The chance to benchmark a car powered by Vauxhall’s new high-output version of its all-aluminium 1.6-litre diesel was too good to pass up – and it has produced some impressive results.
Even in estate form, the new Astra CDTi Biturbo recorded an 8.4sec 0-60mph acceleration average, managed 30-70mph through the gears in just 7.7sec and completed the same incremental sprint in fourth gear in 9.1sec.
In all three respects, that’s considerably quicker than the 148bhp Audi A3 2.0 TDI we sampled in 2012 and the 148bhp Mazda 3 2.2-litre turbodiesel figured in 2013 – which were both tested as hatchbacks.
Flexibility, or pulling power, is the engine’s big draw. That 258lb ft may not sound outstanding in isolation (although it’s a lot to conjure from just 1.6 litres), but the motor’s twin turbochargers allow it to be accessible from just 1500rpm.
There’s also less mass to move here than in rival wagons, meaning the Astra picks up speed from low revs strongly and with good throttle response by diesel standards. The A3 mentioned – which is pretty typical of 2.0-litre diesel hatchbacks on performance – took fully 3.4sec, or 27 percent, longer to get from 30-70mph in fourth.
A downsized diesel engine working hard enough to produce that kind of performance might suffer some compromise on refinement, but this engine runs the same compression ratio as its more economy-minded siblings and proved to be quieter than the 134bhp 1.6-litre diesel Astra hatchback we tested last year.
The difference in the cabin was worth three decibels at idle and at 30mph and two decibels at 50mph. The CDTi BiTurbo seemed smoother and quieter-running than its less powerful sibling subjectively, too.
It pulls cleanly and progressively up to 4000rpm, though, and has the right balance of tractability, refinement and fuel economy for a load-carrying family estate. You certainly wouldn’t trade any of those key assets for any extra high-rev operating range.
But you might expect a company capable of producing such a fine engine to give you slightly more progressive, positive-feeling controls than Vauxhall does with the Astra. The shift quality of the six-speed manual gearbox is light and poorly defined, the clutch equally light and spongy and the brake pedal spoiled by a dead zone of initial travel followed by inevitable grabbiness.