This Jaguar F-Type cabrio is thought to be engineering development prototype for Jaguar Land-Rover’s all-new four-cylinder turbocharged engine.

It’s also possible that this mule has an experimental all-wheel drive system. The raised bonnet could a result of the front differential fitted under the engine. Close examination of the scoops shots also seem to show that the front wheels appear to be driven.

Jaguar sources have not hinted at an all-wheel drive F-Type, but the new all-wheel drive XF and XJ models, equipped with a turbocharged 3.0-litre V6 petrol engine, have been a significant sales success in the US. The V6 engine is the only Jaguar powerplant engineered for all-wheel drive at present.

The car pictured not only has a slightly different bonnet, with a slightly raised centre section, but its also clearly has a prototype exhaust system.

With an inline four-cylinder engine only having a manifold on one side, a new exhaust has to be designed and detail work such as optimising the back pressure has to be carried out.

Last year Ian Hoban, the F-Type vehicle line director, was quoted as saying that there were a "whole host" of powertrains and drivelines that could be fitted into the F-Type architecture. He also said he saw "great potential" in fitting a high-output turbocharged four-cylinder engine in the F-Type.

Jaguar has never before built a four cylinder sports car (although there were plans for a four-cylinder version of the original XK120) but the new generation of turbocharged engines are capable of extremely high outputs in both power and torque.

In any case, four-cylinder F-Type will also be slightly lighter overall than today’s V6-powered version and should benefit from improved agility because the new ‘Hotfire’ engine will sit further back in the car’s nose and put less weight over wheels. Fuel economy should also see a noticeable improvement.

The use of a high-powered four-cylinder engine in conjunction with a four-wheel-drive system could also go some way to compensating for the additional weight penalty of fitting a larger-displacement engine and four-wheel-drive drivetrain.

However, any four-pot F-type is not likely to arrive before late in 2015. According to Wolfgang Ziebart, JLR’s Engineering Director, says that the first pre-production versions of the new engines will be diesel and will roll down the line at the new i54 factory this spring. He also claims that the new engine family will set benchmarks in terms of ‘efficiency, weight and power’.

When full-scale production of the new engine begins at the end of this year all the engines will be diesels for the new baby Jaguar, which launches in Europe before it launches in the petrol-friendly US market.

The petrol Hotfire engine is expected in the second half of 2015, so any entry-level F-Type is unlikely to announced before the Frankfurt motor show in September 2015.