Like several other manufacturers that sell cars in Europe, Volkswagen has a growing lineup of vehicles that run on natural gas and liquid petroleum gas (LPG), or autogas as it is commonly called in Europe. The newest models are the Golf BiFuel and Passat TSI EcoFuel.
The Golf BiFuel uses a 97 horsepower, 1.6-liter four-cylinder engine that can run on either gasoline or LPG. Autogas is readily available throughout Europe, and Germany alone has about 4,500 LPG filling stations. Drivers of the BiFuel Volkswagen can chose to run on either LPG or regular gasoline using a simple switchover system.
The Golf BiFuel uses Volkswagen's first factory-installed LPG system. According to Volkswagen, the Golf BiFuel system offers significant advantages over aftermarket conversions often used by competitors. The most important: the Golf BiFuel's engine was designed specifically to run on LPG so it is more durable than a converted gasoline engine. Plus, the car has been crash tested with both gasoline and LPG fuel tanks installed as a total system, meaning greater safety.
With its space-saving installation in the spare wheel recess, the LPG tank holds 41 liters of autogas at 8 to 10 bar (1175 to 1475 psi). The gasoline tank holds 55-liters (14.5 gallons). The Golf BiFuel consumes 9.2 liters of LPG per 100 kilometers on average with 149 g/km CO2 emissions. This provides a range of about 420 kilometers (261 miles) on LPG alone. On gasoline, it uses 7.1 liters of unleaded gasoline per 100 km (33 mpg). Using both fuels it has a range of 1,100 kilometers (684 miles).
The Passat TSI EcoFuel is powered by a turbocharged direct-injection, 1.4-liter 148 horsepower TSI engine designed for natural gas operation. While it does have a small gasoline tank, its purpose is just to serve as a fuel reserve if natural gas runs low.
Since natural gas does not provide any supplemental lubrication and the pressures are greater, the valves, piston rings, and pistons were hardened or reinforced. The turbocharger is also smaller and special gas blow-in nozzles are integrated in the induction pipe. A newly developed control module manages the tuning and switchover between the two operating modes.
The engine features both a supercharger and turbocharger that operate sequentially to provide relatively high power outputs from a small displacement engine. On natural gas, this Passat accelerates to 100 km/hr (62 mph) in 9.7 seconds and has a top speed of 210 km/hr (130 mpg). This is impressive performance for a car running on natural gas.
Fuel consumption for the Euro-5 compliant vehicle is 4.38 kilograms natural gas per 100 kilometers, with CO2 emissions of 119 g/km. With 22 kilograms of CNG stored under the vehicle floor in three tanks plus 31 liters (8.2 gallons) of gasoline, the Passat 1.4 TSI EcoFuel can cover a distance of nearly 900 kilometers (559 miles). By itself, the natural gas supply is enough for a range of 500 kilometers (311 miles).
The Passat and Passat Variant TSI EcoFuel will be available in Europe early in 2009 with either a standard 6-speed manual transmission or an optional 7-speed DSG, the first DSG for front-traverse installation. It is also the first with a dry sump. This not only saves considerable weight and improves the efficiency of the system, but also makes the new gearbox more compact.
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