The most powerful version of the rather handsome new Volkswagen Passat is a four-cylinder diesel.
With quite complicated plumbing arrangements, this engine is force-fed by twin turbos, one low pressure and one high, and to pretty good effect given the 369lb ft of torque that you can undam from 1750rpm. The blower’s turbines are of different sizes, and arranged to ensure that you’re rarely short of the kind of low rev thrust that diesels are so good at delivering.
But while engineering this was an effort, it appears to have been nothing compared to the challenge of persuading the Wolfsburg management to approve an engine capable of delivering enough thrust for a range-topping Passat.
According to VW’s head of product development Jens Andersen, the powertrain department presented several engines to the board, including a transverse five cylinder, a transverse six (it was too wide with the gearbox, he says) and the final twin-turbo four among others.
The stumbling block each time was cost, the earlier solutions generating too much of it for the bosses to be convinced that it could be viable.
As it turns out, the twin-turbo four hasn’t been a cheap motor to engineer either, turbos being expensive devices, the precise control of a pair of them an involved development process and most of its innards have been beefed up to cope with the forces of its extra power. It wasn’t easy to fit the engine beneath the Passat’s bonnet either, given the bulk of the extra plumbing.
So how did this engine get past the board? In the end, says Andersen, enough money had been spent on it that it was cheaper to finish the job rather than abandon it, he explains with a grin.
It’s an engine that will eventually appear in a few other big VWs (it’s too bulky for the Golf) although Andersen isn’t saying which. His hope now is that the engine will find enough buyers to justify the outlay.
And does it deserve to? It certainly delivers a solid stream of stream of thrust, and it’s impressively smooth at higher revs, but the taxi-ish pulse at the lower revs that you often run at is a disappointment. And the extra go sometimes proves a severe test for the Passat’s electronic dampers.