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1. Rayfield (rayfield@poa.st)'s status on Sunday, 17-Sep-2023 11:46:44 JST Rayfield

   • Woggy's Zeonic Frolicks
   • 🎀Udon🥛
   • hobosaurus
   • 🧩 :_no::_za::_ki: 🧩
   Oh man I was doing a bunch of reading on this because I've been tweaking my car for more mpg (successfully, now I'm getting 33.5 on the highway instead of 26).
   
   According to what I was reading cars are tuned to run fairly rich so the catalytic converter can fire off and do its thing. Running too lean will inhibit the cat from working but also reduces some emissions while increasing NOx emissions, to a point. When you start to get really lean NOx goes back down.
   
   Another guy I was talking to told me that Lycoming aircraft engines use a process of leaning the engine to find peak EGT @75% power. Then +100 deg richer EGT for power or -50 deg leaner for best economy. That works out to 18:1 economy and 14.5 power ( @WashedOutGundamPilot Is this accurate? Do you know if this guy was full of shit or not? )
   
   It was making me wonder if there are better ways to cut back on car emissions instead of the federally mandated catalytic converter that requires you to run much richer than necessary and sacrifice how many miles per gallon you get.
   • Woggy's Zeonic Frolicks likes this.
   • Woggy's Zeonic Frolicks (washedoutgundampilot@poa.st)'s status on Sunday, 17-Sep-2023 11:46:43 JST Woggy's Zeonic Frolicks

     in reply to

     • 🎀Udon🥛
     • hobosaurus
     • 🧩 :_no::_za::_ki: 🧩

     Most GA pilots are pretty sloppy about mixture, most of the young kids now don’t seem to understand how it works, they just pull back on the mixture knob as they climb according to the checklist. Only the enthusiastic pilots (invariably white guys) will pay enough attention to the EGT gauge to accurately measure it out.

     With the push/pull knobs, you can do rough adjustment by yanking it back and forth, and make small adjustments by rotating it in or out. The easy way to do it is to get it straight and level then pull mix back until the thing starts to shudder, then you give it a couple tightening turns to the right to enrichen it. It’s a rough system, but it lets you get just a little rich of peak in any aircraft you do it with.

     Lean of peak tends to be a little iffy across the board. My eyeball method is to get within noticeable shuddering, then fine tuning it by backing off the mixture to see where the rpms top out at. That’s peak, and that’s as far as I’ll go, though some manuals allow you to go a bit leaner than that. I’ve heard of some methods like pulling back 4 turns, but it’s not worth it to me if it sacrifices engine longevity.

     Since I’m in customer planes 90% of the time, I just run ROP all the time. I do tend to be much more proactive about leaning it out, even on the ground, have had issues in GA planes from people running them in hot climates at full rich all the time, builds up carbon to burn off. Here’s the Lycoming manual for the skyhawk series of engines. It’s kinda the baseline for everybody

   • Woggy's Zeonic Frolicks (washedoutgundampilot@poa.st)'s status on Sunday, 17-Sep-2023 12:14:50 JST Woggy's Zeonic Frolicks

     in reply to

     • 🎀Udon🥛
     • hobosaurus
     • 🧩 :_no::_za::_ki: 🧩

     Yeah, there are some cool trinkets and sensors, the better piston stuff will have a cylinder head temp probe on each one so you can lean it out to the average, or prevent damaging one problem child among the bunch. Problem is, the vibration, heat, and time seem to knock them out of commission often enough that I basically never check to see if they’re active to begin with.

     Since most of this stuff is air cooled, we have to pay attention to how much air flow the heads are getting too. Something like an early baron can end up cooking itself pretty bad, because the cowlings are too close to the heads and without cowl flaps, it hardly gets any airflow over the finds inside each nacelle.

     Also it might be interesting to read about the carb heat systems, usually it’s just a non-filtered air intake that ends up drawing fresh air from inside the engine compartment instead of direct from the external intake. This is one of those helpful little teacher sites, might be of note. Keep in mind this stuff burns 100 octane, leaded fuel so the stoich may be a bit diff. from all the corn swill they use as mogas.

     https://www.cfinotebook.net/notebook/operation-of-aircraft-systems/aircraft-induction-systems

   • Rayfield (rayfield@poa.st)'s status on Sunday, 17-Sep-2023 12:14:51 JST Rayfield

     in reply to

     • Woggy's Zeonic Frolicks
     • 🎀Udon🥛
     • hobosaurus
     • 🧩 :_no::_za::_ki: 🧩
     Thank you, it's even got graphs!
     I stopped with my car right around 16 to 16.5 afr because I don't have any kind of EGT probe (yet).