rv9aviator

Well Known Member
Here's the details. 0-320 E3D low compression 150HP. Max RPM 2700, Ed Sterba 68-74 wooden prop. RV-9A. The highest RPM I can get is 2550 RPM in flight. The Manifold pressure always runs higher than RPM. At 2300 RPM I am getting 24.5 inches. Down at 1900 RPM I am still getting 19.5 inches.
I never had a MP gage on a fixed pitch prop before so I don't have anything to compare with.
Any thoughts?
 
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Yes, the prop is over pitched, IMHO. Call Catto props and have them build a nice 2 blade for you. It will add more RPM and 10 MPH.

What is your static rpm?
 
Static 2250 RPM. I wanted a Catto prop but ran across this used but in great shape prop for not much money. At the time I needed to save dollars where I could so here I am. The previous owner said it came off a 150 HP 0-320 on an RV so I thought it would be fine. One thing about it maybe it helped seat the rings on the rebuilt engine.
 
Static 2250 RPM. I wanted a Catto prop but ran across this used but in great shape prop for not much money. At the time I needed to save dollars where I could so here I am. The previous owner said it came off a 150 HP 0-320 on an RV so I thought it would be fine. One thing about it maybe it helped seat the rings on the rebuilt engine.

That prop might work good on a THREE..........
 
isn't that a 'recommended' pitch?

....so as a data point, I have the same 150 hp engine on my -9a, and use a Sensenich metal 70x77, which is the recommended prop.
why is Jim overpitched at 68x74?
Mine is pulling even more air, and I see about the same WOT rpm, and no more than 2150 on t/off, which I agree is poor performance ( only 90 hp available!).
Sounds like the Van's pitch advice is in error.?
 
flyboy1963, Manufacturers measure pitch in different ways. thus they arent the same. I customize the propeller for what the pilot/builder specifies he wants in rpm range/performance. Cruise or climb and sometimes in between.
 
Your static isn't bad. If you're content with takeoff and climb performance, leave it as is. You may get 10mph more with the Catto but it will be at the expense of a significant increase in GPH.
 
Ditto above. You have a nice general use prop on the cruise side (verses the climb side).
All fixed props are compromise. Your prop sounds ideal for general use, cruise, cross country and light aerobatics. What kind of wide open throttle cruise are you getting, MPH and RPM, at 8000'?

Here is a tip/hint.... Go on a drag reduction program.... look at all the fit, finish, wheel and gear fairings (upgrade, re-do), goto a sealed plenum and round inlets (which can be retrofitted). It sounds like you could reduce drag? What speed are you getting full throttle at 8000 feet? Is it jive with Van's numbers? Common wisdom for a good middle of the road prop, is good static RPM + 2700 RPM full throttle @ 8000 feet. A real climb prop would give you even more 8K RPM. Keep in mind if you go to a climb prop (lower pitch, higher take off and cruise RPM for given throttle), you have the option to throttle way back, keep GPH in check, but it will be less efficient than the prop you have now in cruise. Your prop is a tad on the cruise side, more than than climb prop side. IMHO I think your prop is a nice compromise for cruise and some light aerobatics (if your performance is in the "RV ballpark" for other 150HP RV's).

Remember not only airframe drag affects RPM, but ACTUAL ENGINE HP AFFECTS RPM. Not all LYC 320's make 150HP at SL and 2700 RPM, depending in induction, exhaust, ignition and condition. You could increase HP! clean the air filter, add electronic ignition, improve the exhaust, clean and gap the plugs, all in an effort to make another few HP..... this will get your RPM up as well. How is your MIXTURE? Can you lean at 8000 feet at full throttle? Opening up the jet can add HP! Most carb'ed 150HP RV's run very lean. Time to drill the jet a drill size or two up.


(Note - "red line" by Lyc is 2700 rpm, but I recall Lyc allows a transient 5% over-speed (~2835 rpm) with an inspection. Over that they talk about tear down! Of course Lycs have been abused with much higher RPM for a half a century. At RENO they run Lycs way over red line, but that is racing.)

Going to a climb prop, you will add MPH and increase GPH..... Props can not cover all sins.... Low drag is always a crowd pleaser..... The effort to go through and upgrade your plane, lower drag will cost you less than a new prop. Lowering DRAG and increasing the engine HP, more efficient airframe and engine is better than a new prop!

Do you like to take off and cruise or do you do aerobatics?
Do you like to travel or do you like to local airport hopping?

Do you have good cruise speed, ~190 mph? With my C/S prop RV, 8000' cruise I dialed the RPM back to 2450. MAP is what ever you get at full throttle. At lower altitude cruise I would still set 2450 rpm but need to throttle back to keep it "square"... although you can run about 1" more MAP than RPM with out the end of the universe happening.

If you fly out of short strips or higher DA this is not the ideal prop. However the performance of a RV has lots to spare, compared to a Cessna or Piper. At high gross weight, takeoff from a high hot mountain strip, caution and calculation is needed regardless of prop. However if this is your KIND OF FLYING, you need a prop that gives you much higher static RPM... it however will be inefficient high speed cruise. You have to make a choice, be happy or change. I am a C/S man... and have not looked back since. If I had to do with fixed pitch I would consider ground adjustable. If your CG can take it, look at the Sensenich.com metal props. They are more efficient than the wood props at the cost of weight. There is something nice about light light wood props. They tend to be "smoother".

Don't worry about NUMBERS (RPM); are you happy with the cruise speed? How is your cruise speed and what is your GPH? That info would help you decide if your prop is over-pitched... but don't worry about numbers.... 2500 rpm is a good 8000 foot cruise RPM at full throttle. If you can NOT get 2700 at lower altitudes, then you might be a little over pitched, but again lower drag, increased HP is where I'd go first. The trick is not to get a specific RPM, but to get a more efficient, faster climb and cruse, lower fuel burn plane... If all your buddies are passing you as you cruise to the pancake fly-in, take off in 1/2 the runway, get to altitude minutes ahead of you... then worry. :D How does you plane compare to other RV's?
 
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Thanks for the input GMC. I think one factor I was overlooking was drag. I don't have wheel pants or fairings on yet and won't have any good numbers until all that is finished. I do want a cruise prop as I plan on using the plane for traveling and since it is an RV-9A there will be no aerobatics. The climb is so much better than my old 172 I certainly can't complain. I was more concerned about the engine running oversquare than the lack of climb or speed. I guess that is not a problem either.
 
That prop might work good on a THREE..........

Which it does very well.:D @2300 I get 180. although I've never checked, Fuel burn is ok. Take off is impressive, even in the Florida heat! Climb is typ. 1400ft/min. Static is 2250. I have more power than I need sometimes. (did I just say that?????):eek: If you are unhappy with it, just send it back to Ed, and he will re-pitch it for you.
 
Thanks for the input GMC. I think one factor I was overlooking was drag. I don't have wheel pants or fairings on yet and won't have any good numbers until all that is finished. I do want a cruise prop as I plan on using the plane for traveling and since it is an RV-9A there will be no aerobatics. The climb is so much better than my old 172 I certainly can't complain. I was more concerned about the engine running oversquare than the lack of climb or speed. I guess that is not a problem either.

If this was mentioned in post one, you would have had your answer in post two.
 
I'm at the same place . . .

Running an IO-320 w/ 9.0 jugs which is rated at 165HP and the Van's recommended Sensenich FP prop. Static I get 2250 @ 28". WOT at 4,000' I only get 2350 @ approx 26". That yields me about 135KIAS. I too do not have my wheel pants and gear fairings on - but heck, could I get another 250 RPM (sensenich limit) by adding these?? Seems like I'm not getting the full bang I would have expected. Time to switch to the 200RV CS prop$$$???
 
I just want to welcome George back. George I have missed you! I have not seen a post from you on this forum for several years now. I am glad to know I might be reading more of your wisdom again soon. :D
 
8A 0-360 Sensenich FP 86"

I gained in between 25-30 mph adding the fairings and 175-200 rpm on the top end. It feels better in the air also. You will have a different plane when you get those fairings on.

Randy
 
Sterb prop

My opinon about Sterba props is you get what you pay for. I've owned and used his props on other aircraft with simular results.
Charlie
 
read my article

Read my article on speed mods on this website. One of the best investments I made was changing a Sterba wood prop for the Catto Glas prop. I gained 8 knots in flight with NO increase in fuel usage. If you read the article you will see how much a part parasitic drag plays in top end and fuel consumption.
Woodman