Porsche's new baby Boxster

Porsche is preparing to roll out a new entry-level sports car that will help underpin the maker’s long-term future as part of the giant VW Group.

Dubbed by some insiders as the “new 356”, the mid-engined machine will not, however, be a bargain basement model, despite initial rumours to the contrary. Given the final green light, it would cost from about £33,000 in today’s money.

See the 356 artist's rendering in hi-res

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Instead, the 356 is expected to be based on a new steel and aluminium platform that’s being developed by Audi for its own R4 mid-engined sports car.

Work on the R4 is already well advanced, and it’s due to launch in June 2011. However Porsche’s version of the car, which won’t arrive before late 2012, is expected to be significantly different.

Aside from its unique styling inside and out, the 356 is also expected to be one of the first Porsches to be fitted with a forced-induction flat-four engine that is currently under development.This unit will also help ensure the Porsche and Audi have sharply different characters, even though the two cars have the same basic architecture.

As well as their common structure, the two cars will share many other costly sub-systems. These include the electrical architecture, climate control system, basic suspension layout, electronic chassis systems and innumerable hidden parts, such as seat frames and door locking mechanisms.It’s also likely that the Porsche will share its transmission with the Audi because the longitudinal unit used in the 911 and Boxster is thought to be too costly.

Not much is known about the flat-four engine at this stage, but Porsche sales and marketing boss Klaus Bening told Autocar earlier this year “That there is a clear trend towards downsizing, using smaller powerplants and supercharging. We will find our own conclusion to downsizing”.

Using today’s flat six as a starting point, a new flat-four engine would come in at just over 1900cc and could use either a light-pressure turbo or a supercharger. The light-pressure turbo set-up is already said to be under development for 2012’s 911.

It’s highly likely that such a unit would be good for about 250bhp. That’s virtually the same as today’s entry-level Boxster, although fuel economy would surely be better.

However, there’s little chance that the 356 and Boxster will clash because, according to one rumoured product plan, the next-generation Boxster and Cayman could be moved sharply upmarket.

Porsche has a financial problem with today’s Boxster/Cayman/911 line-up. According to an analyst’s report seen by Autocar, the cost of the components that make up one of the flat-six models is perilously close to the base price of a Boxster.