CVT transmissions

[KrisZ]

Originally Posted By: emg
Originally Posted By: KrisZ
It's weak argument.


CVTs being banned from Formula One because they made traditional transmissions uncompetitive is a weak argument in their favour?

Funny world I woke up in today.


f1 is a very high power, low torque application with little regard to cost and longavity.
If you find it so funny, then please share with us how requirements for racing translate to the requirements for every day commute vehicles and put some "meat" behind it. Otherwise it still is a weak argument.

 

[robertcope]

Originally Posted By: KrisZ

f1 is a very high power, low torque application with little regard to cost and longavity.
If you find it so funny, then please share with us how requirements for racing translate to the requirements for every day commute vehicles and put some "meat" behind it. Otherwise it still is a weak argument.


Are you trying to suggest that the ability to hold an engine at an optimum RPM would not benefit commuter vehicles? We know that CVTs can be made cost effectively and reliability enough for mass produced passenger vehicles. People "just don't like them" because they're not used to them.

 

[KrisZ]

Originally Posted By: robertcope

Are you trying to suggest that the ability to hold an engine at an optimum RPM would not benefit commuter vehicles? We know that CVTs can be made cost effectively and reliability enough for mass produced passenger vehicles. People "just don't like them" because they're not used to them.


What I'm trying to explain is that no engineering solution is without sacrifices and just because one technology excels in one application, doesn't mean it's a superior design overall.
CVT ability to hold the engine at certain RPM is counterbalanced by its inherently weaker design and inability to handle large torque. All these things are quite inconsequential in F1 since the transmission and the egnine only has to last the length of the race, at least that was the rule back then, and F1 engines, although produce huge amounts of HP for their displacements, their TQ numbers are quite low. A perfect application for CVT.

Hybrids are another perfect application for CVTs, since the engines in these are quite weak and low torque and they operate often as generators, so keeping them closer to peak TQ is preferable. This way the engine can rotate at fairly constant RPM, while the CVT and electric motors control the speed. Even then, Toyota refused to use the belt and pulley design and instead implemented a planetary gear set driven by two electric motors to achieve the same thing, but a lot more reliably.

Basically, don't bring the F1 baloney if you have no idea why a certain solution was implemented over another. The mere fact that something is/was used in F1 or another racing application is a weak argument by itself.

 

[bbhero]

You make a number of really good points KrisZ.

One odd observation I have noted in all my CVT research... It's the lower power motors which gave had more trouble than the bigger ones within the Nissan's. The 3.5s have done a lot better than the 2.5 or smaller motors with their CVTs. The 3.5 has 270 hp and 258 lbs of torque vs 160 hp for the 2.5 (I believe). That is something I've picked up on in all my reading.

 

[KrisZ]

Originally Posted By: bbhero
You make a number of really good points KrisZ.

One odd observation I have noted in all my CVT research... It's the lower power motors which gave had more trouble than the bigger ones within the Nissan's. The 3.5s have done a lot better than the 2.5 or smaller motors with their CVTs. The 3.5 has 270 hp and 258 lbs of torque vs 160 hp for the 2.5 (I believe). That is something I've picked up on in all my reading.


I would imagine that the the 4 cylinder models outsell the V6 models by a lot. More models = more problems reported.

 

[HouseTiger]

My wife's 2006 Ford 500 has a CVT that has 187,000 miles on it. It had the transmission fluid and filter changed about every 75,000 miles (give or take a few thousand miles). There have been NO issues with the transmission. I do notice a difference in shifting when I get into my 92 Ford truck, and the annoyance lasts about 0.34 seconds.

 

[bbhero]

I'd still say quite strongly though the 4 cylinders had more problems percentage wise.

Though you are correct in your math analysis here in one aspect. Mo sold... Mo problems.


I have heard one person hypothesize the bigger motor maintained more pressure on the belt. Makes sense to me in a way.