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flydjd2

Member
Hi from Germany (and the UK)

I am building a 7A here in N Germany and am planning to fit a IO 320 (probably Aerosport) with FP Sensenich FP.....320 due v high price of avgas in Europe....
(RV 7's not cleared for aeros yet in Germany or UK)

Any general advice plse...thks
 
Fine choice

However,

If money isn't a huge issue, I would strongly recommend a constant speed prop. It will help with climb and efficiency.

Good luck!
 
The only thing I've come to find out is that the -7 line likes a little more weight up front for balance issues.
Your metal FP Sensenich prop is a little lighter than a CS prop setup would be so try to mount any accessories you can in front of the cockpit.

I won't get into the CS vs FP thingy other than to say that an RV with a FP prop like the Sensenich will cruise just as fast as a CS prop will, and it will still climb more than twice as fast as any typical GA aircraft will. The RV ain't no slackard with a FP prop.
The only reason I'd persuade you to spend the big $$$ to go CS would be if you are into high altitude airports frequently.

So mainly, get any weight you can up front while you're building.
 
Flydjd2,

There is a common misconception that smaller engines will result in lower fuel burns. For a given speed it is not true. For example, 2 RV-7As (one with a 160hp O-320 & FP prop and the other with an O-360 & C/S prop) fly together for a hour in roughly a straight line at say 140 to 150 kt indicated. The O-360 aircraft will burn between 1 and 1.5 gallons less than the O-320 aircraft. I have found this several times with several different aircraft.

If both aircraft flew at 75% power the story might be different. Clearly the 180hp aircraft could burn more fuel if it chose to.

An O-360 is not very much heavier or expensive than an O-320, so the penalties for going to the larger engine are small. You may also like to consider fitting fuel injection as you are much better able to operate lean of peak EGT, thereby saving an additional 1 gph or so. A c/s prop is also very desireable in reducing fuel flows. Electronic ignition also has the reputation for producing more power/ reducing fuel flow for a given speed.

So, if your primary aim is minimum fuel burn I would go with an injected O-360 with a c/s prop & elctronic ignition. The Hartzell blended aerofoil props do seem very good value right now.

Yours, Pete
 
TMX IO-390 Or 0360 For RV-7A

Also in engine market so what about The TMX IO-390 for a RV-7A? I understand it incorporates larger displacement cylinders then the standard Lycoming IO-360 Angled valve engines and thus is able to produce 10 more horsepower then the standard 360 cubic inch engine. At $27,600.00 outright and complete with new Unison/Slick magnetos, new Unison/Slick ignition harness, new Unison/Slick spark plugs, new lightweight Sky-Tec starter, new Lycoming fuel pump and a complete new Precision Airmotive SilverHawk EX or Airflow Performance EX fuel injection system. Not a bad price for all new. Are the Weights about the same? I heard that the RV7A needs a little extra weight in the nose anyway. Can anyone help with this decision 0360 C.S. or 0390 C.S.?

Finishing Fuselage and Finishing Kit on the way.
Squeak
 
There is a common misconception that smaller engines will result in lower fuel burns. For a given speed it is not true. For example, 2 RV-7As (one with a 160hp O-320 & FP prop and the other with an O-360 & C/S prop) fly together for a hour in roughly a straight line at say 140 to 150 kt indicated. The O-360 aircraft will burn between 1 and 1.5 gallons less than the O-320 aircraft. I have found this several times with several different aircraft.

You missed the point of your comparison, the 180 is constant speed, and that does save fuel by allowing the engine to run wide open (better flow) but at any rpm.

But if you equalize that, all things equal a heavier airplane will not fly on less fuel than a light one will. And a heavier or larger engine will not fly at the same power as a smaller one with less fuel...greater pumping losses to begin with.
 
Good plan

flydjd2 said:
Hi from Germany (and the UK) I am building a 7A here in N Germany and am planning to fit a IO 320 (probably Aerosport) with FP Sensenich FP.....320 due v high price of avgas in Europe....
(RV 7's not cleared for aeros yet in Germany or UK)

Any general advice plse...thks
Click to expand...
I think your base line choices are great.

I'm a big fan of C/S props and have one on my RV7, but the Sensenich is a great prop and cost vs. performance is excellent. One of the advantages of the C/S prop comes in when doing acro, but it sounds like you will not be doing any? By the way how do they know if you do acro or not? :D

Guess some might argue about engine size vs. fuel economy. I know the RV-7/A is tail heavy, in other words saving lots of weight on the noise is not all good. Do the weight and balance and you will see what I mean. Since the (I)O320 and (I)O360 is about the same cost I would go for more power. The main factor in fuel economy is the throttle hand of the pilot.

If you want best fuel economy you want fuel injection, probably c/s prop and dual electronic ignition. Again 320/360 is up to you but I like the extra power for a little extra weight. However when I say best econ we are talking a few % not huge difference in carb, fixed pitch and magnetos. Although to me electronic ignition is a no brainier option. George
 
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Jconard said:
You missed the point of your comparison, the 180 is constant speed, and that does save fuel by allowing the engine to run wide open (better flow) but at any rpm.

But if you equalize that, all things equal a heavier airplane will not fly on less fuel than a light one will. And a heavier or larger engine will not fly at the same power as a smaller one with less fuel...greater pumping losses to begin with.
Click to expand...
I only have data for a fixed pitch carb'd O-320 and a c/s carb'd O-360. Results as above. I agree in theory that the smaller engine should burn less gas - but that doesn't seem to be true in practice.

I'm with George, O-360 seems the best bet. As for aeros, I used to fly in the UK, although they haven't yet "approved" aeros in sbs RVs I not aware that that actually stopped any one.

Pete
 
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