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-   -   CHT Overheating issue (https://vansairforce.net/community/showthread.php?t=174812)

727TT 08-31-2019 01:08 PM

CHT Overheating issue
 
We installed the Dynon HDX in our RV7A over 2 years ago. We also redid all of the engine baffling. The CHT on #4 always ran hot on takeoff. We replaced a number of components and traced it to a wire. The probe itself was ok.

Now, on take off 2,3 and 4 all show hot at 410 to 425 on #4.

Any thoughts?

It was suggested I install cowling Louvers to provide more air flow.

The carburetor was overhauled last year and I installed a new fuel pump. It came out of annual this past spring.

Thanks.......

Steven
Superior 0-360 with fix pitch

jjbardell 08-31-2019 01:35 PM

CHT
 
I just went through it myself. I can share what my issues were.

History: O320 and installed a Dynon system. New probes, wires. Conditioned in May 19. No issues found.
Issue: High CHT (405-425)

Solution:

1) Timed both mags. They were advanced a few degrees. Ok, maybe a lot of degrees. Lol. It was a certified new engine w 250 TTSN.
2) Dynamically balanced the prop. It was .034”. It’s now .006”

The timing dropped my CHT so much that I can now climb at Max gross at 1,900 ft/min through 5,000. Then 1,200 ft/min through 9,500 and stay below 400. Cruise is now 360s.

And my fuel flow went from 7.5 to 6.7 gph at 65% / 142kt.

Not sure if it helps, but if you haven’t checked timing in the last 50 hours, I’d start there. Good luck with your search.

N941WR 08-31-2019 02:26 PM

Check your magneto timing.

If you have P-mags, PM me your number and I'll walk you through it.

If you have even a small leak in your baffles, it can make a surprisingly large difference in CHT's.

Louvers are a last ditch effort and should be avoided.

jjbardell 08-31-2019 07:25 PM

CHT
 
I forgot a third change that helped a lot

3) Cut the bottom cowl back at a 45 degree

ALagonia 09-01-2019 06:39 AM

Quote:

Originally Posted by jjbardell (Post 1370700)
I forgot a third change that helped a lot

3) Cut the bottom cowl back at a 45 degree

Can you post a pic of the cut you made? I have a 9 and yesterday in cruise 1:44 flight my #4 was at 411. Reduced power from 70% to 64% and #4 CHT only dropped to 401. Burning 9 gph at 6000?, OAT 70 degrees.

scard 09-01-2019 07:37 AM

Quote:

Originally Posted by ALagonia (Post 1370759)
Can you post a pic of the cut you made? I have a 9 and yesterday in cruise 1:44 flight my #4 was at 411. Reduced power from 70% to 64% and #4 CHT only dropped to 401. Burning 9 gph at 6000?, OAT 70 degrees.

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

ALagonia 09-01-2019 07:50 AM

Quote:

Originally Posted by scard (Post 1370770)
There is something else going on there. More mass flow isn't what you're looking for here.

What are your thoughts? Please share

rjcthree 09-01-2019 08:11 AM

Other temps and info required
 
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.

ALagonia 09-01-2019 09:00 AM

Quote:

Originally Posted by rjcthree (Post 1370777)
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.

I wrote them all down but left my pad in the airplane but other CHT?s were well below 400 rich of peak, carbureted and all EGT?s were below 1400. O-360 Barrett engine with less than 200 hours since new.

ALagonia 09-01-2019 09:00 AM

Quote:

Originally Posted by rjcthree (Post 1370777)
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.

Not electronic ignition. Straight mags


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