Fuel Burn

[Throttle Pusher]

What is the fuel burn on a lyc 320-b and 360 at full throttle and 75% at sea level.
I've looked around a bit and found only one chart and it showed the 320 burning more
at F/T than 360. Go figure.
What have you all found, out there in the real world.
Ken

[Jeff J]

What is the fuel burn on a lyc 320-b and 360 at full throttle and 75% at sea level.
I've looked around a bit and found only one chart and it showed the 320 burning more
at F/T than 360. Go figure.
What have you all found, out there in the real world.
Ken

I seem to get about 9 gph at full and 8 in cruise with my O-320-B3B. Nearly all of my flying is below 1500 MSL with mixture full rich.

Jeff

I wasn't very clear with the 9 gph, That's what I figure for the first hour of flight which would be an average of climb out and cruise. I have never tried to fly a plane at full power longer than needed to climb to altitude. My prop is a Sensenich 7458.

[Steve Pierce]

Doug and Dan Stewart have a 150 hp Clipper and a 180 hp Pacer. When they fly together they burn the same amount of fuel. I have been flying the 160 hp Super 20 Pacer with an Electronics International FP5L fuel flow meter. I am burning 13 plus on climb out and lean it out at 2450 rpm to around 8.3-8.5 gph.

[Throttle Pusher]

Steve
what kind of prop do you have on the Super Pacer?

[Gilbert Pierce]

Fuel burn is a function of the horsepower developed. A Friend of mine has an o-320 Tri-Pacer that burned 6 gallons per hour. It had flat cam and climbed at 200 ft/min. New cam, now he burns 9.0 gph in cruise.

A properly operating O-320 burns 9.2 gph leaned plus or minus at 75% power with the normal Sensnich prop of 58 to 61 inches of pitch. Go down in pitch and my experience with a 54 and 56 inch prop indicates you will burn more fuel. On a trip to Alaska with a 160 HP Pacer and 125 HP Trii-Pacer and me with a 150 HP Clipper and a 54 inch prop I always burned more fuel-considerably more. The 58 inch prop solved that problem. If I cruise with a 108hp Clipper I burn the same fuel he does.
Oh! you say, my O-320 burns 8 gph. If so you are not making 75% of 150hp. 75% power in an O-320 is generally considered to be 2450 rpm at sea level. You then add 25 rpm for every 1000' above sea level you are flying.

I can cruise anywhere from 6 gph to 13.5 gph depending on how much RPM I want to turn and how much cockpit noise I want to make. My O-320 at full power in a climb burns 13.5 gph to 14 gph depending on temperture and density altitude. Incidentaly, I always lean. Flying at 500 msl in cruise I am leaned. I lean as I climb. My sea level EGT at full power and full rich is 1180 degrees. I lean to 1180 degrees as I climb. Been doing this for 10 years. I have about 1000 hours on an engine Steve and I rebuilt 10 years ago. About 80% of that time is on auto fuel WITHOUT ethanol contaminating it. It has Millennium cylinder and no issues.

To try and answer the full throttle O-360 fuel burn question- I don't have an owners manual for the 360. However, the O-320 at full rich and full power has a brake specific fuel consumption of .55 lb/bhp/hr. At 150 hp that is 13.75 gph. What did I say my fuel flow gage showed I burned at full power? Extrapolating that out to 180 hp would be .55x180/6=16.5 gallons per hour for an O-360 180 HP.

Incidently the Brake Specific Fuel Consumption for the 160 hp O-320B is better then the lower compression 150 hp models. It is .52 at full power rich. That means the 160 burns the same fuel as the 150 hp. The higher compression makes it more efficient. FREE HORSEPOWER! Detroit has iknown that for 100 years. That's why we have 100 octane fuel.

I don't have a power chart for the O-320 that shows brake specific fuel consumption when leaned to best power or best economy or I could extrapolate the 75% fuel burn for the O-360. Working backwards on the 9.2 gph lean cruise burn on the O-320 yields BSFC (Brake specific fuel consumption) of .49. Using that on the 180 hp is 180x.75x.49/6=11gph in cruise lean at 75% power. That is probably a little high as I believe the compression ratio of the 180 is little higher then the 150.

[Steve Pierce]

Steve
what kind of prop do you have on the Super Pacer?

Been testing an 8243 McCauley prop and a Sensenich 7458. Should have an 8244 McCauley tomorrow for some better testing. Trying to get a decent cruise and short field performance.

[Jeff J]

Based on Gilbert's info I am not running 75%. I cruise at 2300 RPM.

Jeff

[Gilbert Pierce]

Based on Gilbert's info I am not running 75%. I cruise at 2300 RPM.

Jeff

Jeff,
That's why you are only burning 8 gph. Most folks don't run 75% power. When someone says their O-320 burns 7 or 8 gallons per hour you can be sure they are running less then 75%. I run 75% in a headwind and back off with a tailwind. At 2300 leaned I burn about 7gph. I always lean. Come annual time I have nice clean spark plugs.

[taildraggerpilot]

I've been running my engine (160hp) in cruise between full power and 2600 rpm at full rich with an average fuel burn of 13 gph, truing out at 120kts.

Gilbert: Where is your EGT probe? I'm typically getting 1400 degrees on the #3 and #4 cylinders and about 1200 on the #1 and #2 cylinders.

[Jeff J]

Most of my flying is short, low hops. Even when I fly to the next airport to buy fuel (about every 3rd or 4th flight) the flight takes about 15 minutes each direction. I only have one EGT probe connected to a gage without numbers and I know too many people who have similar setups in their aircraft who have burned up cylinders flying too lean. I'll take the safe route and stay rich until I have better instruments. BTW, I have never had fouled plugs in mine though sometimes at annual I wonder how. A nice side effect of using unleaded fuel is cleaner plugs and I would switch except the savings isn't that great when you have to buy premium and locally it's harder to find uncontaminated premium than regular.

Jeff

[Gilbert Pierce]

Ben,
Glad to see you have that beautiful airplane in the air.

My EGT probes are 1.5" below the exhaust flange. The distance to the probe from the port will have an effect on the temperature you see. Attached is a note from Electronics International about what to expect on various engines regarding temperature spreads.
Below is a cut from my EI engine monitor from last years trip to Sun'n Fun taken at different times. 7500' msl full throttle. 2650 rpm leaned at 9.2 gph.

EGT 1 CHT 1 EGT 2 CHT2 EGT3 CHT3 EGT4 CHT4
1342 331 1377 339 1462 370 1508 371
1335 332 1386 338 1465 377 1518 368
1347 329 1379 335 1459 369 1516 363

At lower altitudes and part throttle the EGT's spread out with 3 and 4 hotter then 1 and 2.
This was a low altitude trip with OAT in 30's and part throttle at 3500' leaned 2550 rpm
1327 305 1313 304 1448 337 1491 349

I have since replaced the baffle seals and get a little tighter temp spread on the CHT's.

Look at the EI attachement. You are probalby in good shape. The more you lean the closer the temps get to each other.
I am sure your much cooler temps are a result of running rich.

[Steve Pierce]

Most of my flying is short, low hops. Even when I fly to the next airport to buy fuel (about every 3rd or 4th flight) the flight takes about 15 minutes each direction. I only have one EGT probe connected to a gage without numbers and I know too many people who have similar setups in their aircraft who have burned up cylinders flying too lean. I'll take the safe route and stay rich until I have better instruments. BTW, I have never had fouled plugs in mine though sometimes at annual I wonder how. A nice side effect of using unleaded fuel is cleaner plugs and I would switch except the savings isn't that great when you have to buy premium and locally it's harder to find uncontaminated premium than regular.

Jeff

Jeff, I don't have any of that fancy stuff either but I lean all the time including ground ops except in the climb. I use the old lean till she stumbles and then enrichen her a bit like Lycoming shows in their literature. What kind of problems are people having that are attributed to running too lean?

[Tadpole]

Jeff, I don't have any of that fancy stuff either but I lean all the time including ground ops except in the climb. I use the old lean till she stumbles and then enrichen her a bit like Lycoming shows in their literature. What kind of problems are people having that are attributed to running too lean?

I've been doing that with the IO-320 that's in the Citabria I'm renting..stumble..then richen a bit till she feels nice and smooth. There is an EGT gauge, though I don't think it works very precisly. Looks like where I feel it runs nice is around 75° rich of peak

[taildraggerpilot]

Gilbert:

Thanks for providing the info, it's very informative and helpful to have a baseline.

I'll probably start leaning a bit after the first oil change, which is due in a few more hours and report back what I'm experiencing. As a side note at 2700 rpm, full rich I get about 50 degree cooler EGT than at full rich and 2600 rpm.

Thansk again for the info.

[Steve Pierce]

This Lycoming Service Instruction on Leaning has some good information. http://www.lycoming.textron.com/support/publications/service-instructions/pdfs/SI1094D.pdf

[Jeff J]

Jeff, I don't have any of that fancy stuff either but I lean all the time including ground ops except in the climb. I use the old lean till she stumbles and then enrichen her a bit like Lycoming shows in their literature. What kind of problems are people having that are attributed to running too lean?

I'm not sure what the problems they were seeing because they do their own work. I think one mentioned sticking valves on a Continental. The last one was told by the cylinder shop he was running it too lean and that was the second time in 3 years he had replaced his cylinders on his 150. The only cylinder not ruined was the one with the probe. Knowing how tight some of these guys are, it is possible they were trying for LOP operations and not just leaning. Right or wrong, I am simply following what I was taught 17 years ago and reinforced by several different instructors since.

Jeff

[Gilbert Pierce]

Most of my flying is short, low hops. Even when I fly to the next airport to buy fuel (about every 3rd or 4th flight) the flight takes about 15 minutes each direction. I only have one EGT probe connected to a gage without numbers and I know too many people who have similar setups in their aircraft who have burned up cylinders flying too lean. I'll take the safe route and stay rich until I have better instruments. BTW, I have never had fouled plugs in mine though sometimes at annual I wonder how. A nice side effect of using unleaded fuel is cleaner plugs and I would switch except the savings isn't that great when you have to buy premium and locally it's harder to find uncontaminated premium than regular.

Jeff
I agree with Jeff about being consevative if you don't have all cylinders monitored.

When I had only EGT/CHT on #4 cyl. I was a little more conservative with my leaning. I would for peak and then enrichen to 100 degrees rich of peak. Ater I got the engine analyzer I quickly realized that under certain circumstances (altitude and throttel setting) that #3 sometimes peaked first. #4 always has the higher CHT and EGT but at times #3 can peak first. That is why some folks recommend 100 degrees rich of peak if you only have one cylinder monitored. I have also determined that leaning to a rough engine and then adding just enough mixture to smooth it out on my airplane results in lower CHT's. This is the way I lean usually.

[Gilbert Pierce]

Gilbert:

Thanks for providing the info, it's very informative and helpful to have a baseline.

I'll probably start leaning a bit after the first oil change, which is due in a few more hours and report back what I'm experiencing. As a side note at 2700 rpm, full rich I get about 50 degree cooler EGT than at full rich and 2600 rpm.

Thansk again for the info.
Ben,
My experience is you get better fuel/air distribution at full throttle. I believe the throttle plate being in the partially full open position causes turbulent air or a burble in the intake which causes less then optimum fuel distribution
I asked a Lycoming rep about that and he verified that their carburated engines had better fuel distribution at full throttle. For that reason on a long cross country I like to high. Plus it's cooler and smoother.

[Todd]

Gilbert - thanks for the detailed info. I'm shopping for a new Sensenich prop for my 150 h.p. 22/20 and it sounds like a 58 pitch is the magic number. I'm curious about the difference you experienced in takeoff distance and rate of climb with the 54 and 56 compared to the 58 pitch.

[Gilbert Pierce]

Gilbert - thanks for the detailed info. I'm shopping for a new Sensenich prop for my 150 h.p. 22/20 and it sounds like a 58 pitch is the magic number. I'm curious about the difference you experienced in takeoff distance and rate of climb with the 54 and 56 compared to the 58 pitch.

Todd,
I really had a hard time distinguishing between the 54 and 56" prop in climb at VX. The 56 was about 5 mph faster. The 58 just feels right. It does not accelerate on the ground quite as fast. The climb rate is slightly less but it is much faster. I usually am flying off grass, 2700' and 400' msl with 40 foot trees at one end. Fully loaded, 1800lbs, I use about 1200' normally. Temperature does not seem to effect the takeoff roll much but it does impact climb rate when the temp gets close to 80. My Clipper empty wt. is 1034. With full fuel (36 gal) and 20 lbs. of STUFF and me at 170 lbs I see 1200 ft/min on a cool day (65 to 70) regularly. I have had it to 13,500 density altitude and was still climbing at 150 ft/min. The Clipper is powered by an O-320-B2B but with 150 hp cylinders on it. 60 lbs. of fuel and me on a 50 degree day on grass I am off in 500' and can get it down and stopped in 400' with no wind.

Off the grass at home loaded and slightly uphill I count 13 seconds. I am always off before that. If I ever go beyong a 13 second count I will abort. That leaves me at least half the runway to stop in.

On a trip to Seattle in 04 fully loaded (1800 lbs) with my wife aboard I came to the conclusion the airplane will always get off asphalt in 1200' no matter what the density altitude is. I went thru the Southern Rockies and back down I90.
Notes from my flight log:Takeoff from Sheridan 81F, Altimeter 30.1 4024 msl. Used 1200’ of runway. That is 6400' density altitude. Climb was poor.
Scotts Bluff to Norton Kansas. Runway Temp was 102, AWOS was reporting 7000’ density altitude. Used about 1500’ but climb was slow.
I think the temperature effected more then the denisty altitude on this departure. My initial climb rate was about 300' per minute or less as I remember. I didn't write it down.

[Stephen]

Gilbert, why did you chose to keep your engine at 150 hp?

[Gilbert Pierce]

Gilbert, why did you chose to keep your engine at 150 hp?

So I could burn 87 octane auto fuel.

The stuff they put in Avgas to purge the lead from the cylinders and spark plugs is corrosive. Lead gets in your oil and forms a paste that stops stuff up. Auto fuel burns cleaner. It was easier to get 87 octane auto fuel then 91 octane. I have Melinnium cylinders that are purported to work fine with no lead.

Below is from an article by Mike Berry that was published in Light Plane Maintenance and Sport Aviation. http://www.eaa.org/autofuel/autogas/articles/1Autogas%20vs%20Avgas.pdf

Additives
One problem with lead mixed with avgas is
that lead requires the addition of a bromine
compound to scavenge lead residue from the
engine.
The burning of the lead with the bromine
compound produces lead bromide that is
carried out with the exhaust gasses; however, a
small amount remains within the engine. This
lead bromide, when mixed with water, metals,
and lubrication oil, produces a corrosive liquid
very damaging to engine components.

So for a lot of reasons I use Auto Fuel when I can get it. Yes it has it's storage problems but I fly often enough that is not a problem. I also test my source for ethanol contamination. I fly from a grass strip with no fuel so I have tank in my truck and an electric pump. It is just as easy to haul auto fuel as go thru the locked gates and security at the local big airport to get 100 LL at $5.00+ a gallon.