2008 Subaru Tribeca debuts new 6-cylinder 3.6-litre H6 engine

The all-new engine delivers more power, more torque, improved fuel economy and emissions performance - all on regular petrol.

The larger engine displacement increases engine torque to 247 lb.-ft. at 4,400 rpm, and horsepower to 256 at 6,000 rpm, providing improved low-end torque without sacrificing high-rpm power. The new engine package, which adds displacement without adding overall size, not only maintains excellent emissions levels but delivers improved fuel efficiency in real world driving situations.

The new Tribeca is very powerful, and Subaru has also improved the driving feel by carefully tuning every element of the powertrain that connects with the driver, from the transmission to the power steering. The result is an increased sense of controlled performance that drivers demand in a premium SUV.

In addition to generating more overall power, the engine also increases available torque in the low- to mid-range engine speed, which improves fuel efficiency as well as performance.

To achieve these goals without affecting engine packaging, a unique shortened con rod was created to allow for a new and larger displacement engine without increasing the physical dimensions of the power unit; keeping the deck height of the engine the same, the Tribeca is also able to maintain its excellent low centre of gravity.

Improved cooling efficiency - needed to achieve the use of regular fuel - was achieved through a new common rail cooling system that individually cools each cylinder with water separation chambers rather than allowing water to flow from cylinder to cylinder. This allows for increased engine efficiency and standardized timing for all cylinders.

The new 3.6-litre engine features Active Valve Control System (AVCS) variable valve timing on both the intake and exhaust valves (the 3.0-litre engine had AVCS on the intake side only).

Redesigned exhaust, cooling and power steering systems are carefully matched to the new engine's output and torque curve, to further enhance Subaru's signature balanced handling, and improvements to the drivetrain layout, sprocket dies and cam chain pitch mean the new engine is also quieter.

The new 3.6-litre engine is connected to a 5-speed automatic transmission with SPORTSHIFT that features an all-new torque lock-up converter and a new transmission control unit. The result is faster gearshifts with less lag time and smoother, more linear acceleration.

New shift logic also improves performance in hilly terrain. The new shift control system uses the car speed and accelerator opening to determine available driving power while simultaneously calculating the optimum gear position for the road gradient. This not only results in fewer unnecessary gear shifts when climbing or descending grades, but also results in a further improvement to fuel economy.

The transmission drives through the Subaru Variable Torque Distribution (VTD) Symmetrical All-Wheel Drive system. Enhancing the AWD system are standard Vehicle Dynamics Control (VDC) and four-wheel traction control system (TCS).