Going into Silverstone, expectations are high that the racing between Mercedes teammates Lewis Hamilton and Nico Rosberg will be close, as this is a track where both drivers excel. What is perhaps unexpected is that Williams is now a legitimate contender for podium finishes and race wins after their upgrade at Austria.
As we've seen over the past several races, the Mercedes split-turbo makes it the team to beat this year. But Mercedes isn't the only team running its engine. Customer teams Force India, Williams and McLaren all run the same motor. But until now, none of them have been able to match the "works" team in terms of pace. This is especially disappointing for McLaren, which is used to having a front-running car.
The problem is, there were a number of changes to the Mercedes engine right up until the start of the season. The late finalization of the compact log exhaust manifold meant that McLaren was left with large sidepods compared to other Mercedes-powered teams, sized to house a much bulkier exhaust system. They've been playing catch-up ever since.
But it isn't just the exhaust that allows the ultra-slim sidepods that help make the Mercedes team faster than its customer teams. Its clever intercooler packaging allows its cars to be slimmer still. Unlike most other teams, which feature intercoolers mounted in the sidepods, McLaren's intercooler is built into the center of the car, right behind the driver.
How does that work?
We've covered turbochargers in a previous technology-spotlight article. These wondrous devices provide extra power by cramming huge amounts of air into the engine by pressurizing the air intake using a compressor. Unfortunately, even with Merc's clever split-turbo, blades spinning at 150,000rpm still generate a lot of heat. Heat that has to be removed before the air is fed into the engine.
Road cars shed this heat using intercoolers, heat exchange devices that transfer heat from the intake air to another medium. Most turbocharged cars use "air-to-air" intercoolers, which use ambient air to carry away the heat. These cars often have hood scoops or large grille openings feeding their intercoolers. This is necessary because air is a lousy carrier of heat.
For neater packaging, some F1 teams use "air-water-air" intercoolers. Water is a more efficient heat carrier, which is why all engines now are water-cooled rather than air-cooled. It cools down the intake charge very quickly. And the extra liquid stage allows teams to have a shorter path between the turbo and the engine, for better response, as the intake piping doesn't have to snake out to the sidepods as with air-to-air intercoolers. While this system adds weight and complexity, it's worth it because it allows for smaller sidepods, as you don't need to package large intercoolers in with the radiators.
What Mercedes has done is build the intercooler into the center of the car, behind the driver. This means the path the air takes from the intake over the driver's head--through the turbo and intercooler--to the engine is very, very short. Mercedes needs an extra radiator to feed the intercooler, but its front-mounted compressor and intercooler make the pipework incredibly simple, further increasing the slimming effect of the system.
Some of the other Mercedes teams, like Force India, use more conventional air-to-air intercoolers, which are bulkier. But the customer teams are finally learning from the Mercedes example. When Williams introduced its own centrally mounted intercooler in Austria, that simple change gave the team the pace to snatch pole position away from Mercedes. Whether McLaren and Force India will follow suit, only time will tell.
One thing's for sure, though: This season is finally getting interesting.
Photo from Mercedes AMG Petronas