LOP - Do's and Don'ts

[Webb]

After researching lean of peak, info seems to be a bit sparse but after doing enough searching, this is what I've found:

- Don't do it below 6,000 feet. You can't run greater than 75% power above.
- Make sure you are WOT. Detonation can occur for 2 reasons, too lean or too low rpm.
- Shoot for 50F LOP
- Best if engine is fuel injected
- Engine monitor is needed to do it properly
- Temps should be fairly even
- Expect about a 10 knot drop in speed
- Lycoming does not recommend

Any more experience/advice for those that are in the know would be great.

[ronschreck]

Originally Posted by Webb

After researching lean of peak, info seems to be a bit sparse but after doing enough searching, this is what I've found:

- Don't do it below 6,000 feet. You can't run greater than 75% power above.
- Make sure you are WOT. Detonation can occur for 2 reasons, too lean or too low rpm.
- Shoot for 50F LOP
- Best if engine is fuel injected
- Engine monitor is needed to do it properly
- Temps should be fairly even
- Expect about a 10 knot drop in speed
- Lycoming does not recommend

Any more experience/advice for those that are in the know would be great.

I have been running LOP at ANY altitude for over 600 hours. Just pull the throttle back to 75% power at lower altitudes. You do not need to be at wide open throttle. Agree with the rest of your post. BTW, Lycoming did not recommend MOGAS for their engines until last year!

[Russ McCutcheon]

This comes up often and has been beaten to death, but it is an interesting topic. I run mine LOP at any altitude and at less then WOT if I so desire, so long as it?s below 75%!

Yesterday we where going from Bend OR to The Dalles OR then down the Columbia Gorge to home in Vancouver WA. The first lag was at 9000msl, less then WOT, 22? and 2400rpm and LOP, I did a little checking to and all four where LOP buy 50 degrees or so, was burning about 7.4 GPH. On the leg down the river we where at 2000msl and it can be bumpy so we where going slow, still 22? and 2400rpm but once again LOP about 7.2 GPH this time, still running very smooth and far LOP, when we thought it was good to go faster (not bumpy) we went ROP to 8.5 GPH and we where ripping along, the same power setting was giving us 140 indicated very LOP and 160 indicated ROP, never changed the throttle or the RPM just the mixture.

200hp angle valve IO-360 A1A with CS prop, I do have 4 probe EGT but you have to switch between each cylinder to see there readings, not very high-tech, at 9000? I decided to check each cylinder, I had not done this in the past, so I leaned the engine four times, once wile looking at each cylinder EGT, sure enough even though each reads a different value they all went LOP 80+ before it would start to go ruff.

I only have one CHT probe and it runs cooler LOP then at peak or ROP, I will assume the other three cylinders follow the same pattern since they are all LOP they all will be making less power and less heat, not very high-tech.

The best thing to do for your engine is maintain it properly and fly it often, we did a very major OH 5-9-06 and the engine now has almost 700 Hobbs hours, 233 per year and no issues, should make TBO in 10 years at this rate.

[hevansrv7a]

I'll just join the chorus. I do it all the time and most often at lower altitudes and power settings. I make sure the engine is at least as lean as GAMI says. On the GRT, that means that it will compute a SFC of 0.38 or less. The reading is lower than reality, but it's a good way to be sure. In Michigan in the winter that leaves the engine so cold I worry about that, not detonation.

[SebsRV7A]

Link to John Deakin's articles on the subject. Long read, but my reference on LOP ops...
Note the Red Box power settings - I have them posted on my panel...

http://www.avweb.com/news/pelican/182179-1.html
http://www.avweb.com/news/pelican/182176-1.html
http://www.avweb.com/news/pelican/182583-1.html
http://www.avweb.com/news/pelican/183094-1.html

Seb Trost
RV-7A 325 hours
Boulder City, NV (BVU, formally 61B)
Always LOP at cruise, sometimes in climb, too!

[lucky]

http://www.warmkessel.com/jr/flying/td/jd/65.jsp

[erich weaver]

I commonly see folks here saying to limit people LOP to <75% power and have kept my LOP operations in that range, but I dont recall a specific limitation to that in the Deakin articles. In fact, there are a few places where he refers to going LOP during climb, using what he calls "the big mixture pull" (something like that anyway), to quickly transition from ROP to LOP. THis tecnique is distinct from the less aggressive one he describes in later articles, where you slowly lean as you climb by adjusting mixture to keep your egt approximately constant, then go LOP naturally above around 8ooo feet, or if below that, by leaning a bit more . By either method though, its always full throttle according to Deakin, as anything else would be "like operating with a dirty air filter".

Clearly you are not at full power anytime you are LOP, but it would seem likely that its at or above 75% using his "big pull" method, no?. And as he points out, the majority of the "red zone" is on the rich side of peak. Maybe it really can be done at >75% power??

I havent tried the big pull method myself, and Im not making any recommendations here either - just trying to promote further discussion and understanding.

regards

erich

[rv7charlie]

Lots of stuff about setting mixtures here:

http://www.lycoming.com/support/tips...Operations.pdf

While it recommends against lean of peak, it *does* recommend operation *at peak* for best economy cruise power settings. Interesting, since conventional wisdom for the entire time I've been flying has been to stay away from operation at peak in all circumstances.

FWIW, I've seen a document from Lyc in the past that actually details how to operate lean of peak, including the turbocharged models, but I can't find it now. Seems as if engine info is a lot like the weather. If you don't like what you see, just wait; it will change.

Charlie

[Webb]

I differ with Russ about this being beaten to death. I've learned more from these post with their the web links than I have anywhere else. I do agree with him that it is an interesting topic.

Thanks to the info. By far more complete than I've been able to find.

[Geico266]

Originally Posted by Webb

After researching lean of peak, info seems to be a bit sparse but after doing enough searching, this is what I've found:

- Don't do it below 6,000 feet. You can't run greater than 75% power above.
- Make sure you are WOT. Detonation can occur for 2 reasons, too lean or too low rpm.
- Shoot for 50F LOP
- Best if engine is fuel injected
- Engine monitor is needed to do it properly
- Temps should be fairly even
- Expect about a 10 knot drop in speed
- Lycoming does not recommend

Any more experience/advice for those that are in the know would be great.

Webb, before you run LOP you need to "tune" or "balance" the injectors. They need to peak at nearly the same time. If you don't you run the risk of having a cylinder running at peak.

Call Don at Air Flow Performance and he will walk you though the procedure to gather the data, then you can replace the injector nozzles as needed.

http://www.airflowperformance.com/