9/10 speed automatic vs CVT

[ykX]

I just read an announcement that Honda will start producing 10-speed automatic, seems GM and Ford are going that route as well.

Could somebody explain to me what is the advantage of going to high number speed automatic instead of CVT?

Seems to me unnecessary complexity of using so many gears. 

[ccap41]

Efficiency, I'd assume.  When those transmissions are in full lock you're getting 100%(theoretically) from the engine whereas CVTs are belts and whatnot stretching and giving losing more power to the wheels. More power loss = more efficiency loss.

This is just my theory on them. Similar to DCT vs torque converter as well.

[David]

13 minutes ago, ccap41 said:

Efficiency, I'd assume.  When those transmissions are in full lock you're getting 100%(theoretically) from the engine whereas CVTs are belts and whatnot stretching and giving losing more power to the wheels. More power loss = more efficiency loss.

This is just my theory on them. Similar to DCT vs torque converter as well.

In talking to a number of Transmission Mechanics, I have yet to hear a single one say they preferred a CVT over a true Gear transmission other than the simplicity of rebuilding.

Geared transmissions are superior as CCAP41 mentioned in regards to getting more power and holding strength over CVT to the wheels. Efficiency is questionable in regards to CVT compared to a Geared transmission.

[hyperv6]

The CVT is the most efficient model out as it can pace the engine right on the power sweet spot no matter where it is. Nothing is more efficient. 

The down side is the CVT is not as strong or durable. They have made gains but the life and ability to take power is nil. That is why you only see them in the smallest and lightest cars ans why companies are now dumping more money into 8-10 speed trannys.

While a CVT can slip some the ability to keep the engine engaged right on the most effective power spot makes up for it. The CVT can vary the ratio to where ever it needs to be and not to 8 or what ever geared fixed points.

Now with more gears you cut down on the gaps and keep the RPM more even and constant for emissions and mileage.  

Ideally if we could get an engine to one RPM and let it remain there it would provide the most efficient power we could get. This is what they do on trains and the Chevy Volt. It is not as easy to use this in a car but like any generator a single RPM is where you can plant the sweet spot. 

Someday they may fix the durability but as of now they are still not where they need to be. A heavy more powerful vehicle would chew one up and spit it out. 
 

[David]

48 minutes ago, hyperv6 said:

The CVT is the most efficient model out as it can pace the engine right on the power sweet spot no matter where it is. Nothing is more efficient. 

From an Engineering exercise, you are right about efficiency, sadly from real world use the design of the dual cones and slippage will always keep it from fulfilling its full potential.

Outstanding explanation, thank you.

An Engineer I am but an English writer I struggle to be.

[hyperv6]

The cvt reminds me of the old cone model t clutch. It was simple but it used leather to give it bite if I recall correctly and it would slip if you loaded it down.

[ykX]

@hyperv6 Thanks for the explanation, I guess that is what I suspected.

I just hope that in order to make this more complex  9 or 10 speed auto transmission smaller and lighter the manufacturers will not sacrifice durability.

[David]

3 hours ago, ykX said:

@hyperv6 Thanks for the explanation, I guess that is what I suspected.

I just hope that in order to make this more complex  9 or 10 speed auto transmission smaller and lighter the manufacturers will not sacrifice durability.

I truly believe we can have high durability with more gears. A perfect example of this is the Mountain bikes that have 20-30 gears and smoothly shift from 1 gear to another or jump up or down between gears and yet are strong, smooth and yes durable in a very hostile grit destroying area.

I believe we can have 10-15 gear transmissions that are strong and smoothly move from gear to gear or jump between gears and still give us strength, durability and better MPG.

[hyperv6]

Strong and durable is not an issue but the fact you add more parts and more moving pieces you automatically add to the number of things that can fail. Just the nature of numbers.

The Powerglide was strong but the key to it was it had so few parts and was small. Racers love small and simple.

There is no reason for the new tranny to be solid as long as they do the proper development. The old GM 200TH and other 1980's Transmissions they had issues with them because GM tried to save money and cut much of the development work they used to do. Well we know that did not work and so now they have gone back to the same way of vetting the durability they used to do.

Today GM still makes some of the best transmission in the world. They still supply others with their work and even Ford partnered with them.

GM did the bulk of the work with funding supplied by Ford and as well as some technical help to give Ford what they needed to use these in their cars.

It was funny to see the new Aluminum F150 still in cammo coming out of the GM Warren proving grounds. A prototype Ford on GM property was a real event.

Note the VVT I think may some day make it but to make it strong enough I fear the cost would still be very high.

 

[Drew Dowdell]

GM's new 9-speed has all sorts of patents on it because they managed to get 9 forward gears while using about half the parts one would expect in a transmission with that many speeds. I don't understand the full technical ramifications of what GM did, but apparently it is fairly groundbreaking transmission design.  It's seriously tiny as far as transmissions go. Physically, there's no reason they couldn't fit it in cars as small as the Spark or Adam, though they won't do it for cost reasons. 

[Paolino]

So with the new FWD 9-speed coming out, would you think they'd throw it in vehicles like the LaCrosse and Impala?  Or no, because they just came out with the new LaCrosse and don't want to change the mechanics yet?

[Drew Dowdell]

28 minutes ago, Paolino said:

So with the new FWD 9-speed coming out, would you think they'd throw it in vehicles like the LaCrosse and Impala?  Or no, because they just came out with the new LaCrosse and don't want to change the mechanics yet?

Next refresh on those.  There is an XTS refresh coming, so I might expect that to get the first 9-speed in the Epsilon cars.   Cadillac is doing yearly rolling changes to their cars, so the XT5 could be right there behind it. 

for the RWD cars, Cadillac is sticking with the 8-speed for the moment, which is fine with me because it is an excellent transmission.

[Drew Dowdell]

I was going through old pictures today and found this one of GM's new 9-speed fwd auto.... With my cocktail for size comparison. Look how small it is.

[David]

21 minutes ago, Drew Dowdell said:

I was going through old pictures today and found this one of GM's new 9-speed fwd auto.... With my cocktail for size comparison. Look how small it is.

That is very cool and amazing how technology has changed the size of things.

[balthazar]

Technology in automobiles has basically made them all MUCH heavier, tho.

[Drew Dowdell]

1 hour ago, balthazar said:

Technology in automobiles has basically made them all MUCH heavier, tho.

and safer, and more efficient, and quieter, and more powerful, and cleaner, and more reliable

[balthazar]

3 hours ago, Drew Dowdell said:

and safer, and more efficient, and quieter, and more powerful, and cleaner, and more reliable

One could certain argue those are not universal; not everything is better done.

[hyperv6]

On 3/11/2017 at 11:29 AM, Paolino said:

So with the new FWD 9-speed coming out, would you think they'd throw it in vehicles like the LaCrosse and Impala?  Or no, because they just came out with the new LaCrosse and don't want to change the mechanics yet?

They have announced the  lacrosse is getting it in 2018 and I expect the Impala will get it too. 

No refresh needed. 

 

Actually of late technology is making cars lighter like the Camaro, Malibu, CT6 and Nox. The Trucks will be next with the new aluminum/steel welding. 

 

New steel, more mixed materials and the new processes needed to find weight loss have been invested in. 

[Drew Dowdell]

14 hours ago, balthazar said:

One could certain argue those are not universal; not everything is better done.

They are, by far, the norm.  You don't see a manufacturer throwing a bunch of new technology at a vehicle and then have it end up less safe than its predecessor.  The only time you see a vehicle with less power, the engine has been drastically downsized.  Sure, the Mitsubishi Mirage may not be all that safe nor powerful... but even then, it is leagues better than the Mirage of 15 years ago which was rated one of the worst vehicles in its day in crash tests. 

[balthazar]

I dunno, some of the recent recalls are for some horrific potential byproducts of new technology/ manufacturing lapses.  But they are, by far, the norm; yes.

Now if technology could erase some of the detrimental compromises instilled under 'new technology'… that would truly be celebratory.

[Drew Dowdell]

What was the new technology in a spring of insufficient tension in an ignition switch?

Even the Toyota unintended acceleration wouldn't have changed things had the car had a physical throttle cable instead of drive by wire.... a floormat certainly isn't high tech. 

[Drew Dowdell]

And now the latest rounds of CVTs are going to have artificial steps in them to fool people into thinking they are regular automatics.

I wonder if someone who is efficiency minded could go get those steps removed from the program to get ultimate efficiency. 

[David]

13 minutes ago, Drew Dowdell said:

And now the latest rounds of CVTs are going to have artificial steps in them to fool people into thinking they are regular automatics.

I wonder if someone who is efficiency minded could go get those steps removed from the program to get ultimate efficiency. 

Sounds like something a 3rd party programmer could due to improve performance by removing OEM coded pauses to mimic a real traditional transmission.

[trinacriabob]

I was hunting around Chevy's website and believe that the new (2019?) Malibu might/will be coming with a CVT with the base engine.

I don't understand why a CVT would not be as long lived.  With fewer parts, one would think that those parts could be strengthened and make for a more reliable unit.

I am comfortable with a 6 speed automatic.  You don't feel the last 3 shifts as it is in most cases.  As for 8 gears, I know that the highest gear took a rented Dodge Charger (V6) down to about 1,600 rpm and delivered over 31 mpg going between 60 and 65 mph on cruise.  And that's a 4,000 pound car.

 

[Drew Dowdell]

6 minutes ago, trinacriabob said:

I was hunting around Chevy's website and believe that the new (2019?) Malibu might/will be coming with a CVT with the base engine.

I don't understand why a CVT would not be as long lived.  With fewer parts, one would think that those parts could be strengthened and make for a more reliable unit.

I am comfortable with a 6 speed automatic.  You don't feel the last 3 shifts as it is in most cases.  As for 8 gears, I know that the highest gear took a rented Dodge Charger (V6) down to about 1,600 rpm and delivered over 31 mpg going between 60 and 65 mph on cruise.  And that's a 4,000 pound car.

 

CVTs have built in slip that a conventional automatic doesn't and the belts that run them can't handle higher amounts of torque of bigger engines.  

Yes the 1.5T in the 2019 Malibu will be paired with a CVT.