Mercedes split turbo design was 'bloody hard' to get right

Mercedes AMG

Mercedes engine boss Andy Cowell suspects one of the main reasons rival manufacturers have not copied his power unit's split turbo design is because it is so difficult to get right.

Mercedes stole a march on its rivals with the introduction of the current V6 turbo engine regulations in 2014 and has won two dominant back-to-back titles since. A large part of the team's success has been attributed to its power unit, which was producing in excess of 900bhp in 2015 with more to come in 2016.

At the heart of the power unit is a novel split turbo design whereby the turbine and compressor are located at either end of the engine with a shaft running through the vee of the engine to connect them. The design has several benefits, including packaging of the power unit, a reduction in pipework and a separation of the hot turbine and the compressor, which also allows for a smaller intercooler.

The split turbo received a lot of media attention in 2014, but so far none of Mercedes' rivals have run similar designs. Asked if he thought it had been given too much attention by the press, Cowell said: "I don't think it was overplayed.

"Is it the silver bullet? I think it is something where there are a lot of positive contributions that go into make that decision, so it's not done for one reason, it's done for many reasons to make it something that we think is still attractive.

"I think the thing that goes against it is that it's bloody hard! In the whole debate there wasn't one big reason why we should do it, but there were a lot of medium-sized reasons why we should do it. On the contra side of the table there was the question of 'bloody hell, how are we going to do this?'

"That was the thousand pound gorilla. But there was nothing that said it couldn't be done, it was just that it hadn't been done. And that's quite fun, isn't it?"

Mercedes started work on its power unit three years before it was introduced, but Cowell admits his team had little in the way of expertise at that stage and even borrowed some ideas from Mercedes' truck department.

"There were not many of us who had worked on turbos back in 2011 when we started looking at the regulations. I think there were two people who had worked on turbos, and one of those had changed a turbo on his Subaru that had failed! It was a completely different technology and way of approaching it.

"Daimler with their truck engine division, and the turbo chargers involved in that, helped tremendously. There were several thermodynamic sizing areas where they helped and several reliability issues where they helped as well.

"Really it was a clean sheet start with lots of analysis and various architectures that could be used for the boosting and then we came up with this layout with the split assembly. There were a multitude of reasons why, but the one that made me smile the most was when people said 'where's the turbo?' because it's buried in among the internal combustion engine.

"All the bits are positioned exactly where the engine would like them to be positioned and exactly where the car would like them to be positioned. But there was an awful lot of analysis went into it -- 600 CFD simulations to get the primary design phase kicked off."