CHT Overheating issue

[lr172]

Originally Posted by scard

There is something else going on there. More mass flow isn't what you're looking for here.

+1

especially since this is a new development for the OP. Best to look for what changed and resolve it. Cutting more opening will just create more drag. MANY planes like yours run under 400 in cruise without cutting the cowl, so best to look for other issues causing the overheating condition.

Larry

[Mike S]

Intake flange leak is one possible cause. Also intake tube coupler hoses and clamps can leak.

Pretty common problem.

[ALagonia]

Originally Posted by rjcthree

What are your other CHTs, oil temp, are you running
rich, at or lean of peak, carb or injection, what injection, ignition? Engine model? Thx.

Here is the data from two flights.
Sam James plenum
Carburetor
ROP

Flight #1
CHT's at cruise
-375 - 395 - 394 - 411
EGT's at cruise - 1261 - 1327 - 1267 - 1328
6000 feet 72% power 9.0 gph 71 degrees F
14.5 gph at take off power (full throttle)

Flight #2
CHT's at cruise
365 - 384 - 380 - 401
EGT's at cruise - 1259 - 1318 - 1263 - 1330
7,000 feet 70% power 9 gph 67 degrees F


Any thoughts about CHT on #4 cylinder?
Each of these flights lasted right at 2 hours. The numbers above did not change much. On the second flight the #4 CHT did eventually get down to the 390's.

[oaklandaviator]

Is the oil cooler mounted on the baffle behind the number four cylinder?

[ALagonia]

Originally Posted by oaklandaviator

Is the oil cooler mounted on the baffle behind the number four cylinder?

Yes it is.

[Carl Froehlich]

#4 cylinder is leaner than the others. As you have a carburetor I would assume an air leak on the #4 inlet.

Carl

[oaklandaviator]

I would try making a curved aluminum piece to wrap over the number four cylinder and reduce the air lost over the oil cooler. By slowing the air down with a curved blocking plate, you'll increase the pressure available for cylinder cooling and also not adversely affect oil temps because the less air is slowed down and spends more time in the cooler.

[jjbardell]

I added a small air dam in front of my #2 to balance the #2/4 cylinders. Not sure if it?ll help you much since your #2 is also a little warm.

https://photos.app.goo.gl/CVvbLtQsJKH1ruuN8

For my lower cowl mod, here are a few pics. This was very helpful And worth 10-20 degrees.

https://photos.app.goo.gl/jJnxB4WmZxrdQjoN6

https://photos.app.goo.gl/TAgmEaLKyiC5ZGv27

[ALagonia]

Originally Posted by jjbardell

I added a small air dam in front of my #2 to balance the #2/4 cylinders. Not sure if it?ll help you much since your #2 is also a little warm.

https://photos.app.goo.gl/CVvbLtQsJKH1ruuN8

For my lower cowl mod, here are a few pics. This was very helpful And worth 10-20 degrees.

https://photos.app.goo.gl/jJnxB4WmZxrdQjoN6

https://photos.app.goo.gl/TAgmEaLKyiC5ZGv27

Hard to make out your first two,pics. The last pic showing the exhaust was clearly understandable. I have a Sam James plenum. Any idea how your suggestions would help/affect my CHT?s with my plenum?
Thanks for posting

[jjbardell]

Originally Posted by ALagonia

Hard to make out your first two,pics. The last pic showing the exhaust was clearly understandable. I have a Sam James plenum. Any idea how your suggestions would help/affect my CHT?s with my plenum?
Thanks for posting

The first pic is looking into the air intake at cylinder #2 (Lyc). The second is the side profile of the cowl cut back 45 degrees to open it up more.

Sorry, no experience with a Sam. They do look sexy though.