High CHTs on engine break in

[carrollcw]

Originally Posted by N941WR

That was going to be my recommendation.

Also, have you sealed all the gaps in the baffles? Even a small hole or gap will let a LOT of cooling air out.

I'm going to double check tomorrow. Thought I had sealed everything pretty well, but who knows.

[Ironflight]

How many hours on it now?

[rvbuilder2002]

Originally Posted by carrollcw

I'm going to double check tomorrow. Thought I had sealed everything pretty well, but who knows.

One way to know is by doing a light test with the hangar dark.
Seal every light pathway that doesn't travel between cooling fins.

The most common leak locations are where the baffles interface to the engine case ( particularly at the back), and the inner cyl baffles.

[alpinelakespilot2000]

Originally Posted by rvbuilder2002

One way to know is by doing a light test with the hangar dark.
Seal every light pathway that doesn't travel between cooling fins.

The most common leak locations are where the baffles interface to the engine case ( particularly at the back), and the inner cyl baffles.

Not just for Scott, but I am curious...

While I strive to seal all gaps not going through cooling fins, and believe I understand the theory, one question I've always had is how does sealing up a couple pea size leaks do much when there is a 2" diameter hole for the heater scat tube leaking tons of air into the bottom of the cowl? Would it be worthwhile to block off this opening in the baffles during the summer months? Again just curious.

[rvbuilder2002]

Originally Posted by alpinelakespilot2000

Not just for Scott, but I am curious...

While I strive to seal all gaps not going through cooling fins, and believe I understand the theory, one question I've always had is how does sealing up a couple pea size leaks do much when there is a 2" diameter hole for the heater scat tube leaking tons of air into the bottom of the cowl? Would it be worthwhile to block off this opening in the baffles during the summer months? Again just curious.

Everything has an influence.
Some parts of the system are a compromise, but it is obvious that air flowing through an undesirable leak is 100% waste.

Engine break in is going to produce the highest need for cooling performance. Blocking the cabin heat flow path during that time would be one way to improve overall cooling. If you do that, the heat muff should be removed so that it and the pipe in that location don't get overheated (no cooling flow through the heat muff).
In summer I often fly high enough under an overcast to have a desire for some cabin heat so disabling would not be something I would do on my airplane, but if someones summer operation don't need it, it would be a way to gain a slight improvement in overall cooling (oil temp, CHT, etc.).

[carrollcw]

Including the 3.5 hr dyno run, about 8 hours now.

[Titan-Xpert]

Originally Posted by Kyle Boatright

At least in the short term, 425F CHT's will not hurt your engine. However, running the engine gently those first few hours will. For break-in, I suggest running it hard and keeping the CHT's below Lycoming's 450 limit. That said, make sure you look for and eliminate leaks which waste cooling air.

Regarding the dams, the bigger they are, the cooler 3 and 4 will run and the warmer 1 & 2 will run. Sounds like you need to leave the dams alone or 3 will get even warmer.

As a data point, what type of CHT thermocouples do you have? The ring type tend to read higher than the bayonet type.

I agree with everything you said but Lycomings CHT limit is 500 degrees.

[Jesse]

You could tape over most of the cabin heat scat hole, which would allow some cabin heat and heat muff air, but let most of the air that would otherwise be going through there go through the cylinder fins instead.

[tim2542]

Originally Posted by carrollcw

Including the 3.5 hr dyno run, about 8 hours now.

With 8 hours on it excess heat from break-in is no longer an issue. I doubt you'll see any further drop in temps now with additional flying.
Tim

[DanH]

Originally Posted by carrollcw

All altitudes, oat, and fuel flows. I am trying to push the engine as hard as possible to break it in, but am having to run really rich and less than 23 man pres to keep CHT 3 below 425.

Is "really rich" based on an F/A meter, or a relationship to peak EGT? Can you offer some numbers?

EFii ignition has two available timing maps. You would have specified a compression ratio when ordering. What CR do you have?