High CHTs

[hoyaj]

What year, serial number did this become standard?

My understanding is that these are standard beginning with S/N 361.

I just installed the GAMIs and Powerflo, but those changes proved ineffective.

[Roxi5m9]

I’ve been reading a lot on operating these engines certain ways, ROP vs LOP, the scary red box, etc. I get it all and I like it. I try to fly my 04 DA40 LOP. I seem to be able to smoothly run her anywhere from peak to 25 LOP depending on the conditions. No Gamis, no fine wire plugs. Keep the CHTs below all the certain temps we talk about, etc. But being your typical guy who learned how to fly always looking at an EGT gauge and not even caring about CHTs, I keep wondering....do we care at all anymore about what the EGT is? Does it matter if my EGTs are 1400 or 1500 or 1600? And if not, does running at peak vs 10 or 20 LOP matter? From what I’ve witnessed, as long as I’m at peak or leaner, my CHTS are cooler than anything from 5 to 100 ROP. And where I am going with this is that on some days I can only get my engine to run smoothly at peak or maybe 10 LOP. Anything leaner, and she’s unsettled. Other days, 25 LOP. So, while I cruise along, 5 LOP, I wonder as my CHTS are at 360, do I care that my EGTS are at 1500? Is there an EGT temp that is too high and am I risking abnormal engine wear by being at above a certain EGT? Maybe another way to put it...would Deakin tell me to run a peak vs 50 ROP because the CHTS are cooler at peak?

[rwtucker]

I take a part of your question as pertaining to the metallurgy of the valves and valve seats. I don't know the answer but my turbocharged engine (another aircraft) has exhaust limits of 1550 and 1650 degrees F depending on internal pressures. I don't think 1500 degrees F is destructive at powers below 75%. At the same time, we know that the life of barrels declines as sustained temperatures exceed 400-450 F, depending on the specific type of barrel. Most guidance related to engine life is to focus on CHT when you are below 75%.

[blsewardjr]

After years of trying to get our CHTs down, I think we've finally succeeded. Before we had added the Arizona baffle, filled the holes, filled in the valleys on the flexible top baffling, and added GAMI's, all to little improvement. This year at the annual we went all out on the flexible top baffling, building a couple of inches wide ridge around the entire top of the engine, putting wax paper on it and letting it set over the weekend with the cowling on. We also tightened up the rigid baffles around the front and rear of the engine so that they fit flush with the cooling fins. I'm not sure whether it was due to one or the other or both, but CHTs have dropped dramatically, on the order of 30-40 degrees in cruise flight. We also can now climb at full RPM and 105 knots and stay in the mid-380's. (Climbing at 90 knots at full RPM still sends the CHTs into the 390's). I'm looking forward to having the option again to run at 75% power without using 12-13gph to cool things.

[rwtucker]

This is great news Bernie. I’m going to look closely at mine.