Blown Diffuser 101, McLaren Update
McLaren Mercedes boss Martin Whitmarsh remains optimistic the team’s blown diffuser will be working in time for the German Grand Prix. The first time the Woking-based team tried the diffuser was at Silverstone, however it was removed from the car on Friday after the outfit struggled to find a good balance with it. There were also some issues that arose due to the heat generated from the diffuser.
McLaren engineers have been steadily working towards another trial of the concept. In two weeks the team will try the improvements during the practice at Hockenheim. Whitmarsh is hopeful that with a little more time the diffuser will be good enough to remain on the car for the entire weekend.
“I’m quite optimistic now,” Whitmarsh said, “I was looking at the data and I think we now have some understanding of the issues, if not all, and we can devise some experiments.”
The operation of getting the blown diffuser mounted on the car proved to be more difficult than the team had anticipated. The decision to abandon the diffuser for this race was one Whitmarsh is still toiling over.
“That could have been a mistake, but I’m glad we did it and I’m glad we took it off...ultimately it was my decision and I think it was the right one...I don’t think we’d have made much better results this weekend. We’ve got some good ideas now that will hopefully take us forward on Friday in Germany.”
So what is a blown diffuser?
A blown diffuser is a device that sucks the air out from a cars under tray. The diffuser plates are mounted low in the rear of the car, and help re-equalize pressure by accelerating the velocity of airflow under the car. It is energized by pushing exhaust flow into the diffuser and blowing it with the exhausts.
How does a blown diffuser work?
When the air passes quickly under the car it creates a low pressure ‘balloon’, so to speak, that creates drag and thus slows down the car. The rear diffuser sucks out the air from a car’s under tray in a process that creates downforce – essentially sucking a car to the track. Downforce allows a car to travel faster through a corner by increasing the vertical force on the tires by generating more grip.
What is downforce?
Downforce is the same principle that allows aeroplanes to rise off the ground, but in reverse: It helps push tyres into the track. The designer of a Formula One vehicle has two main concerns: creating downforce and minimizing drag.
Millions of dollars are poured into aerodynamic research and development each year. The floor of a Formula One car is responsible for creating around 40% of the downforce. This percentage can be increased with developed diffusers. The diffuser expels air from under the car over its curved surface. The speed at which the exhaust travels over the contoured shape varies depending on the dips and elevations on the model.
The design varies between cars, for instance Red Bull pioneered the technology and is using a diffuser with a pointed top section on the outer edge, very similar to McLaren’s, but they have also included a round shape to the inner point where the vertical middle plate meets the top edge of the diffuser.
Teams have struggled with getting the exact maximum increase of suction from their diffusers. The exhaust is a fast moving stream of gas often reaching temperatures of 1000 degrees Celsius, so it is key to find a lightweight material that can withstand this extreme temperature for extended periods of time.
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