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BlakeB

Well Known Member
Piston Question?

I currently own a RV8 with a 0-360 A1A. The guy I bought it from had 7.3. to 1 pistons in it. Not sure how much horse power it produces and I'm thinking about changing them to 8.5 to 1 or 9.1 pistons. I have a 3 blade catto prop. The plane perfoms great, it just seems to be a little sluggish on take off. I'm not an engine guy, but my understanding is my engine is derated right now and is very capable of producing 200hp. Any advise would be greatly appreciated!

Thanks,

Blake:confused:
 
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Engine Compression

My understanding is the 8.5 to 1 will make close to 180. The 9 to 1 will make close to 186 (I have 9 to 1). Im not a fan of increasing beyond 9 to 1 but this is only a personal opinion. If you want 200+ HP I belive the best option is another engine with fuel injection. I would also make sure your prop is rated for what ever decision you make. A lot of people spend a lot of time and money on the HP issue on the 8 however the best opportunity to increase power, especially take off performance is to build the airplane light.

Pat Stewart
 
Sluggish on take off isn't something you normally hear about an RV. Could be a number of things and best diagnosed by an experienced RV guy. Your engine is probably giving you around 168 HP on a good day if it is in reasonable health. Of course it's less if it isn't in top form.

My advice would be get with an experienced RV pilot/builder that can evaluate what you have as far as engine/prop combination. HP is only part of the issue.
 
O-360 A2A Boost

I just had the power of my O-360 A2A Catto (fixed pitch) prop powered RV-8 boosted. Added the 9.1 compression pistons and the new Superior oil sump. The engine shop owner said the pistons would add about 10 hp (over the 8.5 pistons) and the improved airflow with the new sump would add 3 to 4 hp. I'm still doing some additional mods to the aircraft, so it has not yet flown with the 'new' engine.

The pitch of your fixed pitch prop will also impact the takeoff performance. Craig Catto might be able to give you some insight into the performance characteristics of your prop (i.e., primarily a climb or cruise prop).

Jay - N817J
 
Ours...

Hi Blake,
Ours is sluggish compared to CS propped RV's but still gets off in around 600 feet, climbs between 1700-1900 FPM at 135 MPH since I asked Craig to pitch it for max cruise. Perfomance numbers like these blow most spam cans away. We only turn 2200 on initial takeoff but it's no slug. If you'll experiment by trying climbs at 150, 160 , you'll be amazed because the extra speed translates into more RPM and more power. I often cruise/climb at 160 and around 900-1100 FPM.

Regards,
 
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