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PostPosted: Sun May 08, 2011 8:36 pm 
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N3576X - FlightAware user avatar

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I own a 1980 Piper Turbo-Saratoga with the Lycoming TIO-540-S1AD engine. I have owned it since 2004. The engine recommended TBO is
1800 hours. It currently has 1925 hours since major overhaul. It has never been top overhauled. I run it 50 degrees lean of peak TIT.
I have a GEM engine analyzer and Shadin fuel flow monitor. The maximum recommended TIT (turbine inlet temperature) is 1650 degrees.
I run it 1625 to 1650 degrees. This is an updraft cooled engine which means the cooling air comes in the bottom and goes up through the cylinders. Some exits out of the louvers on top of the cowling but some goes back down the back near the firewall and exits out of bottom louvers.
These cylinders have cross flow heads which means the air from the fuel injection servo comes in the bottom of the cylinder and the exhaust exits out the top of the cylinder. It has factory stock fuel injectors and it runs smoothly with good fuel balance at 50 degrees lean of peak. To give you an idea of how much higher the cylinder pressure is when running 50 degrees rich of peak these high time cylinders have oil blow by the rings which causes oil to come out of the seals and on an updraft cooled engine the oil comes out the top louvers and gets on the windshield. The cylinder pressures are low enough at 50 degrees lean of peak that no blow by comes around the rings and gets on the windshield. It runs dry.
The cylinder head temps run about 380 degrees at 50 degrees lean of peak and about 410 degrees 50 degrees rich of peak. You don't get something for nothing. It takes fuel to produce horsepower. The advantage of a turbocharged engine is you can increase the manifold pressure to recover the lost power from running lean of peak. The fuel flow goes up in the process. The advantage then of running lean of peak is the cooler cylinder head temps CHT) and cooler turbine inlet temps.
(TIT). Even though these cylinders have 1925 hours on them they still have better than 70/80 compression. One nice thing about this engine is it is derated for 300 HP at 2700 RPM and 36 inches of manifold pressure.
This same basic engine produces 350 HP in some Piper Navajos. They do it at 2700 RPM and 42 inches of manifold pressure. I think this is one reason this engine has lasted so long. It is loafing at 300 HP. This same engine is used in the Turbo-Lance and Piper publishes an 81% cruise power setting for it. 81 % of 300 HP is 243 HP. 75% of 350 HP is 262 HP.
So this engine is still producing less HP than it is capable of at 81% cruise.
My recommendation is for you to run your engine at whatever makes you comfortable. You can always hear stories of how some engine has blown up or did not make TBO. There are so many variables that it is hard to make sense of isolated failures. Poor maintenance and poor pilot technique is usually the cause. I feel more comfortable running my big turbocharged Lycoming 50 degrees lean of peak with cool cylinder head temperatures.


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 Post subject: piper saratoga lean of peak operations
PostPosted: Wed May 11, 2011 7:35 am 
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victorjuliet - FlightAware user avatar

Joined: Sun Jun 07, 2009 8:00 am
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Location: KBLM
Read "Fly The Engine" by Kas Thomas.


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 Post subject:
PostPosted: Wed May 11, 2011 8:12 am 
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N3576X - FlightAware user avatar

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Kas Thomas is a good author. Founder of Light Plane Maintenance.
I read all of his articles when he wrote that publication. I notice there is a new edition of Fly The Engine available now.


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 Post subject: piper saratoga lean of peak operations
PostPosted: Wed May 11, 2011 5:30 pm 
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victorjuliet - FlightAware user avatar

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I get LPM too. It's a gold mine of info. (Also recommend Aviation Safety, Aviation Consumer and IFR Magazine). What gets me is that the more I read LPM, the more I realize that it is really a publication intended to give advice on keeping increasingly antique machines operating safely.


The fear with lean of peak is destructive detonation, the same issue if I don't put 93 octane in my old 1969 427 Vette. Old technology. Not an issue in my 2010 Volvo which I run on regular and still get 300 hp. How many pilots think of a 1969 Piper or Cessna as a "classic" in the same sense as a 1969 car?


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 Post subject:
PostPosted: Wed May 11, 2011 6:26 pm 
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You might want to figure out the differnt between 93 octaine and 89.


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 Post subject:
PostPosted: Wed May 11, 2011 7:38 pm 
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victorjuliet - FlightAware user avatar

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flyboy97222 wrote:
You might want to figure out the differnt between 93 octaine and 89.


Whaaa? Compressing the fuel air mixture heats it up. In high compresion engines, the fuel air mixture heats up faster due to higher compresion and can explode before the spark plug ignites it. That is known as detonation. Higher octane fuel, because it burns slower, helps prevent detonation. Stick to your turbine engines :lol:


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 Post subject:
PostPosted: Wed May 11, 2011 8:28 pm 
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flyboy97222 - FlightAware user avatar

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victorjuliet wrote:
flyboy97222 wrote:
You might want to figure out the differnt between 93 octaine and 89.


Whaaa? Compressing the fuel air mixture heats it up. In high compresion engines, the fuel air mixture heats up faster due to higher compresion and can explode before the spark plug ignites it. That is known as detonation. Higher octane fuel, because it burns slower, helps prevent detonation. Stick to your turbine engines :lol:


DA*M my bad i was reading your last post on my tiny iPhone screen and didn't see that you DON'T put in your low compression 427.

MY BAD :oops:


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 Post subject: piper saratoga lean of peak operations
PostPosted: Wed May 11, 2011 9:13 pm 
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victorjuliet - FlightAware user avatar

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No problem Bro. I should have said that the higher the octane the fuel, the harder it is to ignite, so you need it in high compression engines to avoid detonation prior to spark.

Sorry I'm rambling

:roll:


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 Post subject: Re: Piper Saratoga Lean of Peak operations
PostPosted: Fri May 13, 2011 12:52 pm 
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N3576X - FlightAware user avatar

Joined: Mon Jun 26, 2006 6:00 am
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My son also owns a Turbo-Saratoga SP. His is a 1981 model with the intercooler and LoPresti speed mods on it.
I think you will enjoy reading my email to him and his answer.

Steve,
I am looking at my Saratoga Cruise Performance chart in the POH. One thing that doesn't make any sense
is how they have a line for 55, 65, and 75% power based on 100 degrees rich of peak and one at peak EGT or TIT.
As an example 75% power should be 225 HP. How can they then show two different 75% power speeds?
If the engine is producing 225 HP then the speeds should be the same. Do they really mean the engine is
developing 225 HP at best power mixture and less than 225 HP at peak TIT mixture? I know that is what the
engine is doing but they don't express it that way in the charts. It looks like they are basing their % power
numbers on RPM and Manifold Pressure settings only and not taking into consideration the fuel flow. There
is another table that shows 75% best power fuel flow to be approx 18.7 GPH and another table shows
75% best economy fuel flow to be 16.5 GPH. I wonder which one of these is really producing 225 HP which
is 75% of 300 HP? When running 50 degrees lean of peak TIT at say 16.5 GPH is that producing the same HP as
peak TIT at 16.5 GPH?

If you study what Insight says about the new G3 and all of the variables in displaying % HP it makes you
wonder about these engine analyzers that show % power and are they very accurate.

I did a lot of reading about intercoolers and how one of the companies developed new power charts when their
intercooler was installed. They actually measured the HP or torque with a gauge in flight. They claim that
their method is more accurate than the differential cooling and calculation method that yours uses. The best
way to determine which one is producing more HP is to measure true airspeed at the altitude your are flying.
The best power fuel flow is probably wasting fuel to produce more HP. Stoichiometric ratio refers to the optimum theoretical mix of fuel and air to achieve complete combustion of that fuel. Sometimes called stoichiometric air ratio.
This occurs at peak TIT mixture settings.
Dad

Here is his reply!

You are going through the same thoughts that I had been going through when I first got my plane.

I decided to hell with it, and just run 2400 RPM, some manifold pressure, peak EGT as long as the TIT is below red line and then it is what it is. :)

Go fast!

He gets 180 knots true airspeed at 16,000 feet on 17 GPH.


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 Post subject: Re: Piper Saratoga Lean of Peak operations
PostPosted: Fri May 13, 2011 1:02 pm 
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N3576X - FlightAware user avatar

Joined: Mon Jun 26, 2006 6:00 am
Posts: 5
Here is another email to my son about lean of peak operation:

Steve,
When the Piper Malibu came out in 1984 with the Continental TSIO-520 engine it had power charts
that apparently were made for running the engine 50 degrees lean of peak TIT at cruise power.
Old time pilots were not used to running lean of peak so they would dial in the RPM and Manifold
pressure shown on the charts but set say 100 degrees rich of peak TIT like they did on other engines.
If you think about it with no accurate HP indication they were running maybe 85 % power not 75%.
Those engines gave a lot of trouble until pilots were educated to run them lean of peak.
Dad


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 Post subject: Re: Piper Saratoga Lean of Peak operations
PostPosted: Sun Apr 17, 2016 4:12 pm 
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texasags - FlightAware user avatar

Joined: Sun Apr 17, 2016 3:19 pm
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I have a PA32-301T. I would like a general rue of thumb on EGT/CHT. I have been assuming that CHT should be below 400 degrees (375-380)and TIT/EGT below 1500 degrees. Can someone give me their thoughts on this


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 Post subject: Re: Piper Saratoga Lean of Peak operations
PostPosted: Wed Feb 08, 2017 1:40 am 
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N581C - FlightAware user avatar

Joined: Wed Feb 08, 2017 1:26 am
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texasags wrote:
I have a PA32-301T. I would like a general rue of thumb on EGT/CHT. I have been assuming that CHT should be below 400 degrees (375-380)and TIT/EGT below 1500 degrees. Can someone give me their thoughts on this


The redline TIT for this engine is 1650 degrees. I usually run about 1625 to 1650 degrees TIT with no appparent problems to the turbo or exhaust system. I also keep the CHT at or below 400 degrees on the hottest cylinder. Again no problems noted with the engine.


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