Here is a graph that illustrates the values of EGT and TIT for a Continental TSIO550-C engine.
In 1 is the initial climb, then I pull the power back to 30"/2400 RPM for cruise climb and in 2, reaching cruise, I pull back the mixture to somewhere in between between 1620 and 1650°F TIT, or between 16 and 16,5 GPH. The CHTs are around 310°F. Power output is about 70% BHP
The engine runs just as smoothly ROP as LOP – in other words the cylingers are well balanced. It is a “Platinum Ed” engine, and as such was delivered with tuned injectors from Continental AFAIU. When you pull the mixture back you can absolutely not feel any difference, except for the loss of power.
Peter wrote:
- With balanced injectors, LOP should work fine because it is cooler than peak (obviously).
- LOP delivers less power than peak EGT, obviously, because while both are stochiometric, less power is being burnt when LOP, so you will be going slower.
LOP your cylinder temperatures will be quite a bit cooler than the equivalent power setting ROP.
LOP operation does not need to deliver less power than ROP. You can achieve for example 70% on both sides of peak. Of course if you set 70% ROP and just pull back the mixture to LOP, you will loose 5-10% power. If your targeted power setting is 65%, you can set MAP and RPM for 75% (or a little less) and lean to LOP.
I think the difference is that a particular EGT is just an average of the hot gas pulses, which on a 4-stroke come out on every 2nd revolution of the crank, while the TIT is a combination of the gas pulses from all 6 cylinders (if single turbo) or a combination of 3 cylinders (if twin turbo). So the temperature of a large component (not an EGT probe but e.g. a turbine disk) is going to be higher when subjected to TIT than EGT.
Timothy wrote:
Hence my keeping TIT in limits. I am asking whether I should worry about EGT as well.
What exactly is the difference between the temp at EGT and TIT position? I mean, when running outside BEP (ROP for instance), fuel may still burn when exiting the cylinders, it is burning inside the exhaust pipes. Wouldn’t excessive EGT temps simply mean you are rather way off with the mixture on those cylinders? It can’t be good for the turbo either way. (Even though TIT is below limit, it is still much higher than what it should be).
Something doesn’t hang together here.
I guess it may be peak.
Essentially, if I am not flying LoP (which loses me a lot of speed at lower altitudes) I try to fly at the lowest fuel burn that keeps TIT comfortably below red line. At that fuel burn, which may or may not be peak, I get EGT alarms on L5 and L6. To go RoP sufficiently to lose the alarms can cost about 8 lph.
Above about 6000’ I can happily fly LoP.
At 65%, it is my understanding that peak is fine, provided the CHTs are not high, which they are not.
For sure all this has been done to death but I still think an EGT this high is not right. Especially as Timothy wrote “ROP”. But he didn’t say how far ROP, etc. Something is missing…
For my (small) part of the panel, my beliefs haven’t changed since this discussion.
The general wisdom is that EGTs don’t matter because the EGT value is only a proxy, and is just an average of low duty cycle gas flows from combustion events. The actual peak gas temp is a lot hotter.
Also, the reset only works until the next drop below limits, so is unlikely to be resilient.
That is specifically not what the other manual I have says; it says the alarm is cleared until the next power cycle. Maybe the 760 is different.
Here is the 760 config stuff
and this is very interesting (my yellow)
so I reckon the crappy manual just omits to say that either there is an EGT MAX config item or it tracks the TIT MAX like the other instrument does.
Do check the Type J versus K config.
I think that it is strange that your EGTs are higher than your TITs. I know that does not help much.
What could help is downloading the data from the EDM and uploading it to Savvy Analysis or Cirrusreports.