Q: Is it possible to increase the horsepower of this engine to 260? or even 300? I’m a relatively new to all things airplanes as I have just been flying rental planes, but I just picked up a Velocity XL-RG and an O-540 from a Piper Cherokee. The Velocity requires at least 260 hp, but ideally if I could get to 300 hp safely I would like to do that. I would also like to add fuel injection.
Michael J. Baron
A: I’m afraid I’ve got some bad news for you regarding the horsepower for your O-540-B2B5 Lycoming engine.
This particular engine is FAA certified and rated at 235 horsepower at 2575 RPM and the compression ratio is 7.20:1. This engine was used primarily on the Piper Pawnee PA-24-235 and the Piper Cherokee PA-28-238. It was configured for a fixed pitch prop only.
When I research the genealogy of this series of Lycoming engines, I can tell you that since you’ll be using this engine in an experimental category aircraft, the best you can do horsepower wise is 250 horsepower.
Again, since it’s an experimental category aircraft, you could consider installing 8.5:1 compression ratio pistons and at 2575 RPM that should give you 250 horsepower, but that would be about it, and you’d be on your own as far as reliability, etc.
By changing the compression ratio, it actually falls in line and would be similar to the Lycoming O-540-A1D5 engine that is rated at 250 horsepower at 2575 RPM with the 8.5:1 compression ratio pistons.
I can’t emphasize enough that the most reasonable thing you can do to get the 250 horsepower is to change the pistons to a higher compression ratio, remembering that it’s done as an experimental configuration.
There are 260 horsepower O-540 series Lycoming engines, but they have many different components, such as the crankshaft making it uneconomical to try to convert your engine to that type of configuration.
The 300 horsepower engine is a completely different breed altogether and you can’t get there by converting your engine unfortunately.
Michael, I apologize for putting a damper on your project, but I’m certain there are other options that you’ll be looking at that will allow you to complete the project.