What is it?
Subaru’s third-generation flat-four engine makes its debut in this 2011 Forester, the boxer motor benefitting from a sump-up rework principally focused on reducing emissions, and improving economy.
Increasing its torque output has been the key, a goal that has induced a total redesign to accommodate a longer, torque-promoting piston stoke within the same dimensions as the previous engine.
Preserving the motor’s size has been no small challenge, Subaru aiming to increase the cylinders’ stroke without making it any wider, which would force costly changes to its cars’ body structures. Reducing the size of the heads has forced narrower valve angles, but the smaller combustion area resulting produces a more efficient burn, aided by variable valve timing.
Internal friction has been reduced by 28 per cent, these mods producing the same 148bhp, 10 percent better economy and a fractional increase in peak torque, which still occurs at a high 4200rpm. Good news for longevity is the switch from toothed-belt to chain-driven timing gear.
What’s it like?
The Forester also get minor tweaks signalled by a fresh grille intended to make it appear more SUV-like, while comfort is improved by modified dampers claimed to reduce roll, enhance stability and smooth the ride. There’s new upholstery and an improved dashboard finish - though it’s still constructed from hard-feel plastics – and high-trim XS models get luminescent dials.
But the new engine is by far the biggest improvement. It’s smoother, sounds far less strained and delivers solid acceleration in the first two gears if not third, whose rangier gearing serves relatively flaccid performance unless the engine is pulling 3800rpm or more.
Acceleration in the upper ratios is often leisurely enough to require some downshifting, although the boxer engine’s lightly eager warble is compensation – if you’re in the mood, it’s fun to get the best from this smoother flat-four. Revs that tend to hang when you’ve released the accelerator have you lifting off a little earlier than you’d expect during gearchanging.