I just did a fuel flow test between the IO-520 and the IO-550 at 11,000 feet my findings really surprised me
IO-520
12.5 TAS 171 CHT 183
13.0 TAS 171 CHT 183
IO-550
13.4 TAS 175 CHT 182c
14.0 TAS 176 CHT 180c
IO-520 and IO-550 fuel flow test
Re: IO-520 and IO-550 fuel flow test
Was this with the same MP and Prop settings?
The 520 would be better for long distance cruising and 550 better for getting in and out of tight valleys I expect.
Do a time to climb comparison.
The 520 would be better for long distance cruising and 550 better for getting in and out of tight valleys I expect.
Do a time to climb comparison.
Cheers
Trev
Trev
Re: IO-520 and IO-550 fuel flow test
Their specific fuel consumption are rather similar, though in practice IO-550 should score a bit higher.
If we normalize this a bit unfairly, and say that we output 200 hp from each engine, and use "minimum allowable fuel flow" for IO-520, we burn approximately 84 lbs/h. With IO-550 at peak EGT we burn approximately 87 lb/h, producing the same 200 hp. This slightly worse burn comes almost certainly from the need of having throttle the IO-550 more as we are at lower power percentage.
However, if we took Continental's graph for IO-550 at 50 degrees lean of peak for the same 200 horsepower, we now burn only something like 77...80 lb/h. My manuals have no lean of peak graphs for IO-520.
If we compared the engines at, say, 75 % power instead, the IO-520 at the "minimum allowable fuel flow" consumes about 88 lb/h while producing approximately 214 hp.
The IO-550 at 75 % power, ran at 50 °F lean of peak, consumes approximately 86 lb/h while producing 225 hp, a clear winner here.
Of course, nothing would prevent one from ignoring that "minimum allowable fuel flow" and getting similar specific fuel consumption from the IO-520.
-Esa
If we normalize this a bit unfairly, and say that we output 200 hp from each engine, and use "minimum allowable fuel flow" for IO-520, we burn approximately 84 lbs/h. With IO-550 at peak EGT we burn approximately 87 lb/h, producing the same 200 hp. This slightly worse burn comes almost certainly from the need of having throttle the IO-550 more as we are at lower power percentage.
However, if we took Continental's graph for IO-550 at 50 degrees lean of peak for the same 200 horsepower, we now burn only something like 77...80 lb/h. My manuals have no lean of peak graphs for IO-520.
If we compared the engines at, say, 75 % power instead, the IO-520 at the "minimum allowable fuel flow" consumes about 88 lb/h while producing approximately 214 hp.
The IO-550 at 75 % power, ran at 50 °F lean of peak, consumes approximately 86 lb/h while producing 225 hp, a clear winner here.
Of course, nothing would prevent one from ignoring that "minimum allowable fuel flow" and getting similar specific fuel consumption from the IO-520.
-Esa
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