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RV8 Performance and GA prop pitch

smithflys23

Well Known Member
I'm wondering if I've got my prop pitched correctly. I am also wondering what others with the same prop are seeing, and what pitch pin they are using. I have the Sensenich GA for IO-360. Currently using the #6 pitch pin.

TO RPM is about 2330, in the climbout it was lightly lower around 2250. Below are some of the numbers I was seeing at cruise.

8500'
153 IAS 180 TAS
20.2" MAP
2620 RPM
8.5 GPH
377 401 389 394 CHT's
1439-1444 EGT's

9500'
150 IAS 179 TAS
19.5" MAP
2620 RPM
8.4 GPH
375 395 383 389 CHT's
1409-1417 EGT's

Am I working the engine hard enough? Am I working it to hard?
 
Hi there,

Sorry, not that i have any proven advice, but i have the same engine-prop combination on my -8. Maiden flight is postponed after the virus-thingy.

What hp is you engine rated?
Is that number by the books or was it dyno-tested?

I would try the #5 pin to get the cruise rpm up to 2700 and therefore maximum power output. From my point of view a T/O RPM of 2300-ish is quite normal for a fixed pitch prop. This number will also increase with #5 pin.

I think that you are not too far from a perfect setting!
The speed is excellent, the fuelflow more than acceptable and the CHT?s below 400 (for longevity of the engine).

If you try #5 pin, please post your results here!!
 
Hi there,

Sorry, not that i have any proven advice, but i have the same engine-prop combination on my -8. Maiden flight is postponed after the virus-thingy.

What hp is you engine rated?
Is that number by the books or was it dyno-tested?

I would try the #5 pin to get the cruise rpm up to 2700 and therefore maximum power output. From my point of view a T/O RPM of 2300-ish is quite normal for a fixed pitch prop. This number will also increase with #5 pin.

I think that you are not too far from a perfect setting!
The speed is excellent, the fuelflow more than acceptable and the CHT’s below 400 (for longevity of the engine).

If you try #5 pin, please post your results here!!

My engine builder claims 190-195hp. That is with some of the engine tweaks he does, and 9:1 pistons.

I think I could get to 2700 RPM at cruise with the current setting, but I had it pulled back. I'll give that a try next time I'm out flying.

The 5 pin wasn't enough pitch, the engine kept wanting to over speed.

I talked to Sensenich about getting a 5 and 1/2 pin, and they suggested wrapping a piece of tape around the 5 pin to get a little more pitch. I checked the pins, and there really isn't a big difference in diameter between the different sizes. So, I believe that tape might work.
 
My engine builder claims 190-195hp. That is with some of the engine tweaks he does, and 9:1 pistons.

I think I could get to 2700 RPM at cruise with the current setting, but I had it pulled back. I'll give that a try next time I'm out flying.

The 5 pin wasn't enough pitch, the engine kept wanting to over speed.

I talked to Sensenich about getting a 5 and 1/2 pin, and they suggested wrapping a piece of tape around the 5 pin to get a little more pitch. I checked the pins, and there really isn't a big difference in diameter between the different sizes. So, I believe that tape might work.

TAPE !! I love Experimentals !!! Can you imagine someone telling a guy in a Cessna to put tape on something and have a overzealous IA tell them "you're grounded"? :D

I'm currently considering buying back a Citabria I owned and sold about 20 years ago. The same guy who I sold it to restored it and offered to sell it back to me. The only thing holding me back is that it's Standard category. Hard to go back after tasting Experimental freedom again.
 
My engine builder claims 190-195hp. That is with some of the engine tweaks he does, and 9:1 pistons.

I think I could get to 2700 RPM at cruise with the current setting, but I had it pulled back. I'll give that a try next time I'm out flying.

The 5 pin wasn't enough pitch, the engine kept wanting to over speed.

I talked to Sensenich about getting a 5 and 1/2 pin, and they suggested wrapping a piece of tape around the 5 pin to get a little more pitch.

I had mine on the dyno with 8,5:1 pistons @3000ft density alt. producing 188 hp. So i hope i will end up with roughly the same numbers.

I plan to set my prop for WOT cruise turning 2700rpm @ 8000ft-ish.
So next time you go flying, i would appreciate if you would post numbers for WOT cruise on your setup.

I also didn?t know that sensenich offers half-sizes of the pins. Even so i also like the tape idea i would be interested if they are really available from sensenich.

Please keep me and all of us posted on your results.

Really interesting thread!!
 
I had mine on the dyno with 8,5:1 pistons @3000ft density alt. producing 188 hp. So i hope i will end up with roughly the same numbers.

I plan to set my prop for WOT cruise turning 2700rpm @ 8000ft-ish.
So next time you go flying, i would appreciate if you would post numbers for WOT cruise on your setup.

I also didn?t know that sensenich offers half-sizes of the pins. Even so i also like the tape idea i would be interested if they are really available from sensenich.

Please keep me and all of us posted on your results.

Really interesting thread!!

They don't offer half sizes, that's why they suggested wrapping tape around the 5 pin. I found that if I wrapped twice with electrical tape, the diameter was greater than the 6 pin. That's why I decided to go with the 6 pin.
I'll see what I get next time out, and give you an update.
 
TAPE !! I love Experimentals !!! Can you imagine someone telling a guy in a Cessna to put tape on something and have a overzealous IA tell them "you're grounded"? :D

I'm currently considering buying back a Citabria I owned and sold about 20 years ago. The same guy who I sold it to restored it and offered to sell it back to me. The only thing holding me back is that it's Standard category. Hard to go back after tasting Experimental freedom again.

Well, I think you have to understand what were talking about. To set the pitch of this prop, you insert a pin into the hub, then rotate the blades against it. That sets the pitch of the blade. Once its set, you tighten the clamp bolts, and remove the pin. Tape is just a way to give the pin more thickness. It comes off with the pin, when you remove it from the hub. Its not as crazy as it sounds.
 
If your speeds are in knots you’re doing great. If not you are a little slow for a 8.
One of my pet peeves is using mph anywhere in aviation except antiques. Heck my 1964 Travel Air has knots only. No maps or charts use mph.
Rant over.
Bob Bisbee
RV7A under construction
 
I'm wondering if I've got my prop pitched correctly. I am also wondering what others with the same prop are seeing, and what pitch pin they are using. I have the Sensenich GA for IO-360. Currently using the #6 pitch pin.

TO RPM is about 2330, in the climbout it was lightly lower around 2250. Below are some of the numbers I was seeing at cruise.

8500'
153 IAS 180 TAS
20.2" MAP
2620 RPM
8.5 GPH
377 401 389 394 CHT's
1439-1444 EGT's

9500'
150 IAS 179 TAS
19.5" MAP
2620 RPM
8.4 GPH
375 395 383 389 CHT's
1409-1417 EGT's

Am I working the engine hard enough? Am I working it to hard?

It's a FP prop, so you have to pick speed (6th gear), climb (1st gear) or something in between (3rd gear). You should do all testing at DA 8000. Your numbers look fine if they are in kts. I'm running a 180hp FP prop with similar numbers. I figure it costs me around 10kts on the top end AND some climb performance. You and I both have a corvette stuck in 3rd gear (yours might be in 4th) It's the very reason I'm going to a CS prop.
 
If your speeds are in knots you?re doing great. If not you are a little slow for a 8.
One of my pet peeves is using mph anywhere in aviation except antiques. Heck my 1964 Travel Air has knots only. No maps or charts use mph.
Rant over.
Bob Bisbee
RV7A under construction

Everything is in KTS. I don?t like using MPH either.
 
It's a FP prop, so you have to pick speed (6th gear), climb (1st gear) or something in between (3rd gear). You should do all testing at DA 8000. Your numbers look fine if they are in kts. I'm running a 180hp FP prop with similar numbers. I figure it costs me around 10kts on the top end AND some climb performance. You and I both have a corvette stuck in 3rd gear (yours might be in 4th) It's the very reason I'm going to a CS prop.

I?m strongly considering a WW CS prop.

What numbers are you expecting to see once you convert?
I thought I would lose some top end speed with a CS.
 
I thought I would lose some top end speed with a CS.

This is opposite of my experience. My first RV (8A) started off life with a FP prop. After 300 hours I back fitted the very nice Hartzell BA CS prop. Performance dramatically improved across the operating envelope.

My second and third RV builds also fly with this Hartzell prop.

But - as always these decisions should be based on the mission priorities you establish for your airplane.

Carl
 
If anyone has the WW 300 series on their -8, I'd really appreciate some data on that prop. That is the replacement I'm considering.
 
I’m strongly considering a WW CS prop.

What numbers are you expecting to see once you convert?
I thought I would lose some top end speed with a CS.

I don't have any real number in mind other than to get Van's published performance numbers. I've flow -8's with CS and FP props, and the CS variant is my preference by a very wide margin. I'm replacing the prop and engine, so my new numbers won't be very meaningful. I should have around 200-210HP on the dyno with my new engine and I'm using the Hartzell carbon fiber "claw" prop. The prop is sitting in my foyer and my engine is in parts with Tim Hess. My bride has been pretty tolerant of the prop in the living area - makes for good conversation. The engine build has been slowed down by this pesky virus, so no telling when I'll be flying behind it! I'll post the numbers when I do. I currently get around 160kts TAS at 2450RPM with 19-20in of MF pressure at 8000ft DA. The low MF pressure makes me think the engine isn't working all that hard and I'm sitting in 3rd or 4th gear! :).

I can't think of any reason at all that you would lose on the top or bottom end with a CS prop when compared to a FP prop, unless the prop airfoil just wasn't as efficient. A FP prop is stuck in some gear and in theory a CS prop should be able to shift into that same gear - and any other gear.
 
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Gee whizzum

Your constant speed props are wonderful. The OP would like to discuss his aircraft performance with his ground adjustable prop. Pity the poor pathetic pilot. But, at least he doesn?t have fixed pitch like some of us. Can we stick to the subject at hand?
 
It?s all relevant to the discussion, so I don?t mind.
Eventually I?ll upgrade to CS, but for now, I?m trying to get the best performance possible, with the prop in hand.
 
Thread drift

Is real :).

My FP Sensenich runs 25-30 rpm over redline wide open and leaned for best power at 8,000ish. I figure it is about optimal as far as it goes. Giving consideration to the ga Sensi, but I’m not sure there is much to gain. Maybe a little more acceleration on takeoff and climb, maybe not. Sounds like yours is performing well.
 
Last edited:
It?s all relevant to the discussion, so I don?t mind.
Eventually I?ll upgrade to CS, but for now, I?m trying to get the best performance possible, with the prop in hand.

The good news is, these are wonderful planes even with a FP prop. You have a great, light, versatile prop and I would do exactly what you are doing if I had your prop. You just need to pick your flying objectives; cruise speed, take off performance or someplace in between and set your prop accordingly. However, I don't think you can get Van's published numbers (cruise/rate of climb) @ specified horse powers and weights with a FP prop, so set your expectations accordingly.
 
I have an RV8...180hp Superior IO360 Eng!....Ram air induction..WW200 CS prop....at 7500ft...(full throttle!).. MP23.5....RPM2360..fuel flow around 33lt/per hr....I see an IAS 147kts...TAS 168kts.. CHT range from 318....325...EGT ..around 30 LOP!......At 1500ft ..flat chat everything forward ..she does 186kts....Ps .. I love the WW200...
 
I have an RV8...180hp Superior IO360 Eng!....Ram air induction..WW200 CS prop....at 7500ft...(full throttle!).. MP23.5....RPM2360..fuel flow around 33lt/per hr....I see an IAS 147kts...TAS 168kts.. CHT range from 318....325...EGT ..around 30 LOP!......At 1500ft ..flat chat everything forward ..she does 186kts....Ps .. I love the WW200...

2360rpm, and 168kts, seems a little low. Or am I missing something?
 
I had mine on the dyno with 8,5:1 pistons @3000ft density alt. producing 188 hp. So i hope i will end up with roughly the same numbers.

I plan to set my prop for WOT cruise turning 2700rpm @ 8000ft-ish.
So next time you go flying, i would appreciate if you would post numbers for WOT cruise on your setup.

I also didn?t know that sensenich offers half-sizes of the pins. Even so i also like the tape idea i would be interested if they are really available from sensenich.

Please keep me and all of us posted on your results.

Really interesting thread!!

Today I gathered some more data.

Climbed to 8000? DA (6000? or so) and got the following.

2700rpm 185TAS 10.6 GPH 22.9 MAP
I had to pull the throttle back in order to keep from over speeding the engine. That?s with the 6 pin.

Climbed up to 8500?
2700rpm 186TAS 9.0 GPH 21.3 MAP

Pulled back the throttle at 8500?
2630rpm 179-180TAS 8.3 GPH

I might consider adding slightly more pitch, but I think this is about as good as it will get with a FP GA prop. I?m pretty happy with 180TAS and 8.3-8.5GPH.
 
Today I gathered some more data.

Climbed to 8000? DA (6000? or so) and got the following.

2700rpm 185TAS 10.6 GPH 22.9 MAP
I had to pull the throttle back in order to keep from over speeding the engine. That?s with the 6 pin.

Climbed up to 8500?
2700rpm 186TAS 9.0 GPH 21.3 MAP

Pulled back the throttle at 8500?
2630rpm 179-180TAS 8.3 GPH

I might consider adding slightly more pitch, but I think this is about as good as it will get with a FP GA prop. I?m pretty happy with 180TAS and 8.3-8.5GPH.

Those numbers are pretty respectable. I assume you leaned your engine.

If your static is 2330rpm and 2250rpm on climb and you think you are putting out 195hp, those look like good numbers. I have a 180hp, and I'm doing 2300rpm on take off and around 10kts less on top end w/out over speeding. I'm probably pitched a little more for climb if I'm getting similar RPM on TO with less HP.

Given your manifold pressure, it would stand to reason you could increase your blade angle some for a more optimal cruise, but at the expense of poorer take of and climb.
 
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