An efficient engine equals race wins
The six-cylinder Lycoming engine has a solid history in the world of competition aerobatics. However, the versions used in the raceplanes have been customised to the exact specifications of the Red Bull Air Race and were built in Lycoming's Advanced Technology Center.
To make a raceplane's engine as powerful as possible it needs cool, dense air running through it. That's the job of the inlets on the front of the engine cowling. If you look closely at the front of a raceplane you'll notice that every team has a slightly different look, that's because each technician has his own thoughts on the best way to cool the engine.
You can almost guarantee that temperatures will be more than 25°C at the season opener in Abu Dhabi, meaning keeping the engine's temperature cool will be essential in posting a competitive time.
The technicians in the Red Bull Air Race know that the air inlets of their raceplane can create the difference between winning and losing. The engine needs plenty of cool air to be sucked in, whilst getting the hot air out quickly as well. Optimising the airflow over the cylinders and the oil cooler is a difficult challenge for every track and climate.
Think of when exercising, if you're running in high temperatures, at low density (meaning high altitude), you'll find it difficult to breathe and not perform at your best. A clear, cool day, close to sea level is what you need for good running easy breathing. A highly tuned race engine works the same way, but the 'breathing' has to be a compromise – make the inlets too small and the engine will get hot and lose power, make them too large and there will be too much drag, slowing the raceplane down.
Unfortunately the pilots can't change the weather, so it's the technicians job to make the engine run as cool as possible. They have difficulty working out what will be best on the aircraft because the type of flying in the Red Bull Air Race is unique and can't be compared to anything else.
Even though the pilots can't control the temperature, they can ensure they are running their engine at it's optimum performance by getting 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's a delicate balancing act.
If there's 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. Similarly, 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 'lambda' sensor.
"The sensor measures the CO2, similar to a sensor in a car. There is a display in the cockpit that reads the stoichiometric number, which measures particle density," explains Red Bull Air Race Technical Director Jim "Jimbo" Reed. "If you have more fuel per air then it reads a lower number because there's 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 14/1 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," continues Reed.
According to Reed, getting the mixture right is essential as it 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 stoichiometric mixture correctly, you'll get maximum power. 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%!"
You'll be able to see how efficiently the teams run their engines at the season opener in Abu Dhabi on 02-03 February. Get your tickets HERE.