spwolf

i meant more like higher end luxury vehicles than small cars.

CVTs are superior to small cars but they do have a NVH problem in small NA 4cly engines where they have to keep engine in 5000-5500 RPM range to accelerate, thats pretty annoying but overall it is still better than small AT from efficiency/cost perspective. CVT's in small turbos should be quite good, since they wont rev past 3000 rpm... I believe that in new small 1.2t Toyota turbo engine, CVT transmission is rated better than long geared 6 speed manual.

Toys4RJill

I think you are right but you are also wrong. CVTs can replace ATs as long as the manufacturer wants to do it. Strength and performance have nothing to do with as long as the manufacturer wants to do it. The LS600h weighs 5600 lbs, that is Toyota Tundra territory and it uses a CTV, and has AWD.

A CVT just has to be set up in a way that it can replace a modern day AT.
Like I said earlier, my CVT has 7 simulated shifts, those who have driven my vehicle would never know that it was a CTV. Other CVTs obviously do not have this set up as they are more like the traditional style that everyone hates (I hated my CT200h drivetrain)

CVTs are usually set up for fuel economy first and driving performance second. But a CVT can be set up so it simulates an AT.

I have also heard from a few friends who work in engineering at Ford that ultimately a CVT will out perform an AT in the long run.

Just some food for thought, the 290hp Nissan Maxima has a CVT and it can do 0-60 in 5.8 seconds, it has 6 simulated shifts and has over 700 shift points programmed for real world driving.

doge

Let it have a million gears!! Who cares as long as its smooth, fast, and efficient.

mmarshall

In most cases, CVTs don't wind the engine out that far, unless you mash the pedal. If they did, they would lose some of the good fuel economy standards they now have. Around 3500-4000 RPM or so is more typical in regular acceleration from low speeds.

airgas1998

you need to educate yourself more on how my cvt works in the subaru i have. nowhere near your claimed 5k+rpms pretty much all your doing is shooting at a target in the dark with your erroneous claims.

Mr Bond

I have CVT in both the IS 300h and CT 200h and it works perfectly for daily driving. The only problem is when it comes to sporty driving. The delay in throttle response is from another world, I have actually driven my CT on a track and its the only car I know you almost need to floor before the turn in to get full power when you reach the straight again. Yes , I know that the CT wasn´t made for that kind of driving.

Sulu

The eCVT (Electronic CVT) in Toyota and Lexus hybrids is not a real CVT. In fact, it is not even a real transmission at all because the gas engine never directly drives the wheels; the electric drive motor is always directly driving the wheels. So a Toyota / Lexus hybrid vehicle is actually an electric car with a petrol engine backup.

The eCVT is a Power Split Device, a computer-controlled gearset that allows the engine to do 2 functions:

1. The engine can add power to assist the electric motor (when accelerating hard or driving at higher speeds, since neither the electric motor nor the hybrid battery are that powerful);
2. It can recharge the hybrid battery; or
3. It can both assist the electric drive motor AND recharge the hybrid battery at the same time.

Since the petrol engine's job is to assist the electric drive motor by providing extra power most efficiently, and because it never directly drives the wheels, the engine can turn over at the most efficient rpm (for either maximum torque or maximum power, as needed). It is this fact that makes the Power Split Device SEEM like a CVT.

Current state-of-the-art belt-and-pulley CVTs would not work on the Lexus LS, since the 5-litre V8 engine (on the LS 600h) would have too much torque for the gearless belt-and-pulley CVT. So much torque would make the belts slip on the pulleys.

chromedome

Slightly incorrect, the gas engine *can* drive the wheels directly at high speed. This usually happens at freeway speeds with the traction motor adding more power if necessary.

I think Toyota calls their hybrid transmissions eCVT because there are no set gear ratios, with the traction motor and ICE both providing continuous power up to a set RPM limit. The planetary gear set Power Split Device used in Toyota hybrids is totally different than a typical Honda or Nissan CVT with belts and cones.

Sulu

The petrol engine does provide all of the power at high speeds but it does not directly drive the wheels; the electric drive motor (MG2) continues to regulate the speed of the car. There is no direct mechanical connection between the petrol engine and the drive wheels; that mechanical connection is provided by the electric motor.


The main difference between a belt-and-pulleys CVT and the eCVT is this:

1. In the CVT, the car's speed is regulated by the variable gear ratios of the belt and pulleys. As the car speeds up or slows down, the gear ratio changes, allowing the engine rpm to remain constant.
2. In the eCVT, the car's speed is regulated by the electric drive motor (Motor-Generator 2 or MG2). As the car speeds up or slows down, the speed of MG2 changes; the engine rpm remains constant. If the engine were directly connected to the drive wheels, engine rpm would have to change as the car's speed changes; it would no longer be an engine rpm-constant "CVT". Excess power produced by the engine that is not needed by MG2 to drive the car is absorbed by Motor-Generator 1 (MG1) acting as a generator to recharge the hybrid battery.

Hoovey689

iTrader: (16)

Lexus's eCVT is

spwolf

of course, I am talking about maximum rpm's when you accelerate at fastest rate, like merging on the highway, or up steep hills and such... at low and mid speeds, CVT's even on small cars work fine and are quiet and smooth.

But yes, in smaller 4cly vehicles, when you need full acceleration, they will certainly go to high rpms and produce pretty annoying noise, which is basically not fault of CVT, but combination of less powerful engine, less luxurious soundproofing and need for maximum acceleration. When paired with smaller cheap vehicle, it gets annoying.

I recently drove Yaris 1.33 CVT and while I would buy it for my wife, I could never own it myself... less powerful engines and cvt means high rpm's, and cheap car with poor sound insulation means a lot of annoying noise... new MMC Yaris is supposedly much nicer but I dont think it can ever be awesome with that engine getting up to hwy speeds.

Hybrids PSD (aka eCVT) gets extra benefit of electric motor acting like 40-50hp instant turbo so you dont get anywhere as much annoying noise since you accelerate much quicker with 40hp boost.

spwolf

i dont think so... thats Volt.

mmarshall

According to Lexus specs, curb weight on the LS600hL is 5159 lbs.....but, yes, that's still rather porky.

http://www.lexus.com/models/LS-hybrid/specifications

Sulu

I am not sure that the Volt can either, but Honda claims that the current Honda Accord Hybrid can.

The HAH is the only 2-motor hybrid that I know of in which its petrol engine can directly drive its wheels at high speeds. Of course, all the 1-motor hybrids (like Audi, Hyundai, Honda IMA, etc.) that merely add an electric motor to the front of the transmission, have the petrol engine directly drive the wheels at high speeds.

mmarshall

What you are talking about, in Hybrid-speak, is the difference between a series hybrid and a parallel hybrid. The original first-generation Honda Integrated Motor Assist and some early GM hybrid units were good examples of series hybrids, where the gas engine was the primary power source and the electric motor simply boosted the gas engine when necessary, or as a starter-motor to get the gas engine going again after it occasionally shut off at stop-signs, traffic-lights, etc.....

Parallel hybrids, on the other hand, were like those pioneered by the Toyota Prius and similar Ford units first built under Toyota license....the gas and electric motors can each drive the wheels independent of the other, as conditions and battery charge warrant. Since then, of course, several other types of hybrids have also been introduced, some with individual electric motors at each rear wheel and behind or parallel to the gas engine.