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Hyundai-Kia Developed Its First CVT for the LPI Hybrids

Hyundai-Kia developed the CVT applied in the Elantra and Forte LPI Hybrids. Source: Hyundai. Click to enlarge.

Hyundai-Kia developed its first, independent Continuously Variable Transmission (CVT) for application in the Hyundai Elantra LPI Hybrid (earlier post) and the Kia Forte LPI Hybrid (earlier post). The work on the CVT, which took three years, as well as other components of the hybrids, was carried out at the Namyang Research and Development facility in South Korea.

The LPI Hybrid is a mild hybrid powered by a 1.6-liter Liquefied Petroleum Injection Gamma engine; a 15 kW /105 N·m pancake type Permanent Magnet Synchronous Motor; the CVT; and a 180V, 5.3 Ah lithium-ion polymer battery (LIPB) pack (with cells from LG Chem) with forced air cooling. The Elantra LPI HEV emits 99 g/km of CO2 and 90% fewer emissions than an equivalent standard gasoline-powered Elantra. It qualifies as a Super Ultra Low Emission Vehicle (SULEV).

The Elantra LPI Hybrid has a fuel economy rating of 17.7 km/l (5.7 L/100km or 42 mpg US); gasoline-equivalent fuel economy is 22.7 km/l (4.4 L/100km, 53 mpg US). This represents a 47% improvement over a conventional 1.6L Elantra.

As we developed the Kia Forte LPI Hybrid it was clear that to maximize fuel efficiency we needed to use a CVT because its infinite number of gear ratios allowed us to optimize fuel consumption according to driving conditions.

And because of packaging issues a traditional transmission would have increased the overall length of the powertrain. Using the CVT allowed us to delete the torque converter of a traditional automatic transmission because we were able to utilise a starter clutch with a direct control solenoid valve to allow precise pressure control. All of this contributes additional reduction in fuel consumption.

—Soo-Jin Hong of Hyundai-Kia’s Research and Development Planning Team

In general, use of a CVT contributes approximately a 7% fuel efficiency gain compared to standard four-speed automatics, and the calibration of the CVT allows for a smoother shift feel.

Hyundai-Kia engineers used a single-mass flywheel and one clutch—rather than the more normal dual-mass flywheel and two clutches—in order to reduce cost, length and weight. The additional benefit was that by careful tuning of the set-up the engineers were able to deliver a better response and performance.

Although Hyundai and Kia may consider applying the new CVT in other vehicles, modifications to the system would be required.

In the hybrid vehicle we have an additional electric motor available and that means we can use the starter clutch without changes to the final drive ratio. To use the CVT in non-hybrid vehicles we would have to add a torque converter in order to deliver acceptable uphill and start-up performance. But this development means that as our range of hybrid vehicles continues to develop we already have our own independent technology that we can apply to those future models.

—Soo-Jin Hong

Hyundai plans to launch a full-hybrid version of the Sonata in the US in 2010, equipped with its Blue Drive hybrid system, which uses a 6-speed automatic transmission. (Earlier post.)



It seems that CVTs are being redesigned by up to 20 different world car makers. Isn't that an example of multiple wasted efforts to arrive at the same end product? Couldn't three or four standardized mass produced CVTs fit on all cars and light trucks produced worldwide?

Such level of duplication, if avoided, could liberate enoguh resources to improve, standardize and mass produce e-storage units for PHEVs and BEVs.


It seems that vehicles are being duplicated all over the world.
Isn't that an example of multiple wasted efforts to arrive at the same end product? Couldn't three or four standardized vehicles adequately fit all requiremets for cars and light trucks produced worldwide?

Such level of duplication, if avoided, could liberate enoguh resources to improve and standardize people.

Diversity is evil, resistance is futile.



In the Dark Ages every man-made objects were hand made. No two objects were exactly the same.

The industrial revolution brought mass production. Machines could then stamp million identical pieces. Unrequired part by part diversity was forcibly reduced. That's how mass production cost is reduced.

If we want to go back 300+ years and have every tires, wheels, batteries, transmissions, heaters, A/C, generators, controllers, cars, trucks etc very different for diversity's sake, we would lose the advantages of mass procution. Could you imagine a car with four different wheels and tires? Bumpers height has been standardized and regulated to reduce accidents impact. Diversity would allow bumpers to be 0-in to 60+ inches in height. Oh! what a beaudiful diversified world that would be.

Could you imagine a world where every hand gun would be different with each it own bullet size. Crime rates may go down because it would almost impossible to find the proper ammo.

Our diversifed languages (around 6000 at one time) is going down quickly to improve communications and reduce interpretation cost. EU is having a hard time to cope with only 27 languages. The universal translator is not here yet.

Nick Lyons

@HarveyD: Let a thousand flowers bloom...

Roger Pham


Only through duplication of efforts but in diverse ways can we really have evolution...via natural or human selection of the best or the fittest. This how more complex life forms came about in the biosphere, and how capitalistic system triumphed over socialistic or communistic system.

This is how any technology is perfected thru time...different groups of people trying to make similar devices but with subtle improvement in design...and the better design usually win market shares, to be replaced with even better designs later on...Better products will be made cheaper and cheaper via more efficient production technologies, and less efficient companies will go out of business...

Duplication of efforts is good...it keeps more engineers and scientists employed, more young people encouraged to enter the technological careers...

Duplication of efforts is good...it keeps more engineers and scientists employed, more young people encouraged to enter the technological careers...

you forgot your Thorazine™ again.


Clearly, there should be 7 different CVT designs because 7 is a lucky number.


Clearly, there should be 7 different CVT designs because 7 is a lucky number.


Clearly, there should be 7 different CVT designs because 7 is a lucky number.


Over diversity can become a waste of time and effort.

Some people will use 4 colours in each room (at an extra $100 per room) and others will paint all walls and ceilings the same colour and safe up $600 to $1000 for an average house.

Who needs that many colours?

Modern cars, from the 20 major makers, look more and more the same but many parts are not interchangeable. Did GM need 70+ models and 7 divisions? Half that would have been more than enough.

Roger Pham

"Over diversity can become a waste of time and effort."

This is a statement that no doubt Carl Marx would approve! In a free-market economy, diversity will be supported by market forces of cost vs demand. If diversity can be provided at affordable cost, then the market will support it. We all are unique individuals, due to the unique genetic make up of our DNA's. The reproductive process involved in sexual reproduction guarantees that each offspring will be unique, unless in identical twins or triplets. As such, we have the tendency to prefer as much diversity as can be supported by cost. By guaranteeing individual variation in preferences and attributes in the reproductive process, the survival of the specie can be much enhanced than when there is a lack of diversity.

Modern production and marketing practices now can allow you to order many products tailor-made to your specification instead of having to buy boring generic items on the shelves.


I don't know why my comment displayed in triplicate. I was implying that there's no right number because eventually a free market determines design diversity.

Roger Pham

You prefer to give out unemployment benefit and welfare checks instead?
When different creative people are trying to redesign something, improvements invariably will occur over existing designs. This is evolution. This is the mechanism for progress.


In the interest of preventing return of the Dark Ages, I will support legislation prohibiting a single car from having four different wheels and tires; but three is OK, since front and rear might be different and a dinky spare saves space, weight and fuel.

Bumper heights should remain standardized but diversity should allow all car makers to make their own bumpers, even if there are hundreds of different types.

If you want to market a hand gun that has a different caliber than 22, 25, 30, 32, 357, 38, 44 or 45; Or 7.62mm, 9mm or 10mm – go ahead. Good luck trying to sell it – unless it offers some breakthrough - go ahead.

I was truly shocked to learn that some people will use 4 colors in each room (at an extra $100 per room). There aught to be a law.

The free market determines how many different transmissions will exist - and guess what – the BEST will survive.



You mix up two things when you talk of the industrial revolution. True, the industrial revolution enabled to mass-produce millions of identical parts. But that is for one given model.
All the CVT models that are being designed now will all be mass-produced so that they are all exactly like their respective models.
So it is not going back a couple of centuries to have a lot of different models, and IMHO, the more you design, the more the chances are you will find something better.
You would never say that the world only needs 4 types of solar panels, or 4 types of electric motors, so why CVTs?


There's a lot to be said for sufficient level of standardization. For years we had 14-in amd 15-in wheels or tires with very few differnt widths and heights. Now we have everything from 11-in to 22-in wheels. Tires inventories are a real nightmare. Do we really need 10 or 12 different wheels diameters multiplied by 10 to 12 different tires width multiplied by 10 to 12 tire height multiplied by 20 tire types multiplied by 50 tire manufacturers for a total of 1 000 000 to 1 720 000 possibilities.

Wouldn't half or even one quarter of those possibilites be more than enough?

Where do we stop? Should every car have specific/unique tires, at $1000++ each?

Should each BEV have a unique battery pack? Why couldn't we have a few standardized plug-in battery modules, i.e. 2, 4, 6, or 8, Kwh each. The owner could buy one to six modules to satisfy his needs and pocket book.

On-board aircraft electronic plug-in modules have been standardized decades ago.


It's for the market to decide, Harvey.

If the customers are ready to pay for unique tyre size, then why not?
In the case of BEVs, I agree that having the same standardised battery pack would bring down cost, and maybe the market will go in that direction. Again, maybe not. But this is clearly a case where the market is apt to decide, and it doesn't need help.
Forcing standardisation would just kill innovation and we would still have heavy, bulky and costly battery packs in 20 years.

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