Shadrach Posted May 11, 2011 Report Posted May 11, 2011 Quote: Skywarrior Quote: Magnum Don't fly at peak, even with 65% or below. I burned my exhaust system within 150hrs flying at peak (the flame tubes in the muffler were gone). Quote: jetdriven Also, logic says 50 LOP is the exact same as 50 ROP so I do not know why the flame tubes are burned away in your muffler, EGT is EGT. ROP or LOP. He wrote PEAK, not 50 LOP. Chuck M. Good catch, but I still think it unlikely that his engine settings destroyed his old muffler. Quote
jetdriven Posted May 11, 2011 Report Posted May 11, 2011 50 LOP at 75% power is about the same is peak at 65% power, around 1580 EGT. still, with 5 or 10$ avgas, a new muffler every 150 hours is cheaper than fuel. I will order them happily. Sounds more like the OWT "run your engine too lean and burn it up". 50 ROP in our plane is 10 GPH at 25-2500. Peak is 9 GPH. 50 LOP is 8.2 GPH. @ Shadrach: we may run WOTLOP belop 5000' but for now, just figuring out what the plane likes and doesnt like. What do yuo think about 45 minutes at 1000' firewalled and full power? We have the lone star 150 air rally next weekend. Im thinking all 3 knobs full forward. Quote
Shadrach Posted May 11, 2011 Report Posted May 11, 2011 Quote: jetdriven 50 LOP at 75% power is about the same is peak at 65% power, around 1580 EGT. still, with 5 or 10$ avgas, a new muffler every 150 hours is cheaper than fuel. I will order them happily. Sounds more like the OWT "run your engine too lean and burn it up". 50 ROP in our plane is 10 GPH at 25-2500. Peak is 9 GPH. 50 LOP is 8.2 GPH. @ Shadrach: we may run WOTLOP belop 5000' but for now, just figuring out what the plane likes and doesnt like. What do yuo think about 45 minutes at 1000' firewalled and full power? We have the lone star 150 air rally next weekend. Im thinking all 3 knobs full forward. Quote
Tom_Veatch Posted May 11, 2011 Report Posted May 11, 2011 Quote: jetdriven ... Also, logic says 50 LOP is the exact same as 50 ROP so I do not know why the flame tubes are burned away in your muffler, EGT is EGT. ROP or LOP. ... Quote
Shadrach Posted May 11, 2011 Report Posted May 11, 2011 Quote: Tom_Veatch Not necessarily. If I understand it correctly, the exhaust gas in an LOP operating mode would be an oxidizing environment with excess oxygen in the flow. In an ROP mode, the exhaust would be a reducing environment with insufficient oxygen for complete combustion. That could have a different effect on downstream components. Don't know enough about the chemistry to say it would, but the possibility exists. Quote
N33GG Posted May 11, 2011 Report Posted May 11, 2011 Quote: trey2398 Thanks for all of the info. I guess the last part of the first article sums it up. Never thought of it this way.... "If shock cooling were a definite hazard, your engine should fall apart when you bring the mixture into idle cutoff at the end of a flight. CHTs fall at a rate of 100°F/min or more in the first seconds of shutdown—triple the rate that starts the typical "shock cooling" annunciator blinking. Does anyone complain that repeated shutdowns are causing head cracking? Of course not. Then why are we worried about pulling the throttle back?" Quote
Magnum Posted May 11, 2011 Report Posted May 11, 2011 Quote: Shadrach Perhaps, but the symptom is unique to Magnum as I've heard of no others experiencing this problem; Including me and I fly Peak, and LOP most often with a some ROP thrown in for good measure... Quote
Magnum Posted May 11, 2011 Report Posted May 11, 2011 Quote: jetdriven 50 LOP at 75% power is about the same is peak at 65% power, around 1580 EGT. still, with 5 or 10$ avgas, a new muffler every 150 hours is cheaper than fuel. I will order them happily. Sounds more like the OWT "run your engine too lean and burn it up". 50 ROP in our plane is 10 GPH at 25-2500. Peak is 9 GPH. 50 LOP is 8.2 GPH. Quote
Shadrach Posted May 11, 2011 Report Posted May 11, 2011 My peak EGT will only top 1500 down low or on cold high pressure days. As I said, I am almost always WOT unless descending. I fly LOP over peak under 5000 because I can develop plenty of power and keep CHTs low and best BSFC is achievable at good speeds. My stock F model will run 145kts+ LOP at 4500 to 7500 and a little faster down low. Quote
Frosty Posted May 16, 2011 Report Posted May 16, 2011 Boy has this topic ever wondered from subject to subject. It started with a question on shock cooling, covered ROP-LOP, POH v.s. GAMI/American Pilot, engine temperatures, throttle management, percentage power, and mooney mpg effeciency. I'll add a couple of thoughts but I won't quote my POH or Braly, just thoughts, or maybe better expressed as my philosophy based on reading many sources and boiling it down. The critical temperature for aluminum is about 350 degrees. Above that temperature it starts losing strength. Somewhere north 400 the effect gets serious, 450 is excessive (my opinion). I like 380 as a target for max CHT and start making adjustments to cool things down when any cylindar exceeds that. For my engine, TSIO360LB in a 231, I don't worry about shock cooling. I just plain don't believe it is a factor for CHT's below 350. If I start under 380 I'll be under 350 before I get a 30 degree drop. On the other hand if I started at 450 I might be concerned about sudden changes. For the record: I have both feet planted firmly in the WOTLOP camp. Big pull to lean early when climbing to altitude and stay lean until I start my descent by leaning agressively, way before I start reducing MP. By the time I start reducing MP my CHTs are 320 or below. Shock what? My engineis already cool. Also I don't mind running a tank until it's dry. Hows that work out for shock cooling... WOT cruise fuel set to stay under 380, then out of fuel until I switch tanks. My JPI doesn't show much CHTchange, not enought to cause concern. Understand, I am not suggesting anyone else should run their engine this way but it works for me. Quote
jetdriven Posted May 16, 2011 Report Posted May 16, 2011 Frosty: I do it the same way, LOP, lean to keep it under 380-400. Usually our CHT is 350-360. And just as we land I have checked it several times, its around 330-350. Cant shock cool it if you aren't cooling it. Also, the mixrture is only ever full rich just before takeoff power to 1,000'. Also, run that tank dry! You got 8 gallons on board, legal 45 mins fuel. Do you switch tanks? Do you have 3 gallons in one side or 5? How do you know? You do if its all in one tank. Quote
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