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KSPG shows new compact two-cylinder range extender for EVs, variable valve system

The KSPG-FEV two-cylinder range extender. Click to enlarge.

Automotive supplier KSPG Automotive (formerly Kolbenschmidt Pierburg), a subsidiary of Rheinmetall AG, and FEV have jointly developed a concept for a compact, 30 kW range extender for battery-electric vehicles. KSPG is showcasing the unit, along with other of its engine efficiency technologies such as the UniValve variable valve system, at the Detroit Auto Show.

The new power unit consists of a two-cylinder, 800 cc V-type gasoline engine with a vertically positioned crankshaft and two generators with gear wheel drive. The use of two generators (2 x 15 kW) serves to provide balance for the two-cylinder V-configuration to help to reduce NVH (noise, vibration and harshness) from the engine—especially important in a range-extending application for a battery-electric vehicle, which normally is quiet.

The system also includes FEV’s Full Engine Vibration Compensator (FEVcom), which has been designed into the range extender to reduce NVH. With FEVcom, a reduction in the engine vibration of more than 95% at the engine mount could be measured in various engine applications, according to FEV.

KSPG sized the output to 30 kW, said Dr. Hans-Joachim Esch, Chief Technical Officer, based on the need for the target A-segment vehicle “to be faster than a truck”. KSPG analysis found that 26 kW was sufficient to move the car up a grade of 3% at 100 km/h; they chose 30 kW.

The engine, with a 90° V, is port fuel injected, with two valves per cylinder, and meets Euro 6 emission requirements. A combined cooling circuit serves the inverter, generator and combustion engine.

Except for the fuel tank and the radiator, all components, including the power electronics, are mounted on a support frame. The vertical crank shaft requires only a short construction height, such that the module can be integrated beneath the floor of a small passenger vehicle and, for example, be placed comfortably within a spare tire well in the trunk. This installation option offers the easiest and least expensive modification procedure relative to conventional vehicle construction and leaves room for interesting compact vehicle packaging and styling options.

The range extender weighs a little more than 60 kg, together with the generators and all related parts.

The power unit is conceived in such a way that the vehicle interfaces are reduced to a minimum. Vehicle integration thus proves comparatively unproblematic and installation or disassembly can be performed easily and efficiently, according to KSPG. This enables the range extender to be reduced to an additional accessory equipment option. The automobile can thus be delivered with or without a range extender and allows for a modular design concept.

A bridge technology such as a range extender could expedite market entry for a new generation of battery-powered vehicles and support legislators in their efforts to reduce CO2 emissions, KSPG suggests. The advantages of such power units lie in the fact that they reduce battery size and costs and lower additional related weight. With range extenders, normal ranges can be achieved even without long en route recharging periods.

Variable valve system. KSPG acquired the rights to the “UniValve” variable valve system conceived by enTec Consulting GmbH and is now pressing ahead with development toward series production. UniValve is a mechanical system for the simultaneous and continuous adjustment of valve lift and opening event. The control shaft is driven by a wear-free, brushless electric motor. Dyno tests with a complete engine have already been conducted with an early group of customers and have demonstrated attractive potential for reducing fuel consumption and emissions with high operating reliability, according to KSPG.

In a gasoline engine with fully variable valve train the fresh air-fuel mixture providing the engine output is no longer controlled by the throttle flap, but rather through the selection of valve timing and valve lift. Through early closure of the intake valve, both the gas exchange work and the (directly related) specific fuel consumption steadily decrease. In order to reap the advantages of very early closure, the opening event must therefore be as short as possible. For engines with conventional, i.e. non-variable valve trains, this represents a trade off to the maximum engine performance, calling for longer opening events and late intake closure.

By contrast, UniValve allows continuous variation of the valve opening event with a simultaneous, operationally specific adjustment of valve lift all the way down to zero lift. The system on the one hand thereby reduces partial load fuel consumption due to less pumping work, an optimized residual gas control and a high dilution capability of the combustion process, and on the other hand through the reduced power demand for valve activation.

When used on the intake side, UniValve can lower partial load fuel consumption of conventional, naturally aspirated gasoline engines in combination with cam-phasing systems by up to 12%. At the same time, its high flexibility also allows an increase in low end torque and engine performance. A smaller engine can thus deliver the same driving performance and open up additional consumption advantages through this downsizing.

The exhaust side also considerably influences the gas exchange process and consumption to such an extent that at least cam phasers should be available. An engine with fixed exhaust valve timings cannot fully utilize the large potential of the UniValve that has been opened up on the intake side; it is therefore more advantageous, KSPG suggests, when the UniValve system is also used on the exhaust side. This is especially true for the increasingly popular turbocharged four-cylinder gasoline engine.

The trade-off between partial load fuel consumption and high low end torque can be significantly mitigated. In a test involving a turbocharged 2.0-liter, four-cylinder gasoline engine, it was possible to reduce fuel consumption in a representative partial load point by 9% compared to throttled operation with direct fuel injection. At the same time, torque was significantly increased at low end.



"KSPG analysis found that 26 kW was sufficient to move the car up a grade of 3% at 100 km/h; they chose 30 kW.. The range extender weighs a little more than 60 kg, together with the generators and all related parts., for example, be placed comfortably within a spare tire well in the trunk.."

A 'nearly plugin' range extender. The German Rotax engine powers most ultralight/sport aircraft.

Still, if present batteries can cover 90% of daily EV range needs, it would seem an air-cooled Wankel with one generator could do the remaining 10% usage at ~half the weight and cost.

In any case, the KSPG could also power a Kei car, with perhaps only a 5-10Kw battery(http://www.zeromotorcycles.com/zero-ds/specs.php ?) for most cruise/acceleration.


Finally, somebody is coming up with a common sense, downsized, more efficient genset for small PHEVs. The same unit could most certainly be upgraded for larger PHEVs. Mass produced in China (or in other lower cost labor countries) this unit could further reduce PHEVs and KEIs cost and selling price.


I would produce twice the capacity with separate electronics for mid sized cars like Camry and Fusion. When you talk about cars up hill, count on 3500 pounds up a 5% grade at 65 mph. Remember there were those that said the Volt would have "no problem", but they have a mountain mode in the final design.


Im interrested to buy. That's a nice complement to any battery car or suv, also the mpg in gasoline operation should be better then an ice with a transmission like 99% of actual cars on the road selled by gm, toyota, ford, volkwagen, bmw, audi, mercedes, ford, chrysler, honda, mitsubishi, mazda, hyundai, kia, subaru, daihashu, fiat, peugeot, reneauld, ferrari , porsche, caterpillar, tata, freightliner, lexus, volvo, aston-martin, roll-royce, etc.


It is a pity EV manufacturers don't pick a standard size for a range extender (say the size of this one) and pre install fuel tanks and radiators, so it would be easy to add a range extender.
You just need 1 or 2 standards (30 / 60 kw) for instance and let a market develop.
The range extenders don't have to be all that efficient, they just have to give extra range, so you can get to a charging point at a time and place that suits you.

It might cost $500 extra to make an EV "range extender ready", and I think most people would go for it, if they could add a range extender for $1-2K when they needed one (if they ever did).


You'd think that Honda would get into range-extender research and development, especially with all their experience in small engines. Honda makes some of the finest generators & lawnmowers...should be easy to jump to ultra-efficient range extenders.


I don't know why EV producers are not considering this option. It would be better for everyone having one car instead of two (one ICE another EV). I believe that this could become mainstream. Pure EV mainstreaming hundred years away.


Already, in less than 2.5 hours, seven of the most informed and interested parties on this forum have spotted a winner.

If only the auto gov/corporate wizards actually cared about reducing oil, war, and and personal transportation costs.


You are trading extra batteries for an extender, 8 kWh of batteries and an extender instead of 24-32 kWh of batteries. Long charge times versus 600 mile range...a NO brainer.


Excellent suggestion SJC......what is stopping major car manufacturers from doing it?


Probably an uninformed question: Why not simply use FCEVs?


This appears to be an engine with variable throttle.. with all that text about VVT and improved low end torque.. so perhaps not what we think is needed for an EREV but more of a hybrid engine with a smallish battery.

Apparently it uses the generators to actively control vibrations, a good idea.

In any case the important thing about a range extender is light weight, and 60kg is not bad.


Ed, got a spare 6 figures and nation-wide H2 infrastructure?

However, it would be nice to have a cheap, gas/diesel FC option.


I'd thought of something similar using a 2 cylinder boxer engine with the generator mounted underneath.

You'd manage with a shorter 50-100 mile battery range and the RE would start when batteries dropped below 50% or on demand if you wanted it.

With good aerodynamics 30kW is plenty to cruise at highway speed and the second or third generation of this sort of engine could be even smaller and lighter



28kw/11kg Wankel w/o generator.


We could see several genset models. Think of 24 kWh extra batteries. They take 4-6 cubic feet, weigh 200-300 pounds and cost a lot. Now produce 24 kW with a genset, it takes less than 2 cubic feet, weighs just over 100 pounds, costs less and goes farther.


There are a few issues with pre-plumbing for a genset you might not put in the car:

  1. It adds weight and structure.
  2. Radiator openings increase aerodynamic drag.
  3. Fuel systems require emissions testing, crash-test spill tests, and the whole raft of environmental and safety details that ICEVs have to handle.
But given the cost of batteries, just deciding "this will be a PHEV" and going with this range extender sounds pretty good to me. About the only thing you wouldn't be able to do with it is towing.


Ed - Fuel cells are not yet ready for prime time. Look around the Internet and you will learn why. It's my opinion that fuels cells as we know them today will never become practical for automotive transport.

As I posted ten years ago - We need a genset powered by a two cylinder opposed, air cooled, two cycle diesel. No need for a new infrastructure. Algae diesel with - dispersed production - can eventually replace fossil fuels.



Basically, the OPOC, right? :)

Thomas Pedersen

Kelly, being quick on the keyboard and commenting a lot does not count as being informed. Until we convince Rafael Seidl to revisit this site, I don't think we can claim this engine is a 'winner' ;-)

However I agree that this engine looks very interesting indeed. A little on the weak side for many people, though. I wonder if more revs could be coaxed out of it for higher peak power. It would be relevant for range extender engines to have both rated sustained power (at reasonable efficiency) and and overload in case you need to climb an unusually high grade.

For PHEV, I have thought of a parallel concept where the engine is only engaged above a certain speed, corresponding to e.g. 1500 rpm in highest gear. The idea is that there is no gearbox, because the electric motor is strong enough to accelerate the car to highway speed, where the speed is high enough to engage the engine. ICE's have good efficiency over a relatively wide range of rpm, and definitely wide enough for highway cruising - e.g. 45 - 100 mph. With a parallel hybrid there is no need for generators, which increase cost and weight more than a simple clutch.

Well, just an idea. And it certainly requires a battery strong enough to cope with high power output for acceleration without the engine and enough charge to drive around the city without the possibility of running the engine for sustaining the charge.


It comes down to what do most people want a car to do? Do they want it to tow 3000 pounds? Do they want it to climb a 5% grade at 70 mph? Maybe they just think they do because other vehicles can and they might want to some day.

The parallel method with a clutch and no transmission is one idea of doing highway cruising more efficiently. With enough genset, motor and batteries they a can do city and highway travel rather efficiently. It is a matter of buyer requirements and perception of over all utility for the life of the car.


The small ultra light weight on-board genset has two main functions:

1. To keep the batteries charged for extended range when needed.

2. To add extra power to the drive train when needed.

Basically, in an ideal PHEV, it should not run much more than 5% of the time. The genset size/power is a calculated compromise based on what you want the PHEV to be and to do.

For most small PHEV, a 24 Kw genset should be enough. One can always rent a light truck when towing is required.


A transformer gives up the ghost somewhere... The sound of EB's cherished notions re FCEVs biting the dust.


The one concept that seems to allude some is the genset has to power the car and charge the batteries at the same time. It comes on and off like a refrigerator or furnace in your home. I was told that was not how it worked by some seemingly wise people on here years ago...oh well.


Thomas, not being quick on the keyboard and not commenting a lot does not count as being informed.

The KSPG comments indicated a light, compact, genset range extender could be a winner.

Perhaps, if only minor ~10% extended duty cycle is needed, a Wankel-based genset might be lighter and cheaper, hence lowering costs and increasing EV sales - esp. if gensets downsize presently expensive batteries.

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