rorythedog Posted October 29, 2013 Report Posted October 29, 2013 Does anyone here cruise at higher power settings than 75%? I normally don't, but yesterday I was in a hurry and used 26" x 2600 rpm at 4500' against a headwind and got 159kts true. Oat was +15. I was using 11.5 gph and cht was at 380 across the board. Pretty fast, I think. I normally cruise at about 152kts at higher altitudes, lower power settings, and lower fuel burn. It probably only saved 15 minutes or so in a 3 1/2 hour flight..... I guess that's significant if you have an aching bladder-ha. But...It just "feels" better to go faster! Is it really harder on the engine?
OR75 Posted October 29, 2013 Report Posted October 29, 2013 not sure it is harder on the engine. but it probably was a bit louder .
Bob - S50 Posted October 29, 2013 Report Posted October 29, 2013 From what I've read, the only thing that really matters is keeping your CHT under control, which you did.
rorythedog Posted October 29, 2013 Author Report Posted October 29, 2013 not sure it is harder on the engine. but it probably was a bit louder . It was actually strangely quiet. We were returning from a john fogerty concert(which btw was wonderful). That might have something to do with it-ha. 1
Bob_Belville Posted October 29, 2013 Report Posted October 29, 2013 My IO360 with a Scimitar prop seems to prefer ~ 2550 RPM to lower. With NC David Clarks noise is not really an issue.
aaronk25 Posted October 29, 2013 Report Posted October 29, 2013 Does anyone here cruise at higher power settings than 75%? I normally don't, but yesterday I was in a hurry and used 26" x 2600 rpm at 4500' against a headwind and got 159kts true. Oat was +15. I was using 11.5 gph and cht was at 380 across the board. Pretty fast, I think. I normally cruise at about 152kts at higher altitudes, lower power settings, and lower fuel burn. It probably only saved 15 minutes or so in a 3 1/2 hour flight..... I guess that's significant if you have an aching bladder-ha. But...It just "feels" better to go faster! Is it really harder on the engine? I do this a lot but I will raise the rpms up to 2700 and then pull the fuel back to the same 11.5gph you were flying wich effectively makes the Cht go down to 360ish as your running more lean of peak.
Jeff_S Posted October 29, 2013 Report Posted October 29, 2013 I've never paid much attention to what power settings I'm at. I generally cruise at WOT and 2550 RPM which my engine seems to like for some reason. Then I just lean for whether I want ROP (seldom) or LOP (usually). But if I choose to suck the gas at 12-ish GPH then at optimum altitudes I can get close to 160 KTAS, so your experience jives with mine. As has been noted, I pay most attention to CHTs and do what it takes to keep them all below 380. 1
PTK Posted October 30, 2013 Report Posted October 30, 2013 Ditto Jeff. Here's my data point: Typical cruise is 2450 RPM, WOT, LOP ~8 gph (~60% power) and CHTs 315-340 range. At 8k with middle of the road atmospheric conditions I see an honest 155 KTAS.
aaronk25 Posted October 30, 2013 Report Posted October 30, 2013 I'm at 146kts at 8gph.148kts 8.2gph and takes 9-more likely 9.2gph to run 155kts undersame conditions.
Bob - S50 Posted October 30, 2013 Report Posted October 30, 2013 I'm at 146kts at 8gph.148kts 8.2gph and takes 9-more likely 9.2gph to run 155kts undersame conditions. Same for me. I run about 9 to 9.3 GPH to get 155 KTAS.
wishboneash Posted October 30, 2013 Report Posted October 30, 2013 You're a good 10 knots faster than I am, Doc, if you can get 155 KTAS at 8,000 feet at just 8 GPH. I would be a very happy camper if I could do that. There is room for improvement in my rigging. I'm going to work on that. And my airframe is stock and doesn't have aileron and dorsal fin gap seals. But my paint is slick and clean and I have fewer antennas than most and no step. My engine is at 1750 hours, too. Byron, I'm curious. What kind of speed can you get now at 8 GPH at 8,000? 155 KTAS at that fuel flow would be intoxicating for me. Jim Ditto Jeff. Here's my data point: Typical cruise is 2450 RPM, WOT, LOP ~8 gph (~60% power) and CHTs 315-340 range. At 8k with middle of the road atmospheric conditions I see an honest 155 KTAS. There's no way mine does 155kt @ 8gph. What TAS would you get if you decide to become a gas guzzler and run at 11 or 11.5gph as the original poster did?
rgpilot Posted October 30, 2013 Report Posted October 30, 2013 I've been in several air races with an M20J and fly at 1000 feet balls to the wall. Max out at 167 knots and never had any engine problems.
fantom Posted October 30, 2013 Report Posted October 30, 2013 I've been in several air races with an M20J and fly at 1000 feet balls to the wall. Max out at 167 knots and never had any engine problems. We have someone else around here who 's had a different result
PTK Posted October 30, 2013 Report Posted October 30, 2013 OK, I did say approximately 8 gph (~8 gph), certainly under 9. Next time I'll check it more precisely and report back! And yes, I did say an honest 155 KTAS.
fantom Posted October 30, 2013 Report Posted October 30, 2013 And yes, I did say an honest 155 KTAS. Yeah....but we're talking level flight, not a dive!
PTK Posted October 30, 2013 Report Posted October 30, 2013 Oh, you're talking about level flight! I thought you were talking climb! It's not called the Screaming J for no reason!
aaronk25 Posted October 30, 2013 Report Posted October 30, 2013 I think we got some guys with fuel flow instruments reading to low , descending or looking crooked at the speedo
Bob - S50 Posted October 31, 2013 Report Posted October 31, 2013 I think we got some guys with fuel flow instruments reading to low , descending or looking crooked at the speedo Ya, you cannot assume that just because you put in the factory listed K factor that it will be accurate. I know we had to adjust our JPI 730. On the flight to CA it was off by about 6 gallons vs actual used. Adjusted the K factor for the flight home and it was off the other way by about 1.5 gallons. Made one more adjustment and we'll see how close that gets us.
Bob_Belville Posted October 31, 2013 Report Posted October 31, 2013 I changed the K factor from 29.65 to 30.86 based on using 139.8 gal vs. JPI 145.4 since then I've used 420.2 gal vs. 421.6 JPI. -0.3% (1.4 gal in 8+ full tanks is about 0.2 gallon per fill. Close enough I'd say!)
Bob - S50 Posted October 31, 2013 Report Posted October 31, 2013 I had to change our K factor from 29.86 to 33.48 and then subsequently I reset it to 32.50. Only time will tell how close the puts it.
fantom Posted October 31, 2013 Report Posted October 31, 2013 I assume the K factor adjustment is a simple software setting for the JPI 830/900/930. It's a PIA rear switch adjustment in the 700 series.
Bob_Belville Posted October 31, 2013 Report Posted October 31, 2013 I assume the K factor adjustment is a simple software setting for the JPI 830/900/930. It's a PIA rear switch adjustment in the 700 series. Yes, on the 930 there are a number of parameters accessible though the menu. Only takes a couple of minutes.
Marauder Posted October 31, 2013 Report Posted October 31, 2013 I assume the K factor adjustment is a simple software setting for the JPI 830/900/930. It's a PIA rear switch adjustment in the 700 series. Yes, on the 930 there are a number of parameters accessible though the menu. Only takes a couple of minutes. Same on the 830, access through the menu options.
mike_elliott Posted November 1, 2013 Report Posted November 1, 2013 I assume the K factor adjustment is a simple software setting for the JPI 830/900/930. It's a PIA rear switch adjustment in the 700 series. Gary, my JPI 700 K factor is adjustable from the menu settings. Do you have an old ver of the firmware, by chance?
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