the pulley was variable: at low speeds, the diameter was large and as the pulley sped up, the diameter shrunk. Newer CVTs are vastly superior of course, but DKW was the first.

Originally posted by hakka


Actually, F1 cars rev to 18K:) Doesn't Audi have a CVT in the A6?

Yes Audi has one, but also Nissan has one, wich came before AUDI!! In the 2000 Primera (G20 in the US), has a CVT Tranny, the Primera was the first car in the world (within its class, (no equal sized or bigger sized car) had got CVT when the Primera got it! Nissan sets the pace!

Nissan, king on-road, king off-road!:smoka: :smoka:

I was reading a few years ago about a Nissan Concept vehicle, kind of like the Audi Steppenwolf... a Sportyish SUV kind of thing. Anyways, it had height adjustable suspension and CVT or a 6 speed. It was going to be something of a big to do. I can't remember if it was turbo or not, but I remember it making a really good impression on me at the time. When I read about it, Nissan called it the Trailrunner. Anyone know any more details on it?

Originally posted by F=ma
I was reading a few years ago about a Nissan Concept vehicle, kind of like the Audi Steppenwolf... a Sportyish SUV kind of thing. Anyways, it had height adjustable suspension and CVT or a 6 speed. It was going to be something of a big to do. I can't remember if it was turbo or not, but I remember it making a really good impression on me at the time. When I read about it, Nissan called it the Trailrunner. Anyone know any more details on it?

Yeah, I rember it. I had a SR20DEV Engine, with 190 HP. Same engine as delivered in Primera 2.0GT in Japan. It also had 4wd, it was based in Primera platform I belive.
I`l try to dig up some old Nissan News broschures and scan some pics and specs.

:dogpile:

Yes Audi has one, but also Nissan has one, wich came before AUDI!! In the 2000 Primera (G20 in the US), has a CVT Tranny, the Primera was the first car in the world (within its class, (no equal sized or bigger sized car) had got CVT when the Primera got it! Nissan sets the pace!

Nissan, king on-road, king off-road!


the nissan m6 hyper-cvt sucked. it gave the feeling of a slipping clutch because the engine revs and it takes a long time for the CVT to catch up. the nissan extroid CVT was better because of the use of pairs of rollers.

Perhaps post DKW, the little Dutch 1960s-70s Daf range would have to be the first commercially successful CVT vehicle. Known as 'the rubber band car' and initially with a 2-cylinder engine it was perfect for Holland's ultra-flat terrain (their biggest 'mountain' is 300 metres high!) though not quite the deal for touring the Italian Alps. The CVT was nevertheless durable enough to later cope with Daf's excellent 1300cc 4 cyl engine, which became a successful powerplant in Formula 3.
btw: The Daf platform eventually evolved into the Volvo 3 & 4 series, which explains that model's rear-mounted gearbox/transaxle.
I hear that the new Audi CVT which has been widely lauded as the worlds finest auto transmission uses electronics to maintain a higher ratio and 'torque it out' under medium power demands, as even mild acceleration has previously resulted in unacceptably high revs as Hermunn explained.

The tach readings on most rotaries go to 9k RPM on the tach, but the engine itself is doing three tiems that, so at redlines the engine 27k RPM.

You sure about that? The output shaft sping three times the speed of the motor. I'm not sure which RPM you were talking about. So at 9K the output shaft is spinning at 27K..not the motor.

Seabass

Originally posted by Psman32@af
The tach readings on most rotaries go to 9k RPM on the tach, but the engine itself is doing three tiems that, so at redlines the engine 27k RPM.

It was my undestanding that the tachometer read the speed of the engine AND the speed of the output shaft, since they were the same thing. You're saying that a rotary engine is "geared down" 3:1 before it gets to the transmission?

I've been around engines all my life and this is the first I've ever heard this. Do you have any proof of this?

A Wankel Rotary Engine spins the output shaft 3x faster than the rotor in the engine. The output shaft in a rotary engine works like a crank in a piston engine. I'm not sure where the rpm's are read on a rotary engine. I always thought it was at the output shaft and the rotor spun three times less than that. But it could be the other way around.

I've been around engines for quite some time...but a rotary is a whole different animal.

Seabass

You've got a point about the rotor in the Wankel engine not running at the same rotation as the shaft. But the engine speed is still measured by the rotation of the shaft, not the number of times the rotor goes around.

The rotor does move once around the engine for every (I'm assuming you're right on the ratio) three times the output shaft moves. A gear on the output shaft moves around a geared ring inside the rotor, therefore it takes more turns of the output shaft to make one revolution of the rotor.

exctly....so the point made previously about the engine spinning 3x faster than they RPM's is wrong. IF the RPM's are measured at the shaft (which seems right to me) and it's spinning 3 times faster (which is right) then the rotor....it's the fastest spinning thing in the car. So at 9000rpm...the rotor is spinning at 3000RPM. Nothing is spinning at 27K.

Seabass

That's the way I see it.

Must feel weird when you open the throttle wide, and it feels like you have an obliterated clutch melting at the burn of high spinning engine--but the car still charges forward. Hmmm... can't wait to take a test drive behind the wheel of an A6 Multitronic next year or so. That thick linked chain belt they use looks pretty unusual.

It's almost eerie when the vehicle moves and accelerates and the engine stays at a steady speed. I enjoy pointing it out to (non-car) people and they just look at the gearshift in awe. When you need more power, the ratios will adjust and the engine will rev, but under light load, it doesn't have to.

Wouldn't it be kinda cool to have a manually adjustable CVT? as a knob or lever? that way you can match the way you drive and handle the pedal with your gearing, and you don't have to rely on the car to be able to 'read' into what you're doing. Leave it in as short as possible a gear until you hit redline, then constantly gear it down so that you make peak hp until you reach your desired goal. Acceleration doesn't get any more ideal than that.

Once you learn how a CVT works (not in theory...but by using it), you can actually do things like that. Some cars even have "gear" that you can place CVTs in...just like if you were shifting. I think it kinda defeats the purpose of the CVT, but somebody must like that.

I'm a "row-your-own" kinda person. But the current crop of CVTs aren't performance transmissions. When they get up to that range, you'll see that you don't need a shift lever to do what you want.

think about the way a snowmobile work's.it is the same way with out all the parts...

HOLY POST REVIVAL BATMAN!!


Well.....that'd be a good idea, but they still can't do it, since they don't have stuff that can spin at 15k rpm constantly.

Anyway I'd be willing to bet if it can't handle torque very well, it wouldn't be able to handle high horsepower levels very well either...its probably just not as big of a problem. I don't know though, I haven't really looked into cvts in too much detail yet.

Either way though...

With the wisdom that the last 4 years have given me since this post...I can say I was a complete moron. Of course it wouldn't be able to handle high horsepower...we're talking about a transmission. The transmission makes no distinction between horsepower and torque..they're all the same to it. So no matter how you're making engine faster, the CVT (of those times) wouldn't be able to handle it.

So that whole discussion was pointless.