The Bentley Continental GT coupe and Flying Spur saloon are to come in for what looks like the mildest of mild mid-life facelifts next year. Autocar's spies caught these development mules out in the cold in Sweden earlier this week, and they are sporting at least one significant styling update; a redesigned front valance with a broader central air dam.Elsewhere on the car's exterior, changes have been kept to a minimum, a tactic favoured by car-makers like Bentley because it better protects the residual values of its existing cars. Styling and equipment updates inside the car could be more extensive, however. Expect various trim options introduced with the Diamond Series special editions, and the huge carbon-ceramic brake discs of the 60th anniversary GT, to transfer across to the standard car's catalogue.So if it's such a minor one, why bother with the facelift at all? Well, it could be because Crewe is upping the engine performance in both of its Continental models, and is having to provide better engine cooling capacity as a result.Both Bentley and parent company Volkswagen are known in the motor industry for the thoroughness of their approach to engine cooling. The 6.0-litre W12 powerplant that powers both cars was engineered with an unusually specific cooling target in mind; it had to have sufficient cooling capacity to keep the cabin at a steady 22 degrees centigrade while travelling at 186mph, in an ambient temperature of 50 degrees centigrade. That was for its first application in the VW Phaeton; it has since been applied, in twin-turbocharged form, to power Bentley's Continental siblings, for which the cooling requirements must be even more demanding. A larger front air dam would therefore allow Bentley to turn up the boost on its W12 without sacrificing any of the car's air-conditioned luxuriousness.When we put that prospect to Bentley, we were told that its policy was not to comment on future product. However, given that the Continental twins currently produce 552bhp each, we'd expect a tweak like this to allow Bentley to turn the wick up to 600bhp without a problem.