Lean-of-peak WITHOUT balanced fuel injectors?

[rdv]

Has anyone experimented with running LOP without balanced injectors? Is it safe to experiment with the help of engine analyzer only? (no fuel flow)

 

Ryan

[danb35]

You will need to have fairly well-balanced injectors to run LOP smoothly.  Some engines come from the factory that way; others will need GAMI injectors to manage it.  My IO-360 runs fine LOP, and I don't have GAMIs.

You don't need fuel flow instrumentation to run LOP safely.  You do, however, need it to determine how much power you're making, as the standard power charts go out the window when you're LOP.  You'd also need fuel flow to measure the so-called "GAMI spread" (the difference in fuel flow between your richest and leanest cylinders).  But you can still run LOP just fine without fuel flow information.

[Cruiser]

For NA engines above 7000' run WOTx2500 and lean so your RICHEST (last cylinder to peak) is at least 10dF LOP. You should be near 9.5 gph and about 148 kts. In you have a turbo, lean to at least 25dF LOP or more if you add MP back in to regain speed.  

At 9000' and above just run at peak.

If your cylinders are not balanced you will know it by the roughness in the engine. LOP the roughness is caused by the difference in power from cylinder to cylinder caused by the uneven fuel flow. Give it a try.

[Immelman]

I run LOP w/ stock injectors, IO-360-A1A, but its a real crap shoot as to whether it will run smooth at above 60% power or so. It will run very nicely LOP at low power settings (5-7gph) all day long at low altitudes, but going to WOT seems to make it unacceptably rough most times. On my last trip this past weekend, I managed somehow (luck) to have it run smooth LOP @ 4,500' MSL, at wide open throttle, ~9gph witht the ram air open.

The reason is that my stock injectors seem to have two that peak at the same time, and then I have to get them about 40dF LOP before the other two reach peak. As you can imagine, this kind of imbalance means a significant reduction in power from those first two cylinders to peak, by the time the last two get to peak EGT.

 

[Ned Gravel]

I ran LOP successfully for the first time last week.  On stock injectors.  The narrative below was previously posted on http://mooneyspace.net/index.cfm?mainaction=posts&threadid=1848&forumid=2&postid=19967&page=1#post19967 and has been modified slightly from more recent experience to take out the invalid statements.

Took off from du Page near Chicago for my trip home on 10 November (near Toronto, Ontario) and when I was finally released to cruise altitude of 7000' I decided to try LOP for real.  I had previously tried it but the engine always went really rough on me.  This time it worked and I learned a few things.

First, I set up LOP at or below 70% when it is much easier to slowly go through peak EGT and determine the numbers myself (I know that the monitors all do that, but the process was not making me feel comfortable).  At 7000' and pulling 2500/22" is shown as 72% BHP in my owner' manual (POH) so any reduction in any of these two parameters will keep it below 70%.  At or below 70%, I am told that I do not have to worry about the Red Box where internal combustion pressures will hurt the engine.

Here are my numbers with Peak EGT determined to be 1480 degF.

7000' 10 degrees LOP

          Cyl 1     Cyl 2     Cyl 3     Cyl 4

EGT    1467     1472     1440     1433

CHT      313      291       325       289

 

7000' 43 degrees LOP

          Cyl 1     Cyl 2     Cyl 3     Cyl 4

EGT    1417     1437     1394     1383

CHT      305      285       316       268

The engine sounded only slightly less solid than it does at or beyond 50 ROP.   But it did not sound rough (Finally!!!!).  I lost about 2-3 knots indicated for 10 LOP and another 1 or 2 for 40 LOP.  I should have made careful measurement when I filled it up to leave, but I did not know I was going to try this.  I left the tanks an inch below the caps when I filled up to leave and attendent filled them up all the way after I landed.  I should have payed more attention, but the result was 33 gallons for a three hour flight.  So, slightly more than 10 gph.

One observation was the extreme sensitivity of the last cylinder to peak EGT reading from mixture knob inputs when lean of peak.  Quarter turn and I was down 30 degF.  Another is that once the system is set, it will wander as much as 15 degF up and down without making any changes other than direction (no altitude changes).  Mind you the QNH varied by as much as .04 inches during this flight.  I was travelling from a lower pressure area to a higher one.

Way forward?  Do more of this.  Get up.  Get settled and when it is safe (70% or below with all other parameters operating nominally) rotate the mixture knob through peak.  I have also been told that peak at altitude is "best power" mixture and I am OK with this so long as it is not in the Red Box.

Feel good about this.  Been wanting to do it for some time.  Just need to see a start point that did not make me worry and when I recognised the condition as less than 70% BHP, it all fell into place.

I also think I may end up swapping some injectors to even out the temperatures a little more.  (Next annual).

This is me saving gas money now.........

[carusoam]

Ned,

I agree with Jim... The data that I have seen presented is the red zone ends at 65% (OK to run at peak lower than this BHP value)

Best regards,

-a-

[Ned Gravel]

Quote: carusoam

Ned,

I agree with Jim... The data that I have seen presented is the red zone ends at 65% (OK to run at peak lower than this BHP value)

Best regards,

-a-

[jetdriven]

Ours as delivered would start to shudder about peak. The GAMI spread was 2.5 GPH. we swapped #1 injector with #4, cleaned them all, and it would run smoothly to 10 LOP.    Installing tempest fire wire plugs now it runs smooth to 70-90 LOP.   GAMI spread is somewhere less than .1 GPH.   This on stock injectors, now we can run WOT LOP at 4,000' and control airspeed with the mixture, around 8.4-9.0 GPH,  330-360 CHTs as well. 

[Shadrach]

Quote: rdv

Has anyone experimented with running LOP without balanced injectors? Is it safe to experiment with the help of engine analyzer only? (no fuel flow)

 

Ryan

[1970m20e]

Great information here.  Thanks.  I've been experimenting with my IO360 and LOP operations.  I use 70-75% power settings to determine when to LOP.  My EDM700 with the EI5L fuel flow next to it allows me to monitor LOP CHT temperatures as well as fuel flow.  I too have a GAMI spread on OEM injectors at 1.0 gph between the peak cylinder (#3) and the leanest cylinder (#2).  I've asked my mechanic to see if he could look at these numbers and see about swapping injectors around to try and swap the richest with the leanest and see if that helps balance the fuel flow to a closer GAMI spread.  He doesn't believe in LOP operations or any of this information.  He believes in low CHT's as being the best for your engine.  I'll just have to bring him up for a ride sometime to show him what I'm seeing or download the EDM700 data.

 

One weird thing is my engine runs smooth regardless of how much I lean the mixture.  I guess this is good.  I can lean until the engine basically loses so much power that it's on the verge of shutdown!  So I would guess the balance is actually pretty good.

Again, this is great information on LOP ops.  Thanks.

[KSMooniac]

You might repeat your GAMI lean test, because I don't think you would have smooth LOP ops all the way to shutdown with a 1.0 GPH spread.  You're likely closer to 0.0 than 0.5 GPH in my opinion...as most IO-360s are so long as they don't have any induction leaks or clogged injectors.  Repeat your lean test, and if it is still >0.5 GPH, then clean your injectors and thoroughly check for induction leaks.

I agree with everything Ross has posted on the topic too.  I'm glad more of us are out there preaching the gospel of LOP!  

[WardHolbrook]

Quote: 1970m20e

...I've asked my mechanic to see if he could look at these numbers and see about swapping injectors around to try and swap the richest with the leanest and see if that helps balance the fuel flow to a closer GAMI spread.  He doesn't believe in LOP operations or any of this information...

Taking advice on LOP operations from most A&Ps is a little like having a concert pianist take advice on how to play the piano from the piano tuner.  

[jetdriven]

clean them and swap them around.  Ours peaked #1 at 8.8 GPH, #2 was 8.2, #3 was 8.3, #4 was 7.9.   after they all peak at the same FF, in this case, 4K, 62% power, at 8.6 GPH.

[Shadrach]

Quote: WardHolbrook

[DaV8or]

Quote: 1970m20e

 He doesn't believe in LOP operations or any of this information.

[DaV8or]

Quote: WardHolbrook

[jetdriven]

Many more pilots run their engines ROP than LOP, and shops do many cylinder replacements and top overhauls.  SO I'd say that more engines need cylinders that are run ROP than LOP. These are air-cooled engines and exceeding CHT of 400 dF will damage them. 

Most of this advice hanst been updated since the 1960s.  However Lycoming recommends peak up to 75%, so if your engine can run smoothly past peak, why not?  I do know that LOP is lower cylinder pressure, lower FF, lower CHT, and a slight speed loss, perhaps 5% of power, which can be recovered with 1-2" more manifold pressure.  

There is a place for ROP also, such as takeoff, final approach,  full speed air races, and anytime you are so high you can't maintain acceptable airspeed LOP or at peak,  because ROP does make more power. 

We save 10-12$ an hour running 65-70% at LOP.  Its basically, "Free engine reserve when operated LOP". 

[jetdriven]

Here is our latest GAMI test.  Notice all EGT peak at a FF of 9.0 GPH.  This is stock injectors, 1 swapped for 4 and all cleaned with acetone. 10 GPH is 50 ROP, 9 GPH is peak, and 8 GPH is 50 LOP.   It costs us 13 MPH but we save  2  GPH.  Figuring in fixed costs, somewhere around 10-30 LOP is the most ECON cruise.  This is around 65-70% power.  

 

CHTs are around 370 at 50 ROP, in the 330 range at 30-50 LOP.   70 LOP they are around 300. 

 

[jetdriven]

double post.  delete

[WardHolbrook]

Quote: DaV8or

[Shadrach]

Quote: DaV8or

[scottfromiowa]

I have an IO360A1A engine in My M20E model.  My engine runs LOP (as Ross describes) beautifully with Cylinder temps @ or below 350.  I don't lean in climb, but may start to experiment here...otherwise I pull till rough and enrichen to find peak and fine tune from there.  I have a four probe EGT/CT engine monitor and fuel flow.  I am at or just under 10gph flying LOP.  Those that don't or can't fly LOP in their birds seem to cast warnings and creep into these threads...How about doing an ROP thread of your own camp?  What I have read is that four cylinder fuel injected engines don't benefit "as much" from Gami's vs. six cylinder engines.  My engine runs great LOP 400+ hours post MOH.

 

Any suggestions on fuel flow during climb that is sweet spot for I0360A1A?  At what altitude do you start to lean?  It seems that using fuel flow vs. EGT would be easier in climb.  Thoughts/strategies?  When I tried leaning in climb (before) using EGT I think I was to aggressive as cylinder temps started climbing...This was pre-fuel flow monitor (installed in December).  I do a cruise climb 120MPH with cowl flaps open.  My fuel flow is about 15gph running 2650RPM.

[FAST FLIGHT OPTIONS LLC]

...Not sure if this is unusual but on my 1982 M20K 231 I’m able to run 100 plus degrees LOP with the stock injectors.  What’s even more unusual is that I have the GB engine and it doesn’t run all that hot.  I always fly/cruise at 28” MP and 2500 RPM with a Fuel Flow of 9.5 GPH.  I’m seeing 165-170 KTS with a TIT around 1500 or 1550.  When I venture in the flight levels I leave the cowl flaps in trail for the purposes of ADDITIONAL engine cooling but I don’t really have to.

 

I climb at 110kts – 120 kts 40”MP 2700 RPM 22-24 GPH TIT 1400

 

[scottfromiowa]

Hey Nick, Why aren't you "231" flyer or "K-Flyer"? :<)

[1964-M20E]

I have a GEM 602 in my 64 E model and no fuel flow meter.  During climb out I note about where the EGTs are sitting at full rich and full power then as I go up I gradually lean keeping the EGTs right about where they were just after takeoff.  The GEM 602 is programmed to fly at ROP i.e. find the first cylinder that peaks (i.e. leanest cylinder) and drops then richen to 50 ROP.  I have played around some with LOP ops but not much.  Just trying to think how I can fool the GEM to find the LOP sweet spot as easy as it find the ROP spot.

I might try leaning until rough and starting the leaning program form there in reverse I think that would find the richest cylinder first and then lean slightly from there.

I’m with Scott on the climb out and after I have reached 1000’ AGL I’ll generally back off to 25“MP and 2500RPM