Does the world need another turbocharged Cirrus SR22? Continental thinks so, because at AirVenture Oshkosh it rolled out its long-rumored TSIO-550 demo project for the SR22. We know this project has been an on-again, off-again effort between Cirrus and Continental and now it looks like its on again, at least from TCMs point of view. Currently, Cirruss turbocharged offering-its best seller-is the turbonormalized set-up engineered and provided by Tornado Alley Turbo. The aircraft retains the stock 310-HP IO-550-N but with the addition of two turbochargers and lots of intercooling. Unlike traditional systems from Continental, the Tornado Alley system doesnt ground boost the engine but allows it to maintain sea-level manifold pressure we’ll into the 20s. Technically, the turbonormalized system doesnt have a critical altitude since it boosts to sea-level to the airplanes certificated ceiling of 25,000 feet. Continental-and Lycoming-have always had a beef with turbonormalized systems because they retain the normally aspirated engines high-compression (8.5 to 1) pistons, which the factories believe reduces detonation margin below acceptable limits. Tornado Alley counters by saying that with correctly engineered intercooling and careful baffling, the high-compression engine has more than enough detonation margin. By now, there are several hundred Cirrus TNs flying and owners weve interviewed havent complained about high heat or apparent detonation. Service history for the TN airplanes appears to be favorable, according to Cirrus and owners.
Why Do This?
So, why would Continental bother with offering an engine thats ground boosted but ostensibly the same power? Because TCM asserts that its engine provides better performance, has better detonation margin and because it would like to get back from Cirrus some of the business it lost to Tornado Alley.
One reason Cirrus went with Tornado Alley in the first place, Dale Klapmeier told us two years ago, is because Continentals turbo project didnt perform as well. It had heat problems that Cirrus didnt like and Tornado Alleys system was proven and ready to go off the shelf. Further, Klapmeier said, because it was an STC addition, the Tornado Alley system could be removed if high octane fuel availability became an issue.
Continentals plan, at this juncturet, appears to be to offer its 310-HP TSIO-550-G as a straight-up replacement for the turbonormalized engine when those engines come up for overhaul, which some likely will in the next year or two. Although no prices were quoted at Oshkosh, owners would presumably be offered sweet deals on an overhaul/STC package.
Were also quite certain that Continental would like to woo Cirrus away from Tornado Alley and to get the factory to begin installing TSIO-550s as original equipment. We don’t know if Cirrus will bite or not.
Performance
In our view, there’s no compelling reason to switch from a 310-HP turbonormalized engine to a 310-HP ground-boosted engine. Horsepower is horsepower and the two