Hello all,why does four pyston engine used in an aircraft( for example cessna) consume about five times more fuel than four pyston engine used in a car.The reason is torque? or anything else?

The engine in a typical light single, is an IO-360 ... 360 cubic inches (aproximately 5.9 liter)A typical 4 cylinder automobile engine is less than 2.0 liter

You say that the reason is the cylinder volume.. Okey thanks mate..

Yup, unless you have something like a Rotax 912 in a microlight, a converted VW engine, or a vintage aircraft with a very small original engine, aero engines will pretty much always be of a higher cubic capacity than those in your average car, and there is also the fact that the gearing on a car is invariably much more of a practical arrangement in terms of efficiency than what you'd find on a typical aero engine, which usually has to employ variable propeller pitch to make it more efficient, and that is not something every aeroplane has anyway.The upside is that there aren't many traffic jams in the sky, and you can go as the crow flies, so it balances up in fuel consumption to at least some degree.Al

For comparison sake, my four cylinder, Cessna type (Lycoming 0360 AIA, 180 HP) engine pulls my plane along at close to 200 mph cruise. It's also giving me around 20 miles per gallon. But, my plane is a two seater, and weighs less than a typical Cessna 172. Of course, it climbs a whole lot faster......too! :( I can always figure on getting to a distant destination, three times faster, than in a car.L.Adamson

The one that's got me stumped, is the difference in range of the 747-400 and 747-400F!Both have the same MTOW, same amount of fuel, same type of engines, yet, the 400 has a range of 7260nm and the 400F only 4445nm? What makes freighters that much less efficient?

The one that's got me stumped, is the difference in range of the 747-400 and 747-400F!Both have the same MTOW, same amount of fuel, same type of engines, yet, the 400 has a range of 7260nm and the 400F only 4445nm? What makes freighters that much less efficient?

Payload. People weigh less than freight. Both aircraft may have the same maximum takeoff weight, but the freighter will have much more of that weight taken up by payload than fuel. The efficiency of both aircraft are exactly the same, but the numbers for the freighter in the brochure use a different fuel fraction due to the different nature of the mission.

Hello all,why does four pyston engine used in an aircraft( for example cessna) consume about five times more fuel than four pyston engine used in a car.The reason is torque? or anything else?

I think another factor is just the way power is used.Aircraft regularly operate with a full throttle for extended periods.Takeoff for sure...but even cruise power at altitude may use an open throttle.Certainly, aero engines still need to be operated within their specific MP and RPM restrictions......but still I can’t imagine running my car at anything close to that ;)And you mentioned torque...I think that’s a very good point.I don’t know enough to really comment.But, 180HP@2700RPM and 180HP@6000RPM won’t be equivalent with respect to economy…or even “strength”My hunch is the economy discrepancy isn’t as big as it appears – once all the proper units and factors are considered.I know of another RV pilot that considered his 200HP-IO360 to be about equivalent to his wife’s Camry when it came to long distances.Could be a bit of exaggeration on his part ;) I don’t know.

For comparison sake, my four cylinder, Cessna type (Lycoming 0360 AIA, 180 HP) engine pulls my plane along at close to 200 mph cruise. It's also giving me around 20 miles per gallon. But, my plane is a two seater, and weighs less than a typical Cessna 172. Of course, it climbs a whole lot faster......too! :( I can always figure on getting to a distant destination, three times faster, than in a car.L.Adamson

Wow, just did some simple calc and I came up with this (I always knew the plane I had been flying [a six seater though] was far too thirsty...): Cruise at around 140 knots, ~160mph. Boozing 22 US gal on average, yields a whoppin ~7 MPG... Or how we calculate across the pond, 32 liters/100km. Whereas the average car should remain way below 10... OMG. I should look out for different business. :(Assuming $12 per gallon of Avgas renders $264 only for fuel per hour. The same distance covered in a car would cost me $36. Indeed, I'll be there almost three times faster but the time made good has its price in terms of fuel flow which increases almost linear it seems... LOL

Wow, just did some simple calc and I came up with this (I always knew the plane I had been flying [a six seater though] was far too thirsty...): Cruise at around 140 knots, ~160mph. Boozing 22 US gal on average, yields a whoppin ~7 MPG... Or how we calculate across the pond, 32 liters/100km. Whereas the average car should remain way below 10... OMG. I should look out for different business. :(Assuming $12 per gallon of Avgas renders $264 only for fuel per hour. The same distance covered in a car would cost me $36. Indeed, I'll be there almost three times faster but the time made good has its price in terms of fuel flow which increases almost linear it seems... LOL

Maybe you need a new airframe :biggrin:XP-360 suggested economy is about 10GPH@75% power.That's suggested to give around 199mph cruise in an RV - so nearly 20mpg.Of course the useful load makes it a Miata - not your roomy Suburban

Also... modern automobile engines have very sophisticated computers... spark timing, and fuel mixture (and even cam geometry in some cases), are constantly tweaked to be optimal.Some newer aicraft have FADEC-type systems.. but for the same reason that airplanes still use magnetos (simplicity and reliabilty) .. they aren't as comlex/advanced as automobile systems.

Yes I was about to say... you are talking about 1940s (or even older) technology (Date of Application for the O-360-A1A for Type Certification was January 17, 1955) with its Marvel Schebler float carb, "dual magneto" ignition, and single intake / exhaust valve design.Now compare that with a DOHC 16-valve i-VTEC / MPFI / ETC / EFI design used in the 2010 Honda Accord engine...Companies change products because they are either cheaper or better (or both) and they can justify it based on expected ROI. The reason airplanes still use 1930s & 40s technology is because of certification costs (here in the U.S.) make it prohibitive.

Yes I was about to say... you are talking about 1940s (or even older) technology (Date of Application for the O-360-A1A for Type Certification was January 17, 1955) with its Marvel Schebler float carb, "dual magneto" ignition, and single intake / exhaust valve design.Now compare that with a DOHC 16-valve i-VTEC / MPFI / ETC / EFI design used in the 2010 Honda Accord engine...Companies change products because they are either cheaper or better (or both) and they can justify it based on expected ROI. The reason airplanes still use 1930s & 40s technology is because of certification costs (here in the U.S.) make it prohibitive.

Airplane engines may be 1940's.............but they still work better for small aircraft than modern auto designs. Builders are always installing auto engines in the front (or back) of numerous experimental class airplanes. There has been many problems to over come. One of the main ones, is cooling. Radiators create drag, and getting enough radiator surface area has been a big problem. And while auto engines create rated horsepower at 6000 rpm or so, they have to use reduction gears to get that 2700- 3000 rpm prop speed. That's been another weight & maintenance problem. And then there's the auto engine computer to run the engine. They sometimes go into failure modes that don't work well for airplanes. It also means a requirement for redundant electrical systems, since the car engine requires electronic fuel injection, computer, and ignition. So all in all, the auto engine usually weighs more, is noisier, and doesn't get as good fuel economy.As of now, us airplane builders are much better off sticking a Lycoming or similar on our airplanes. If we don't, we spend more years building, fabricating, and experimenting. Over the years, there have been many companies who have tried to bring converted auto engines into the certified market. Porche did this with Mooney. But.........they just haven't worked out. Airplanes engines are light and simple. It's just that that 40's technology hasn't really been bettered. They knew what they were doing....back then. And of course, some modern technology has now worked it's way into systems & production.L.Adamson

Yes sir like I said "cheaper or better (or both)" :( And I do remember the single lever PFM... I had just graduated from Purdue's Aviation Maintenance Program the year before its release... quite a unique experiment that was and I hoped it would do "well" but... :( Edit: I was just thinking... those were the days before any "consumer oriented" internet... I bet I have at least three aviation rags that covered the PFM B) (Private Pilot, Flying and AOPA Pilot). :(

Aircraft engines,being air cooled,have larger cylinder wall to piston clearances for thermal expansion,therefore less horsepower,and higher fuel and oil consumption. For example a 520 cubic inch fuel injected,turbocharged engine in a Cessna 402 only puts out 300 or so horse power.But these engines have proven themselves over the years,for example, Vans RV will try to talk people out of using automotive engines in there aircraft,because of quality control, reliability issues.