Representatives of Superior Air Parts and AC Aeronautical will introduce at this week’s Reno Air Races the new 230 hp, four-cylinder XP-408 Advanced Competition (AC) engine for the high-end experimental aircraft market.
“Superior has always led the industry in introducing emerging technologies that advance the performance, efficiency and reliability of piston aircraft engines beyond what our competition can offer,” stated Tim Archer, Group CEO, Superior Air Parts. “When I first saw the amazing work that the team from AC was doing, I knew that it would be ideal to collaborate with them in creating this new-generation engine.”
“The XP-408AC has been designed with safety as a priority; efficiency as a requirement, and performance as a positive result,” explained Andrew Higgs, director and chief architect of the 408 program at AC Aeronautical. “To be able to achieve these high goals you need to start with an engine that is made to the highest quality standards. That is what we have available by using Superior’s outstanding XP-360 as the base engine. Take its proven quality and durability and add our racing inspired upgrades and you get an engine that delivers 230 horsepower and can do it reliably for a long time.”
Higgs said that the AC Aeronautical engineering team drew on many years of experience in professional motorsports and competitive flying. Each of the company’s directors holds a pilot’s license and their team boasts a World Record Holding pilot (Steve Noujaim) and a Red Bull Air Racing double world champion, (Paul Bonhomme).
To advance the state-of-the-art in piston aircraft engine design, performance and reliability, the AC Aeronautical team took cues from the world of Formula One auto racing to develop the engine’s key components including the new crankshaft, connecting rods, pistons and piston pins, company officials said.
“Our team use the latest techniques in finite element analysis to select the most appropriate material for these new parts,” he said. “They are designed to the very highest quality standards and manufactured to exacting tolerances. The results are components that provide higher performance and higher reliability, while being overall significantly lighter than the stock parts they replace.”
Advancements introduced for the XP-408AC are:
- Dynamically balanced crankshaft designed to dampen firing order vibration and increase the engine stroke to 408 cubic inches. Reduced vibration minimizes engine component stress and helps maximize engine reliability and efficiency.
- New four-bolt connecting rods, which better distribute the clamping loads to help stop bearing distortion.
- New heavily bridged slipper-racing pistons that are stiffer than standard pistons. The new design is also 42% lighter than stock pistons. Each piston set is matched to within 0.5 gram.
- A weight reduction in the dynamically balanced crankshaft rotating assembly, resulting in a significant reduction in inertia with a corresponding reduction in the stress and vibration that is found in the traditional engine.
The main goal for the designers was to move as much weight from the reciprocating parts to the rotating parts to ultimately reduce engine stress and vibration. “During our testing, we found that even while producing its full 230 horsepower, the XP-408AC engine actually generates lower peak to peak stress levels than a similar specification 360 engine at a similar RPM setting,” Higgs said. “Even with this increase in performance we have less stress on the standard components and hence a larger safety margin.”