Advanced leaning - Mike Busch

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astaib
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Re: Advanced leaning - Mike Busch

Post by astaib »

Hi Torkell,

I will try the GAMI test then...

For information, I have sent my previous oil analysis (not the very last one) to Saavy and they advised me to go back on mineral oil, run the engine hard for 10 hours, and come back to synthetic oil.
I fear to ask this to my mechanic!

Regarding the baffle-seals, it is a "epic" topic, because the fact that they are worn-out didn't appear from one day to another, they are just victim of time (I bet that they are in place since de beginning: 17 years...).
But I came to this topic because when I was prebuying the plane I noticed that cylinder #1 ran hotter than others (+50 F), and at this time I didn't knew that it was not a lot. Then I started to investigate and we have noticed that the rod than maintain the front and rear baffles was missing: we replaced them temporary with wires, this improved the cooling slightly. But I continued to dig, and the seals were obviously worn-out(visual aspect, weavy...), so my mechanic ordered them, but still not received yet. Then I heard about the Arizona baffle with the bigger air intake with 11 cm diameter compare to 8 cm from mine (original one). And as the baffle for cylinder #1 was a bit worn-out too, I decided to order the Arizona one instead of the standard one. But same, still not received yet.

Here is the situation :)

Arnaud.
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Torkell
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Re: Advanced leaning - Mike Busch

Post by Torkell »

Colin wrote:Engine manufacturers argue against LOP. If you are above 5,000 feet you can't hurt the engine trying.
Engine manufacturers used to argue against LOP. This has changed over the past few years, and when I asked Lycoming CEO, Michael Kraft, at Aero Friedrichshafen i 2016 about Lycoming's take on LOP operations as a then-journalist, he confirmed that Lycoming no longer warns against it. (Even the infamous article "Experts are everywhere" seems to be off Lycoming's web site.)

In other words, the counter-arguments have finally won: https://www.advancedpilot.com/articles. ... cleid=1838

As for the DA20, it uses a Continental engine (if not a Rotax), but according to Avweb, Continental is even less skeptical than Lycoming these days:

"Even Lycoming and Continental weren’t exactly warm to the idea. The arguments against LOP were largely emotional and anecdotal, with a heady dose of not invented here. Both engine companies eventually came around, Continental more than Lycoming. Continental, as you may know, supports lean of peak in turbocharged Cirrus engines, having been led there by GAMI."

More in this entertaining article: https://www.avweb.com/blogs/insider/Lea ... 794-1.html
Last edited by Torkell on Mon Nov 12, 2018 4:25 pm, edited 1 time in total.
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Torkell
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Re: Advanced leaning - Mike Busch

Post by Torkell »

astaib wrote: I discussed with the shop where my engine was overhauled and they advised me to be very carefull with LOP as it will make the engine run hotter and risk for exaust valve to burn. I answered them that it is not hotter regarding CHT, but they explained me that the valve guide won't be correctly lubrificated, etc....
Perhaps the lubrication argument is linked to richer mixtures providing more lead? If that's the case, it is strange that the IO-360-M1A engine can happily run on avgas UL91, according to Lycoming SI1070Z page 5: https://www.lycoming.com/sites/default/ ... 0Fuels.pdf

If your mechanic disagrees with Lycoming and EASA that UL91 is safe – because of lack of "lead lubrication" – the lubrication argument has in any case been addressed many years ago:

"The last refuge of someone really backed into the corner in opposition to LOP is the old valve lubrication argument and yes, my friend told me he had heard that, too. This holds that lead builds up on the valve seats and lubricates and protects them, preventing something called valve seat recession. The engineering on this is mixed, but there’s nothing in the historical technical data that suggests lead was added to aviation gasoline for anything other than to increase octane.

The FAA’s technical center tackled the valve seat recession issue in a test (PDF) more than 25 years ago when unleaded fuels were being considered. In a test cell, it ran like engines on both 100LL and unleaded fuel. The conclusion: “… the results indicate that no significant difference in effects were observed in the valve seat recession of intake or exhaust valves between the unleaded fuel and 100LL aviation gasoline.” A second study (PDF) found limited recession in test cell runs, but no evidence of it actually occurring at all on automotive engines."

[From this article: https://www.avweb.com/blogs/insider/Lea ... 794-1.html ]
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astaib
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Re: Advanced leaning - Mike Busch

Post by astaib »

I downloaded these pages and will read tomorrow when I will be in a commercial flight!

Arnaud.
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Re: Advanced leaning - Mike Busch

Post by Torkell »

astaib wrote:I downloaded these pages and will read tomorrow when I will be in a commercial flight!

Arnaud.
A final thought: Lycoming does not see any benefit from lead in the fuel on low/medium compression engines like the IO-360-M1A. On the contrary, Lycoming warns against valve guide problems as a consequence of excessive – not too little – lead in SI1425A:

"Operating with any of the following conditions present can promote deposit build-up reducing valve guide clearance and result in valve sticking.

a. High ambient temperatures
b. Slow flight with reduced cooling
c. High lead content of fuel

If any of the above is present or hesitation is observed, then inspection and cleaning is recommended (Refer to Part III of this instruction). Inspection and cleaning intervals can only be determined as a function of individual operating conditions."

The problems associated with leaded fuel explains why engines operated exclusively on unleaded avgas (UL91) can be operated on on extended maintenance intervals, according to Lycoming Service Letter L270: https://www.lycoming.com/sites/default/ ... uels_0.pdf
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Re: Advanced leaning - Mike Busch

Post by dwurfel »

On a related subject not sure how many people attended the EAA webinar that Mike did last week on oversquare.
He basically recommend keeping the mp lever full on, reducing prop speed after 1000 feet agl, and leaning as gaining altitude, then running 100 degrees lean of peak at cruise. He recommended lower RPM's and not touching MP until descending.

I am going to try this on a long distance trip this weekend. I normally go by the tables in the POH almost religiously in cruise flight.

Love to hear thoughts.
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Re: Advanced leaning - Mike Busch

Post by Rick »

dwurfel wrote:On a related subject not sure how many people attended the EAA webinar that Mike did last week on oversquare.
He basically recommend keeping the mp lever full on, reducing prop speed after 1000 feet agl, and leaning as gaining altitude, then running 100 degrees lean of peak at cruise. He recommended lower RPM's and not touching MP until descending.

I am going to try this on a long distance trip this weekend. I normally go by the tables in the POH almost religiously in cruise flight.

Love to hear thoughts.
I totally agree with the wide-open throttle in cruise until descending - this is how we've run our DA40's for 10 years now, without any problems. Also agree with reducing RPMs at 1000' AGL - I go to 2600 to climb, then 2450 when reaching cruise altitude. But 100 degrees LEAN of peak is probably going to be way too much, and I'd be surprised if Mike recommended that! I bet he said if you were going to run RICH of peak, you should be 100 deg RICH of peak. But if you are going to run LEAN of peak, you will typically end up more like 10-20 degrees on the lean side. I'm pretty sure my engine will quit at 100 deg LOP! Power drops off really quick on the lean side of peak, so you have to make really fine adjustments of the mixture (which is a pain in our DA40's).
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