I’m told you can get rid of the carbon deposits by running very lean to the point of detonation.
„I’m told“ is hardly ever a good advice anyway.
Also because by going leaner on the lean side, your detonation margin will increase, not decrease…
Exactly. Super lean is great and takes you further from detonation. I run mostly 100 LOP with balanced injectors and it keeps everything squeaky clean.
What is curious is that the patterns on the valves remain largely constant from one service to the next. Look closely.
So what is causing these?
It is unlikely to be patterns of heat conduction from the valve to the cylinder head; this happens via a) the valve seat contact and b) via the valve guide. These should be uniform, at least for identical CHTs.
The gas (the mixture) entering the cylinder is probably the reason, since different cylinders get it via different routes. Another might be differing exhaust back pressure patterns on the exhaust stroke.
Pity there are not more people doing borescope inspections. I don’t personally know anybody else who does it. And if your maintenance company claims to do it, ask them for the photos…
@Peter wrote:
Pity there are not more people doing borescope inspections. I don’t personally know anybody else who does it. And if your maintenance company claims to do it, ask them for the photos…
The Savvy guys say that they have a lot of borescope photos.
https://www.savvyaviation.com/savvys-borescope-initiative/
I assume that they will probably learn something from all these photos, particularly if they throw them into an ML engine to try to find patterns.
Sadly they don’t ask people that upload data things like oil type, additives, fuel type, spark plugs, ignition type, etc. Hopefully @Snoopy and his team will add these kinds of features to their system, and we can finally get some data that helps us manage our engines better.
The real problem is a lack of owners willing to participate.
Next lot. It is amazing how similar they are to previous. Same order 1 2 3 4 5 6 and inlet then exhaust for each.
But #6 exhaust looks a lot better this time. Also the weird deposit near #4 is gone:
I have to wonder what is the mechanism that not just creates these patterns but also maintains them over years of engine operations.
@Peter wrote:
I have to wonder what is the mechanism that not just creates these patterns but also maintains them over years of engine operations.
Lots of things in our aircraft engines are a mystery to me, and the “experts” tend to just gloss over things that they have not yet developed a theory for. Can’t recall if you are a Savvy subscriber @Peter, but if you are, and you upload your borescope pictures, they will have someone look at them and give you some feedback.
New pics:
As I keep saying: amazing how little changes!
