Directions on how to lean a Lycoming 360 - A3A
Hello All,
Can someone tell me the proper way to lean an engine? I have a '65 Cherokee 180C. I have just installed a Vernier Mixture nob and a JPI 700. I want to keep my engine happy AND not waste fuel. Now, please remember I am an Army Tanker - so I need simple yet detailed instructions.
Most of my recent flying has been at or near Sea Level.
I am about to take my first long distance trip this summer from Atlanta (4A7) to North East Philadelphia (either Wings or North East Philly).
I'll make one stop for fuel in VA probably at Middle Peninsula Regional (FYJ) depending on my bladder and fuel. I'd like to remove the Fuel concern with good leaning procedures.
Thanks,
Martin
Can someone tell me the proper way to lean an engine? I have a '65 Cherokee 180C. I have just installed a Vernier Mixture nob and a JPI 700. I want to keep my engine happy AND not waste fuel. Now, please remember I am an Army Tanker - so I need simple yet detailed instructions.
Most of my recent flying has been at or near Sea Level.
I am about to take my first long distance trip this summer from Atlanta (4A7) to North East Philadelphia (either Wings or North East Philly).
I'll make one stop for fuel in VA probably at Middle Peninsula Regional (FYJ) depending on my bladder and fuel. I'd like to remove the Fuel concern with good leaning procedures.
Thanks,
Martin
Comments
Best power is max RPM.
Best economy is lean till it runs rough, then enrichen till it runs smooth.
Simple enough for a Tanker?
The JPI is a GREAT diagnostic tool but won't save any money on gas.
PilotKris
I can't help you with the JPI 700, but here are the instructions from Lycoming for doing it the low-tech way: Leaning Procedures.
For best economy mixture, refer to paragraph B.4. As stated in the Service Instruction, as you slowly lean the mixture, you will note a gradual rise in RPM. Eventually, though, the engine will begin to run a little rough, and the RPM will drop. At that point, enrich the mixture until the engine fires evenly and you see the RPM rise. I don't have a vernier knob on my 65 Cherokee, but the Cessna 172 I fly does have one, and I find that two full turns is about right. This is called running rich of peak, as opposed to lean of peak. Refer to the chart in your POH for the RPM setting that achieves the desired power level for your altitude. I generally lean for 75% power. (By the way, "Standard Altitude" in the 65 POH is the same as "Density Altitude" in later Cherokee POHs.)
I have an Alcor EGT gauge in my Cherokee, but I find that it simply confirms what my eyes and ears tell me per the instructions above.
Lean when over 5,000 density altitude (I'm almost always over 5,000 in a single) to:
Best Power = Max RPM
Best Economy = Lean till it runs rough then enrichen till it runs smoothly
But I always fly a 180 at best power.
Flying that 0-360 at best power will give you pretty much exactly 10GPH tach time. So, even at todays fuel prices, a 10% fuel (if you can even get that much) savings is only $5 per hour.
Why fly to go slow?
That's all you need to know.
PilotKris
Thank you for the informative and easy feedback. I had heard about the lean till rough then add more - but I wanted some Cherokee Experts to let me know.
I do agree with Kris that I am not here to fly slow OR improperly - and I am a HUGE advocate of throttle wide open; as are all of my instructors.
I will let You all know this weekend how it goes / went.
I am just looking forward to flying more than just 2-3 hours on a weekend.
I've been to PA and NJ several times over the years - but not up to Wings or PNE.
Thank you all again,
BTW - Yes - I did go dig out the POH and it will be handy just in case.
Martin
On level-off, let the plane accelerate then power back to 75% on the RPM table. At full rich and less than max gross, that table is incorrect on the high side I figure.
Lean until power drops off or I get peak. Usually, the power drops off noticeably before I get to a clear peak.
Set throttle for 7 GPH which is 65% power by the 15 HP/GPH formula.
> On level-off, let the plane accelerate then power
> back to 75% on the RPM table.
Power back to 75% power? How low do you cruise?
Personally, I like to have at least 5,000 between me and terra firma, (or water) especially in a single (and Hershey Bar wing Cherokees are not exactly known for their good glide).
Other advantages of higher altitudes:
Cooler
Better economy
Better radio coverage
Better nav reception
Better ride
Better visibility
(and the list goes on).
WOT and the (density)altitude that gives you the power setting you're wanting will give your the best economy.
WOT in a 140 isn't going break the bank at any altitude. I think you'll find your mileage will increase, you'll be safer and cooler if you climb 2-3,000' higher. Oh, and you'll get there faster too.
Come on Tim, Live A Little.
Life is short, fly FAST!
PilotKris
Question. So if I am going to cruise at 7500 or 8500. Keep, WOT without redline and lean until rough or rpm drop? Then enrich until smooth rpm increase?
Lean for Max RPM/IAS, Best Power (what I do)
Lean till it runs rough and then enrich just till it runs smooth, Best Economy
This all assumes you are keeping it at redline RPM or below which is most likely unless you have a very aggressive "climb" prop.
PilotKris
> Power back to 75% power? How low do you cruise?
PK - Speaking only for my Warrior, WOT in level flight at anything less than 6000-ish MSL puts it past redline. Home base is 800 MSL and, while I completely agree with you in principle about flying high, particularly for cross countries, sometimes it's neither practical nor warranted to do so (short hops, high headwinds aloft, etc).
I'm going to guess what the next question will be: Why don't I increase the pitch on my prop if WOT in level flight gets me to redline so easily? The answer is that the prop was already pitched higher (62") when I bought the airplane, but it wouldn't pass the static RPM criterion given in the TCDS (too low) and my mechanic would not sign it off as airworthy without the prop being pitched back to the maximum allowed per the TCDS (60"). And yes, the tach reading was independently verified.
So...Tim's approach makes sense to me. I also realize that I'm speaking to a different engine/airframe combination than Martin asked about, but I think most of the advice given was meant to be generally applicable.
Martin -
Because you have the JPI-700, you might be interested in this article. It may muddy the water for you even further, but I think it provides good insight from a well-respected source on how to use that analyzer to monitor engine health while leaning:
http://www.avweb.com/news/savvyaviator/savvy_aviator_59_egt_cht_and_leaning_198162-1.html
Best wishes for a successful long x-country flight! I visited Wings Field once a couple of years ago. It struck me as a vibrant, healthy airport. Lots of people flying. Cool place.
What are the possible problems associated with running to rich or to lean?
> Stupid question
>
> What are the possible problems associated with
> running to rich or to lean?
That's not a stupid question - it's an important one.
The price of running too rich is (1) wasting fuel and (2) the potential for carbon fouling of your plugs. I say "potential" because some engines are more prone to this than others (my Warrior has fouled a plug exactly once in six years of ownership).
The issues with leaning depends a lot on power setting and engine type (particularly whether it's got a carbureted or fuel injected). Running too lean at full power raises concerns about detonation and cylinder damage. Otherwise, the main issue is temperature and engine longevity - see the AvWeb article I posted earlier in this thread for a discussion on that, along with introducing the notion of lean of peak vs rich of peak leaning (this is where carberation vs fuel injection comes into play). At the end of the day, you don't want your cylinders running too hot. As you saw from the exchange between PK and MikeL, there's some debate out there about whether Lycoming's recommended operating limits are too high. There are some high profile folks out there with compelling arguments that CHTs of 400F° should be considered an operating limit rather than Lycoming's recommendations of 500°F (I thought it was 500, MikeL notes 550°F - either way, both are higher than I've ever seen).
If you don't have a fancy engine monitor that can show you what your CHTs are doing, follow your POH and, unless you're at 5000'+, if you firewall that throttle, make sure the mixture goes full rich with it!
Before anyone asks, I'm a chemist and probably just as untrustworthy as an electrical engineer. And, of course, I've simplified my response a bit. I'm sure others here will be more than happy to fill in the gaps. :-)
I cruise high, in the 8-12K altitudes if I am going somewhere far enough to bother or around the summer's thunderboomers. For my most common trip, X09-GTU which is just a 1-hr flight, I don't get much above 6. The additional climb doesn't seem worth it for a 1-hr flight.
At altitude, I am not power limited but ROM limited. I have to keep the power trimmed back to keep the RPM from redlining, especially in the turbulence in the above-mentioned TS areas. Leaned as I suggested, I am getting CHTs <330, TAS around 115-120 and fuel flow at 7-ish GPH.
As MikeL said, I am just relating my experience. Like your opinion, mine is probably worth what Martin H paid for it when he posted. He can take from this discussion what he will and I can read your comments and take from that what I will.
> My experience is that cruising at 75% best power
> mixture yields CHTs in the 475-500 deg range
Dude, there is something seriously wrong with your engine and/or airplane.
Your 180 was certified without a CHT gage meaning Piper demonstrated during certification that it wasn't possible to exceed the CHT limits...at all.
The only way you would see those kinds of temps is if something is seriously wrong. Engine timing and baffles are where I'd start to look. It isn't likely to be a mixture problem as even at Best Power mixture (at <75%) which would be the hottest CHTs, you shouldn't be seeing temps that high.
PilotKris
> I have my first plane(140) and I am
> concerned about protecting the engine over saving
> fuel.
Just follow your POH and you won't have any issues.
Most of what you read about leaning "techniques" is written about/for high performance engines were the detonation margins are narrow, heat produced great, and cowling very tight. You just don't have the same issues in a 140. So not-an-issue are CHTs, Piper didn't even put a CHT gage in your plane.
The 140 has been around for 50 years (the 1st 30 without the "benefit" of engine monitors) and even being mostly operated by student pilots, there are no specific CHT/temperature (mixture related) issues. In fact, the only real mixture issues are running to rich and fouling plugs, dirtying oil, running out of gas and not getting full power and crashing (DA issues).
I'll even go so far as to say that whatever you do with that little red knob is going to have little effect on engine longevity.
PilotKris
> MikeL Wrote:
>
>
> > My experience is that cruising at 75% best
> power
> > mixture yields CHTs in the 475-500 deg range
>
> Dude, there is something seriously wrong with your
> engine and/or airplane.
Agreed.
Certainly, MikeL could check for a gross calibration issue simply by checking the CHTs before starting the engine. If they're reading significantly above ambient, there's the problem. My A&P and I once checked mine while hot by using an infrared thermometer to compare engine temperature with CHT readings.
How does the paint on the cylinders look? If they're routinely running that hot, the paint will start flaking off. Ask me how I know... :-)
So what I'm saying applies to my IO-360 and not the OP's O-360, but once stable in cruise at WOT I'll lean to between 20-50 LOP (depends on altitude) which generally puts me at 8.7 to 9.0 gph. This keeps all my CHTs between 360-380, although #1 sometimes creeps up to 389 in warmer temps.
And not to rub it in for all my Piper friends, but in my M20J that 9.0 gph is still getting me 150 KTAS! (That's at 2500 RPM.)
:-)
> MikeL Wrote:
>
>
> > My experience is that cruising at 75% best
> power
> > mixture yields CHTs in the 475-500 deg range
>
> Dude, there is something seriously wrong with your
> engine and/or airplane.
>
>
> PilotKris
The Lycoming 0 360 Operators Manual indicates Max CHT up to 75% power for all models at 500C except for two engine model exceptions and those are 475C.
What is the seriousness?
> The Lycoming 0 360 Operators Manual indicates Max
> CHT up to 75% power for all models at 500C except
> for two engine model exceptions and those are
> 475C.
>
> What is the seriousness?
I didn't say the temps were serious, I said there was something seriously wrong (twice).It should not be possible to see temps that high in a 180 absent a mechanical problem.
The seriousness comes, as Mike pointed out, from the lack of any safety margin.
BTW GM, at 500C, the engine (at least the pistons) would be a puddle of molten aluminum. The limits are 475F/500F.
Mike, you have a problem. It might be possible with the extra instrumentation you have to keep the temps under control but why not simply fix the problem?
PilotKris