PF22 Exhaust System Design and Manufacturing
The exhaust system was manufactured from 18-gauge, 1.5in OD, 304 stainless steel to prevent corrosion and endure high temperatures. 18-gauge was selected over a thinner lighter material because we did not want to worry about the header becoming a wear part through strenuous testing. The header is 19.7in long from engine to muffler. A WAVE simulation indicated that header length did not make a significant impact on efficiency / torque / horsepower. Therefore, this length was not optimized. Instead, packaging within the vehicle was prioritized. A Lambda sensor was incorporated as it is required for closed loop engine operation. An Exhaust Gas Temperature sensor was also incorporated to help monitor engine performance.
Lot's of dyno time was accumulated on the header throughout the season. A slip fit muffler joint was used to be able to test and swap different mufflers on the car. Because the formula car can pull an excess of 2G's of lateral acceleration, rod ends and thin steel tubes were used to make 2 force support members. In addition, a flexure was used to mount the header to the chassis, with mica shims for thermal insulation.
The header flange, tubing, EGT, and O2 sensor weighed a total of 792 grams. Pretty good if you ask me.
FSAE muffler setups are difficult. The initial muffler we selected was too thermally stressed and blew a hole in the side. The second one would thermally expand axially and have lug shear problems with the riveted construction. We added support brackets to help unstress this. A 90 degree pipe was used to help pass sound limits for rules. Without it, sound would reverberate between the rear wing endplates.