Open heart surgeryThe Volkswagen XL1 is a super-efficient diesel plug-in hybrid that, sadly, will only be made in very limited numbers. But VW doesn't want to let what it learned with the XL1 go to waste, so it did some surgery and transplanted the advanced powertrain into another one of its very efficient small cars, the versatile Up!, which has also been converted to run on compressed natural gas (CNG), and on pure electricity.
As you can see above, the powertrain which was mostly at the back of the XL1 (except the battery) ends up at the front of the Twin Up!, except for the battery which in this model sits at the back. This makes the 4-seat Up! achieve a combined fuel consumption of 1.1 liters per 100 km, which converts to 214 MPG US, though that's on the NEDC cycle, not the EPA one. That's only 27 g/km of CO2 emissions!
Here's another view of the powertrain. VW explains: "The twin up!’s 55 kW (75 PS) drive unit—consisting of a 35 kW (48 PS) 0.8-liter TDI Clean Diesel engine, a 35kW electric motor, a seven-speed DQ200 DSG transmission, and the power electronics—is mounted at the front of the car. Installed at the back, behind the rear seats and under the trunk, is the 'fuel storage system': an 8.6 kWh lithium-ion battery, the 12-volt battery for the electrical system, and an 8.7-gallon fuel tank."
The Twin Up! concept is also very aerodynamic, with a drag coefficient of only 0.30 and relatively low weight (2657 pounds).
Now if only VW moved it from "concept" to available everywhere at an affordable price.
By the way, VW insists on writing "up!" and "twin up!" without capitalizing the words, but that's just confusing and looks wrong, so I took the liberty to capitalize them. Hopefully VW's goons don't come knocking on my door...