What engine makes sense?

I’ve been researching how to have my cake and eat it, too. How can I build an RV-8 that is plush but also accepts a parachute that has modern & redundant systems but is also lightweight? I’ve been looking for places to shave some weight here and there in my build.

The IO-390 is the most powerful engine the RV-8 can accept, but it also weighs a lot more and is only available from Lycoming as it’s not sold in kit form for other companies to assemble. The most common engine used in the RV-8 is an IO-360 or its carburated cousin, the O-360. As I am building an aerobatic RV-8, I need fuel injection, so I’m discounting the carbonated versions as considerations.

O-360-A1A180 HP285 lbs (parallel)
O-360-A4M180 HP285 lbs (parallel)
IO-360-M1B180 HP290 lbs (parallel)
IO-360-A1B6200 HP325 lbs (angle)
IO-390-A3B6210 HP315 lbs (angle)
IO-390-EXP220 HP315 lbs (angle)
Weights from KitPlanes Review

I’m also talking to Aero Sport Power as I’d love to build my engine. After all, part of the reason I chose to go experimental is so that I can do my maintenance. How could I do that if I don’t have a deep understanding of the entire plane? Aero Sport Power will sell you an engine kit and assemble it with your help so you know everything in it.

AeroSport Power offers an engine based on the IO-360 called the IO-375. This engine, by default, will offer 195, 200, or 205 horsepower, depending on cylinder compressions. All three options weigh 6 lbs more than a standard IO-360 180HP engine.

IO-375205 HP296 lbs (parallel)
AeroSport Power information

You can reduce this weight with lightweight rings and induction sumps. Then, we need to add an inverted oil system to it, so I’m sure that the entire AEIO-375-M1S will net out around 300 lbs.

The IO-375 (and the aerobatic version, the AEIO-375) has a counterweighted crankshaft, which is essential to note when looking for a propeller. After limiting my search to constant-speed aerobatic props, the choice seems almost made for me. A Whirlwind 330-3B prop weighs 53 lbs, including the spinner and related hardware. Hartzel has yet to respond to my questions, and I still need to reach out to MT-Propeller before making any final decisions.

Having an aerobatic prop is essential because a standard constant-speed prop can overspeed when inverted for any length of time due to a drop in oil pressure. Aerobatic props work with counterweighted governers that force the prop to a coarse angle, thereby preventing any overspeed condition.

2 responses to “What engine makes sense?”

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