CHT variation between cylinders

[DragonflyAero]

I have just over 14 hours on my new Superior IO-360 engine. CHT's are within range, running up to 435 or so on climb and then settling in just below 400 once in cruise settings. I am still using break-in settings of 65%-75% power for the majority of my flight time. My #3 cylinder is running 10-15 degrees hotter than the others and also has a higher EGT. Does anyone have any thoughts on whether this is a function of cooling air or has this cylinder not fully broken in yet?

How matched should I expect CHTs to be between cylinders?

Thanks!

[Carl Froehlich]

10-15 degree spread is is typical. If #1 and #2 are consistently cooler you might add a 1" or so air **** in front of them to deflect more are aft.

As you work this, strive for 380 and below for cruise CHTs.

I'm guessing you have your oil cooler or oil cooler air coming off behind #3.

Carl

[flyingriki]

The photo process on this forum is so ridiculous! Have a great shot from a Busch newsletter to share but don't have a link to my photo sharing site at work and it's not worth the hassle.

Here's the link: http://us5.campaign-archive2.com/?u=...&id=607891e493

Busch suggests: Set an alarm at 390-400 and when it gets there back off! Max cylinder life is cruising at 350-380? roughly. Max about 300 and that is limited life. Over 400 is unacceptable.
I took about 25 hours for all my cylinders to come down in temp but after beating them at first I now baby them to stay below 400 in climb and preferably in the 370? range in cruise for max life.
Good luck!

[lr172]

For others reading this, it is far more important to keep your temps under 400 or so than it is to run at 75% power. Lower power settings will allow your rings to seat, it just take longer. High temps WILL cause glazing. I speak from experience on this, having glazed a cylinder due to high temps (mine happened from 1 minute at 450*) in the first hour or two. I had major fuel distribution issues with my carb.

The first few hours is where this is most critical as most of ring seating takes place there.

Larry

[Aiki_Aviator]

Curious on what the glazed cylinders look like with a borescope.

I have not actually seen what people are describing and would be interested.

[DragonflyAero]

I am also interested in what symptoms a glazed cylinder causes and what is done to correct it.

[Toobuilder]

Originally Posted by DragonflyAero

...My #3 cylinder is running 10-15 degrees hotter than the others and also has a higher EGT. Does anyone have any thoughts on whether this is a function of cooling air or has this cylinder not fully broken in yet...

I'm not going to comment on your progress with the break in, but the "hot" #3 is a widespread issue and almost always related to the non symmetrical fins on the Lycoming head. In short, the heads have essentially zero fin depth on one side and are designed to work in pairs, with one head providing the airflow path for both. When placing the "zero fin" head up against the rear baffle (as on #3), there is no path to the bottom fins.

The good news is that this is easily fixed with the addition of a bypass duct. Plenty of threads on this very subject.

[tim2542]

Originally Posted by Aiki_Aviator

Curious on what the glazed cylinders look like with a borescope.

I have not actually seen what people are describing and would be interested.

You can see it as a brown or tan patch or section on the cylinder wall.
I agree with the previous post, far better to keep the temps down than worry about the keeping the power up. Most of the ring seating probably occured before you turned crosswind anyway. The temp drop seen later in my opinion is the carbon layer building up on the pistons and combustion chamber rather than any drop in friction between the rings and cylinders.
Tim Andres