George Braly the co-inventor of GAMI’s regularly posts on the Bonanza list. His articulate description of the benefits of “properly” running lean of peak are worth reading but unlike most aviation pundits, he backs his words with money so here is a snippet regarding running lean of peaK. Jim McKeith
I can show you a Turbo 210 owner who operates the engine LOP 100% of the
time, at very high power settings. Hell, just for the “shock effect” …
I’ll let you in on a little secret: He even does climbs, lean of peak.
He has been doing this since he replaced the engine, about 1100 hours back.
Engine is perfect, in every way.
BEFORE he changed and started operating lean of peak, he had the normal TCM
set of engine problems.
I can show you a turbo C310 owner that is now at 2800+ hours since overhaul
on both engines. He has been operating lean of peak since 1500 hours.
The problems this T210 is experiencing is a lot like the problems the Malibu
owners experienced with the TSIO-520BE some years back… when they were
told to operate it 50 LOP… but they didn’t believe it and they ended up
operating it at peak or 25 ROP, because they thought (wrongly) that would be
“cooler”. They cratered a lot of engines, prematurely.
I teach approved A&P and IA renewal seminars for the FAA on engine
management. I have been through about 500-600 mechanics, so far this year.
In my experience, from quizzing the folks in those classes, they are at
least 90% very, very badly misinformed about the effects of operating lean
of peak. Many of them are almost in shock when they see TCM’s own data that
shows that CHTs get cooler when operated lean of peak… because they have
been telling pilots the “wrong” information for so many years.
The most important information you received from the SR-20 driver was the
He had no idea what the previous operation of the engine was like; and
He had no idea how the other pilots had been operating the engine.
Last, 800 hours is considered good for a lot of T-210s, when operated as
TCM and Cessna recommends.
I have seen a bunch of them lunch engines before 500 hours.
I have a standing offer to pay anybody $1000 bucks, if they can show me hard
data that establishes anything to the contrary to the following:
At a given horsepower, in an otherwise apples-to-apples comparison:
1) LOP operation results in lower peak cylinder pressures;
2) LOP operation results in lower cylinder head temperatures;
3) LOP operation results in lower ring blow-by;
4) LOP operation results in cleaner oil at oil changes;
5) LOP operation results in 10% or more fuel savings;
6) LOP operation results in cleaner combustion chambers;
7) LOP operation results in cleaner piston faces;
8) LOP operation results in cooler exhaust valves;
9) LOP operation results in cleaner exhaust valve seats;
10)LOP operation results in fewer valve guide deposits;
11)LOP operation results in cleaner spark plugs;
12)LOP operation results in 90+% reduced carbon monoxide...
As compared to operation of the same engine at the same horsepower at 75F
ROP fuel/air ratios.
Two issues here:
- In a turbo Continental doing a top overhaul at 50% of the TBO is typical - especially if its run at 75% a lot, or run high/hot a lot. TBO of the TSIO520 is 1600 hrs, so a top at 800 hrs is about right. It should be budgeted into the hourly reserves on the engine usage.
- The TSIO520, even with GAMI’s has a mixed reputation on running lean of peak. Most of the talks on running this way revolve around the IO550 engine, which is of course not a turbo, and has a different induction system as far as I have read. I think this makes it a candidate for running lean of peak, rather than the turbo TSIO520.
Some time back I wrote a small treatise on the wonders of agressive leaning. Until my SR 20 comes I am flying a Cessna 210 owned by a couple of doctors. It’s a Turbo Centurian II and very nice. Well kept, well mainatined, etc.
When I first started flying the beast last year I was sent an article from one of the owners on leaning lean of peak. Since the plane has an engine analyzer and Gami injectors, it was believed that you could lean 75 degrees lean of peak EGT and the plane would work fine. The article on leaing was very convincing with charts and scientific data etc.
The problems is that we are now replacing the top end of the engine at 800 hours. Culprit? Exhaust valves so burnt that some were sticking open. Lot’s of evidence of extremely high temps.
Before we gorunded the plane I was the last to fly it. It ran very well after a 100 hour. Except is was blowing out about 4 quarts of oil an hour through the new oil / air separator we installed. Apparantly, the stuck exhaust valve(s) were allowing gasses to pressurize the crank case above tolerances which led to the blowing of oil out of the crankcase point where there is supposed to be no pressue (return area for the separator).
I spoke with the mechanic about what I had been doing (leaning practices) and he nearly flipped. Told me to fly rich of peak (75 degrees) and ignore all the other recomendations.
Anyhow, I was wondering if anyone else has had a similar experience flying lean of peak. Not being the only pilot of the plane, I don’t know what the other guys are doing. Also, the plane was purchased used so the history is not well known either.
PS - For those of you wondering how the plane flew with valves stuck open, the mechanic has guessed that the turbo pressurized the cylinders enough to get some power. A normally aspirated engine would not have worked at all…