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Ricardo, QinetiQ and PSA Peugeot Citroën Reveal Efficient-C Low-Carbon Diesel-Electric Parallel Hybrid

Architecture of the Efficient-C. Click to enlarge.

Ricardo, QinetiQ and PSA Peugeot Citroën today presented the results of their Efficient-C two-year collaborative research project: a parallel hybrid-electric diesel demonstrator vehicle emitting just 99 g/km CO2 (equivalent to 3.75 liters per 100km or more than 63 mpg US) based on a fully featured Citroën Berlingo Multispace family car.

This represents an improvement of 30% in fuel economy and concomitant reductions in carbon dioxide emissions when compared to the equivalent diesel production vehicle. The same diesel hybrid powertrain fitted in a C-segment 5-door sedan would also only emit 90g tank-to-wheel CO2.

The Efficient-C.

The Efficient-C was one of five proposals selected to participate in the UK Department for Transport’s Ultra Low Carbon Car Challenge. The UK Government launched the Ultra Low Carbon Challenge on 29 April 2003 and invited proposals from individual companies and consortia to demonstrate the feasibility of a family sized ultra-low carbon car in the UK. The five winning proposals, which included the Efficient-C project, were announced on 15 October 2003.

Ricardo was the project leader and contributed program management and hybrid vehicle systems; PSA Peugeot Citroën provided the base vehicle and expertise in vehicle architecture; and QinetiQ contributed expertise in the areas of energy storage, battery management and high voltage wiring systems. The company also provided prototype energy storage and management hardware to support the demonstrator vehicle.

The Euro-IV compliant Efficient-C demonstrator comprises the following integrated technologies:

  • A PSA Peugeot Citroën 92 hp (69 kW), 215 Nm, 1.6 liter HDi, turbo-charged and inter-cooled common rail diesel engine.

  • A compact 23kW, 288V DC electric motor mounted between the engine and the transmission, providing up to 130Nm electrical torque assist, efficient electrical power generation, regenerative braking and full electric vehicle (zero emissions) operation at low speed. The clutch is mounted between the engine and the motor, allowing the engine to be disconnected from the rest of the drivetrain in order to provide an all-electric mode where only the electric motor propels the vehicle.

  • A 5-speed automated manual transmission delivering cost-effective automatic functionality.

  • A 288-volt, 2 kWh Lithium-Ion battery pack and battery management system to monitor state-of-charge, cell temperature, and cell voltage balance.

  • The engine is started by a 12V starter-alternator. Other supporting systems include a low-temperature cooling circuit to protect the electric motor and power electronics, an electro-hydraulic power assisted steering system, electrically powered air conditioning and a touch-screen driver display.

  • Advanced supervisory control system based on the Ricardo rCube prototype controller to co-ordinate the many vehicle systems to meet driver demands whilst optimizing fuel economy.

The diesel hybrid offers six operating modes:

  • Mode 1. The Internal Combustion Engine drives through the clutch and gearbox to the wheels—i.e., conventional vehicle mode, used on the highway.

  • Mode 2. The motor absorbs torque from engine, generates electrical energy. This forces the engine to operate more efficiently, and stores energy in battery for later use.

  • Mode 3. The motor draws power from battery and provides additional torque to wheels to boost acceleration.

  • Mode 4. Electric drive using stored electrical energy. The motor is used for pull-away and low load operation.

  • Mode 5. Regenerative braking. The engine is off, and the vehicle’s kinetic energy is captured by the motor and stored in the battery.

  • Mode 6. Battery charging with vehicle stationary, allowing long term use of electrical equipment such as air conditioning.

Efficient-C vs. Berlingo
Berlingo 1.6 HDiEfficient-CBenefit
Fuel consumption (urban) l/100km 6.7 3.7 45%
Fuel consumption (hwy) l/100km 4.7 4.0 15%
fuel consumption (comb.) l/100km 5.4 3.75 30%
CO2 g/km 143 99 30%
Max speed (mph) 99 106
0-62 mph (sec) 14.8 13.4

We are delighted with the results from this research project which demonstrates the potential for a step change in CO2 emissions reduction with a diesel parallel hybrid. The challenge now is for the motor industry and its suppliers to achieve the cost reductions required for the mass production of diesel hybrids to be considered.

—Alain Klein, Director of Hybrid Vehicles Development at PSA Peugeot Citroën

The team estimates that the current additional cost for the hybrid powertrain would be approximately £3,000 ($US5,600) over the cost of a conventional diesel vehicle.

The other projects selected in 2003 were the MG Rover Group working on a four-wheel drive IC engine-electric hybrid powertrain; ZyteK Automotive working with a diesel plug-in series-hybrid architecture (earlier post); Bertrand UK working on a hybrid powertrain with a contra-rotating flywheel energy storage; and Artemis Intelligent Power, working on a hydraulic hybrid powertrain.


Mike Weindl

Finally they did it! The first Diesel-Hybrid by a major
car company. Hope they bring it on the road soon!


In 1999 Ford announced their Prodigy designed within the PNGV program. It seated 4 people, got 70 mpg. and was a diesel hybrid. The plan was to produce the car by 2003. The new government for 2001 came in and the program was shelved. The other two US car makers also made similar cars under the PNGV program. I wonder how the US auto industry would be doing now if the plans to produce these cars was not shelved.

Eric S. Johansson

it occurs to me that the cost delta the between a conventional automobile and an alternative fuel/hybrid type vehicle represents a market-driven value of reducing one's carbon footprint. unfortunately, given that the carbon footprint cost of traditional vehicles is displaced to anonymous third parties, it puts the hybrid vehicle at an economic disadvantage.

One way to help remove this disadvantage is to add a carbon tax based on the average cost and carbon footprint deltas between traditional and hybrid vehicles. the carbon tax could and should be used to subsidize the migration to lower carbon footprint vehicles but we all know how likely it is for that to happen. :-)


It is all good stuff. It may take a few goes to get a decent diesel hybrid, but it should be a reality within 5 years or so.
No reason not to make it plug in as well once we get the batteries.
Nothing like $70 oil to spur innovation.

Harvey D.

Very good news. This seems to confirm that world leadership is progressively shifting from USA to Europe and Asia

Rafael Seidl

$6500 premium over and above the regular diesel engine. Ouch. Even at European fuel prices of ~$6/gal of diesel, this doesn't even make financial sense for small businesses that can amortize the purchase price but not the cost of fuel. The Berlingo cargo variant without the rear seats is a popular small delivery van.

Note that the regular starter motor was retained to allow the electric traction motor to be placed on the gear box side of the clutch for improved recuperation efficiency. This being Europe, an step-by-step transmission is used. Clutch and synchronization are automated to permit co-ordination of the tow motors. The electric motor presumably kicks in during gear shifts to limit the torque loss.


Currently, hybrids have the best well to wheel efficiency of any powertrains, including EV. Although EV has a better W to W efficiency than a conventional ICE, it has a lower efficiency than hybrids, whether they be gas or diesel.

Given the above premises (feel free to challenge them), doesn't this mean that we should stick with hybrids and not lower their overall efficiency by making them plug ins.

I recognize that their would be an oil savings, but I am more concerned with overall efficiency of fossil fuel use. If one is not concerned about fossil fuel use in general,e.g., coal, then plug ins might be the way to go --- assuming, of course, that we can lower their weight, increase their range, and lower their battery costs.


Diesel-Hybrid? Fine, but put it in a Porsche or Gallardo suit.
Life is to short to drive ugly Berlingos even at $16/gal.
Rafael Spin, take Navi + Leather + Xenon and you got your 6k premium. Sure it makes no financial sence if you cram a Berlingo with that technique. How far are Audi, BMW or Mercedes developments in this sector? Please give us insider infos. Oh, I forgot they just heard about hybrids. hehehe


The biggest advantage with the Plug-in hybrid is their affect upon land-use and development. Their limited, battery-only driving range encourages patronage of local economies. Their growth, in time, develops more destinations that are accessable without having to drive. The Plug-in Hybrid is the singular vehicle technology that can reduce dependence upon driving. Duh. Other means of travel, walking, bicycling and mass transit, far more energy efficent, become viable. We shouldn't be trying to eliminate the larger battery pack for that reason and many others. Such a power supply will prove invaluable in an emergency. Their weight lowers vehicle center-of-gravity, improving stability and handling - a perfect application for top-heavy SUVs.

The Plug-in Hybrid is hands down state of the art in transport.

john galt

What, limited range is the biggest advantage of the plug in hybrid? Wells, that is some weird trippin' conclusion you've came to. Okay, just put a 2 gallon tank on every ICE car, limiting trips to something like 60 miles a tank. Then limit the amount of fill ups through some form of smart card token used at the gas pump. Wouldn't this encourage people to limit travel to localities? Duh you say. Better yet, increase taxes for licensing and registration like Singapore, where the cost to purchase a Honda Civic is something like $60,000 US once you get it street legal (license, tax, registration, etc.) That should price lot's of people into walking and riding a bike. We are dealing with a automobile and highway centric society. Why do you think all the the effort is being demonstrated on this website to the quest for improving the automobile? As long as businesses are making money selling cars and SUVs, they are not going to dumb engineer them to shorten the range. The number of do gooders (myself being one) are a very small minority who voluntarily walk or ride a bike to reduce trips taken by automobile. Most people are too selfish and self absorbed to think otherwise. The mass of the bell curve will adopt plug-in's, etc. when they become an economically viable option versus the status quo.


Rafeal- A regular starter motor is not retained on this vehicle. Look again, it is a starter/generator. Not a regular starter at all.

tony chill

Another electro-blivit which is not needed.
1)costs too much
2) less reliable with the added sub-systems for diesel emissions
3)I bet full energy cycle( Manufact to grave) less efficient.
4) plus the drama of diesel fuel.

Just bring back the good'old VW diesel rabbit with maybe a mild hybrid, and I'll live with the drama.
And stop the emissioms reduction. Global warming is coming no matter what we do.


SJC, fyi...

Not all that glitters is gold.

It’s not really dead, just refocused.

“But the high-mileage concept cars built by the Big Three part of the program have proved, so far, to be a dead-end. They weren't clean-burning enough to meet U.S. pollution standards. And they would have been too expensive to build. "High cost is a serious problem in almost every area of the PNGV program," reported a committee of the National Academies of Science, which reviewed the effort in 2000”*

This program was replaced in Jan. 2002 by FreedomCar.
Under C-A-R (Cooperative Automotive Research), the Department of Energy and auto makers Ford, General Motors and Daimler-Chrysler will join in a public-private partnership to develop technologies for hydrogen-powered fuel cell vehicles that will require no foreign oil and emit no harmful pollutants or greenhouse gases.”*

*Per Business Week 2-22-06

Tony Chilling

Thank you George for the quote.
What approach did the National Academies want to recommend?
Is that where the Goverment got the fuel cell/hydrogen route?

Does the above quote look more realistic than this:
"public-private partnership to develop technologies for FUSION powered vehicles that will require no foreign oil and emit no harmful pollutants or greenhouse gases." ?


Interesting that they need to explain the six "modes". For every hybrid driver, it's pretty obvious that a combination of the six is what defines normal operation of a full hybrid. But maybe not everyone knows yet. :-)

By the way, nothing new here. Peugeot/Citroën already presented the same kind of stuff in a less ugly automobile, who emits only 90g CO2 per km as they say :

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