CHT/EGT Temps

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Ultrapilot1
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CHT/EGT Temps

Post by Ultrapilot1 »

Any recommended rough numbers for setting ROP and LOP?
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RMarkSampson
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Re: CHT/EGT Temps

Post by RMarkSampson »

Steven,
Both ROP and LOP will be about the same as the EGT will drop on either side of the peak value. For my DA-20 I have found "the peak" to be around 1480'ish. I do have an VM1000 Engine Management System that tracks all four cylinders so the values are different depending on what cylinder you are looking at. Toggling button 1 I can see either Absolute or Relative EGT Graphic (two modes). Button 2 display each cylinder’s EGT and CHT (1-4) – or Mode 5 Peak EGT/Hottest CHT.

Note that I do not LOP below 5K - there is really no advantage I can see. But when cruising at a level altitude above 5K then I can get the same EGTs at LOP while burning about 1 GPH less than ROP. Normal CHT per the POH are less than 420F, Max CHT is 460F -- I am normally in the mid-300's and usually start taking action if I see 380F - sometimes in a sustained climb on a hot day or if stuck on the ground waiting for a departure clearance.

For "Rich of Peak" Leaning
o Initial climb, roughly lean to “rich of peak” using target EGT of ~1,400F
o To fine tune at altitude, use Relative EGT Graphic ( - button 1 - ) on EMS, progressively lean until EMS sounds. Enrich mixture until EGT drops ~75-100 degrees

For “Lean of Peak” Leaning
o Best fuel economy method above 5K MSL
o Do not "lean of peak" while in a climb (CHT will dramatically increase)
o Once cruising at altitude, start with high Engine RPM (3/4 throttle) then lean until RPM drops to desired level
o Fine tune RPM with throttle, ensure engine runs smooth and does not detonate - EGT ~1,400F
o Fuel consumption: expect ~1 GPH less than Cruise Performance tables

Remember, there is no warranty with my words - pay attention to you engine, its gauges, oil consumption etc and it will tell you what it likes. Good flying!
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RMarkSampson
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Re: CHT/EGT Temps

Post by RMarkSampson »

I've upgraded my panel to JPI's EDM-900 since my 2015 post on this subject. That upgrade has certainly enhanced my visibility and understanding of how the mighty IO-240B performs. Still not an expert, but we all gain experience with each and every flight.

So I have one caveat to mention about Lean of Peak (LOP) flying. I previously stated LOP works best above 5K MSL but it is also impacted by Density Altitude. In the summer I normally see DA around 1,500. But if a wintertime high pressure system parks over you, DA could be a minus 1,500 - a 3K difference in DA. So as I found out yesterday, LOP flying might require you to climb higher in winter vice what you can do in summer. It was cold yesterday and my altimeter setting was around 30.40. I was not being successful in setting my engine controls to LOP at the same altitudes that I easily do in summer. Vice climbing, I just kept it ROP.
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