Bendougy...

I can tell you this:

A horsepower is a horsepower is a horsepower.

You can get hp in many flavors. 340, 360, 375...etc...

Fuel burn is equal to HP used.

What I just recently discovered is that dollars per hp increase GREATLY after 180 hp.

My best bet was parallel valve 180hp configuration 360.

How many horses do you want? A 360 can throttle down but a 320 cannot throttle up.

I have been flying an RV-6 with 180 carbed horses and burn has been 8.3 gph at 2500 rpm.

More horses is more speed and more fuel burn.

Does this help?

:confused: CJ
 
CJ is right on. As long as you install a minimum of 180 HP, everything else is cost/benefit/preference.
 
I need to re engine. Drag cubes with speed incease so ground miles to fuel burn decrases with speed increase thus my need for bare figures to decide on engine
 
Actually drag varies as the square of the speed and hp required as the cube of speed.:) So you can say that fuel flow varies pretty much as the cube of the speed at a given altitude. 180hp is a nice compromise between cost, climb rate, speed and fuel flow but you can always throttle back or use less rpm with a 200 or 210 hp engine too and have that speed and ROC when you want it.
 
Like Captain John said...

Think back to the total drag curve, the sum of the induced drag curve and the parasite drag curve.

The total drag curve can also be thought of as the "horsepower required" curve. How you make that is up to you. :D
 
What I am trying to find out is the efficiency of a IO-360, IO-375, IO-390 to produce say 180 HP. This may be due to cylinder efficiency parallel valve verses angle valve (exhaust scavanging), swept volume differences due to crankshaft throw design ie; IO-375 or due to Compression ratios. Efficiency could be affected by engine size ie O-360 going flat out compared to an IO-390 at 75 % Power to produce the 180 HP. In efficiency I mean power to fuel burnt. I am not concerned with engine weight or purchase cost,just fuel cost to produce the 180 HP
 
If I understand the question correctly you want the most efficient engine to produce 180 hp.

Every engine will produce 180 hp and use almost an equal amount of fuel doing it. A HP is a HP is a HP...

That being said, an engine is most efficient when the throttle plate is wide open. See the Vans instruction manual (I think it is in 11-8??? I just read it) it says it in there.

If efficiency is what you want, you can operate any engine efficiently... simply open up the throttle plate all the way and dial in the mixture. I know you already know this. That is what makes me think I am missing your question.

:confused: CJ
 
Food for Thought

I've flown a Zlin 242L and it's got the 200hp angle valve AEIO-360 lycoming. It burned 39 liters per hour at 65%.
The Piper Seminole I flew has 180hp O-360 lycomings and it burned 10.2USG/hr per side at 65%.

Do the math and both engines come out to within half a liter, or 1/8th of a gallon. Leads me to believe that the angle valve engines are more efficient.

Take all this with a grain of salt, Everything I say came from the POH, I never verified any of it. I once encountered a 172, 150hp O-320 and 75% power would burn around 10usg/hr. That's leaned to max rpm in cruise.
 
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Thanks John. In my mind the different engine/cylinder designs have to change effieiency. I want as much speed as I can get with efficiency. Since I am not changing airframe, my engine is the only variable. Lets say all engines can achieve 175 knot in my frame, will one engine type IO360,IO375,IO390 do it for less fuel burn. If the answer is no they will all be the same then it is just a matter of how big I want to go.
 
Efficiency

If efficiency is what you are looking for, you can also have a look at electronic ignitions to replace the magnetos. I won't start a debate but I think they worth it. Some dealers claims 10-15% fuel reduction ( I don't think at 75% but maybe at lower power settings).
Running LOP is also a way to save gas. In my case I purchase an EMS to help me with the leaning process when the aircraft will be ready to fly.

My IO-375 weights 126kg (approx 280lbs) which is lighter than an IO-360M1B with 15 to 25 hp more. But now it cost more than the M1B...:( The choice isn't simple.

I asked Aerosport Power when I ordered the engine and if I recall correct (it was a 1 1/2 year ago) they claimed 0,43 or 0,45 lbs/hp/hr.

Hope this could help you.

Have a good day
 
You are welcome! The engine really isn't a variable either but another way of looking at it is to compare the DISTANCE over ground at the higher speed of having more ponies!

Sooo just to confuse the matter, the more ponies propels the plane faster and covers more ground thereby saving fuel.

HOWEVER, the RV already moves pretty well even on modest power.

It is more like comparing a 200HP Maule to a 200HP Mooney. THERE the Mooney wins the efficiency nod!

Bastian, YES!!! You are correct! That is why I installed the G3ignition system in my project. I want to be as efficient as possible too!

The EI will burn more completely and combined with LOP, I ought to get some good distance covered at the smallest fuel penalty.

Good conversation!!!

I like this stuff!!!

:D CJ
 
Light is on

Thanks guys. After Your help and 10 hours reading old threads, the cost of a certain speed is the same for all engines. If I have a larger engine I can throttle back and it will cost the same per mile as a smaller engine. A smaller engine cant go faster. I can see a IO-390 on its way
Thankyou all
Ben
 
In my mind the different engine/cylinder designs have to change effieiency. I want as much speed as I can get with efficiency. Since I am not changing airframe, my engine is the only variable. Lets say all engines can achieve 175 knot in my frame, will one engine type IO360,IO375,IO390 do it for less fuel burn. If the answer is no they will all be the same then it is just a matter of how big I want to go.
Click to expand...
I would suggest all will be roughly the same.

As above, efficiency can be markedly improved by other factors however:
  1. Electronic Ignition (I would say the 15% is about right at Cruise with 2x P-Mag)
  2. Carb v FI
  3. Intake system / design
  4. VP v FP Prop
  5. Airframe cleanliness / optimisation - both absolute (no mud!), but also minimal aerials, decent fairings
  6. Flight profile (e.g. Climb Speed / Power)
The sad fact will be, that if you really want "efficiency", slower will be best, and something other than an RV :confused:

Some of the above will not necessarily be more efficient absolutely e.g. VP v FP, but the VP would give you a wider range of choice of efficiency v speed etc.
 
bendougy said:
Thanks guys. After Your help and 10 hours reading old threads, the cost of a certain speed is the same for all engines. If I have a larger engine I can throttle back and it will cost the same per mile as a smaller engine. A smaller engine cant go faster. I can see a IO-390 on its way
Thankyou all
Ben
Click to expand...

In the real world the difference in speed (as it relates to trip time) between a 180hp RV and a 200hp RV is insignificant. About all the extra 20hp is worth is bragging rights. ;)
 
Sam, True statement!

The other thing it gets you is vertical performance. The cost associated with those 2 factors was too high for this schoolteacher!

I went ECi 180...

I do like the 390 though!!!

Have fun!

:) CJ
 
I could be wrong (and hope that someone will say if so) ...

I think the electronic ignition systems give the most efficiency gain when combined with fuel injection and balanced injectors. That combination makes it easy to run LOP.

With a carbureted engine, the deltas on CHT are enough to make good LOP operations challenging. I'm surevtherecarecsome well balanced carbureted engines that have all CHT tightly clustered but I think that is the exception rather than the rule.
 
Performance

160 hrs. on my -8A and still collecting / analyzing / tweaking data. Aerosport IO-360 180 HP with 1 mag and 1 LSI. 8 gph at 2450 RPM (75%) appears to be near a reasonable sweet spot - around 150 KIAS true at 5-8000 ft. I say "around" because it will vary a few kts - but seems centered around 150 KTAS.

Everyone has their own opinion, but for normal cruise 150 KTAS seems a reasonable compromise between additional fuel cost and getting there in a reasonable time.
 
Yes I agree with you all. At present I have a Worn out IO-360 AIB6 TSO 2000 that indicated 155Knots.Have the Rod Bower intake. ( that gave me another 1 inch MAP or 6 knots) . I have flown 340 hours in the year. I use it for work and regularly fly 5 hour legs. Jon Johanson Tip tanks. I have 1 slick and 1 LS ignition. My frame was built with no drag parasitic or form drag. Digi trac auto with rate of climb ( best autopilot I have flown) I use the speed but have the option of slowing down for efficiency. Burning 1L of oil to 2 flying hours. Did not want to waste money on cylinders when I want a new engine. I hear there are new wing tip that give 10 knots more. Does anyone know anything about them
 
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tips

"I hear there are new wing tip that give 10 knots more."
Yeah, they have JATO bottles mounted on them.
 
If you do not have a constant speed prop, that may offer greater utility than a larger engine. At least rate of climb.
 
IO-390

Thought I would post my thoughts after installation of my IO-390 X. I removed my IO-360 AIB6. The 390 fits in the 8 without a trouble. I put a larger cooler on and never go near redline in 40 degree heat. The IO-360 baffles fit with very minor trimming. I needed a longer prop governor cable. Had to change to the later model lightspeed single point pick up due to less room at the nose. I fly LOP at 37L/H. I fitted a Rod Bower air scoop and that was the bst mod I fitted. Full throttle hight is 8000 ft. With tip tanks ie total of 230L I get over 6 hours to dry tanks. Have flown 120 hours on new engine. Have no regretts at all with the bigger engine.
 
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