AUDI is uprating its big SQ7 and SQ8 performance SUVs fitting them with twin-turbo V8 petrol engines that deliver more power and sports car-like performance.

The new engines replace the previous diesel offering in the two cars and in the case of the latest models it results in a 0 to 60 time of just 4.1 seconds. Top speeds are restricted to 155mph.

Prices are said to be in the region of £78,000 for the seven-seat SQ7 with the more sporty SQ8 coming in from around £83,000.

Both cars will be available in the autumn and come with air sports suspension and all-wheel-steering as standard.

On high specification Vorsprung models of the SQ8 an active roll stabilisation system is also being fitted.

Compared to the earlier diesel engine, power output is up by some 72ps to 507ps.

Andrew Doyle, director of Audi in the UK, said: "Petrol engines are becoming increasingly prevalent in the high performance SUV segment on the strength of the great efficiency gains made in recent years, and we are acknowledging that trend with these upgraded models.

"By equipping the SQ7 and SQ8 with a new TFSI unit which enables them to break through the 500PS barrier for the first time and deliver even more stirring performance we are ensuring that they remain firmly rooted among the front runners in the pack."

An eight-speed tiptronic transmission and quattro permanent all-wheel drive are also standard features while the all-wheel-steering, which was previously reserved for only for the Vorsprung versions of the SQ7 and SQ8, is fitted across the range.

At low speeds the system it turns the rear wheels by as much as five degrees in the opposite direction, reducing the turning circle to improve manoeuvrability.

At speeds of 37mph and above, the wheels turn slightly in the same direction to boost stability during fast changes of direction.

The new SQ8 Vorsprung has electromechanical active roll stabilisation and a sport differential which reduce roll during fast cornering and improve handling characteristics.