Porsche is set to crown its upcoming Macan line-up with a fiery 370bhp-plus Turbo-badged range-topper that will establish a new performance 4x4 niche when it hits UK showrooms in October next year.

In the absence of dedicated performance variants of rivals such as the BMW X3 and Range Rover Evoque, Porsche expects the Macan Turbo to carve out a niche as the fastest and most dynamic model in the class — something that it achieved with the bigger Cayenne.

The top-of-the-line Macan will be the first car powered by Porsche’s still-secret new twin-turbocharged V6 petrol engine, details of which are revealed here for the first time.

Developed in-house at Porsche’s R&D centre in Weissach, Germany, the twin-turbo V6 is understood to have a 90deg vee and a capacity of 3.0 litres. It is believed to be a variant of the 3.6-litre V6 that powers entry-level Cayenne and Panamera models.

Peak power and torque are said to be in the region of 370bhp and 400lb ft thanks to twin sequential Borg Warner turbochargers, an air-to-air intercooler system and other internal modifications, including a lower compression ratio than that of the normally aspirated 3.6-litre engine. That’s an increase of about 80bhp and 105lb ft over the non-turbo 3.6.

The Macan is based on the Volkswagen Group’s next-generation large front-wheel drive and four-wheel drive platform, known as MLB. As a result, the new V6 is mounted longitudinally and drives all four wheels through an Audi-engineered, Porsche-tweaked Torsen torque-sensing differential. The rear axle features electronically controlled torque vectoring for the rear wheels to improve turn-in and cornering grip.

The choice of transmissions will be a standard seven-speed manual (a development of the latest unit in the 911) or an optional seven-speed, dual-clutch PDK automatic (also 911 derived).

The powertrain has already been undergoing intensive testing under the bonnet of inconspicuous-looking Audi Q5 and Cayenne prototypes.

Porsche’s engineers have also been working hard to provide the Macan with a more sporting character than its Q5 twin by comprehensively retuning the underpinnings.

So although the mechanical componentry — including strut front and multi-link rear suspension — is shared, the Macan gets unique elasto-kinematics thanks to specific bushes, springs and damping rates.

The same goes for its electro-mechanical steering system, which has benefited from Porsche’s experience in tuning similar hardware now used across its line-up.

“We’ve surprised even ourselves,” said Porsche development boss Wolfgang Hatz. “It drives incredibly well and, from what we’ve seen from the competition, will be the most sporting car in its class.”

Among the developments that Porsche is working on is a unique, wide-track front axle and rear-drive torque bias from the Torsen centre differential.

At the same time, Porsche insiders suggest that their new junior SUV will boast sufficient ground clearance to ensure that it delivers what they describe as “confident off-road ability”. This is despite the lack of low-range gearing and locking differentials.

As confirmed in an official sketch of the new model made public in February, the Macan will feature a five-door layout similar to that of the Cayenne. It will be the fifth main model line for Porsche, joining the existing Boxster/Cayman, 911, Cayenne and Panamera lines.

Considered a crucial component in chairman Mathias Muller’s plans to lift Porsche’s annual sales above 200,000, it will be assembled at the German car maker’s Leipzig factory alongside the Cayenne and Panamera.

The Macan is somewhat smaller than the Cayenne, with an overall length of about 4.6m, width of 1.89m and height of 1.65m. That’s about 210mm shorter, 50mm narrower and 40mm lower than its bigger brother.

It will have a modern-looking cabin closely related to the Cayenne’s, complete with trademark features such as the dashboard-mounted starter, sited to the right of the steering wheel on UK models.

With seating for up to five, the Macan is tipped to offer 520 litres of luggage volume, slightly less than an X3 or Q5.

As well as launching the new twin-turbo 3.0-litre V6 petrol engine, the Macan will be distinguished for another reason. It will be the first Porsche since the 968 ceased production in 1995 to be sold with a four-cylinder engine.

Nothing is official yet, but Porsche sources acknowledge that their new model will follow the Q5 in offering a base 2.0-litre turbo petrol motor.

Set to become the volume seller of the line-up, the four-cylinder petrol unit is likely to deliver about 220bhp in the base Macan — sufficient for projected 0-62mph acceleration of 7.5sec and a 143mph top speed.

It won’t be the only four-cylinder engine for the Macan, though. Also planned is a 190bhp 2.0-litre turbodiesel that’s said to have recorded 45mpg in testing — a figure that promises to make it the most economical Porsche model yet to make series production.

In line with other Porsche models, the Macan will come as standard with a range of fuel-saving features, including automatic stop-start, brake energy recuperation, on-demand operation of engine ancilliaries and, in higher-end models, a ‘sailing’ function that uses a clutch to disengage the engine on a trailing throttle and during descents.

Sitting just below the Macan Turbo will be an S model powered by the same 295bhp normally aspirated 3.6-litre V6 used in the Cayenne.

It will be joined by a Macan Diesel S using the 250bhp 3.0-litre V6 turbodiesel found in the Panamera.

Also planned, primarily to boost North American sales, is a Macan Hybrid running the same parallel petrol-electric drivetrain used in the Q5 Hybrid. It mates a 208bhp turbocharged 2.0-litre, four-cylinder petrol engine with a 54bhp electric motor.

Porsche is also in negotiation with Audi to secure the latter’s new 309bhp twin-turbocharged 3.0-litre V6 diesel, recently launched in the A6, for a possible seventh model: the Macan Diesel Turbo. This engine is due to power a hot SQ5 model from September.

However, Audi officials, already smarting from having to share the Q5 underpinnings with Porsche, are said to be resisting pressure to share this diesel with the Macan. Contracts have already been signed for it to go into the Panamera and Cayenne.