[auflauf]

Hello!
Actually, I am narrowing down the list of potential planes. Fuel consumption is a major concern as fuel prices are high here in Europe (e.g. Avgas 14$/usg, Mogas 98 oct 9,2$/usg).

For some xy-320, I found the fuel flow for 75% power setting being given to ~8.5gph. This equals to 118$/h for 100LL

Do you have any experience with lower power settings (55%, even lower)? Is it possible to fly a xy-320 with 6 gph or even 5,5 gph?

Thanks!
Alexander

 

[Ironflight]

Absolutely - just pull the throttle back for whatever fuel flow (and resulting speed) that you feel comfortable with. I can pull the power back on my O-360 to just what I need to stay airborne in the RV-8, and the fuel computer will show me with about an 11 hour endurance (or some silly number).

It's hard not to let an RV run though - but that's a pilot discipline issue...

Paul

 

[n5lp]

Long term effects

I have some experience flying along with a Cessna 150. The very low engine temperatures made me wonder if doing this for a long period of time might have adverse effects.

I have never heard of anything bad, but as Paul says, it is kind of hard to make oneself do this for a long time.

 

[Capflyer]

On my RV4, O320 160hp, at 24sq which is about 75% and aggressively leaned I cruise around 7.5gph. I have the Electroair electronic ignition which made about a 1/2 gph difference in my fuel consumption for cruise flight after I installed it. I am able to run about 25deg LOP now with the EI and my fuel consumption drops to around 7gph and gives me around 150kts IAS at 5000'.

 

[Snowflake]

My O-320 150HP RV-6 cruises comfortably at 170mph and 25-27 L/hr. Conventional ignition (mags) and fuel metering (carb). That's at 2350RPM, roughly, but I don't know the MP as I only have a fixed pitch prop.

 

[L.Adamson]

I have some experience flying along with a Cessna 150. The very low engine temperatures made me wonder if doing this for a long period of time might have adverse effects.

Same here with my 180HP 6A. Fly's, but temps are too low for my liking.

L.Adamson --- RV6A

 

[jmbrwn]

My O-320 150HP RV-6 cruises comfortably at 170mph and 25-27 L/hr. Conventional ignition (mags) and fuel metering (carb). That's at 2350RPM, roughly, but I don't know the MP as I only have a fixed pitch prop.

Rob- I have the same set up as you, and last year flew to OSH at 10,500' average at 2400 rpm and got 25 liters/hr (6.6gal/hr) @ 170mph. I'm turning an Aymar Demuth prop...what prop do you have?

 

[hevansrv7a]

Some basic concepts


1. A fuel injected engine can be run well lean of peak while a carb engine usually cannot. This represents a large fuel savings for a given power. Even a FI engine may require balancing the injectors.
2. A more efficient prop will save fuel. In theory, a C/S prop can be more efficient, especially over a large range of power and speed settings. You can run a C/S prop at open throttle, reducing, thus, pumping losses, even while at lowered prop speeds. Within the range of C/S props, the MT series appears to be less efficient than Hartzell or Whirlwind RV 200. This is second-hand information. For a given speed and altitude, a FP prop can be just as efficient as a C/S prop, but probably not over a wide range of performance.
3. As noted above, you burn less gas if you slow down. For a distance traveled, your best L/D speed is the most economical. The RV-9 is the most economical RV that I know of for mpg or litres/100 km. See the CAFE test on that. The best compromise for speed vs. fuel is the Carson's speed. Look it up or see my info page, linked below. This is really about the drag curve, not about the engine.
4. Also as noted above, you can reduce fuel consumption per hour to even less if you go even slower, but your fuel per distance goes up. That would be the minimum sink speed and it is roughly 76% of the speed for best distance (L/D) while the change in fuel per hour will be roughly -14% from best L/D.
5. In my experience with my io-360, best performance from the engine will not be reached at very low power settings. RV's are fast not only because they are slippery but because they have a lot of power compared to other planes. If you know you don't want to go fast, just inexpensively, a smaller engine may work out better for that reason. The engine is designed to be used at power settings above 60%, I think. I can fly mine at 35%, for example.
6. Also second-hand information: electronic ignitions seem to give some added fuel economy when used running lean of peak.

 

[auflauf]

RV's are fast not only because they are slippery but because they have a lot of power compared to other planes. If you know you don't want to go fast, just inexpensively, a smaller engine may work out better for that reason. The engine is designed to be used at power settings above 60%, I think.

That's exactly what I was suspecting: you may be able to use low power settings, but it is not "practical". Like in a car, there may be throttling losses. But the information given further up, that 6gph may be realistic, at least does not rule out a 320 from the start.
My ideal plane might be a MC100 (the all-metal precessor of this one: MCR01) with a slightly beefed up structure. But they are hard to find - and the composite ones are said to be rather fragile

 

[hevansrv7a]

Very realistic

That's exactly what I was suspecting: you may be able to use low power settings, but it is not "practical". Like in a car, there may be throttling losses. But the information given further up, that 6gph may be realistic, at least does not rule out a 320 from the start.
My ideal plane might be a MC100 (the all-metal precessor of this one: MCR01) with a slightly beefed up structure. But they are hard to find - and the composite ones are said to be rather fragile

Yes, 6 gph is very realistic even for a 360. It may be a little less efficient than at higher settings but it will do it easily.

 

[C-FAH Q]

Yes, 6 gph is very realistic even for a 360. It may be a little less efficient than at higher settings but it will do it easily.

Io-360a1b6. 22" 2200 rpm. 50 lean of peak, 145 kts tas. 6.6 gph. 2500asl
Io-360a1b6. 22" 2200 rpm. 50 rich of peak, 150 kts tas. 7.1 gph 2500asl

On a 500 mile trip.........less than a gallon difference by the time you fly a little longer due to a slower speed.

Your mileage may vary

 

[Finley Atherton]

Do you have any experience with lower power settings (55%, even lower)? Is it possible to fly a xy-320 with 6 gph or even 5,5 gph?

Thanks!
Alexander

Higher cruise altitudes, low rpm and aggressive leaning (allowable below about 65% power) are the keys to good fuel consumption. Electronic ignition and a C/S prop (low cruise rpm) also helps. However I guess with all that controlled airspace in Europe it may not always be possible to cruise at higher altitudes.

An RV 9A with an 0-320 can cruise at around 148 to 150 kts at 8,500 ft DA at 2250 rpm using about 6 US gph if leaned aggressively. An IO 320 may give slightly economy.

Fin
9A