An amusing side note about Mike Busch and the strong following he has for his Savvy Aviator postings.
There is an incredible seller’s market for GA in the USA at the moment, although signs of it cooling. This has led to dozens, many dozens, of hangar queens emerging for sale. Invariably the owners worship at the church of savvy aviation, holding forth that their big bore Conti or Lyco-saurus which may have flown 3 hours a year on average (possibly) in the last decade, and has not had an overhaul in three decades, has been managed according to Savvy Aviators articles of dogma, and is pristine. Obviously the propeller and governor has not been opened up or inspected since the Ark as well.
These engines need regular useage preferably at 65 or 75% power to be happy.
Mike Bush advises to keep this between 350 and 400 degrees F in order to avoid lead deposits on the valve stems and consequently sticking valves.
Mike Busch is smart allright but on the above idea – posted here previously – he is a bit lonely. That’s not to say he is wrong, but there is too much evidence to the contrary; one ought to get sticking valves after every long descent from high altitude IFR flights.
There is also no way to routinely run CHTs in the 350-400F range and still be able to keep them below 400F during a climb on a hot day. I spent a lot of time re-doing my baffle seals to prevent mine going to 400F on every climb (450F in Greece).
It does pay to get the engine to run at the correct operating point. Peak EGT or slightly LOP is the best point. If one just does “cafe runs” it doesn’t matter but if you want to do longer flights which make decent use of the aircraft range, like e.g. this (and I did another one today, to Mt Blanc) then it is worth doing. There is also a big safety value in knowing how close to the line you are flying.
It does pay to get the engine to run at the correct operating point. Peak EGT or slightly LOP is the best point. If one just does “cafe runs” it doesn’t matter but if you want to do longer flights which make decent use of the aircraft range ……. then it is worth doing.
For sure, agree 100%, but then you also need a full set of data to work with….you can’t do anything meaningful with just one CHT and one EGT.
Dbo wrote:
In addition full power EGT at take-off indicating about 16 GPH also showed about a 50 degrees higher EGT than before.
Did you touch air filter or anything connected with induction system?
Maybe there is now a bit more of air entering the system which creates just slightly leaner mixture and higher EGT…?
Jojo wrote:
you can’t do anything meaningful with just one CHT and one EGT.
Many of the engines that don’t have that additional data are carburated, and seeing the CHT and EGT mismatch between cylinders on those engines won’t allow you to do anything about it. As a result, simply leaning just short of misfire any time you’re below 75% power will get you as close as possible to peak EGT (on the average) without instrumentation on all cylinders. It will thereby provide a useful reduction in fuel consumption on any engine for almost any length of flight, including for engines installed in planes with no CHT or EGT instrumentation at all. Those same planes are typically overcooled by design, meaning you’re unlikely to overheat the cylinders like you would with an injected engine in a tight cowl.
a bit more of air entering the system
I recall, from mucking about with the over-rated K&N filters (for which somebody got a dodgy STC – tested it on an old TB but not the GT model) that a filter v. no filter is worth no more than 1/2" on the MP. So even if you hacksawed the whole air intake assembly off, it would not produce a much leaner mixture 
Many of the engines that don’t have that additional data are carburated, and seeing the CHT and EGT mismatch between cylinders on those engines won’t allow you to do anything about it
Yes; I didn’t spot that one. Maybe GAMI will sell you a set of injectors which even it out a bit, for a particular engine model.
Carburated aircraft engines have one place where all the fuel enters the intake manifold, for all the cylinders.
Local friends who were too cheap & simplicity oriented to fuel inject their RVs etc. use Ellison carbs which in addition to working upside down are supposed to provide improved mixture distribution between cylinders. My observation is that this provides a lot of opportunity for experimentation with little improvement
My local RV-8 contact can still do something like 140 kts throttled back to 5.5 GPH, 180 kts IAS max and 2000+ fpm climb so he doesn’t care much.
Peter wrote:
it would not produce a much leaner mixture
Yes, probably you are right but maybe to get just 50F difference you don’t need much leaner mixture – maybe just a little bit leaner…?
I don’t know. Just trying to find a cause.
Maybe just the old magneto before overhaul had slightly different timing?
On any petrol engine, best SFC (specific fuel consumption – power per fuel flow) is achieved about 25F LOP, but the power curve is pretty flat around that point, so anywhere near there will do.
And anywhere near there the power output will be proportional to the fuel flow.
Jojo, Thank you for the figures you are mentioning. They are about the same as I used to see before the magneto overhaul. (EGT 1.350 – 1.400 F, CHT 330 – 350 F, at 23 / 2300 and about 34 ltr. / hour. Of course your LASAR electronic ignition gives a better timed ignition and better spark energy than my good old Slick magneto’s. I think this is exactly the reason why I see different readings after a magneto overhaul. It must have to do with timing or spark intensity, even though the timing adjustment is exactly measured as 25 degrees BTDC. I would not be surprised if I set the timing to 26 degrees or so, the old values would return again. I also wonder why some Lycomings are timed to 28 degrees BFTDC instead of 25 degrees. After all I wish I would have checked the timing before removing the magneto’s.
And again it is in no way the absolute readings of the temperatures (EGT) that keeps me worrying as they are well within limits. It is the sudden change that I see after the overhaul of the magneto. Being a marine engineer in my earlier age, we always considered unexplainable changes on gauge readings after we repaired or adjusted something as the onset for disaster.
To be continued!
