Cruise is 2400 (2200 for really long range at lower levels like FL100-120), max power is 2575.
So the difference is not great.
Looking back on this saga, I somehow ended up with an episode of roughly doubled oil burn, which continued on the first flight in the above table, and then went away.
The most puzzling thing is where this came from…
Sorry, I’ve only read the first 10 pages of this (long) thread, so maybe you’ve already solved the problem.
I got the same issue with a Continental a few years ago. After a long “investigation” by the 145 center, it ended up with all the 6 cylinders being taken out and all the piston rings replaced. Apparently, the crankcase was being pressurized and oil mist was being vented out through the crankcase vent.
Do you remember the, also very long, thread about Rotax engines?…. I’m doing it now!
vic wrote:
When it comes to oil burn I do not believe there is a relation to power. I think it is the high rpm setting that will be noticed later in the oil consumption.
Vic – Your’e missing the main thing here with low MP: Peak Cylinder Pressure. Low power settings produce low cylinder pressure. The cyl rings are designed to work best with a certain pressure for proper sealing.
you may be right, but in any other transport sector, car, truck, tractor, you typically see higher oil burn at high revs. Otherwise many car or truck diesels – the closest sort of engine to air engines – would be dead in short time as these do mostly low power operations. Rings should provide sufficient sealing in all settings, there is always quite a lot of pressure to help sealing combined with ring tension from manufacture. Well, high or low revs with your flat engines seems to be only a few hundred rpms difference in real life. What may effect oil loss is the thermal difference by uncontrolled engine cooling. With a piston clearance of several tenths of a millimeter cold there should be considerable variation in flight at high FL and no way for cooling adjustment on most flat engine types. That is all the consequence of very poor clinder and piston design, running an aluminium piston without heat growth control in a steel cylinder. Nobody would accept that for surface transport. So today you find high tensile steel pistons in modern diesel engines that offer several great features in high performance engines, but development for aviation use will be far too dear so no company will ever start this for the minimal numbers produced. I believe not to live long enough ever to see Nikasil plated alu cylinders or alu cylinders with cast iron liners in aviation, that are held down to the crank case with long tension studs from cylinder head down into the case. The threaded head onto the steel cylinder is just sh***y construction with familiar crack problems – no problem at all for the manufacturer …….
VicI believe not to live long enough ever to see Nikasil plated alu cylinders or alu cylinders with cast iron liners in aviation, that are held down to the crank case with long tension studs from cylinder head down into the case. The threaded head onto the steel cylinder is just sh***y construction
Not exactly how you’d design a cylinder Vic, but not so far apart either…
I agree that the current Lycoming cylinder design is 1920s technology (actually pretty good design practice within the limits of that time) but newer technology cylinders would improve the engines, I think they’re coming as per the link above for uncertified cylinders. Fairly large displacement air cooled motorcycle engine cylinders went to nikasil etc in the early 80s (as you’d understand) and oil consumption dropped from ‘check it weekly’ to near zero on many engines. The main reason they’ve been going to water cooling since then is noise regulations, which are inapplicable to aircraft engines. For my purposes, current four cylinder Lycomings are a practical, serviceable design (mine uses very little oil) but with updated cylinders and modernized self contained ignition, I think they’d be optimized for my use.
vic wrote:
I believe not to live long enough ever to see ……… alu cylinders with cast iron liners in aviation, that are held down to the crank case with long tension studs from cylinder head down into the case.
My engine (Continental Tiara) has alu cylinders with iron linings, and are held down by long tension studs to the case. The cylinders heads are separate from the barrels. That engine was designed about 45 years ago. So it can happen.
The main point to emerge from this thread is that prolonged operation at low power and high RPM can cause high oil consumption. That combination only really occurs at very high altitude in a NA engine.
The main point to emerge from this thread is that prolonged operation at low power and high RPM can cause high oil consumption. That combination only really occurs at very high altitude in a NA engine.
I think you are right, Ted, but how come I have not had this before, despite flying at high altitudes for years?
I think that IF this is the reason, I avoided the issue accidentally, by always interspersing high altitude flights with “high power” local flights are a few thousand feet. In 2015 I did Sweden (FL210 for a bit) and Slovenia-Croatia-Greece-Corsica (also FL210 for a bit) back to back.
The next Q is why is this not being reported much more commonly. I am happy to accept that almost nobody flies non-turbo above FL150 or so 
I don’t like to think I do stuff that few others do but setting up a few alerts on FR24, with a suitable minimum altitude, and seeing how little happens is quite an eye opener.
Peter is it possible that someone put a turbo under your cowl and you dont know about it? 
The computer did the double wink. I guess it knew better than to leave it a one wink.
What is your MP at FL200? Are you flying at Peak EGT or 25 ROP. I cant see you flying LOP at those alts. What do you calculate your HP to be?
