The exploding engine that almost derailed Mercedes turbo hybrid domination

The Red Bull era was over. Winter testing in 2014 made that crystal clear as the Milton Keynes cars stuttered in two weeks of running around Jerez and Bahrain.

Who would replace them at the sharp end of the grid wasn’t obvious though, as Williams set the pace to beat; Ferrari was inconsistent — but quick — and Force India bobbled around the top ten.

Nine months later, and there was no doubt over the team to beat in the hybrid era. Mercedes was celebrating a world championship double, comfortably the quickest team on the grid and unmatched in the reliability department.

The crown jewel was the Mercedes PU106A Hybrid power unit at the heart of the Silver Arrows, powering them to a first constructors’ championship on this day in 2014.

It proved to be the standard-setter in Formula 1 but, on the inside, that domination was far from clear during the winter that preceded the 2014 season, as work on the engine fell alarmingly behind schedule.

“2014 was a nerve-wracking time,” said Andy Cowell, who led the development of the power unit at Mercedes’ HPP division.

Speaking in a 2019 Motor Sport podcast, Cowell said: “We didn’t know if we’d be able to complete the first race, let alone the championship. We went testing super nervous.”

Mercedes notched up 351 laps in the final Bahrain test to rank fourth in terms of laps completed.

It achieved a grand total of 4972.644km, more than any other team but behind the scenes, there was panic at Brixworth.

“Partway through 2013, we asked everyone to work more hours because we couldn’t see how any of the eight cars (powered by Mercedes engines) could finish in Melbourne.

“We painted this horrible image of all eight cars being parked by the side of the track and the Mercedes brand being humiliated. Everybody dug deep and worked incredible hours, with some amazing ingenuity to solve issues right down to the last moment.”

Even then the historic season wasn’t on the cards. Problem solving had fixed some persistent issues with the new power unit but the reliability questions clung on right to the 11th hour.

“The very first engine that we passed off for Melbourne blew up, exploded, crank gear came off. There was a group of us here for 24 hours trying to work out what to do with the next group of engines. Clearly, you couldn’t pass off the next engine because the gear drive destroys lots of hardware that we just didn’t have replacements for.”

Mercedes began the turbo hybrid era with a front-row lock-out as rain arrived to affect qualifying. Lewis Hamilton led Nico Rosberg to head up the field but the opening weekend of the season would prove bittersweet.

“We went to Melbourne not really knowing how we were going to get on. We had that heartbreaking moment of Lewis being at the front but [suffering] a misfire because a rubber tube had split and the spark had jumped across. Something as trivial as a rubber tube causing a DNF.”

Even so, Cowell was the hero of the moment. Not only did Mercedes win, but the Mercedes-powered McLaren of Kevin Magnussen was on the podium too. When second-placed finisher Daniel Ricciardo was disqualified, McLaren’s Jenson Button moved up to third, in a clean sweep for Mercedes power.

Cowell was nominated to receive the constructors’ trophy and he spoke of the emotion of standing there after the Herculean effort of developing the engine. “We had a 1-2-3 and then we just won lots and lots of races,” he said.

Lots of races translates to 16 of the 19 races, translating to an incredible 84.2% win rate on the season and since bettered only once by Mercedes in 2016 — although not a patch on McLaren’s 1988 season.

It took until the seventh round of 2014 for Mercedes to fail. Five consecutive one-two finishes was broken up in Montreal as Red Bull and Daniel Ricciardo broke the vice grip held by the Three-Pointed Star.

“Our reliability was shocking but it wasn’t exposed on the track,” said Cowell. “That safety margin [to operate the power units] was about right.

“Canada was one of the toughest races for the ERS module in terms of K-duty and then we suffered a DNF. Breakfast on the Monday morning, my young son said, ‘Daddy, why did you let Red Bull win?’. And I wasn’t the only one experiencing that in the factory.

“I bumped into Pat Fry who I knew from working with him at McLaren, and he said “Thank goodness,you didn’t win, because otherwise you stood a chance of winning every single race this year and beating the [1988] McLaren 15 out of 16, which he was associated with.”

Back-to-back misses in Hungary and Belgium either side of the summer break were the only other times Mercedes failed to have a driver on the top step.

Rosberg led the championship after Spa but a run of five consecutive wins from Hamilton in response turned the title outlook around once more.

Rosberg claimed a victory in Brazil to set up the decider: F1’s one and only season to feature double points at the final round meant that he was still in with a chance of claiming the championship in Abu Dhabi.

Unfortunately, unreliability denied fans a straightforward fight between the title contenders as Rosberg was crippled with a failing ERS unit, the unreliability the team had worried about all year rearing its head at the worst moment.