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FEV LiiON Vehicle With Wankel Range Extender at the Vienna Motor Symposium

The FEV LiiON Drive with Wankel Range Extender concept. Click to enlarge.

FEV Motorentechnik GmbH (FEV) featured its LiiOn Drive with Wankel Range Extender Vehicle at this year’s Vienna Motor Symposium, 29-30 April, where it was one of the most popular Ride & Drive vehicles. Earlier, at the SAE 2009 World Congress, FEV had displayed a 295 cc Wankel genset for extended range electric vehicles. (Earlier post.)

The FEV LiiON Drive is based on a Fiat 500, equipped with a 12 kWh battery pack mounted under the floor and a permanent magnet synchronous motor with 60 kW peak power. The vehicle can accelerate to 60 km/h (37 mph) in less than 6 seconds, and top speed is higher than 120 km/h (75 mph). Urban use of the vehicle results in an almost emission-free operation with a range of 50 miles. The 20 kW Wankel Range Extender provides up to 190 miles (306 km) of extended range, with 80 g/mile of CO2 emissions.

Powertrain elements. Click to enlarge.   Power electronics. Click to enlarge.

While the vehicle shown in Vienna is a concept, the electric vehicle LiiON Drive with Wankel Range Extender is licensed for public road traffic.

FEV developed the Wankel Range Extender in cooperation with the Wankel engine production supplier AIXRO. The basic powertrain has been comprehensively revised for automotive use. Modern engine management with electronic throttle, inlet pipe injection and three-way catalyst ensure that the exhaust gas emission limits will be met. The heating and temperature preservation strategy of the catalyst has been specifically adapted.

An FEV assessment of the properties of different range extender modules. Click to enlarge.

The partially encapsulated Wankel Range Extender was mounted in the position of the fuel tank, which had been reduced to a capacity of 12L. The engine, which is inertia force-free by design, together with careful tuning of the thermodynamics, yields an excellent, previously unparalleled NVH behavior. All test drivers acknowledged this feature specifically.

The positive response to the FEV concept, which was chosen for the first E-Car Tech Award in 2009, provides further validation among the international powertrain community of the vehicle’s potential, FEV says.



What a sweet little car!
I have several questions though: What is NVH?
Looking at the diagram of FEV assessment, is bigger better, or smaller? I looks to me as though bigger is better, but in that case why is the still costly fuel cell REm (whodat?) given as having favorable costs?


NVH- Noise vibration & harshness. Car designer speak.
What is the actual miles per gal on range extender is what i wanna know. The c02 figures would suggest in the 60s??

Account Deleted

It is impressing to see a 20kW generator with such a small engine only 295 cc. No wonder that the Wankel engine is superior with regard to weight and packaging when compared to cylinder engines or fuel cells. It is also good to hear that it is superior with regard to noise and vibration (NVH). As it has been licensed for road traffic I presume that the engine is currently euro 5 compliant. The Wankel engine’s cost disadvantage must be related to economics of scale. Do a million of these engines per year and I doubt it would cost more to make than a cylinder based engine of comparable power.

A wild guess on costs.

The Fiat 500 would probably sell for 14000 USD in the US and 4000 USD would be expenses for the powertrain. The PHEV Fiat 500 would probably cost 22.000 USD in the US where 12000 USD would be for powertrain cost with 6000 USD for the 12 kwh battery, 2000 USD for 60kW electric motor and power electronics and another 4000 USD for the Wankel motor with generator and power electronics. For these cost to be realistic it needs to be produced at over 50000 units per year.

Would it sell? I my opinion, yes, as it will easily achieve over 200 mpg in annual consumption for the average driver when factoring in that it will run on electricity in over 80% of the miles driven. Also it will be superior in terms of noise and vibration when compared to ICE vehicles. It will still not be economics for the vehicle owner but people buy vehicles for many other reasons than to be economical. Moreover, in the US and everywhere else the 22.000 USD price will be subsidized with several thousand USD because drivers of such vehicles will have to be compensated for their contribution to minimize emissions and making their economies independent of oil price chocks and oil embargoes.


12 Liters tank = 3.17US gallons.
190 miles range = 60 miles/gallon.

Anyone throw any light on the assessment diagram?


Rotary engine = low weight and small size, but also poor thermal efficiency (even compared to a standard otto cycle engine)

Will S

Promising. Look forward to seeing it as one of the choices we have in the very near future.


If he wankel has poor thermal efficiency, it still manages 60/gallon, although of course the 500 is a very small car, and the acceleration above 37mph may be poor.

Account Deleted

Clett, that is right but the range-extender efficiency should not be that important for overall vehicle efficiency when it runs on electricity over 80% of the miles driven during a typical year. To illustrate, it seems to do 60 mpg with the Wankel engine in charge sustaining mode. Factor in the 80% battery electric drive and you get 1/(1-0.8)*60 = 300 mpg in this PHEV Fiat (better than the 230 mpg for GM’s Volt). Using a diesel engine you may get 75 mpg in charge sustaining mode or 1/(1-0.8)*75 = 375 mpg. However, the diesel engine adds weight so you get a penalty probably 5% so end result is perhaps more like 375*0.95= 356 mpg.

To sum up, using a downsized diesel engine should only provide marginally better fuel economy than the Wankel engine and it will come at a price in terms of more noise and vibration as well as less room for luggage something that should be most wanted in such a small car as the Fiat 500.


The EREV logic goes that most of the time your driving will be covered by the battery, but the rare occasion that you need to drive longer distances the genset helps out.. so that it does not really pay to spend too much (weight, bulk, money) to achieve a few more miles per gallon.


I find it interesting that this is developed enough so that even an electric heater is included - see the diagram.
With space at such a premium in this very small car, it would have been easy to leave things like that out. It makes me think that this or a close variant is under serious consideration for production.


I've got my head around the assessment diagram at last
REM = Range Extending Motor.
The further the point is from the center, the better.
(What confused me is that it sometimes is more, sometimes less in numeric terms, as they have gone for a qualitative ranking instead)

The only thing the wankel is lot worse on is fuel consumption, but at least for this small car it still turns out very respectable figures.



I agree with all of your points, but only if people bother to charge at home. I am concerned that the general public won't understand PHEVs initially and could complain about the 'low' mpgs they're getting because they haven't appreciated they must spend as much time as possible in EV mode.


295 cc Wankel

It depends on how you rate displacement. The RX7 was 1200 cc but with the three lobes it was more like 2400 cc. Either way, it is a nice small engine.


Basically, a PHEV genset does not have to have the highest durability or be the most fuel efficient because it will not be in use 4/5 of the time. Other factors like lower vibration, lower noise, potential lower mass production cost, lower weight, lower volume etc could more than offset its slightly lower fuel economy.

A 12 litre fuel tank is very small and 60 mpg on sustain mode is very good. A Prius PHEV and the new Honda HEV/PHEV could operate well enough with a similar genset and a 16 litre fuel tank. The Volt would require a slightly bigger units.


Looking at the ratings against the fuel cell version, it is not clear to me if they are simply comparing plug-in units to generate the power, or if they have allowed for the several parts of the system which could be discarded by going all electric with a fuel cell.
This could substantially alter the balance in weight, packaging and costs towards the fuel cell/battery plug in.


a naturally aspirated Wankel has poor efficiency , but throw in a turbo and you're in the same range as a piston engine


From all the positive comments - put it on the market. Profits and volume will do the rest.

Henry Gibson

All of you together have explored accurately the need for and limited use of a range extender generator. Such machines can operate at very high speeds all the time and with the related high power in a small package. This is demonstrated in a different way with the recent demonstration automobiles that incorporated a 100,000 Hz. turbine generator of relativly lower efficiency than diesel engines. The combination of electric motor efficiency at low speeds and regeneration and the higher efficiency of an engine operating at peak efficiency all the time even over compensates for the lower efficiency of this engine type. ..HG..


Small turbines run at perhaps 3 kHz, not 100 kHz. At 100 kHz you'd need a wheel smaller than your pinky fingernail or it would blow up. Leakage and friction at that scale would make for abysmally low efficiency.

I share the distaste for inefficient Wankels (the very high surface area of the combustion chamber guarantees high heat losses), but if the car runs on wall power 80% of the time the average fuel economy hits 300 MPG. If the entire US fleet could achieve that, the ~3 trillion miles/year driven by light vehicles would require only 10 billion gallons of gasoline compared to the current 100+ billion. OPEC would cease to exist and Hugo Chavez would be strangled and hung on a meathook in Caracas.


The Rotary engine is currently used in one major production car. I think that we all know just how efficiently they are driven.

If this engine is being used only to spin a generator, it should only run at a fixed speed, right? I would think that the genset would be designed to run at peak efficiency. If it has a problem with too much heat, well, I need heat in the car in the winter.


Chavez ........Meathook.......
Change we can believe in!!!!!


The small Wankel engine is small and light for its power output. Since the engine/alternator can run in the engine's "sweet spot" the efficiency is much better than acceleration from a stop through clutch and transmission. The diagram shows that it is not the cleanest nor most efficient method, but when cost, size and weight are considered it is not bad.


Wankel engines have especially a low efficiency at partial load. But this engine won't be operated at partial load.
Since an engine for this application does not need to be run at partial load a 2 cylinder 2 stroke engine with direct fuel injection may also be an option with similar space and weight requirements (fuel is injected after outlet has closed).

fred schumacher

This is the right size genset for a vehicle of this size. With the engine operating continuously, the car becomes a Battery Buffered Vehicle (BBV) providing range only limited by refueling opportunities.

I would rather have a trade-off of reduced battery size for a more efficient engine than the Wankel, perhaps an OPOC HCCI (opposed piston opposed cylinder homogeneous charge compression ignition), or a single-cylinder true Atkinson cycle, with double crank, version of Fiat's 900 cc Multiair twin.

Treating the vehicle as a BBV would reduce initial price, the greatest impediment to consumer acceptance of efficient vehicles, while providing real world liquid fuel economy of over 100 mpg.


Actually in that case an actual hybrid would be preferable over a BBV as the electric motor and generator can be significantly smaller and the electric system including battery is not required to deliver all the power (= lighter and more efficient vehicle).


BUILD THIS CAR !!!! Folks will buy gas when affordable.

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