Sit still Jabba, you're a moving target. Let's just stay with FADEC for the exercise. I decided to do some reading and found good support for LOP and long engine life in a number of reports. Didn't find any recommendation from Continental, and didn't find any empirical evidence for it. The Gami site firmly supported it, and although they are selling injectors, made sense in what they said. They gave an example of a Cirrus SR22 with Continental O-550N engine and FADEC (Full Authority Digital Engine Control) of 2200 hours against the only stated TBO I could find of 1700 hours.
That's one single case, but I read a lot of similar claims where the consensus was that with fuel injection, telemetry and control like FADEC the engine could be managed for a satisfactory life.
Bear in mind, with the pressure of reducing emissions such as cancer causing Nox and Particulates, engine manufacturers are using digital technology to do different things at different times of the stroke including multiple injector shots at different times with the intent of burning non combusted items etc. and also to allow operation at leaner mixtures to substantially reduce fuel consumption because of the ever growing cost of fuel.
Add all this together and LOP makes a lot of sense.
What DIDN'T have much support was running LOP on a carburetted engine because there is a lot less control accuracy, and the power output from each cylinder will be different, so you don't really know what you are doing to the engine with the settings you are using. Flow balancing, where the inlet side of the engine is modified so all cylinders produce the same power, is a way to get closer, but if you really want the reduced fuel consumption maybe the solution is to run the engine out then upgrade to the newer technology.
Maybe I shouldn't have jumped in with basic engine principles because this thread was all about operating an engine at reduced power and lower rpm compared to the full power output situation.
However, some of the comments strayed away from peak exhaust gas temperature and into the combustion chamber itself.
The Chart which Jabba attributed to TCP shows up all over the place, and is part of a powerpoint presentation called gregs_show, and shows a Cylinder Head Temperature curve related to Exhaust Gas Temperature curve in a typical less-than-full power manipulation of air/fuel ratio.
I agree, if I came up Jabba, you could show me how you could replicate this, but then I could show you how I could melt your pistons, because I've melted a few.
The relatively even cylinder head temperature you see on a gauge is the net result of a number of temperature changes dancing around the combustion chamber at various points in the cycle.
My original comments about lean being hotter and rich being cooler relates to gas temperature in the chamber in response to Clint's comment, and your #262 and #264.
The chemical and physical properties of air don't change. When it's compressed it heats, when it expands it cools.
On the compression stroke, intake air is compressed and heats to a peak at top dead centre. The flame front then kicks in and there is a momentary second rise followed by a rapid fall as the gas expands.
If the mixture is too lean, it's all burnt and there is nothing left to cool the second rise, so it doesn't take long for any protrusions such as spark plug electrodes, piston edges and valves to start to deteriorate or melt.
If the mixture is rich, there is a flow of unburnt fuel over these items, cooling them.
Since gasolene has a very narrow band of tolerance for combustion, and doesn't have to be very rich for the engine to run rough, Jabba as you've found you don't see it dripping out the exhaust.
To make this easier to understand, let's look at methanol where the engine will make full power with an extremely rich mixture. Only a fraction of this is burnt, and the methanol is virtually like a garden hose turned on your engine.
I'm able to make an aircooled engine pump out maximum power reliably in an enclosed compartment with no vents, and if you look at a Top fueler dragster you'll see methanol streaming out at low rpm (it's turned into a gas at full power)
So in discussing the subject of this thread, the theory needs to stay out in the exhaust temp, cruise power, and mixture control area.
Last edited by Wallsofchina; 20th Oct 2011 at 00:51.