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Engine/Prop options

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CuriousGeorge

Active Member
Hi Guys -

I'm searching for the perfect flying -4 for me. After countless hours scrubbing the archives, I'm still at a bit of a loss for the best engine/prop combo. Here's what I'm concluding, please tell me if I'm wrong.

1.) O-320 FP (wood/composite) is the lightest, maybe too light if a heavy back seater is along.

2.) O-360 CS gives extra power and shifts CG fwd

3.) An O-320 CS/metal and an O-360 FP (composite or wood) seem to be about the same weight

So why are O-320's so much more common? And with the same weight up front or nearly so, why would acro characteristics be different?

What is the downside of 180 hp if the weights are close? It looks like free power to me, other than slightly more fuel burn.

Anyone? Anyone? Bueller?


Thanks -


George
Current Citabria, future RV-4
 
I just recently bought a flying 4 and was struggling with the same decisions as you. I eventually went with the 0-320 for less fuel burn and the CS for prop for more performance. In reality, the performance boost is not that great if any at all for me. A friend has a 4 with the same engine and a cruise prop and gets much more speed out of his than I do. It could be my power settings, or maybe some tweaks he has done to his engine, who knows? I just know that if I had it to do over again, I would consider the fixed pitch more than I had before.

There are upsides to the CS prop though. I love being able to slow down quick. That comes in handy more times than I would of thought particularly entering the pattern and formation flight. The climb rate is a bit faster. I also assume that it might help for aerobatics though I know very little about it at this point. The forward CG is nice when carrying passengers. I haven't flown a 4 with passengers that was lighter on the nose then mine but I can say that mine flies great with someone in the back. I hope this helps a little.
 
Hi George.....

....My buddy keeps his -4 in my hangar and we fly it often, solo and two-up. I'm 190 and he's 160 and gets in the back.

All he did was leave the big, clunky Lyc starter to help move the CG more foreward. The 160 Lyc gets the airplane off the ground in around 7 seconds and is a dream to fly with the two-bladed Catto....which, by the way, added 6 MPH over the wood Sterba.

A 160 horse -4 with a FP prop is a delight to fly and really nimble. He's a student pilot and has no trouble slowing the airplane down and three-pointing it...it's all in the throttle management.....less revs, slower speeds..

Regards,
 
pierre smith said:
A 160 horse -4 with a FP prop is a delight to fly and really nimble. He's a student pilot and has no trouble slowing the airplane down and three-pointing it...it's all in the throttle management.....less revs, slower speeds..
Click to expand...

"it's all in the throttle management.....less revs, slower speeds.." ............and more space! :D


Sure they can slow it down. But I've yet to meet an RV pilot who hasn't mentioned that he wished he could slow down like us C/S owners can. Unless the fixed prop is purely pitched for climb or the plane is just plain draggy, then the F/P is going to require more area to get slow.

We have a interesting mountain approach to our airport. It's a decent of 2000' a minute, with the airport pattern at the bottom. A C/S can maintain desired airspeed all the way down, and instantly adapt to the airport pattern speed. Try that in an F/P RV. It just can't happen! ;)

L.Adamson --- RV6A (flying)
 
From Pierre

"A 160 horse -4 with a FP prop is a delight to fly and really nimble. "

Is a 180 horse/FP less of a delight to fly and less nimble? Especially if it's a light weight prop?

And with a light C/S prop?

Other than fuel burn and autogas, I'm still not seeing the downside to 180 vs 160, especially if leaving a clunky starter on the 160. Mogas is going away thanks to ethanol, so that advantage seems small.

Pierre, thanks for weighing in - you've contributed a lot of posts that I've read.


George
 
And at a given speed, the O-360 will burn the same gas as the 320... or very close. There is almost NO disadvantage to going with the 180HP over the 160, EXCEPT initial cost. Given the same prop, then engines weigh within a few pounds of each other.
 
CuriousGeorge said:
Other than fuel burn and autogas, I'm still not seeing the downside to 180 vs 160, especially if leaving a clunky starter on the 160. Mogas is going away thanks to ethanol, so that advantage seems small.
Click to expand...

George, Its really down to you, but here's my opinion. The fuel burn from a 180 is less than a 160 for the same speed. I've proven it many times when flying with other people, a c/s prop and an injected engine also help manage the fuel burn. Truth is people with a 180 go faster so end up burning more gas. But, stay at 160 speeds and you will burn less - a regular compression 180 can also burn autogas (compression ratio is only 0.2 higher than a 160).

I think an injected 160 with a c/s prop is the best combination. It pays to keep things light - so a 160 with wood fixed pitch might be best, but usually there is not enough weight up front to keep the cg in the right place 2 up. So adding a c/s prop (my choice would be a 2 bladed MT) would give the advantages of a c/s (good take off & climb, flexibility, good aeros, etc) without adding too much weight. A 180 is around 7 to 10lb heavier, but a 180 c/s prop is much heavier than a 160 c/s prop, so the 180 c/s combination ends up being probably 20lb heavier than a 160 c/s (and up to 35lb heavier if a metal prop is used). That's too much weight on the nose for me. If you don't want a c/s prop then a 180 FP would be my 2nd choice.

Figure what is important to you and tune your airplane for that mission.

Pete
 
Re: Penguin

Thanks Pete -

I just looked up the published weights for the MT C/S and you're right, the 160 hp prop is lighter, 7 lbs they say. But the up to 300 hp prop weight is for a slightly longer prop. Even so, figuring 7 for the prop and 10 for the engine plus a little, it comes to the 20 lbs or so you said.

My weight is about 170 lbs. If I added the 20 lbs to the nose and balanced with say 3 or 4 lbs in the tail if necessary to keep the CG, given my FAA standard weight, any guess as to how significant that extra weight would be? 20-25 lbs for 20 hp seems like a fair trade to me. Probably 95% of my flying will be solo, XC is a big part of my intended mission, and my acro won't be in any boxes, just chasing clouds, frolicking, and attacking intruders in my airspace.

Next, you mentioned compression in the 360. I haven't looked into that. Does that produce the expected result of more power, better economy, etc? I have a 150 hp O-320 in my Citabria. I forget the details, but upping it to 160 didn't seem worth the expense. A friend suggested I go to a 360 on that when the time comes for an overhaul instead.

Any 360 experts please feel free to chime in.


George
 
Hi George,

My battery is in the standard location but if needed or wanted you can mount it under the baggage location or even further aft, so you would never need to actually add weight to adjust the CG to taste.

In my opinion the added power is worth the weight, some others will disagree, there choice is good to, any RV-4 is a blast and is far better then anything you have ever flown!
 
Funny thing Russ, I've only had a very brief ride in a 7 and I loved that plane! However, the unanimous opinion I've read is that the 4 is much more responsive than the 7. Throw in the fact that a built 4 is about half the price of a 7 or 8, plus sitting in the middle is pretty cool, and it's an easy choice for me.

I'm just kind of surprised that in the ones I see for sale, the 180 hp models are in short supply. For what I want to do, I think the O-360 will do nicely.

I guess a rear mounted battery is fine, since that's the way it is in my Citabria. There will be some added weight for the heavy wires though, if it even turns out to be necessary.


--George
 
great topic

George,
Thanks for raising this topic. I hope to be financially able to start shopping next year. Once bought, changing the engine is probably not a reasonable option. As of now, I am leaning toward the 0320 with CS.
My guessing the CS would give more climb on the low end and more speed on the top end with all other things being the same except a fixed pitch prop. It seems there is no right answer.
Thanks again for helping me learn more about this important option on my future RV-4.
Cheers, Dan
 
I just spoke to Robin Reid this morning. He?s an ATP/CFI with a long history in GA who makes the first flight for many RV builders and I believe he?s flown most models and engine / prop combinations.

For overall flying qualities, his favorite of all the RV?s is a -4 with an O-320 / CS prop. Another thing I haven?t seen mentioned is that with an O-320 there?s no RPM restrictions to deal with.
 
need to know

Anybody out there have a flying RV4 with an Lyc. IO-360, 200hp. angle valve eng. under the cowl, spinning a hartzel 73" inch c/s prop.? Came off a wind damaged Mooney. Please advise on how to solve weight and balance/ nose heavy/ forward C.G. problem. Battery is already in the luggage compartment. Figure light weight starter and alt. Approx. how much lead weight would I have to put in the tail section? Actual weight & balance pending complete final assembly.
 
Re: Robin Ried

Do you have a way to contact Mr. Ried? And/or specifics of why he likes the 320/cs configuration best?

And... this probably deserves a different thread, but has anyone played with a movable battery? I'm thinking of some airliners that move fuel to the tail for optimum CG. If the battery could be mounted on a slide of some kind, it would be like elevator trim. Just a thought.
 
manuel gonzalez said:
Anybody out there have a flying RV4 with an Lyc. IO-360, 200hp. angle valve eng. under the cowl, spinning a hartzel 73" inch c/s prop.? Came off a wind damaged Mooney. Please advise on how to solve weight and balance/ nose heavy/ forward C.G. problem. Battery is already in the luggage compartment. Figure light weight starter and alt. Approx. how much lead weight would I have to put in the tail section? Actual weight & balance pending complete final assembly.
Click to expand...

I have a 200+hp angle valve A1A in my old -4.

1. Non weighted/non counter balanced crank.
2. Sky Dynamics magnesium sump.
3. Sky Dynamics cold air induction.
4. Light B&C starter.
5. B&C SD-8 is the soul alternator.
6. Battery in standard location.
7. MT MTV-15-B-183-33 prop.
All this takes weight off the nose, I could not manage with a Hartzel, This engine install is about the same as a parallel valve 180 with a Hartzel, I don’t think it will be so handy as just bolting that engine on there and going flying. I think at minimum you need to sell your prop and get something lighter, that might not even get you there, sorry.
 
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Low n Slow said:
I just spoke to Robin Reid this morning. He?s an ATP/CFI with a long history in GA who makes the first flight for many RV builders and I believe he?s flown most models and engine / prop combinations.

For overall flying qualities, his favorite of all the RV?s is a -4 with an O-320 / CS prop. Another thing I haven?t seen mentioned is that with an O-320 there?s no RPM restrictions to deal with.
Click to expand...


Ditto. I've heard the same thing from Robin, and believe me he has flown everything. About 3 months ago he checked me out in a Bonanza and was teaching acro to a new owner in her Extra 300, and also checking somebody out in a T-28 during the same time period. He's the guy other airline pilots go to for flying lessons in their hot rod personal planes. If you call on Robin ask him about the little trick he played on me in the Bonanza. I'm sure he'll have fun with you laughing at my expense. If I were there I'd join the two of you.
 
RV-4 with the mooney cowl

RV-4 With the mooney cowl needs a new or serviceble C/S prop. My Hartzell Make. HC-C2YK-1B, Blade Model. 7666-2 got bent this past weekend. Can sombody help me find a replacement "yellow Taged" C/S Prop. that will marry my Lycoming IO-360- A1A, 200 Horse Power Engine. and or recommend a reputable repair station. Please advise.

Thanks

Manuel Gonzalez
 
CS v FP on 0.320

Hi

I have flown both, the FP was a Sensenich. The CS clearly had better climb as it was able to use full power on take off, and was smoother in the air than the FP. Having said that I have a FP on my about to be finished 4.

As regards 150 to 160 conversions there are lots of threads on this, I have upgraded mine....... new pistons, gudgeon pins, possibly nitrided bores if not already done, but I suspect a lot are still being run on steel bores.

If I were to start again, I would build it as a fastback, as light as possible..... 160 is fine, but with the lightest CS I could find. I love the CS in my 9.
 
Prop me up, again!

Guys,
Over the past 20 years I have been blessed to fly 200+ different RV's as part of my small consulting business, all the models and every conceivable engine/prop. I also have built and owned a 0-320 RV4, HR2 and 0-320 RVX. I really like how the 0-320 performs (and weighs) in the RV's, even the 7 and 8. With same bore but the shorter stroke/slower piston speed than the 0-360, it just seems smoother and runs cooler.

The best flying RV in my humble opinion is the RV3, hands down and the few owners of HR-1's say it is even better. Randy Lervold's RV-3 being probably the best example ever flown, although several late comers are also very nice.

However, if you can only have one, the Fastback RV4 with a wide deck 0-320/9.0:1 compression/electronic ignition and fuel injection is it. The HR2 is right there with it though as a close second. Constant speed? Nice, but costly and heavy, no matter how you slice it. The Hartzell is still the best value. However, the MT 2 blade C/S is lighter, much smoother, better aerobatic and only very slightly slower on the 0-320.

Steve Sampson's G-IKON is one of the best RV4's out there, set up very much like the perfect RV4 above. Check out his Blog.
http://gikonhome.blogspot.com/

V/R
Smokey
Dues gladly paid in Iraq
Gladly paid to DR anyway...


PS:A light nose, light weight RV4 with a Composite prop will give anything out there a tough 1 V 1, trust me. The true mettle of any airplane is how it handles throughout it's speed range and for me, it's low speed turning dogfight. The RV4 shines in that department, even over a Pitts.
 
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