Tuning Red Bull Air Race Engines Requires Right Mix of Precision, Power

When the Red Bull Air Race World Championship comes Oct. 6-7 to the Indianapolis Motor Speedway, getting the most out of the race plane power plant will be crucial for each team.

One of the sweeping changes in the Red Bull Air Race rules in 2014 was standardization of the race plane engines, making for a more level playing field. Ever since, the teams have all been trying to get more – hopefully much more – out of that race-tuned Lycoming power plant than their opponents. And that means being efficient. 

The six-cylinder Lycoming engine has a solid history in the world of competition aerobatics. But the version used in the race planes has been customized to the exact specifications of the Red Bull Air Race, with every one built in Lycoming's Advanced Technology Center.

To be as powerful as possible, a race plane engine needs cool, dense air running through it. That is the job of the inlets on the front of the engine cowling – what appear like holes near the nose of the plane that together with the propeller often resemble a face. If you look closely, you will notice that the faces of the 14 race planes are each a bit different, and that is because every team technician has his own thoughts on the best way to cool the engine.

The technicians in the Red Bull Air Race know that the air inlets of their race plane can create the difference between winning and losing. The engine not only needs plenty of cool air to be sucked in, but to get hot air out quickly, as well.

Optimizing the airflow over the cylinders and the oil cooler is a difficult challenge in every track and climate.

Think about exercising. If you run in high temperatures and at low air density (the “thin” air of high altitude), you will find it difficult to breathe and to perform at your best. A clear, cool day close to sea level is what you need for easy breathing and good running.

A highly tuned race engine works the same way, but the “breathing” must be a compromise: Make the inlets too small, and the engine will get hot and lose power. Make them too large, and they will create too much drag, slowing the race plane.

Figuring out the best cooling refinements for the race plane is a unique challenge for the technicians because the type of flying in the Red Bull Air Race can’t be compared to anything else.

Even though the pilots can’t control the temperature at the race locations, there is something they can do to ensure they are running their engine at its optimum – get the fuel mixture correct. To run at peak performance and for perfect, efficient combustion to occur, the engine needs the ratio of air to fuel to be 14.7 parts air to one part fuel. The pilots have a manual control that adjusts the fuel mixture, but it is a delicate balancing act.

If there is too much fuel in the mixture, it will be too “rich,” and some will be left in the combustion chamber, meaning the engine will lose power. On the other hand, if there is too little fuel in the mixture, it will run “lean,” again losing power. For the teams to make sure they are getting the correct mixture into their engines, some have added a device called a lambda sensor.

“The sensor measures the CO2 (carbon dioxide), similar to a sensor in a car,” Red Bull Air Race Technical Director Jim "Jimbo" Reed said. “There is a display in the cockpit that reads the stoichiometric number, which measures particle density. If you have more fuel per air, then it reads a lower number because there is not as much carbon produced. As you start to get to the correct mixture, a certain number pops up that tells you you're doing the right thing.”

The lambda sensor, which is placed in the exhaust to collect the readings, works in all conditions, no matter the altitude or temperature.

“The conditions don't make a difference to the 14-to-one ratio, so you want the same readout – but if you're at a higher altitude, you'll be taking in less air, so you need less fuel to keep the same ratio,” Reed said.

Reed emphasized that getting the mixture right can make a huge difference in the racetrack.

“The mixture ratio is linear to the horsepower produced, so if you can keep the engine cool enough and can maintain the mixture correctly, you'll get maximum power,” Reed said. “This is essential to a fast race, because from full-rich to full-lean in the engine you can have a difference in horsepower of 8 percent.”

See which team can run their engine efficiently enough to win Oct. 6-7 at IMS. Visit IMS.com to buy tickets or for more information.