Question for Paul McBride, General Aviation News’ engines expert: I wonder if you would mind another Lycoming Exhaust Gas Temperature (EGT) question?
My partner and I have owned a 1978 Piper Lance II for decades. Love the airplane.
We both use rich of peak (ROP) but his technique gets the average EGT to around 1485° (18 gph) and mine gets it closer to 1510° (17 gph).
The question I have is this: Is an EGT in the 1510 range harmful to the exhaust valves?
Thank you very much for your time and experience!
Pete Bechtel
Paul’s answer: Pete, I’ll respond by first telling you that probably the least expensive thing you can put in your engine is gas.
That being said, I’ll also tell you that the numbers you provided don’t scare me at all. The maximum EGT on most Lycoming engines is 1650° F, which I doubt you would ever see on a normally aspirated engine under normal operation.
Looking at the fuel burn and comparing the EGT readings you’re getting, I’d say both are in the ballpark.
In my opinion, the 1510 EGT reading is okay, but you should also keep in mind that CHT (cylinder head temperature) should be monitored closely as well. The maximum continuous CHT for your engine is 500° F and should be kept below 435° F during continuous operation. If your CHT is running around 385° or so, that’s great.
So basically, I’m saying that I have no concerns regarding your operating procedures, providing the information you provided is accurate.
I might suggest, if you haven’t done so, consider having your instruments calibrated just to be certain that what you see is what you’re getting. As your plane is a 1978 model, the accuracy of the gauges may be somewhat out of calibration. That also includes your tachometer.
Even after all the assurances, I’m still a bit tentative leaning a normally aspirated, carbureted O-360. Fuel injected engines receive a metered, consistent mixture in each cylinder, whereas fuel delivered via induction seems somewhat inconsistent. When the EGTs hit peak on my engine display, then lean, I find I’m holding my breath. CHTs are all good and consistent. Am I just being over cautious to the point of perhaps doing some damage to my engine?
I’d recommend reading what Mike Bush teaches on engines,and his Savvy Aviator program.
His book, ‘ Engines’ is a good read on how to operate, diagnose and maintain an aircraft engine.
Never thought a cable driven tach could go out of calibration.
Absolutely a mechanical tach can go out of calibration. If it were just a simple matter of a gear ratio, then probably not. But a tach converts rotation to a needle angle. The usual method uses a flyweight connected to a lever connected to the indicator needle. Definitely needs calibration.
Why in the world are you running rich of peak? Worst place to run your engine continuously. Thought everyone knew that by now.
I would agree in general, Mr. Maynard, but big-bore Lycoming engines are different than those ususally more agreeable to LOP operations. You can operate LOP, but care must be taken beyond that found with “the big pull” or the “red zone.”
High performance Lycoming engines do not shed heat very rapidly and localized temps not indicated on the panel can be damaging if mishandled.
This might be helpful, but bottom line is Rich of Peak (ROP) or Lean of Peak (LOP) operations, stay out of the “Red Box”
https://www.google.com/url?sa=t&source=web&rct=j&url=https://resources.savvyaviation.com/wp-content/uploads/articles_eaa/EAA_2012-12_red-box-red-fin.pdf&ved=2ahUKEwi8npTboNz-AhVOEFkFHTENBOcQFnoECA8QAQ&usg=AOvVaw00XiVfZaK5Qi1URy32ypJd
Don’t rush power and fuel adjustments. Don’t try to save fuel on takeoff. Taxi is such low power lean for smoothness. Run-up and adjust mixture if your injection/ carb don’t have an auto lean function. Set climb power and let altitude reduce power. Lean for smooth power during the climb and keep climb power until IAS stabilizes, then set cruise power. Then lean conservatively checking for CHT & EGT. & if you’ve got turbo or supercharged induction temperature
Mr. McBride is correct about maximum limits and EGT/CHT values, but consideration for percent power and EGT/CHT readings are equally important. 16-18 GPH at 65%- 70% power is fine. Higher than that will require more fuel to ensure proper localized cooling during best-power cruise configurations.
Fuel burn versus power setting is important for big-bore and turbocharged engines and airframe power/altitude charts do not often reflect what the engine manufacturers publish in their power charts. It’s important to understand this, especially for a Lycoming engine.
Lycoming’s power charts show 130F-150F rich of peak as “best power” regardless of altitude and percent power. That’s a lot of fuel, but as Mr. McBride says, “Fuel is the least expensive thing to put in your engine.” He also knows that while heat is harmful to exhaust valves, what it does to exhaust valve guides is worse. They go first.
In the end, if what you’ve been doing works and valves and guides remain intact over the long haul, leave everything as is and enjoy the airplane. On the other hand, if you’re in the shop on a regular basis for low compression and valve leakage, consider renewing your procedures.