201er Posted December 1, 2011 Report Posted December 1, 2011 During a recent flight I decided to test out my speed at various mixture settings. I'm curious how the real world numbers compare to theoretical values and your own findings: All trials were at 4,500ft, 0C OAT, 25"MP, 2500RPM 150ktas, 30LOP, 10GPH, CHTs: 275, 287, 319, 344 155ktas, Peak, 11.6GPH, CHTs: 304, 337, 349, 371 165ktas, 100ROP, 13.4GPH, CHTs: 295, 334, 338, 358
Piloto Posted December 1, 2011 Report Posted December 1, 2011 Very much like my 1982 M20J. The biggest difference when leaning is on fuel economy and range. José
Hank Posted December 1, 2011 Report Posted December 1, 2011 Mike-- It would be interesting to do a range comparison on those three data sets. Range with IFR reserves, fuel used and time to go the distance. All I know is your plane holds more fuel than mine [52 gallons], but it uses more and goes faster, too. I only see 150 kts when the wind is blowing from behind, or I'm descending.
flyboy0681 Posted December 1, 2011 Report Posted December 1, 2011 I'm with Hank, I'd like to see the difference in range although I know obtaining that information is a tall order.
201er Posted December 1, 2011 Author Report Posted December 1, 2011 Well I have 100 gallon tank so I don't really care about range. That's like 7 hours even at best power with VFR reserve! Cost on the other hand does play a role. We're talking about using 3.4 gallons per hour more to go 15 knots faster. On a 500nm round trip (1k nm), difference in fuel would be $87 to save 35 minutes. If however, it's critical to get there on time or it's a matter of making it there before the weather, it's good to know that it's possible to unleash some more speed from this best power reserve. The stupid POH doesn't even note any speed difference between best economy and best power cruise, yet in practice I found the difference to be more substantial. So is this how all you guys are getting the figure that a 201 is a 160 knot airplane? Are you all flying well rich of peak which leads you to be able to boast that? Or are people really getting 160knots at or lean of peak in a pre-80s M20J?
takair Posted December 1, 2011 Report Posted December 1, 2011 Quote: 201er During a recent flight I decided to test out my speed at various mixture settings. I'm curious how the real world numbers compare to theoretical values and your own findings: All trials were at 4,500ft, 0C OAT, 25"MP, 2500RPM 150ktas, 30LOP, 10GPH, CHTs: 275, 287, 319, 344 155ktas, Peak, 11.6GPH, CHTs: 304, 337, 349, 371 165ktas, 100ROP, 13.4GPH, CHTs: 295, 334, 338, 358
flyboy0681 Posted December 1, 2011 Report Posted December 1, 2011 Quote: JimR There you go screwing up my numbers with Monroy tanks
johnggreen Posted December 1, 2011 Report Posted December 1, 2011 These numbers are interesting. OK, now does anyone have the numbers on specific fuel consumption. The "rule of thumb" on most normally aspirated engines is .43 pounds per horsepower per hour. So at 200 HP, that's 86 pounds and at 6 pound fuel, 14.3 gallons per hour. How does LOP affect that figure? I'm pretty sure somebody on this forum has that number. Jgreen
jetdriven Posted December 1, 2011 Report Posted December 1, 2011 Someone at the mapa convention said a female test pilot did all those spins and they were a non-event.
Cruiser Posted December 2, 2011 Report Posted December 2, 2011 Quote: 201er During a recent flight I decided to test out my speed at various mixture settings. I'm curious how the real world numbers compare to theoretical values and your own findings: All trials were at 4,500ft, 0C OAT, 25"MP, 2500RPM 150ktas, 30LOP, 10GPH, CHTs: 275, 287, 319, 344 155ktas, Peak, 11.6GPH, CHTs: 304, 337, 349, 371 165ktas, 100ROP, 13.4GPH, CHTs: 295, 334, 338, 358
flyboy0681 Posted December 2, 2011 Report Posted December 2, 2011 Quote: jetdriven Someone at the mapa convention said a female test pilot did all those spins and they were a non-event.
jetdriven Posted December 2, 2011 Report Posted December 2, 2011 John, thats prettty close. .43 is a good average number I have .448 from somehwere for 50 ROP on the IO-360-A. LOP drives it down to .40 or .39. When climbing, BSFC is going to be higher due to extra fuel for cooling, so that could be .50. Full rich for takeoff is measured at .54 on ours. It varies with compression ratio and engine architecture. IO-360-A are 8.7:1 C/R. Quote: johnggreen These numbers are interesting. OK, now does anyone have the numbers on specific fuel consumption. The "rule of thumb" on most normally aspirated engines is .43 pounds per horsepower per hour. So at 200 HP, that's 86 pounds and at 6 pound fuel, 14.3 gallons per hour. How does LOP affect that figure? I'm pretty sure somebody on this forum has that number. Jgreen
Shadrach Posted December 3, 2011 Report Posted December 3, 2011 Quote: 201er During a recent flight I decided to test out my speed at various mixture settings. I'm curious how the real world numbers compare to theoretical values and your own findings: All trials were at 4,500ft, 0C OAT, 25"MP, 2500RPM 150ktas, 30LOP, 10GPH, CHTs: 275, 287, 319, 344 155ktas, Peak, 11.6GPH, CHTs: 304, 337, 349, 371 165ktas, 100ROP, 13.4GPH, CHTs: 295, 334, 338, 358
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