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2danglico
Joined: 08 Sep 2008
Posts: 17
Location: Seneca SC
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 Posted: Sun May 10, 2009 7:22 am Post subject: Generac V-twin questions for Jimmy |
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Jimmy, I have been reading your previous posts regarding your 4-stroke endeavor with great interest. I fly a Firestar 1 with a 447. I have two Culver props (climb and cruise) that Larry and Gene sold and service, so I know the guys at Valley Eng, and they do enjoy my trust and confidence.
I was reading about you experimenting with a prop swap. You posted that the larger wood prop that Valley supplied gave alot more static thrust than the IVO and you were optimistic about improved flight performance. But I couldn't find a post regarding your impressions of the big wood prop in flight.
Are you still using the big prop or did you go back to the IVO?
Did the higher static thrust translate to better climb performance?
Sorry if you have already addressed these things and I missed them. Also thanks for posting all the info and data on your engine swap.
John Tempest
Firestar 1
447
Future V-twin flyer?
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Jimmy Young
Joined: 24 Nov 2007
Posts: 182
Location: Missouri City, TX
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| Posted: Mon May 11, 2009 3:56 am Post subject: Re: Generac V-twin questions for Jimmy |
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John Tempest wrote:
>>I was reading about you experimenting with a prop swap. Are you still using the big prop or did you go back to the IVO? Did the higher static thrust translate to better climb performance?<<
I'm using the 78X36 Culver 2 blade right now. It gives the best climb rate, (300- 450 fpm avg.) which still leaves a lot to be desired compared to a 503. It allows the engine to hit 3750 RPM on WOT straight & level, which is what Valley recommends. The 3 blade IVO is the smoothest though. I have a minor irritating "rumm-rumm" sound & vibe that both of the 2 blades produce that doesn't exist with the 3 blade prop.
I pulled the air-cowling off the engine about 6 weeks ago, (see photo) and that got rid of the blower fan HP draw which gave me about an 80 RPM increase in my RPM's. The cyl temps stayed the same, except for about a 20 deg increase when idling or taxiing. Prior to that, prop #1, the 78X41, would allow 3500 RPM max at WOT, & afterwords it would hit 3580 -3600 so I gained a bit of power there, plus cut some weight.
>>You posted that the larger wood prop that Valley supplied gave alot more static thrust than the IVO and you were optimistic about improved flight performance.<<
I was sure hopeful that the performance increase would be big. It was better, but not huge. If I averaged it all out over different air conditions, temps, humidity and such, I would say 100 FPM is what improvement I get out of the 2 blade prop over the 3 blade IVO.
One day I would like to try a 75" 3 blade Powerfin on it.
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_________________
Jimmy Young
Missouri City, TX
Kolb FS II/HKS 700 |
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