McLaren has abandoned its exhaust-blown diffuser for the rest of the British Grand Prix weekend, AUTOSPORT can reveal, after a difficult first day of running with the concept at Silverstone on Friday.
The Woking-based team had high hopes that the update package it brought on to the car for this weekend's race would help lift its performance to take the fight to pre-event favourites Red Bull Racing.
However, both Lewis Hamilton and Jenson Button failed to get comfortable with the new handling and set-up of the revised MP4-25 at Silverstone - with Hamilton running off-track several times as he took the car to the limit.
Button admitted that the car had not felt good with the new parts - and that the team needed to invest much more effort in making them work.
"Today's been a little bit trickier than expected in the car," said the reigning world champion.
"First of all I couldn't get a set-up for the car with the new package, but it improved at the end of the day, but there's still a lot of work we need to do. We are not where we'd like to be. The car is very tricky in a few places around the circuit.
"We've definitely made some improvements in certain places, but we don't have the right balance yet. I haven't had a perfect day today, which is disappointing because even on a Friday it's good to see so many people out there."
With Hamilton ending the day more than 1.5 seconds adrift of the best time from Red Bull Racing, McLaren felt that its chances of a decent result in the British GP would be best served with using the package it knows best.
Late on Friday night, McLaren mechanics were seen wheeling the updated floors out of the Silverstone paddock as work began on revising the cars back to the configuration that has been used up until this race - with the standard exhaust set-up.
Sources have revealed that McLaren understands where improvements can be made with the package, and revisions will be developed to ensure the exhaust-blown diffuser is back on the car for the German Grand Prix.
McLaren had come into the weekend viewing the British GP as a critical weekend in its title challenge - with the performance of the blown diffuser likely to give it a benchmark on its ability to take the fight to Red Bull Racing.
Although removing the blown diffuser is a setback for McLaren's hopes at Silverstone, the performance of the car in recent races means the outfit still has the chance of taking a decent haul of points with the older exhaust concept.
The exhaust-blown diffusers are far from straightforward to integrate into the cars, and Mercedes GP found it had to compromise its version of the design in Valencia a fortnight ago when it encountered overheating problems caused by the exhaust gases.