Fuel burn value when LOP

[Vref]

Your right I should do my math and check from which Altitude(out of the red box) I can run WOT and LOP at 2500 the RPM that my engine likes it seems...

[garytex]

In my SWTA F model I burn high 7's low 8's for 162-165 mph LOP, 2500 rpm, whatever MP, about 30 lop.  Peak gets about 2-3 mph more.  I can get another 5-10 mph at 9.5, or 10 gph.  max is 175 MPH, no matter what I do.  Really only have 2 speeds, and never run ROP, so really only 1.  RPO is just 3 gph down the rathole, higher CHT's.  Engine will run with a little roughness down to about 6gph then quits.  low 7's and it slows down 5-10 mph and is very slightly rough.  Best mpg is 20-30df LOP, 20 to 22 mpg. I think I got lucky with mixture distribution on this engine, it seems very tolerant of RPM, MP and mixture.  It also climbs at 500 fpm, 130 mph indicated at 25", 2700rpm and 8.5 gph.  Thats my hot day low CHT climb.

I love my Mooney

Gary 

[Hank]

Jim--

I thought that was the result of the aerodynamic cleanup moving from F to J. You've both got my C beat!

[garytex]

Yes my cowling is a little bit stubbier than yours and you've got a little more gear fairing than I do.

Today was great.  I made my weekly commute which is about 172 nm.  it was relatively cool, 10 500, 65° Normally I indicate hundred and 42 miles an hour and I was indicating 147 today on 8.2 gallons an hour.  I don't know what true airspeed was, but A 10 knot tailwind was forecast and the GPS was showing about 183 or 4 groundspeed.  Beautiful clear day and I was there in a snap.  I love my Mooney

[jetdriven]

Those inner gear doors are worth quite a bit, around 3 KTAS IIRC from the POH.  

[garytex]

Yeah, I always thought it was a little wierd to argue about the difference between round and flat head rivets on what section of a wing, and ignore a 2 foot hole on the bottom.  Although I am a great enjoyer of speed mods, I have never been a buyer.  But that sure looks like a good place to speed up.  I assume 201 gear doors don't fit on Pre-J gear, as I don't remember hearing about them.  Is that correct?

Byron, good luck, and revel in and cultivate any obsessive side you might have with the motor change.

Gary

 

[DaV8or]

Quote: garytex

Yeah, I always thought it was a little wierd to argue about the difference between round and flat head rivets on what section of a wing, and ignore a 2 foot hole on the bottom.  Although I am a great enjoyer of speed mods, I have never been a buyer.  But that sure looks like a good place to speed up.  I assume 201 gear doors don't fit on Pre-J gear, as I don't remember hearing about them.  Is that correct?

 

[garytex]

Those inner gear doors are worth quite a bit, around 3 KTAS IIRC from the POH.

Anybody play that game on a pre-J? I haven't seen it mentioned, so I'm guessing one doesn't just head to the junk yard, then bolt set on.

[garytex]

Gee Whiz, I asked the question, forgot I asked, got a good answer, didn't check back, was perusing old posts, wondered again, asked again, which put me by DaV8or's answer. Duh!

Thanks Dave, I'll try to keep up a little better in the future.

So the gear's hard to swing, huh?

[jetdriven]

Did a recent 600 Nm trip 9000 Ft MSL most of the time TAS 147 Kts LOP and burning 34L/HR or tiddle less then 9 US gallons/Hrs this is with 2500RPM and 22 MP WOT (more I can't get..)

This includes a ROP climb when reaching cruise altitude I set for LOP. I am rather new at this LOP stuff so it takes some fiddling before fine tuning the right LOP and smooth engine set-up I notice my CHT temps are 10 to 15 degrees celisius lower then when flying ROP .. drawback when flying with a headwind...it slows down the progress.......

When heaving a serious headwind I prefer lower altitude <4000 FT and ROP for better power/speed and staying out of the red-box.....600 Nm with a headwind is close up to 5 hours and that is about my limit..

With a tailwind >7000 Ft the LOP is just great and a money saver...the engine runs smoother also

Our last big trip was Sedona AZ to Llano, TX. We ran 11,500, LOP 10 degrees, 2400 RPM, 7.5 GPH FF, ~145 KTAS, flew 5.2 hours hobbs and burned 39 gallons. 719 NM with a 3-5 knot tailwind. This is a 54 gallon bladder-equipped airplane. I told my wife we could make Houston nonstop, but she wouldnt have it.

it sems anything leaner than 15 LOP or any RPM lower than 2400 or 2450 does not pay off. Someday I'll get off my ass and actually measure it. For now it looks like a loss of 3 knots per 100 RPM, with a corresponding decrease in FF. Running leaner than 15-25 LOP causes a massive speed loss.

[Parker_Woodruff]

Our last big trip was Sedona AZ to Llano, TX. We ran 11,500, LOP 10 degrees, 2400 RPM, 7.5 GPH FF, ~145 KTAS, flew 5.2 hours hobbs and burned 39 gallons. 719 NM with a 3-5 knot tailwind. This is a 54 gallon bladder-equipped airplane. I told my wife we could make Houston nonstop, but she wouldnt have it.

it sems anything leaner than 15 LOP or any RPM lower than 2400 or 2450 does not pay off. Someday I'll get off my ass and actually measure it. For now it looks like a loss of 3 knots per 100 RPM, with a corresponding decrease in FF. Running leaner than 15-25 LOP causes a massive speed loss.

Byron, above about 10,000 in the M20J I would only run as far LOP as required to keep the CHTs below 380dF. RPM always 2550 or greater...generally 2600. Too much speed loss to be any more lean or lower on the RPM.

[jetdriven]

Right, Parker. I have not flown the J above 10K-11K until this trip. It definitely suffers from HP deficit, and the more the better. Looking back, you are right. 2600 or 2700 RPM is best and peak or slightly ROP. CHT was always 350 or so and could use some more fuel. Setting 2200 RPM and 15 LOP the plane lost 20 knots IAS.

[DaV8or]

So the gear's hard to swing, huh?

That's what I have been told and it makes sense. There are people out there with manual gear and lower doors, but I hear many times they take them back off.

[Vref]

Byron, above about 10,000 in the M20J I would only run as far LOP as required to keep the CHTs below 380dF. RPM always 2550 or greater...generally 2600. Too much speed loss to be any more lean or lower on the RPM.

Yepp, this is my experience so far also, too much LOP at higher altitude will significantly drop your speed. My reference LOP hi-up >8500Ft set RPM2550 is CHT 193Celsius (380F) then FF..running too cool with low FF but no speed is no fun neither...

I also have a feeling that the engine runs smoother at 2500...

[jetdriven]

Our plane gets markedly quieter right at 2450 RPM, both with the new and old engine. However, the cruise speed loss is real and perhaps I need a better headset.

[Vref]

Our plane gets markedly quieter right at 2450 RPM, both with the new and old engine. However, the cruise speed loss is real and perhaps I need a better headset.

I had a prop balancing done, the difference was noticeable..less vibration in the higher RPM's....Anyway I noticed the beech-folks don't like fuel subjects.. ...they switch to comfort/speed discussions

[garytex]

Dave Thanks for your answer. The additional force required to swing the gear must be fierce, if folks will take a speed mod off. Especially Mooney drivers. I figure they'd exercise till they had Popeye forearms first.

Temperature sure seemed to make a difference in speed for me today. 8500' 2500rpm 23ish MP, 8.4 gph, 64df (maybe 15 df cooler than of late), at least 50 LOP. I was indicating 155mph instead of the 145 I've been seeing lately, 175 on the gps, and the E6B on my Garmin said 180 mph true, and 10,500 DA. I don't know if I buy that but it was fun. I gotta get a true airspeed.

I am also wondering about this big slowing down you guys are talking about when running slightly (20df) LOP at altitude. Even to MP's as low as 20, I can barely notice any difference in speed as I go from peak down to 50 LOP, maybe 2-5 mph max, and depending on altitude it can easily be 1.5 to 2 gph less fuel. Then in the low 7s it really goes in the toilet. I'm going to get up around 12 k and check again, but I seem to remember the same behavior up high last winter.

Byron, mine gets quieter at 2400, but I get an increase in B frequency vibration in the airframe, so I run it 2500. It still vibrates but at the higher 4-banger frequency that doesn't shake the cockpit quite so much, who knows if it is better for the engine, wires, hoses, etc. Big slow vibrations, or little fast ones - pick your poison. But I don't see things shaking so much, so thats where I cruise. I may be a little over sensitive on vibration, when I overhauled the C-145 (which is 6 cyls) in my first 170, all the reciprocating mass got dynamically balanced by some go fast boys with some very fancy machines, and was glass smooth. I have no idea how they did it. Worked like gangbusters. My feelings were finally assuaged, I thought the first iteration of that engine shook too much, that feeling leftover lots of time spent offshore on inboard boats. If the prop shaft is misaligned to the engine, the boat shakes 1 cycle per rpm, and the repeated bending stresses the shaft are enough that after about 500-1000 hrs, the shaft will twist off. Perfect right angle break. If not stopped by the rudder, prop and shaft depart the boat, accompanied by a huge bang, a runaway engine and a rather large gush of water into the bilge where the shaft was. Been there, done that on a single engine boat, had the pxxx scared out of me, and then with no way to get back to the dirt, floated around for longer than I liked, way too far out to swim to the bank. So I got a little edgy about vibration.

There are many ways a Lyc. 4-banger is better than a small barrel Continental, but they always feel to me like they are trying to shake themselves apart. And philosophically speaking, I guess they actually are.

[jetdriven]

Dave Thanks for your answer. The additional force required to swing the gear must be fierce, if folks will take a speed mod off. Especially Mooney drivers. I figure they'd exercise till they had Popeye forearms first.

Temperature sure seemed to make a difference in speed for me today. 8500' 2500rpm 23ish MP, 8.4 gph, 64df (maybe 15 df cooler than of late), at least 50 LOP. I was indicating 155mph instead of the 145 I've been seeing lately, 175 on the gps, and the E6B on my Garmin said 180 mph true, and 10,500 DA. I don't know if I buy that but it was fun. I gotta get a true airspeed.

I am also wondering about this big slowing down you guys are talking about when running slightly (20df) LOP at altitude. Even to MP's as low as 20, I can barely notice any difference in speed as I go from peak down to 50 LOP, maybe 2-5 mph max, and depending on altitude it can easily be 1.5 to 2 gph less fuel. Then in the low 7s it really goes in the toilet. I'm going to get up around 12 k and check again, but I seem to remember the same behavior up high last winter.

Byron, mine gets quieter at 2400, but I get an increase in B frequency vibration in the airframe, so I run it 2500. It still vibrates but at the higher 4-banger frequency that doesn't shake the cockpit quite so much, who knows if it is better for the engine, wires, hoses, etc. Big slow vibrations, or little fast ones - pick your poison. But I don't see things shaking so much, so thats where I cruise. I may be a little over sensitive on vibration, when I overhauled the C-145 (which is 6 cyls) in my first 170, all the reciprocating mass got dynamically balanced by some go fast boys with some very fancy machines, and was glass smooth. I have no idea how they did it. Worked like gangbusters. My feelings were finally assuaged, I thought the first iteration of that engine shook too much, that feeling leftover lots of time spent offshore on inboard boats. If the prop shaft is misaligned to the engine, the boat shakes 1 cycle per rpm, and the repeated bending stresses the shaft are enough that after about 500-1000 hrs, the shaft will twist off. Perfect right angle break. If not stopped by the rudder, prop and shaft depart the boat, accompanied by a huge bang, a runaway engine and a rather large gush of water into the bilge where the shaft was. Been there, done that on a single engine boat, had the pxxx scared out of me, and then with no way to get back to the dirt, floated around for longer than I liked, way too far out to swim to the bank. So I got a little edgy about vibration.

There are many ways a Lyc. 4-banger is better than a small barrel Continental, but they always feel to me like they are trying to shake themselves apart. And philosophically speaking, I guess they actually are.

We have the counterweighted crank, so no second or third order vibrations. They are absorbed by the counterweights. Lycoming says you can run LOP at and below 75% power, which is 10.0 GPH. Truth is we have run LOP for hours on end at 11.5 GPH which is 86% power. CHTs cool and runs great.

Im not sure about 160 KTAS 50 LOP at 8500'. more realistically like 140 KTAS maybe 145.

[Jeff_S]

At my recent annual, the AP noticed the timing was 2 degrees advanced so he backed it off to 25° before TDC. What's interesting is that I've seen a noticeable change in fuel flow rates since the annual, with my FF rates being slightly higher at peak and LOP numbers than I remember seeing before. I'm assuming this has something to do with the timing, which has altered the EGT readings at similar fuel flows. So I am now running much closer to the 10gph number at LOP values down low, which has me a bit concerned vis a vis the old 10gph rule of thumb for LOP. But the CHTs and EGTs all stay down to the levels I expect, so I assume everything is copacetic.

[Cruiser]

This afternoon I was flying at 5000' LOP and as I set the mixture I was watching the JPI go lean on each cylinder. I stopped at 9.2 gph FF which is 70% power. My preferred setting for cruising. Well as the JPI went LOP on the display and the plane settled in to level flight I noticed the EGT values jumping all over the place from peak to -25/30° lean of peak after I stopped adjusting the mixture. Finally they seemed to settle down and even out at about 10° LOP.

Has anyone else noticed this behavior when setting the mixture LOP?

[garytex]

JimR

I am not too fancy with the JPI. I will be lean of peak and start richening. I think the JPI is in ROP mode when I do this. After a while, the display flashes, and says "leanest", usually #3, usually also the highest absolute value. I then lean from there.

Thursday, I was at 9500 ft, 59 OAT 21.5" MP, on the autopilot and got the following. Airspeed is mph off the GPS,

EGT Fuel Airspeed

1450 9 164

1460 8.7 165

1440 8.2 165

1430 8.2 165

1420 8.0 166

1400 7.9 163

1385 7.5 157

I then reduced rpm to 2000 briefly, speed fell off, but not a whole lot, but I didn't write it down, and it didn't feel like a happy place for engine or airframe, so I spun it back to 2500. The forcast winds were 30 degrees off the nose at 6, and the E6B on the Garmin thought I had about a 10mph headwind, which I think was close to right.

The exciting part is that it'll go around 165 or more at 8 gph, and those are number I see frequently. The sad part is that I can't throw more fuel at it and go much faster. It seems that my speed varies more with temperature than fuel flow. It's all good though. "Identical" mechanicl devises have good, bad and indifferent individual iterations of the type, and we have all suffered through being stuck with a doggy one of this plane or that truck. All in all mine is an adequately efficient example of the type that won't be pushed out of it's comfort zone by more fuel. I wonder what the true meaning (diagnostically speaking) is of what my airplane is trying to tell me. This is anomalous enough behavior that I suspect something is up, wonder if I will ever find out what.

Gary

[jetdriven]

2 weeks ago, speed test:

3-track NTPS GPS GS method,

1000 MSL, 80f, full throttle, 2700 RPM, full rich (18 GPH) 9NMPG, 90% power, 153 KIAS, 162 KTAS

same test repeated at full throttle, LOP 10.0 GPH (75% power), 2500 RPM 14.9 NMPG 149 KTAS

at 11,500', 48f, full throttle (19.5" MP), 2200 RPM, 10f ROP, 21.57 NMPG, 52% power, 108 KIAS 132 KTAS. (carson speed)

this is accurate to +/- 1-2 knots.

50 hours on fresh roller engine

22 degrees timing

[Cruiser]

^{Last week at 7500 MSL, WOT x 2500, 10°C, about 200# under gross.}

^{Peak EGT ~ 1450°F and 8.2 FF. 155 KTAS}

^{and at ~ +110°F ROP and 11.8 FF. 163 KTAS}

^{400 hrs on FREM w/roller tappets}

^{25° timing}