New car focus forces McLaren to run V10s

The team returned to the track with their orange-liveried MP4-20 at Jerez in Spain today but sources revealed that both Gary Paffett and Pedro de la Rosa are running with detuned V10 engines.

This comes despite the fact that the team had run with V8 engines for much of testing in November and December.

Although the lack of available V8s has led to speculation in the Jerez paddock that Mercedes-Benz are currently redesigning their engine following reliability issues in last year's testing, the team have insisted that there is simply a supply problem related to the way the engine fits into the car.

Autosport.com understands that the engine mounting points on the new MP4-21 are different from the interim MP4-20B and, with the current focus on the new car, there are not enough engines with the old mounting points available to allow V8 testing to continue with the interim car at the moment.

The situation means that the team will probably be forced to run with their 2005 MP4-20 fitted with a detuned V10 engine until the new car hits the track later this month.

It is likely that the state of affairs means V10 testing will also continue beyond the start of the season, although there are no suggestions of the team actually racing with a V10.

Mercedes-Benz have played down the significance of the V10 testing this week, however, claiming that it is a necessary sacrifice in a bid to get on with the new MP4-21 programme.

"We are fully on course with the V8 engine production, but there comes a point in time when you have to focus on the new car with its different mountings and this point has come," said a Mercedes-Benz source. "We wanted to fully focus on the new car and that is why we have chosen to use all our capacity for this.

"The reduced power V10 simulates exactly what we need at the moment and that means we can focus on the new car."