Audi is about to kick off a new expansion phase in an effort to establish clear leadership of the world premium car market by 2020.

It aims to achieve this by increasing its model count from 50 to 60, helping it push its current record volume ahead another 20 percent to two million units a year.

Speaking at an event in Copenhagen to mark 25 years of TDI diesel engines yesterday, Audi chairman Rupert Stadler said the company would begin a new expansion phase this autumn to reach its aggressive new targets — which would depend heavily on diesel sales continuing to boom.

Underscoring its continuing dependence on diesel sales, the company is close to approving a new range of high-performance diesel models, possible carrying the RS badge, following a positive reception for its recent 380bhp RS5 TDI-e concept car.

The new range could be topped with a limited edition supercar in the Le Mans mould, an idea first mooted 18 months ago.

The company has so far built 7.7 million TDI-powered cars, he said, and four in every 10 Audis was a diesel. In some markets, the diesel take-up was as high as 90 percent; even in the diesel-sceptical USA, take-up was around 30 percent and rising.

Audi's dependence on diesel sales makes it especially keen to take back the high ground in diesel development. It was led by its rivals to the adoption of refinements like common-rail fuel injection and “intelligent” piezo injector technology.

More recently, the company has announced its intention to bring to production electrically-driven turbochargers (already used in its racing programmes), as a way of cutting turbo lag, in a new range of performance-oriented diesels.

Referring to recent progress with diesel research, Stadler reckons his company "is now the strongest" of the premium marques, noting that on average TDI engines have doubled in power in 25 years, while their output of toxic emissions has declined 90 percent.

Furthermore, Audi engineers believe efficiency advances of another 15 percent are possible before the end of the decade.

Stadler believes diesels could dominate Audi's range as far ahead as 2030, though he believes plug-in hybrids will play an increasingly important role. "Electrification is much more expensive than continuing to improve the combustion engine, so we believe the TDI will continue to have the biggest impact for quite a long time."

On performance diesels, Stadler acknowledges that Audi is working to ensure its diesels “deliver an RS feeling” as well as the expected high torque and good fuel economy.

He is coy about confirming the strong rumours of a diesel-powered R8 supercar, but points out that Audi is the one premium manufacturer that has continued to offer V8 diesel engines. "Why shouldn't we have high performance diesels,” he says, “if that’s what the customer wants?”

Despite reports that Audi is concerned about strong Californian sales of the battery electric Tesla Model S — currently running ahead of Audi’s own sales volume in that area — Stadler insists Audi will stick with plug-in hybrids as its preferred electrification route, rather than chasing Tesla (“a new kid on the block”) into pure electric cars.

“We are thinking of the customer and their needs,” he insists. “They want to be able to drive where they wants, without worrying about battery range, or whether new infrastructure is in place. In a plug-in, they can do that. In an efficient way.”

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