High cylinder head temps

flybikedave · #1 10-19-2019, 08:02 AM

I recently purchased a RV9A and am experiencing high CHT (475+). Single probe on #4, behind which is oil cooler. Would greatly appreciate advice comments. Will cowl flaps be needed?

Mconner7 · #2 10-19-2019, 08:48 AM

Start with the baffles, they cannot waste any cooling air. Buy some high temp RTV and put a light in the lower cowl under the motor. Any light you see other than the cylinder fins needs to be goobered. Check the mag timing, too advanced makes it hot. I hope you are climbing at full throttle, even a small throttle reduction makes the CHT?s on my non-injected -10 go up dramatically, (assuming its auto-rich function of the carb)

flightlogic · #3 10-19-2019, 08:48 AM

Welcome to Van's AF. The search engine is your friend. Trust me.
High CHT's have been experienced and solved by many here. If you search the topic and begin your research, you will be able to approach your solution with data and builder tips in hand.
I own a 9A and even now.... do a step climb on warmer days. With temps as high as you mention... I would do a step climb right away, to mitigate damage to cylinder heads. Just pull the power back a bit and lower the nose. You will see temps drop quickly. Then you can ease the power back in and pitch up.
You will be well served with instrumentation that gives you visibility to ALL cylinders and EGT's. Products are cheaper and better than in the Cessna single probe days. Solutions are not that costly, and certainly less than top overhaul.
Antisplat makes a nice operating cowl flap that may be an option. Simple modifications to baffles are all some owners have needed.
So, begin to look around at previous posts and take notes.
Again, welcome.... and enjoy!

N941WR · #4 10-19-2019, 09:10 AM

Find a local builder and ask them to come take a look. To get CHT's that high, either the baffles are totally messed up, the timing is wY off, there is an induction problem, and/or a mixture issue.

Either way, don't fly it again until you figure this out.

rvbuilder2002 · #5 10-19-2019, 10:00 AM

475 is so grossly high the first thing to look at is to confirm the inst. indication is valid.

BillL · #6 10-19-2019, 10:47 AM

Quote:

Originally Posted by rvbuilder2002

475 is so grossly high the first thing to look at is to confirm the inst. indication is valid.

Easy to test, and timing is too. Both while the cowl is off. Others will require flight testing.

lr172 · #7 10-19-2019, 11:01 AM

Quote:

Originally Posted by rvbuilder2002

475 is so grossly high the first thing to look at is to confirm the inst. indication is valid.

+1

Especially if the other CHTs are substantially lower than 475. You should provide all 4 CHTs to help troubleshoot.

Larry

cojaken · #8 10-19-2019, 12:10 PM

What phase of flight are you experiencing this temperature at?

If you try to climb out at Vy you are likely to experience elevated temperatures. It seems to be a popular choice to climb out at ~110 knts,

jrs14855 · #9 10-19-2019, 12:20 PM

My understanding from OP is that CHT is ONLY on #4

JSOliveira · #10 10-26-2019, 09:43 PM

Quote:

Originally Posted by flybikedave

I recently purchased a RV9A and am experiencing high CHT (475+). Single probe on #4, behind which is oil cooler. Would greatly appreciate advice comments. Will cowl flaps be needed?

I had a similar problem with CHT that would spike very high on #2. Stay there for a while and then go down. Replaced Dynon CHT probe/sensor, and problem went away. Simple check would be to swap sensors 2 and 4 and see if issue follows sensor.

Even on the hottest days I don't see CGTs above 350. and they are all within about 20 degrees. I do not have any RVT sealing my baffles. I just have the close seal created by baffles that fit well.