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Volkswagen to debut XL1 PHEV prototype at Qatar Motor Show; fuel consumption of 0.9 L/100 km (261 mpg US)

The XL1 prototype PHEV. Click to enlarge.

Volkswagen is staging the world debut of its XL1 diesel plug-in hybrid electric vehicle (PHEV) prototype at the Qatar Motor Show this week. The prototype, representing the third evolutionary stage of Volkswagen’s 1-liter car strategy (earlier post), features combined fuel consumption of 0.9 L/100 km (261 mpg US), according to VW.

The new Volkswagen XL1 attains a CO2 emissions value of 24 g/km, due to a combination of lightweight construction (monocoque and add-on parts made of carbon fibre), very low aerodynamic drag (Cd 0.186) and a plug-in hybrid system consisting of a 0.8L two-cylinder TDI engine (35 kW / 47 hp), E-motor (20 kW / 27 hp), 7-speed dual-clutch transmission (DSG) and lithium-ion battery. The XL1 prototype has an all-electric range of up to 35 kilometers (22 miles); total range is approx. 550 km (342 miles) with a 10 liter fuel tank.

Hybrid system. The entire hybrid unit is housed above the vehicle’s driven rear axle. The actual hybrid module with electric motor and clutch is positioned between the TDI and the 7-speed DSG; this module was integrated in the DSG transmission case in place of the usual flywheel.

The high voltage energy flow from and to the battery or E-motor is managed by the power electronics, which operates at 220 Volts. The XL1’s body electrical system is supplied with the necessary 12 Volts through a DC/DC converter.

The E-motor supports the engine in acceleration (boosting), and can also power the XL1 prototype on its own for a distance of up to 35 km (22 miles). In this mode, the TDI is decoupled from the drivetrain by disengaging a clutch, and it is shut down. Meanwhile, the clutch on the gearbox side remains closed, so the DSG is fully engaged with the electric motor.

The driver can choose to drive the XL1 in pure electric mode (provided that the battery is sufficiently charged). As soon as the electric mode button on the instrument panel is pressed, the car is propelled exclusively by electrical power. Restarting of the TDI uses “pulse starting”: while driving, the electric motor’s rotor is sped up and is very quickly coupled to the engine clutch. This accelerates the TDI to the required speed and starts it.

When the XL1 is braked, the E-motor operates as a generator that utilizes the braking energy to charge the battery (battery regeneration). In certain operating conditions the load shared between the TDI engine and the electric motor can be shifted so that the turbodiesel is operating at its most favorable efficiency level.

The gears of the automatically shifting 7-speed DSG are also always selected with the aim of minimizing energy usage. The engine controller regulates all energy flow and drive management tasks, taking into account the power demanded at any given moment by the driver. Some of the parameters used to realize the optimum propulsion mode for the given conditions are accelerator pedal position and engine load, as well as the energy supply and mix of kinetic and electrical energy at any given time.

The 0.8-liter TDI was derived from the 1.6 liter TDI, which drives such cars as the Golf and Passat. The 0.8 TDI exhibits the same data as the 1.6-liter TDI common rail engine in terms of cylinder spacing (88 mm), cylinder bore (79.5 mm) and stroke (80.5 mm). In addition, the XL1’s two-cylinder and the mass produced four cylinder share key internal engine features for reducing emissions. These include special piston recesses for multiple injection and individual orientation of the individual injection jets.

The TDI’s aluminium crankcase was constructed to achieve high rigidity and precision, which in turn leads to very low friction losses. With the goal of reducing emissions, exhaust gas recirculation and an oxidation catalytic converter as well as a diesel particulate filter are used. Equipped in this way, the 0.8 TDI already fulfils the limits of the Euro-6 emissions standard.

Also designed for efficiency is the vehicle’s cooling system. Engine management only cools the TDI by activating an externally driven electric water pump when engine operating conditions require it. This cooling system includes an automatically controlled air intake system at the front of the vehicle to reduce cooling system drag. This thermal management strategy also contributes towards reduced fuel consumption.

A second electric water pump, which is also used only as needed, circulates a separate lower temperature coolant loop to cool the starter generator and power electronics.

Design. Despite the very high levels of efficiency, developers were able to design a body layout that offers greater everyday practicality, incorporating side-by-side seating rather than the tandem arrangement seen in both the first 1-liter car presented in 2002 and the L1 presented in 2009. In the new XL1, wing doors make it easier to enter and exit the car.

The new XL1 is 3,888 mm long, 1,665 mm wide and just 1,156 mm tall. These are extreme dimensions. The Polo has a similar length (3,970 mm) and width (1,682 m), but it is significantly taller (1,462 mm). The height of the new XL1 is about the same as that of a Lamborghini Gallardo Spyder (1,184 mm). In other words, the XL1 is as long and wide as a Polo, but with a low profile like a Lamborghini.

Material. Large sections of the new XL1’s body consist of carbon fibre reinforced polymer (CFRP); the prototype weights 795 kg. Of that, 227 kg represents the entire drive unit, 153 kg the running gear, 80 kg the equipment (including the two bucket seats) and 105 kg the electrical system. That leaves 230 kg, which is precisely the weight of the body.

A total of 21.3% of the new XL1, or 169 kg, consists of CFRP. In addition, Volkswagen uses lightweight metals for 22.5% of all parts (179 kg). Only 23.2% (184 kg) of the new XL1 is constructed from steel and iron materials. The rest of its weight is distributed among various other polymers (e.g. polycarbonate side windows), metals, natural fibres, process materials and electronics.

Specifically, the monocoque with its slightly offset seats for driver and passenger and all exterior body parts are made of CFRP. The layers of carbon fibre, which are aligned with the directions of forces, are formed into parts with an epoxy resin system in the aRTM (advanced Resin Transfer Moulding) process. This material mix produces an extremely durable and lightweight composite.

Volkswagen successfully found a cost-effective way to mass produce CFRP parts in sufficient volumes as early as 2009 in the framework of the XL1 development project.



OK, but probably expensive to build and only a two seater.
I wonder what would happen if you made it a 4 seater (even a 2+2) and substituted aluminium for carbon fibre
a: Build costs
b: mpg or CO2 levels
c: Performance

Plus why use a 10L fuel tank - why not push the boat out and go for a 20 or 30L tank? You would hardly notice the extra weight and bulk, but the range would be spectacular. You could differentiate it from electric cars with the huge range.


When the car is in electric mode the mileage is infinity because you are not using any fossil fuel. So if you drive under 22 miles the mileage is huge. However, if you drive only on fossil fuel, the mileage is a great deal less. Combining the two and claiming this kind of mileage is cheating. The only thing that makes sense is to state the fossil fuel mileage only and claim the electric mode distance separately.


I want one.


Interesting that this is being unveiled at the Qatar motor show.

Is there a message there? "If you don't keep the supply of oil up and the price down, we are not without options."

Nick Lyons

OK, so it goes 22 miles on electricity, then another 320 miles as a hybrid burning 10 liters of diesel. That's 32 miles/liter or 121 MPG. (32/0.2642).

Not too shabby. I wonder if acceleration is reasonable.

As an aerodynamic 2-seater, it's sort of the spiritual successor to the original Honda Insight.


Might they not have done better with EREV and use the .8L to spin the gen? With the light weight a genset should be able to produce enough energy to keep the wheels turning electrically.

Then again, let's see what this looks like IF it ever comes close to production. A cool idea that DOES look like the Insight.


The car that won the X-Prize had a tiny 1-cylinder engine, but no regenerative braking and got near 100 mpg in combined cycle driving. This is similar but with regenerative braking...albeit...even more expensive components.


Finally, somebody may build an up to date light weight car to reduce liquid fuel consumption. Of course, various shapes and sizes could also be built to do 200 empg instead of 261 empg. Even a larger 100 empg unit would represent a welcomed change from current gas guzzlers.

Will there be enough room for our 350+ lbs driver and passenger.

A hand to VW.


"fuel consumption of 0.9 L/100 km (261 mpg US)"

"Volkswagen successfully found a cost-effective way to mass produce CFRP parts in sufficient volumes as early as 2009 in the framework of the XL1 development project."

Wow.. next, a 2+2.


Not happy the car is a plug in now. I would have been more satisfied with the tandem 1+1 hybrid that was "only" going to get 150mpg. Making the frontal area much bigger, and then turning it into a Chevy Volt is a cheesy marketing trick to inflate the mileage numbers.

Volkswagen should produce a cheap 1+1 version for those of us who don't want to pay for plug-in hybrid technology or manipulated EPA mileage figures.


I've always wondered why most cars don't have rear fairings and a body pan- so much light-weighting going on to boost mileage a tiny bit, you'd think a little aerodynamic consideration would be mandatory even small things like aerodynamic wheel covers can make a difference.

Roger Pham

Superb design in every aspects, from high technology to aesthetic! The Parallel-serial Hybrid design with a gear-shift transmission at the end is exactly what I would like to see in an HEV, as the most efficient way and most economical way to harness all the powers from each power unit, ICE and Electric, to the wheels. Hat off to VW!

Making this car into a 4-seater should be fairly easy, and I'll bet that the mpg on the ICE mode would still be above 100 mpg...enough to more than qualify for the X-prize.

For those who are concerned about the cost of PHEV technology, please be reassured that the size and hence the cost of the PHEV drive train will be 1/2 to 1/4 that of the Volt, due to the low weight, lower overall power, and lesser all-electric range (1/2 that of the Volt--So, 1/2 the AE range and 1/2 the weight and 1/2 the power equal 1/4 the cost)!

This should be the future direction of PHEV: keep 'em light, keep'em short-range AE, keep 'em affordable, and sell 'em by the millions...


If we extrapolate this car in size somewhat and give its engine one extra cylinder, it is good bye for Prius & Co...


Love the styling and aerodynamics, but a bit disappointed to see how heavy it is now.

795 kg is hardly any different from VW's Lupo 3L, which was 830 kg, seated twice as many people (4/5 seats) and was on sale from 1999 to 2005.

It had a 61 hp 1.2 litre 3-cyl TDi and managed 78 mpg (US).

The larger Audi A2 3L weighed only 825 kg and gave the same 78 mpg.

Ole Grampa

Volkswagen engineers: this is a triumph of colossal proportions. The balance you have struck here is spot on. Do not take the above comments seriously, not even the weight comment above, because you do not want to get hit driving a car that is any lighter.
At the moment I drive a Jetta TDI which saves me $50/week
... a car that puts other makes to shame. This new car pretty much flattens the competition.

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