Takeoff CHT Bravo Question

[JohnB]

Greetings all!

Question for Bravo owners only. I'm wondering what another Bravo owner's CHT's are on climb?  I have noted that climb at 500fpm/ WOT, full rich , boost pump on, cowl flaps open, empty back seats, on an average day (like 70-79 degrees F) leads to CHT's of up to 390, but at 700fpm, the CHT's are 400, and even though I can climb at 1,000 fpm+, my CHTs would exceed 410 after about a minute or two. I'm wondering if this is typical? Since I installed a more accurate CHT measurement system I'm wondering if I am just noticing this more now that its easier to see or is there some issue I can get improved? II have had my mechanic check baffling which appears to be ok, but before I start throwing money at this one wanted to see what was typical..  Realizing that some may have "tall tales" on answering this question, like "My Bravo can climb 1,100 fpm on a blazing hot day at a CHT of 350".. right! But hopefully looking for an honest CHT as it relates to your rate of climb on takeoff if possible?  Here's what I've noticed on an average day as above at near sea level.

Climb rate          CHT degrees F

500fpm              380-390

700 fpm             400

1000 fpm           410 +

 

Appreciated In advance!

 

[Steve Skinner]

I see your numbers are for a pretty warm day.

i cruise climb at 34 24 130 knots

which usually yields 900 - 600 ft/min as climb progresses.

full throttle climbs would yield the numbers suggested on such a hot day.

Obviously you have a similar personal limit of cht. Mine is 400.

i just adjust IAS to accommodate.


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[David Medders]

This flight launched at 80 degrees OAT on the surface -- 1,200 MSL -- from one per second JPI EDM-900 data:

700 FPM

120 KIAS

34"/2,400 RPM

CHT 342 to 363 at 1,800 MSL, OAT 68 -- The asphalt must have been hot with this big of an OAT drop!

CHTs drop a bit in a continued climb with the drop in OAT.

We did have problems with high CHTs in the climb several years ago -- resolved by correcting ignition timing.

Cheers, David

Note: This is a FIKI TKS airplane, so our climb performance will be less than a non-TKS bird.

 

Edited May 18, 2020 by David Medders
Adding information

[Steve Skinner]

This flight launched at 80 degrees OAT on the surface -- 1,200 MSL -- from one per second JPI EDM-900 data:
700 FPM
120 KIAS
34"/2,400 RPM
CHT 342 to 363 at 1,800 MSL, OAT 68 -- The asphalt must have been hot with this big of an OAT drop!
CHTs drop a bit in a continued climb with the drop in OAT.
We did have problems with high CHTs in the climb several years ago -- resolved by correcting ignition timing.
Cheers, David
Note: This is a FIKI TKS airplane, so our climb performance will be less than a non-TKS bird.
 

These are great numbers.
I certainly understand the link between ignition timing and CHT - been there also.
I find at 34-24 and above F170 I’m looking at closing in on 400.
I need to reduce climb to below 500 ft/m
to keep below 400.
My airplane was rebaffled 10 yrs ago and still in perfect condition.
I do live in Queensland Australia where only in the dead of winter (or thunderstorms) do we find OAT much less than zero.


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[JohnB]

Hugely helpful David and a Steve! My WOT gets me about 36-37”, ( these are on takeoff climb) so if only makes sense that my CHTs would be hotter on climbing like a banshee which then requires a power down / speed reduction to keep them lower. But at 34 I can climb all day without a cht issue,  I’ll have to check what takeoff climb rates I get at that, but nice to know don’t have to spend any money on this one, thanks guys!

Edited May 18, 2020 by JohnB