Help with LOP

[M20E-1964]

So like many of us, my primary training included the "lean only above 3k or 5k" type stuff I've been reading up on LOP extensively, and was trying to fly on the lean side of peak today.

My EGT peaks around 1400 degrees. 1/4 turn leaner brings it down to about 1380 and the engine immediately runs rough.

It seems as nearly anything leaner than peak causes engine roughness. The engine is a PenYan w/ 400 hours and a clean bill of health. What am I doing wrong?

[Lood]

If you haven't already done so, do the Gami lean test to start off with. This will indicate the spread between your injectors, which is rather important for successful LOP flying.

[M20E-1964]

Thanks - I'll have to read up on that.... I have no idea what that is!

[danb35]

Short version (do a web search for a lot more information):

• 
  
• Climb to a high enough altitude that you're not making more than 65% power--8000 MSL should do
  
• Set WOT, 2500 RPM (or whatever you normally cruise at)
  
• Pull the mixture back to ~10 gph--this will be ROP, but not by a whole lot, which will make the rest of the test go more quickly.
  
• Let your EGTs stabilize before proceeding
  
• Slowly lean until every cylinder is LOP by at least 20 degrees, but 50 would be better
  
• Note the fuel flow at which each cylinder peaks
  
• The difference in fuel flow between the first and last cylinders to peak is your "GAMI spread"
  

It's OK if the engine runs rough during the test--as long as it's not shaking the fillings out of your teeth, you won't hurt anything.

If you have data logging on your engine monitor, you can skip the part about writing down the fuel flow and instead download the data to look at it yourself, or upload it to savvyanalysis.com (which seems like a pretty slick service), which will automatically figure it out for you.

A GAMI spread less than .5 GPH is good.  More than 1 GPH isn't so good.  You might need GAMIjectors to run smoothly, but that's unusual for the IO-360s we run.  If you aren't running smoothly LOP, check for induction leaks or ignition problems (an in-flight mag check is a good way for the latter).

[Ron McBride]

How do you do the inflight mag check. What am I looking for?   I did one last flight and the the RPM varied a little and the EGT's went up. Is this correct?   I have a 69F  IO360

Thank You

Ron

[danb35]

In-flight mag check is best done LOP.  Run on one mag, EGTs should all rise (roughly) evenly.  Back to both, they drop.  Other mag, they should again rise evenly.  RPM shouldn't vary much at all (after all, you have a constant speed prop).  Mike Busch recommends running on each mag for at least 30 sec. for best results.

[jetdriven]

Read every thread here containing the keyword "LOP".   Just read the ones with more than 10 replies. Likeweise on Beechtalk and VAF forums.  Then visi t GAMI and read their articles.  Then read all the "pelican's perch" articles about engine management. Then read all the "savvy" articles by Mike Busch. Then watch his webinars on the savvy website.  That should get you going pretty good.  90% of LOP is knowing what is going on and what to avoid doing.  The other 10% is making sure your injectors, plugs, ignition system is up to par.

[M20E-1964]

Thanks.

My only equipment on board to do this is a 4 channel EGT. I dont have any engine analyzer or fuel flow gauges.

[PTK]

Quote: jetdriven

Read every thread here containing the keyword "LOP".   Just read the ones with more than 10 replies. Likeweise on Beechtalk and VAF forums.  Then visi t GAMI and read their articles.  Then read all the "pelican's perch" articles about engine management. Then read all the "savvy" articles by Mike Busch. Then watch his webinars on the savvy website.  That should get you going pretty good.  90% of LOP is knowing what is going on and what to avoid doing.  The other 10% is making sure your injectors, plugs, ignition system is up to par.

[WardHolbrook]

In most cases, operating LOP is not something you just decide one day to do. It takes preparation - both personal (training) and usually some equipment on the airplane. Done properly, there's no risk of hurting anything. Muff it up and things can get pretty expensive. Here's a link to the experts. www.advancedpilot.com/ The cost of the online course is modest but they'll take you buy the hand and explain what's needed, how to competently do it, and most importanly help you to understand exactly what's going on inside your engine. Amortized over the rest of your flying career it seems like a pretty solid investment.

[jetdriven]

Thanks, Ward. I forgot to include the best single source for the best information.  It all goes back to them.

[MooneyMitch]

Hi Ward.

Saw your little blurb in AOPA Pilot.  It was fun reading about your expereince and seeing a name I recognized. 

[danb35]

Without fuel flow instrumentation, it will be impossible to determine your GAMI spread, which is just a shorthand term for the fuel flow spread between your richest and leanest cylinders.  Without multi-cylinder CHT instrumentation, it's impossible to know if you're running too hot.  Both are highly recommended for operating an engine at all, whether LOP or not.

Fuel flow instrumentation isn't too expensive--last time I looked at the EI FP-5L (which is what I have in '48Q, and it works very well), it was around $400.  JPI's FS-450 is comparable in price.  I'd expect there are some pretty good deals going right now with OSH and all.  Installation will add to the cost, of course, but it shouldn't be excessive.

[danb35]

Quote: allsmiles

This is excellent advice Byron is giving you gmcd. Expecially Mike Busch's Savvy webinars: "Leaning basics", "Engine Monitors" and "The EGT Myth". There is a wealth of knowledge there. You will learn theory and lots of practical advice.

Also, you probably should consider the proper equipment for your airplane (an engine monitor and ff) to do this safely. Otherwise you are in the dark as to what your engine is doing making it that much more difficult.

[garytex]

1/4 turn leaner brings it down to about 1380 and the engine immediately runs rough.

Something may up with your engine, assuming that you have an injected engine.  Injectors, plugs, mags, intake manifolds (especially #2), something.  It shouldn't run rough 20df lean of peak.   Look for a low or high egt, do the mag test, talk to your mechanic.   If carburated, it may just be mixture mal-distribution. 

My humble opinion is that whatever is wrong should be fixed even if you decide to run ROP.  The previous owner of my plane ran rop all the time with an intake leak that leaned a cylinder to about peak at 75% of power, and toasted a cylinder.  It'd've been much cheaper to fix the leak.

Persevere, LOP for me means 10 mph slower, 3gph less fuel, much cooler CHTs, less heat gain on the valves, less fuel burning in the exhaust system, easier going combustion pressures, ...such a deal.