New Twin-Turbocharged, Nitrous-Injected Light Sport Engine Provides Wild Power Output for Experimental Aircraft

Special 04.01.23 Parody Edition: A small pet project under the Rotax umbrella was let loose on the world after general manager Peter Ölsinger approved a limited production run of a high-performance, custom tuned crate engine for experimental aircraft.

The engine builds on the popular Rotax engine series, which has seen continuous performance improvements since the original 80-hp 912 ULS years ago.While the recently introduced 916 iS/c provides 160 horsepower with a fuel-injected 4-cylinder, the new 917 iS/TT almost 2 1/2 times the power, with a total output of 341 horsepower. The engine retains the relatively small displacement of 82 cubic inches, making up the bulk of its power with a high-strung combination of 2 turbochargers and an optional (but highly recommended) nitrous injection kit to provide maximum short field takeoff performance.

Like any other engine, there's no free lunch, however. The added piping, intercooling, and turbo means the 917 iS/TT tips the scales around 250 lbs, more than 100 lbs over the common 912 iS. The performance more than makes up for it, though, with an eye-watering 1.36 hp/lb power-to-weight ratio, almost double what the baseline 141-hp 915 iS/c offers. Against the usual 912 iS, that's 2.3 times as much power per pound. The TT will be a bit of a hangar queen, however, with oil changes recommended every 10 hours of engine time, and a fairly high-strung 5,200 rpm cruise. But for those builders looking for the latest and greatest, the 917 iS/TT should make a fine halo model.

"When I saw the plans on the engineer's dry-erase board, I was blown away," said Ölsinger. "They had charted out the design with in-house parts as a sort of pet project for a high-performance, top-of-the-line exhibition of what Rotax could do. But the more we started looking at what we could actually put together, the more the twin turbo setup came together."

Ölsinger said the 917 iS/TT would be a pretty limited production engine for the company, given its niche target market. "We're only going to make 20, 25 engines in the first year to test the waters a bit, and maybe twice that should they prove popular enough," he said.

"We want builders to know that if they want max performance, they want Rotax."

FMI: www.flyrotax.com