Question for Paul McBride, the General Aviation News engines expert: I’m building an F1 Rocket from Team Rocket of Texas and have a question: The Lycoming IO-540-AB1A5 has a rating of 230 hp at 2400 rpm. Can I just change the governor and increase the RPM to 2700 (like the D4A5) to get 260 horsepower or do more technical modifications need to be done?
Thank you!
Tom Wike, Oslo, Norway
Paul’s Answer: Tom, It’s great to see someone asking very important questions before spending money on an engine that may or may not work for your upcoming project of building an F1 Rocket.
That said, I hate to be the one to tell you that there is no way you can go from an IO-540-AB1A5 to something like the IO-540-D4A5 or even close.
The IO-540-AB1A5 was built initially for the Cessna 182 aircraft and was rated at 250 hp at 2425 rpm.
I didn’t conduct much research in comparing these two engines because I think there are just too many differences. To attempt to convert one to another would definitely be a lost cause.
I apologize for being unable to put your dream engine together, but I will offer a suggestion. While I was doing some research regarding your question, I noticed that the Team Rocket Aircraft website includes a link to a forum. Once you sign up you’ll be able to connect with other builders, who can be a great source of information. Go to TeamRocketAircraft.com to sign up for the F1 forum.
Tom, I admire you for asking any questions that may come to mind before jumping into this or any project. It’s a much better way to learn and probably will save you a lot of money in the long run.
In other words: It really IS rocket science!
The IO-540-AB1A5 was used in the Cessna 182S and was rated 230 HP at 2400 RPM as you indicated. Compression ratios, bore and stroke, and displacements are identical to the -D4A5 engine rated at 260 HP and 2700 RPM. But that’s where the similarities end, as Mr. McBride has stated. Crankshaft, damper assemblies, camshaft, oil sump, servo, and induction systems differ by part number, design, and construction. In theory, you could spool the engine to 2700 and re-schedule the fuel servo to get 2600 HP but the operational aspects will affect propeller choice, and the physical differences will impact the design of the Rocket.