Bazillion speed auto trannies.

[elhigh]

Originally Posted by darcane

While you could "get away" with one gear, you need to make compromises that may be undesirable. Either acceleration will be severely hindered, or you need to have a very loose viscous coupling to allow the engine to get up to speed (which reduces efficiency) or you need some other power source to pick up the slack.

Your Viper in 3rd gear would be able to accelerate, but not rapidly until maybe 30-50 mph.

Powerglides (2-speed GM tranny) are often used in drag racing because they are light, can be made to be robust, and only one shift tends to improve consistency. With a loose torque converter, acceleration is still excellent, but you wouldn't want this combo for commuting to work every day.

I agree, the Viper example does bring a lot of required compromises. That 0-100 pull is probably on the flat. You might get away with it in hilly E TN, but pulling away from the uphill stop sign would be accompanied by the delicious smell of deep fried clutch.

The loose torque converter is what really makes the low gear counts work. It makes the tranny behave as a sorta-kinda CVT when pulling at low revs.

Frank's statement that you spend most of your time at speed is a good one, but dang it now I have to confess that it's unrealistic to expect a manufacturer to build one car that is suitable for someone like Frank, happily cruising the midwestern steppes and another car just like it, but with a transmission for someone like me, cruising just a few miles and then cut-and-thrusting through downtown stoplights.

Hang it all, CVTs really are the best option. Or the best of what's currently available. Is anybody building a toroidal unit yet? Besides Nuvinci, that is.

[Ecky]

Originally Posted by Baltothewolf

Tbh I will always protest that CVT's are vastly superior to traditional auto's. I can accelerate with a light foot at 1700rpm in my civic, at a constant rate, all the way up to 65 when the ratio runs out, and cruise at 1900rpm at 70. Or, I can stomp on it and accelerate at 5500rpm all the way to 70, or mild throttle and accelerate at 2000rpm. They gotta be lighter than a 7-9 speed transmission autos, and are more efficient if memory serves me right.

True on all counts. The only problem is their longevity - most CVTs from the early 2000's die before 200k miles, and a lot of them die before 150k. Their lifespan is less than the autos they replaced, but the improved efficiency is worth it - you save enough fuel, it pays for your transmission, which will eventually need replacement. I can't speak for the CVTs they're making now, because they're not old enough yet for us to know, but with previous cars it gets significantly worse as you increase the amount of torque they need to deal with.

[redpoint5]

Originally Posted by Old Mechanic

I now understand why my advocacy for my own design which actually offers a "bazillion" ratios, on a molecular basis, falls on deaf ears in this forum...

Kind of sad to realize my personal failure where my efforts fall on deaf ears. A lot of time and energy wasted here.

I don't think it falls on deaf ears so much as I don't have any expertise with hydraulic hybrids, and have seen no examples of one.

I'd get very excited and rave about it if there was a working example, in a real car, with verifiable results.

I love the idea, but manufacturers aren't utilizing the technology, and there has got to be a variety of reasons that makes it a poor solution for the majority of drivers.

[cRiPpLe_rOoStEr]

Originally Posted by darcane

If you are Koenigsegg, you can build a supercar with one speed... and use electric motors to boost low speed performance:
How The 1,500 HP Koenigsegg Regera Hits 248 MPH Without A Gearbox

However, for a conventional, basic commuter car where efficiency is the primary goal... more IS better (generally)

The setup used in the Koenigsegg Regera actually resembles a little the HSD from the Prius.

[Frank Lee]

A 'Glide perspective:

CC Drive Report: 1958 Chevrolet Impala – Pink Floyd Was Dressed In Business Casual

[Miller88]

Originally Posted by Baltothewolf

Tbh I will always protest that CVT's are vastly superior to traditional auto's. I can accelerate with a light foot at 1700rpm in my civic, at a constant rate, all the way up to 65 when the ratio runs out, and cruise at 1900rpm at 70. Or, I can stomp on it and accelerate at 5500rpm all the way to 70, or mild throttle and accelerate at 2000rpm. They gotta be lighter than a 7-9 speed transmission autos, and are more efficient if memory serves me right.

Now that there are manufacturers OTHER than Nissan making CVTs, I think they will get a better reputation!

The early Nissan CVTs were awful ... some of them still are. I don't mean their behavior, I mean their reliability.

I drove a 2015 Civic with CVT, rather liked it. And I do like CVTs in heavy city traffic. I made the mistake of driving in Times Square the Saturday before christmas in 2014. Lot of sitting and going and then sitting and going. The CVT handled it well, if it were a traditional automatic (and not a rental), I would have been worried about the thing wearing itself out by constantly having to shift. Or killing the clutch on a manual.

[user removed]

Actaully the really crappy CVT's were Subaru Justys and Honda's. Not sure who is making them besides Jatco which is a subsidiary (wholly owned) of Nissan. All are based on the Van Dorn belt drive of the 50s. It took belt technology and development to get them reliable. Nissan gave us a 10 year 120k warranty on our Murano, which was rated to tow 3500 pounds.

Modern CVTs are "push belts" with 400+ steel segments that push against each other instead of the traditional pull we think of in belts.


regards
mech

[H-Man]

Didn't know that.

[samwichse]

It looks like it works kind of like the Shimano internal 11 speed hubs. Multiple planetary gearsets in a row.

Neato.

[serialk11r]

Originally Posted by cRiPpLe_rOoStEr

The setup used in the Koenigsegg Regera actually resembles a little the HSD from the Prius.

Not really, the Regera is a series hybrid that also has a torque converter and clutch for higher efficiency direct drive. HSD can vary the engine speed vs. vehicle speed.