Smaller engine gives Six bigger appeal

Do you want a BMW 6-series? Really want one in the pit-of-your-stomach way that sports cars are meant to be desired? It’s been around for long enough to become a familiar sight, yet remains one of the great automotive opinion splitters – is it a looker or a crooker? Time still hasn’t allowed us car buyers to fully decide: in any given sample of five people you’ll find one completely in favour, one violently opposed and three left scratching their chins.

For the faithful, good news comes with the arrival of the 630i, making the realisation of the dream £5195 more achievable when compared to the V8-powered 645 Ci (£45,255 against £50,450). The 630i is also the first chance we’ve had to drive the new BMW 3.0-litre six-cylinder engine that will eventually replace the existing 3.0-litre powerplant.

And this is a seriously clever motor, even by BMW’s already high standards. Like the V10 in the M5, it’s built on a strength-giving ‘bedplate’, and the crankcase is constructed from magnesium and aluminium composite – reckoned by Munich to reduce weight compared to a conventional cast-iron block by 43 per cent. Alloy cylinder heads with hollow camshafts mean the engine tips the scales at just 121kg, making it the lightest six-cylinder production engine in the world.

It also features VANOS variable valve timing, a second-generation Valvetronic system (which does away with the throttle butterfly to improve economy and emissions) and even an electric water pump, which reduces power loss by 80 per cent compared to a conventional mechanically driven one.

The statistics are impressive: 255bhp (24bhp up on the existing 3.0-litre engine) accompanied by 221lb ft of torque, with 199lb ft of that available from just 1500rpm. The manual coupé version uses just 31.4mpg on the combined cycle and emits 216g/km of CO2.

On the roads around southern Spain the engine immediately feels right: responsive, keen to play and pulling with gutsy determination even from low revs. Fears that this is a cheapo small-engine special (no names, Mercedes CLK 200) are dispelled before we’ve even left the car park. 

It’s a smooth spinner, but without the slightly hesitant, heavy-flywheel feel of the existing engine. And it sounds good: a nice, whirry mid-range becoming increasingly yowly as the tacho needle sweeps round its arc. Which it tends to, thanks to the way the engine spears to its 7000rpm red line. It clearly enjoys being spanked every bit as much as you like administering the slipper.

The rest of the dynamic package isn’t in quite the same league, thanks in large part to the run-flat tyres. There’s no problem with grip levels, which are appropriately high, but ride quality feels uncomfortably choppy on rougher road surfaces, especially with the optional Dynamic Drive electronically controlled anti roll-bar system.

The optional six-speed automatic gearbox also seems to suffer from a lack of confidence in the engine’s prodigious torque, being far too keen to deliver unnecessary part-throttle kick-downs. Fortunately, the snicky six-speed manual is as good as ever.

The 630i is a good car, then, but not as impressive as the new six-cylinder engine.

Mike Duff

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