CVT Transmission Discussion

[rockhopjohn]

The second set of links worked for me. It may be Flickr blocks access to folders, and thats why the first URLs didn't load.

BTW, I also just realized CVT transmission is one of those words like Hot Water Heater, and ATM Machine, with built in redundancy. One of my little pet peeves.

[CNY_Dave]

Originally posted by nipper
yes the push belt was a subaru patented design, it really was a smart way of doing it.

On projected maint and life
http://blogs.thecarconnection.com/ma...ntenance-costs

Now look at this picture
http://www.subaru.com/engineering/transmission.html

Pic from the autoshow (large poics I took)

http://www.flickr.com/photos/nipperd...7616957539400/

http://www.flickr.com/photos/nipperd...7616957539400/

Really goos chain pic
http://www.flickr.com/photos/nipperd...7616957539400/

http://www.flickr.com/photos/nipperd...7616957539400/

The chain has teeth both pins that hold the chain together. They most likely work together to bite the drums.. As with any transmission, as long as the teeth dont slip, there should be no issue that i can see. The hyd fluid aould be acting like cutting lubricant, keeping the teeth sharp. Unlike cutting metal, you are never really going over the same spot for any length of time to do damage. So once again subaru is using the compression model to drive the car. We think of chains that wtretch by the links elongating. The stress is equally split on the link pins and the links.


Will it last? I dont know. Can it, quite possibly.

That does not look like it could function 'pushing'- that's a pull-type?





Dave

[CNY_Dave]

Originally posted by rockhopjohn
The second set of links worked for me. It may be Flickr blocks access to folders, and thats why the first URLs didn't load.

BTW, I also just realized CVT transmission is one of those words like Hot Water Heater, and ATM Machine, with built in redundancy. One of my little pet peeves.

Department of Redundancy Department.

I did that on purpose at work with the acronym for a simulation tool I created.


Dave

[nipper]

Originally posted by CNY_Dave


That does not look like it could function 'pushing'- that's a pull-type?





Dave

Im not sure, as the chain does look a little odd in the middle. Also i was analyzing the pics as i was typing, guess i didnt quite re-edit my thoughts well


i am not having a good day by any measure of the term.


nipper

[nipper]

Originally posted by CNY_Dave


Department of Redundancy Department.

I did that on purpose at work with the acronym for a simulation tool I created.


Dave

Well "steadily variable" doesnt sound good either, and two letter acronyms in the automotive world just aint cool :P

nipper

[CNY_Dave]

Originally posted by nipper


Im not sure, as the chain does look a little odd in the middle. Also i was analyzing the pics as i was typing, guess i didnt quite re-edit my thoughts well


i am not having a good day by any measure of the term.


nipper

The plate pattern looks a lot like a transfer-case chain from a 4WD, but modified so the 'pins' engage the pulley instead of the plates engaging sprocket teeth.



Hope your day goes better-

Dave

[bhayden]

Well, as nipper said:

Will it last? I dont know. Can it, quite possibly.

I guess I'm just not the type that wants to be first in line to find out.

So many places to wear. They're stressing the link pins, the pins are a fairly high point load on the pulleys. It makes more sense than a tapered side link though because with that arrangement there would be metal to metal grinding as the link reoriented it's self from one pulley diameter to another. Whether push or pull, I suspect a bit of both the chain will stretch over time. On level ground at constant speed (freeway driving) the pulleys will always be seeing wear in the same spot.

Do both pulleys exert enough force all the time to prevent slipping? That seems like an awfully delicate balance to maintain but the only way to maintain proper tension in the chain as components wear. Is it adjusted electronicly or through the magic of hydraulics (I'd hope the latter). I'm guessing that this is part of what controls how fast the transmission can "shift" and explain the zero power lag I've experienced with the Nissan CVT. It seems like applying power to the wheels while trying to simultaneously make a rapid change in effective pulley diameter (i.e. "shift") would be very stressful on the system.

Is there any engine braking possible with the CVT?

Does anyone remember why the CVT in the Justy was discontinued? I suspect it wasn't designed to handle higher power engines that the market demanded but does anybody know if it was prone to failure/maintenance, despised, expensive to manufacture? It's taken quite a while for Subaru to re-engineer a CVT system and the impetuous seems to be government mandated CAFE standards.

Also interesting to note that the automatic is always a thousand dollar option irregardless of model. I wonder what the actual manufacturing costs are.

[nipper]

Yes its hydraulic.

CVTS have been around a long time they now how much clamping force they need to make things work. There is no delicate balance here, as they have been around a long long long time in industrial uses.

Yes there is engine braking (this isnt a diesel in the USA). The nice thing about CVTS is that if the belt stretches, over time you hardly notice as some allowances are built into it for this.

I think i talk to myself sometimes, or i loose track of threads. Justy CVTS had a powdered electric clutch, no torque convetrer. Maganitize the two parts of the clutch and a mechanical hook up occures through the powder. They failed due to dealers not knowing how to fix them. Usually the brush assembly would fail for the clutch. Replace that brush and it lasted just as long as any small car auto for that period.

Automatics are far mor complicated then manuals, hence the extra cost. Manuals dont have computers, valve bodys, duty solenoids, pumps, or coolers.


nipper

[bhayden]

Originally posted by nipper
Yes there is engine braking (this isnt a diesel in the USA). The nice thing about CVTS is that if the belt stretches, over time you hardly notice as some allowances are built into it for this.

If they work by controling hydraulic pressure then it seems the system is self adjusting. Engine braking would reverse the tension compression on the chain. I'm curious about behavior going downhill with cruise. It could be very nice if it maintains speed with engine compression and certainly doing away with the hunting would be appreciated.

I think i talk to myself sometimes, or i loose track of threads. Justy CVTS had a powdered electric clutch, no torque convetrer. ... Replace that brush and it lasted just as long as any small car auto for that period.

Sounds a bit like electronic shifting ala the old Renault R10. Doing away with the torque converter seems like a bad idea. It's the one redeeming feature (besides laziness ) that the automatic offers.

Automatics are far more complicated then manuals, hence the extra cost. Manuals dont have computers, valve bodys, duty solenoids, pumps, or coolers.

Understood, but I'm curious as to the true manufacturing cost difference between the different flavors of automatic, CVT, 4EAT and 5 speed auto. With AWD you do have to also add in the cost of the viscous coupling with the manual and of course the clutch, pressure plate, associated pedals and linkage and cost of a machined flywheel vs a pressure plate. A lot has to do with number of each type of unit made and customer demand. On my 1965 Mustang a three-speed manual transmission was standard, a Borg-Warner T-10 four-speed manual was $76 (for V-8s, $116 for the 6 cylinder) and Ford's three-speed Cruise-O-Matic automatic was a whopping $180/$190.

[nipper]

Originally posted by bhayden



Understood, but I'm curious as to the true manufacturing cost difference between the different flavors of automatic, CVT, 4EAT and 5 speed auto. With AWD you do have to also add in the cost of the viscous coupling with the manual and of course the clutch, pressure plate, associated pedals and linkage and cost of a machined flywheel vs a pressure plate. A lot has to do with number of each type of unit made and customer demand. On my 1965 Mustang a three-speed manual transmission was standard, a Borg-Warner T-10 four-speed manual was $76 (for V-8s, $116 for the 6 cylinder) and Ford's three-speed Cruise-O-Matic automatic was a whopping $180/$190.

And the mustang cost how much new? I dont even know where to explain the increase mfg cost, as i thought i just did.



TCU
Torque converter
Front pump
Planetary gear sets (which are not cheap)
clutch packs (ill equate them with synchros so thats a wash)
Acumulators
8 or more duty solenoids
Valve body
Many seals

Best way to get a cost comparison may be to compare a rebuilt auto vs a rebuilt manual. They may actually loose money on the manual, with the auto having the higher markup (hence profit). i am leaving out the AWD units since they both have them so its a wash.

nipper