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wingspan99

Active Member
Does anyone know what size prop is recommended by Van's for the RV-4 with a 150hp O-320? I had a 74x70 Warnke which I thought was too much. Then I put a 68x74 Sterba prop on it and it's still too much, although I planned to go to 8.5:1 pistons with that prop and am about to do so. I thought I saw a 66x68 prop recommended previously, although I could be mistaken. I get only 2050rpm on climbout and 2400rpm in level flight at 23"Hg. I fly from 6100' msl elevation here in Colorado, and typically see 7900' density altitude like yesterday. Climb rate is 1100fpm solo. Plane is light, I weighed it at 964lbs.
-Tom in Yoder, CO
 
a couple of data points

I know the following examples are not RV4s but they might give you some additional insight.

My -9A 150 HP 68x72 Sterba prop gets about 2200 static and about 2450 in cruise but I don't have the wheel pants on yet. I'm thinking I'll pick up some cruise RPM with those installed.

Solo, I've gotten about 1400 FPM climb. My empty weight is about 1040 right now.

Another guy at this field has an RV6 150 HP 68x70 Sterba prop & I think he's getting a bit more RPM than I and his plane performs well according to him.

Our field elevation is 6550 and sometimes our DA gets up there to 8k or more.

Dave
 
Data points are welcome

Thanks for sharing your data, Dave, especially since you're flying at altitudes similar to mine, and you're using the same engine and brand wood prop.
I think when I get the 160hp conversion done, I'll see what rpm I get in climb and maybe I'll probably get the prop repitched to a 68x72 or 68x70. Or maybe it's just time for the Walter 601.
 
Jim Smith with his 150 HP O-320 RV-6 is turning a 62-75 3-blade at 2335 rpm static and about 2700 rpm at 8000' density altitude with a TAS of 190.5 mph with the original tips and 193.5 mph with his new tips.
 
70x69...not enough!

wingspan99 said:
Does anyone know what size prop is recommended by Van's for the RV-4 with a 150hp O-320?
Click to expand...

I have a Colin Walker 70x69 wood prop. I need more pitch as I generally never get it above 70% power, with out overspeeding (150hp O-320)......Manifold pressure with this prop is usually around 20in at 2450 rpm at altitude....It is great for climbing out of short strips though which is why I still have it installed.....I have a 70x73 Colin Walker which I have not tried yet. It came off of an RV-6...and hope to test it out soon..
 
wingspan99 said:
Does anyone know what size prop is recommended by Van's for the RV-4 with a 150hp O-320? I had a 74x70 Warnke which I thought was too much. Then I put a 68x74 Sterba prop on it and it's still too much, although I planned to go to 8.5:1 pistons with that prop and am about to do so. I thought I saw a 66x68 prop recommended previously, although I could be mistaken. I get only 2050rpm on climbout and 2400rpm in level flight at 23"Hg. I fly from 6100' msl elevation here in Colorado, and typically see 7900' density altitude like yesterday. Climb rate is 1100fpm solo. Plane is light, I weighed it at 964lbs.
-Tom in Yoder, CO
Click to expand...

A 69x72 is what I would start with for your application. Then adjust it from there. Sometimes the engine is not making rated power, old tired engine, and this is also a factor to consider. If your going to overhaul the engine soon you may want to wait and adjust the propeller for the new engine. Feel free to call me with any questions.
 
My prop not that far off the mark

I guess my 68x74 Sterba prop is not that far off the mark. With the 160hp upgrade it may be just about right. All I need now is four thickwall wristpins for the higher comp pistons. -Tom
 
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