WW2 aero engine fuel consumption comparison
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Shortround6
Major General
No list.
It is sort of complicated and yet it is not.
Most allied engines used fuel for partial cooling (or to compensate for poor fuel distribution?) and could be run lean at lower power settings (cruise) and rich at higher power settings.
Rich power settings could increase fuel consumption by around 50% per hp/hr.
German and some other fuel injected engines used similar amounts of fuel (10-15% ?) per hp/hr from cruise settings to full power.
Just about everybody's engines would give around low/mid .40s lbs per hp/hour in cruise. Merlins sometimes hit 0.50lb/hp/hr and that was among the worst of the big engines.
Some of the American radials could hit in the low 0.70s in lbs/hp/hr at full power.
In most data sheets for engines they give the cruise consumption.
As can be seen this means fuel consumption is very power dependent. An R-2800 is going to suck up a lot more fuel than an R-1830 just because it is making more power. But they may both be running at 0.46-0.48 lbs/hp/hr in cruise and depending on last spark plug change could swap who was most economic.
If you know the amount of power being used and you know if it was running lean or rich (or German fuel injection?) you can come up with educated guesses.
The Famous economical Sakae engine in the early Zero is a sort of special case but it's economy was only at certain power setting/s.
Cruise at 180kts was 16.4 US gallons an hour (power unknown/ altitude unknown) but at 190 kts it jumped to 24.04 US gal/hr and at 200kts it moved to 26.15 US g/hr. At full power the engine needed 91.14 g/h and at 950hp that is around .574 lbs/hp/hr.
The later 2 speed engines lost the 180kt cruise or rather the 180kt cruise jumped to 22 US gal per hour. Rated power of 1100hp (low gear/ 1100hp/ 115gph)) might have required .627lbs/hp/hr.
Here is where things get tricky, In high gear at 6000 meters the engine may have been making about the same power in the cylinders and burning the same amount of fuel (or close) but the propeller was only getting 980hp because the extra 120 hp was driving the supercharger in high gear.
Making a big assumption (you judge) but if the Sakae 21 engine was using the same 115 US gallons at 6000meters in high gear to get it's 980hp the fuel consumption was now 0.704lb/hp/hr.
Trying to sort through even a fraction of the engines to get the the consumptions for different powers at different altitudes is going to be a lot of work.
The engine spec sheets are advertising figures. Best case, your actual mileage may vary
It is sort of complicated and yet it is not.
Most allied engines used fuel for partial cooling (or to compensate for poor fuel distribution?) and could be run lean at lower power settings (cruise) and rich at higher power settings.
Rich power settings could increase fuel consumption by around 50% per hp/hr.
German and some other fuel injected engines used similar amounts of fuel (10-15% ?) per hp/hr from cruise settings to full power.
Just about everybody's engines would give around low/mid .40s lbs per hp/hour in cruise. Merlins sometimes hit 0.50lb/hp/hr and that was among the worst of the big engines.
Some of the American radials could hit in the low 0.70s in lbs/hp/hr at full power.
In most data sheets for engines they give the cruise consumption.
As can be seen this means fuel consumption is very power dependent. An R-2800 is going to suck up a lot more fuel than an R-1830 just because it is making more power. But they may both be running at 0.46-0.48 lbs/hp/hr in cruise and depending on last spark plug change could swap who was most economic.
If you know the amount of power being used and you know if it was running lean or rich (or German fuel injection?) you can come up with educated guesses.
The Famous economical Sakae engine in the early Zero is a sort of special case but it's economy was only at certain power setting/s.
Cruise at 180kts was 16.4 US gallons an hour (power unknown/ altitude unknown) but at 190 kts it jumped to 24.04 US gal/hr and at 200kts it moved to 26.15 US g/hr. At full power the engine needed 91.14 g/h and at 950hp that is around .574 lbs/hp/hr.
The later 2 speed engines lost the 180kt cruise or rather the 180kt cruise jumped to 22 US gal per hour. Rated power of 1100hp (low gear/ 1100hp/ 115gph)) might have required .627lbs/hp/hr.
Here is where things get tricky, In high gear at 6000 meters the engine may have been making about the same power in the cylinders and burning the same amount of fuel (or close) but the propeller was only getting 980hp because the extra 120 hp was driving the supercharger in high gear.
Making a big assumption (you judge) but if the Sakae 21 engine was using the same 115 US gallons at 6000meters in high gear to get it's 980hp the fuel consumption was now 0.704lb/hp/hr.
Trying to sort through even a fraction of the engines to get the the consumptions for different powers at different altitudes is going to be a lot of work.
The engine spec sheets are advertising figures. Best case, your actual mileage may vary
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