What is your GPH reading at LOP operation?

[scottfromiowa]

I am getting a fuel flow device installed at annual in December.  Just wondering what some others that have I0-360 engine w/fuel flow are seeing for the magic number (gallons/hour) to be 50LOP?  HP?

What do you find to be the best balance for HP/CYL Temps at different altitudes say 3,000/5,000/7,000

Do most fly 25 squared and lean or are many going 26RPM etc.  Interested in hearing how everyone is flying.  Didn't check old posts, so if you know a post title send me there too! 

Thanks for your replies.

[GeorgePerry]

If your an AOPA member you can see a great video at the link below.

http://www.aopa.org/aopalive/?watch=w2ZTZ5OniqfhPd5BKOEsVUrrPpv_04Xm

For LOP operations first you have to be properly equipped.  You'll need a multi probe engine monitor and balanced fuel injectors (GAMI's).   Basic rule of thumb for LOP operations is to keep the engine power below 65% and CHT's below 380 Deg.  You'll hear some LOP experts say it's OK to run a Lycoming engine LOP at 75%, but I think the general consensus for added safety margin is something less than that.  Typically in an IO-360 if you set 20 inches MP and 2500 RPM for best prop efficiency the engine power output will be at or below 65% regardless of altitude.  Those are my benchmark #'s for LOP, others might vary.  With 20in and 2500 RPM at 30 deg LOP and cylinder temps around 310-340 deg, I see fuel burns somewhere between 7.8 and 8.4 GPH depending on altitude.

With LOP in my M20F, I typically see an 8% drop in indicated airspeed (140 IAS ROP to 129 IAS LOP) with a 23% reduction in Fuel burn (10.7 GPH ROP down to 8.3 GPH LOP).  The MPG indicatioin on the EDM-700 Typically goes from 12-13 MPG ROP to 15-17 MPG LOP).  If you account for the slightly longer flight time with the slower airspeeds, the acutal saving are slightly less.  I see a realistic 15% reduction in fuel burn and 100LL costs.  Since I fly about 100 hours a year, LOP saves me about $500-600.  Not to bad, but it'll take about 4-5 years to make back the investment in the EDM-700, GAMI's and installation.

Another Mooney specific issue to keep in mind is that using the ram air may negatively affect your GAMI spread and cause a rough running engine LOP.  The unfiltered ram air seems to cause some uneven induction swirl which causes my GAMI spread to change from 0.1-0.3 GPH to 0.9 GPH.  Anything more than .5 is probably too much to run at 30 Deg LOP.  Again, just my experience, others may vary.

http://www.mooneyspace.com/index.cfm?mainaction=posts&forumid=1&threadid=1698

[N57039]

Climb at WOT (wide open throttle) 2700 rpm. Lean as you climb to maintain the same EGT you had as you took off. At cruise dial the prop back to 2500 (or something in that range that is smooth.) Pull red handle  to LOP. (Leave throttle pushed to firewall and get whatever MP you can) Today I was 20 dF LOP at 5,000' and burning 9.7 gph; later in the flight I climbed to 7,000' and went to 5 - 10 dF LOP and was burning about 9.3 gph. Altitudes selected based on winds (and two passengers with head colds). All other things being equal I'll go higher. 12,000' is nice and you be burning about 8 gph.

Easy, huh.

I do not have GAMI's and many IO360s work just fine LOP without them.

[scottfromiowa]

George and Lance, Thanks for your replies.  George, I have not reduced power (I have taken what I can get) except down low I do reduce to 25MP if altitude or ram air (down low) allows me to reduce to 25MP.  I have a GEM and commonly fly from 3500-10,500 (based on winds and clouds...I'm VFR).  I always climbed max power and prop, but keep climb at 120MPH.  Never a problem with CYL Temps (all 350 or below) and get 750-1,000FPM.  I have always leaned to rough and then enrichened slightly.  Low CYL Temps so didn't think much about it.  About 3 months ago I started wondering "why am I not getting a peak on my GEM monitor?"  I had been flying 75-100 LOP with NO issues (roughness) I am now enriching to FIND PEAK and then had been going rich of peak 50, but based on what I have read and heard (webinar) I am going 20-50LOP...still faster than I had been flying for first 300 hours on engine.  (richer than 75-100 LOP) I don't have Gami's and my cylinders have NEVER seen 400F 325-350F is common in climb and cruise.  I guess I am just "lucky" as I was ignorant to the peak pressures at 50ROP...and really haven't ever flown at that setting with exception of a couple of recent flights.  Perhaps the cylinder temps are more of an issue in IO-550 engine as even at 50ROP I was fine for cylinder temps...although I acknowledge that pressures are highest at this setting and I am used to going slower...and still thinking it was "plenty fast".  Looking forward to seeing what my HP is at 50LOP Peak and also what fuel flow is...

[scottfromiowa]

Lance, I will try leaning to maintain EGT...read about this and it was discussed in Webinar.  Good stuff.  I tried to lean ONE TIME to 100ROP (as Kromer stated in MAPA site)...disaster as I saw my cylinder temps creeping up...quickly pushed mixture in and didn't try again.  Maintaining SAME EGT should be a lot easier process than trying to find peak and enrich to it...as your climbing.

[KLRDMD]

I am getting a fuel flow device installed at annual in December.  Just wondering what some others that have I0-360 engine w/fuel flow are seeing for the magic number (gallons/hour) to be 50LOP?  HP?

[KLRDMD]

Quote: N57039

Climb at WOT (wide open throttle) 2700 rpm. Lean as you climb to maintain the same EGT you had as you took off. At cruise dial the prop back to 2500 (or something in that range that is smooth.) 

[podair]

I fly the same routes at the same levels very frequently in my 1967 M20F , stock airplane with 3 blade Hartzell. I have an EDM 700. I normally always fly at 10k , sometimes 9k or 11k, ram air on (never in IMC) . Those are flight levels (in Europe you fly those above 5k on average), so obviously density altitude makes a difference, with better performance (denser air=more power) in winter. I always fly WOT, 2500 rpm, and lean to peak EGT, slighly LOP. I have stock injectors but they peak at 0.25 us gal of each other (1 litre) so GAMI told me frankly I don't need GAMI (nice professional honesty) after I sent them downloads of the EDM. I always check my TAS with my E6b on the GPS. I pick 2500 as engine seems happy there, 2400 not so happy, 2600 sounds a bit much.

I always get very very close to 143-144 kts TAS at 10k on 33 litres per hour (8.75gph), 2500rpm WOT, within a kt or so. Not bad ! Thats usually around 20/20.5in MAP. Thats normally about 10deg lop, so call it peak egt. Usually Cyl 3 is the one peaking first , sometimes cyl1. This has been so consistent that I tend to set 33 litres, wait for temps to settle down, and tweak it in normalised mode a quarter of a turn or so of the mixture. Usually CHTs are 315ish and 350 ish for cyl3 (which is always the hottest one, havent quite figured out if it is the gasket probe or the true temp). On a very hot day I sometimes touch 400 on cyl 3 in climb, and try not to exceed that. IAS is around 122kts. 

11k I get a litre less,  and maybe a knot or two less. At 9k, 1 litre more, and maybe a knot or two more. On a cold day, 9k I can get 130kts IAS 147kts TAS and 35 litres.

Last week I was flying at 13k , getting 140kt tas on 29 litres (7.75gph) , but 185kt groundspeed (nice tailwind!). MAP was around 19.

It has been so consistent over the last couple of years that a few months ago I was getting 139/140kts and wondering what was wrong. Turned out that my retractable step vacuum hose had become loose and was flying with the step extended!

I tried a bit more LoP but seems I was loosing quite a bit of power , and certainly rougher at around 100lop. I fly quite a bit over water and quite a bit over mountains so not so comfortable there! I know I can t hurt the engine but doesnt sound right. Ram air adds an inch of MAP. Sometimes I get a bit of rough running high up with the ram air open if I lean too much or if we are close to the tops . I wonder if it is ice forming or too lean, so I tend to enrichen a bit or close the ram air for a while (not both). Experimenting with low power settings I can run quite Lop, at low altitude 2200/20in I get something like 125kts on 25litres which is incredibly efficient. Good for loafing around or extending the range if a bit tight on fuel. 

One thing I noticed is my mixture control is sometimes a bit imprecise. Ie turning it just a bit sometimes produces the opposite effect ie trying to increase flow it reduces it by 1 litre , so need to make at least half a turn for the desired effect.

On my 2020 Xmas wish list, I have a Powerflow exhaust, a 201 windshield, and cowl closure of some sort. Intrigued to see what I will get. Hopefully I will be able to afford these earlier!

 

[Jeff_S]

I only fly LOP at any cruise altitude. In order to stay outside the "Red Zone" as promoted by Deakins and the GAMI crowd, I will pull RPM to 2400 at altitudes below 5000', but anything above it I cruise at 2500 RMP always.  Again, to keep HPs down for LOP ops I will keep MP below 24" if below 5000'. I find that to be about the point where my MP won't get more than 24" anyway, although this varies a bit with temps of course.

So with those power settings a rule-of-thumb, once I get to cruise I use the JPI-700 to set LOP at the appropriate highest recommended EGT (again, as per the Red Zone chart...I tried to attach this but I can't seem to find it on my computer). My GPH goes from around 9.5 at the lower altitudes to around 8.5 at the higher altitudes, all else being equal. In general I can maintain 150 KTAS or even a little better at these settings, again depending on outside temps.

 

[Cruiser]

My engine has been run almost exclusively 20 - 50dF LOP since new. It now has a little over 200 hrs. mostly 7k eastbound and 8k westbound. at 8.9-9.0 and 8.2-8.5 gph. with TAS 148 - 150 kts. set to WOT x 2450 - 2500. The last Blackstone oil analysis included this statement. 

".......As it stands, things look pretty good. Your engine produces more copper than most others, but your engine also produces less blow-by (lead) on average. At any rate, things look good here, with no new problems apparent in oil analysis. No water or excess fuel present and insolubles are good at 0.4%."

The lower lead readings must be because of LOP operations. ;>)

[Cruiser]

Normal cruise flight at LOP setting will result in around 15 mpg. with a little tailwind it is not uncommon to see 20+ mpg.

[scottfromiowa]

Thanks Jeff and Cruiser.  Good stuff.

[M016576]

Does anyone fly directly at peak EGT when they are below 65% hp?  After watching some of the video seminars and powerpoints, it seems that it's possible to fly at peak EGT, keep the extra speed(HP) and also get a reduced fuel flow (so long as you're below 65% or so) all while keeping your engine out of the "danger zone".... Does anyone do this?  If so, what are the risks/rewards?

My typical mission is flown between 9 and 11k... 20 deg LOP I normally see 8.5-9 GPH.

 

                 -JoB

[Jeff_S]

Sure...the POH's always used to refer to this as "Economy Cruise" and that's how it's referred to in the standard Lycoming chart. That's where I would fly any time above 8000', where the Red Zone pretty much goes away for NA engines and the GAMI guys say you can lean however you want.  That's what I was alluding to in my note above...at the appropriate density altitude, I lean to the "richest" setting advised in the Red Zone chart which would be pretty much as peak EGT, only leaning it more if I need to reduce temps. (For example, this summer was brutishly hot even at altitude so I had to lean more aggressively.)