Subaru finally has a diesel-and it's the first boxer turbodiesel in a passenger car. Ever. The diesel option not only gives the company a real presence in Europe, but the engine's excellent fuel economy-near an estimated 50 mpg on the highway-will make it easier to comply with the upcoming CAFE legislation. Even though it won't be sold in America for another two years, Subaru gave us the opportunity to try the diesel out in Euro-spec Legacy sedan/wagon and Outback models, which will be officially revealed at the Geneva motor show in March just before they go on sale in Europe.
Powering the trio is a 2.0-liter DOHC horizontally opposed flat-four common-rail diesel putting out 148 horses and 258 pound-feet of torque. (VW's 2.0-liter turbodiesel, coming later this year, provides 140 horsepower and 235 pound-feet.) Its acceleration won't break any records, but its excellent torque, available at a measly 1800 rpm, ensures that this car effortlessly goes up grades in fifth gear and has no trouble merging at freeway speeds. The boxer layout provides the same advantages as in Subaru's gas-powered offerings: lower center of gravity, reduced vibration, lighter weight.
The decision to stay with the boxer layout may have been an easy one for Subaru, but turning that into reality was more complicated. The challenge was to make the engine strong enough to handle the increased demands of diesel without outgrowing the engine bay. Its 16.3:1 compression ratio required a longer stroke (now 3.39 inches compared with the 2.0-liter gas four's 2.95; the bore was reduced by 0.23 inch), a problem solved with Subaru's asymmetrical connecting rod and crankshaft design, seen in the Tribeca's 3.6-liter flat-six. This allows for the longer stroke without making the engine significantly wider. The short, rigid crankshaft also helps reduce vibration and noise as well as engine length.
Subaru moved the variable-nozzle turbocharger to the bottom of the engine (mounted between the exhaust ports and catalytic converter), which improves emissions and helps keep the center of gravity low. The intercooler is still on top of the engine near the intake manifold, with longish hoses connecting the turbo to the intercooler-yes, the hood scoop is functional. Emissions are handled by an EGR system, particulate filter, and an oxidation catalytic converter, making the engine EURO IV compliant. (Testing has not yet been conducted for the U.S., but a urea-injection selective reduction catalyst is likely to be required here.) Backing the turbodiesel in our testers was a new five-speed manual transmission, geared specifically for diesel applications. While Subaru is considering a six-speed manual, expect this and an automatic to be offered in the U.S. Some changes were made to accommodate the new powerplant, including the use of liquid-filled engine mounts, modified spring rates, larger CV joints, electric power steering, and larger front disc brakes.
