Beating the pace car

Audi A6 TDI concept and mean black RS 5 TDI biturbo wait for eager drivers

Modern engine doesn't invite tinkering by amateurs

The Audi RS6 pace car next to me revved its engine; it was a mighty speedy machine – but my task was to beat it off the line.
   My car was an automatic, so we wouldn’t be relying on super-fast gear shifting. Remembering 0-60mph tests for Autocar. I put my left foot firmly on the brake and pressed the throttle with my right. “Go!” said my companion, and it was left foot off, right foot to the floor. Wheels squealed, engines roared and I left him in the dust.
  
It was, of course, a cheat.

If you want to get more power out of an internal combustion engine, you can do worse than to create bigger explosions to send the pistons racing up and down. A turbocharger compresses the air flowing into the engine, so you can cram more of it in the chamber allowing more fuel to burn and make that bigger bang.
   Conventional turbos use the exhaust flowing out of the engine to spin a turbine, which in turn spins an air pump. Trouble is, you have to wait for some exhaust gas to be created, hence the dreaded ‘turbo lag’ before the boost of power.
   The Audi A6 TDI diesel concept car I was driving on the Sturup test track near Malmo in Sweden had an electric compressor serving its turbocharger.  That meant the compressed air was available immediately – and that’s the only reason why I was able to beat a professional driver off the line.
   A seriously clever bit is that the electricity for the compressor is largely recuperated from the car when it’s coasting. So it doesn’t take power from elsewhere, or increase fuel consumption. It gets its power via a separate 48-volt electrical system (most cars have 12-volt) and has its own lithium-ion battery in the boot.

Double the fun
We journalists had a lot of fun on the track with two cars: the Audi A6 TDI concept with a 3.0 V6 ‘monoturbo’ producing 326 PS, and the RS 5 TDI concept with a 3.0 TDI biturbo, producing 385 PS, which can accelerate from 0-60mph in about four seconds. Both cars were obviously fantastic off the line and great fun around the track – the biturbo was a real thug.
   The most important point about both cars, however, is that they demonstrate an alternative to the idea of going from petrol or diesel straight to hybrid or full electric. Instead, electric functions could be added to the car to add performance, or reduce the engine size to allow for lower fuel consumption and emissions.
   It’s another way of improving the internal combustion engine, rather than ditching it for something completely new. As one of Audi’s engineers pointed out, we’ve been working on this engine for more than 100 years, and there’s so much more it can do, why go back to the drawing board?