Friday, August 5, 2016

CVT TRANSMISSIONS - MAYBE THEIR TIME HAS COME?

On the basis there’s nothing new under the sun, a look back at the birth of the Continuously Variable Transmission (CVT) tells us we should never stop celebrating clever people.

In my review of the Subaru Levorg, with its excellent and refined CVT, I highlighted the fact that the original principle was first sketched by Leonardo da Vinci in 1490; and that Daimler-Benz acquired a patent in 1886.

But wait, there’s more! The first car to use the idea was created in Britain in 1925 by cousins Frank and Ailwyn Smith. The boys made excellent motorcycles with CVT transmissions, and in 1927 launched their first car, the CLYNO, with their own 1.5 litre engine and CVT gearbox.


Between 1910 and 1929 they produced 36,000 cars – and were Britain’s third largest manufacturer after Austin and Morris.

Sadly, the boys were hit by a double whammy. The company was grossly undercapitalized, and they won their sales crown by always being about 25% cheaper to buy than their competitors (despite high manufacturing costs). As they had to keep innovating to stay in the game, it all went tits-up in 1930 and CLYNO disappeared.

Then in 1952, Dutchman Hub van Dorne resurrected the idea, using rubber belts and pulleys, and calling it the Variomatic.

He formed his own car company, DAF, and produced the DAF 600 in 1958. The company was renamed VDT, and sold to Volvo in 1975; but the patents were transferred to Robert Bosch AG in 1995 when the company was acquired by the German giant.

However, from that time the CVT idea has been almost universally embraced by a variety of manufacturers, mostly Japanese – Subaru, Nissan, Mitsubishi and Toyota.

Clearly the cost of paying Bosch to use the patented system doesn’t amount to much, but no doubt Bosch is picking up a handy royalty cheque every month as the idea becomes more popular.

Originally most of VDT’s income came from producing the refined metal-link belts for transmissions used by other car companies, and at times the growing popularity of CVTs stretched the company's production capacity.

Okay, you say, what’s the downside?

CVTs traditionally were only 88% efficient than a regular torque-converter gearbox (which themselves are only 95% efficient), but advances over the past decades has seen CVTs become not only more efficient, but also great at helping to maintain low fuel economy.

A CVT enables the engine to run at its most efficient speed for a range of output speeds. When power is more important than economy, the ratio of the CVT can be changed to allow the engine to turn at the RPM at which it produces greatest power. This is typically higher than the RPM that achieves peak efficiency. In low-mass low-torque applications a belt driven CVT also offers ease of use and mechanical simplicity. CVTs are also cheaper to produce than conventional automatics, however, should they need repair, they are much more expensive.

That’s not something that should put anyone off choosing a car with a CVT, because all of the companies now using CVTs will tell you that recent improvements in both design and manufacturing techniques have ensured that CVTs will be as long-lasting as conventional automatics.

I remember driving both the DAF and the original Volvo 340 and thinking how bad the transmission was. They were slow to change, awkward and noisy. They also gave the impression of sapping engine power, and thus being very inefficient.

But,here I must salute Subaru and its current Lineartronic CVT.

I recently returned the Levorg test car, driving the 75km from the Gold Coast to Brisbane, which is 100% freeway. Now, most of us agree, freeway driving tells you very little about a car, but this drive was different.


I found that in mild, and heavy traffic, with a range of speeds – from cruising at 110km/h, down to crawling in a traffic jam, then speeding up for a spell at 100km/h, then dealing with Brisbane’s inner city bottlenecks, the Levorg performed magnificently.

I paid particular attention to how much accelerator movement there was in the varying traffic conditions and road speeds, and the CVT always delivered power when I needed it.

The performance of the Subaru Lineartronic would definitely sway my consideration in choosing a Subaru as a new car.




And, after a week of very fast test drives in the Hinterland, lots of slow traffic, using the aircon continuously, and freeway driving, the overall fuel economy came back at 6.0 l/100km.

So, will we see the CVT employed by more car companies? We already are, because the transmission is ideal for hybrids, and just the contribution to ease of driving and keeping fuel consumption down is definitely appealing.

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