Cylinder low temperature limit?

[Gary0747]

I was letting down from 9000 ft yesterday at 15 in MP ans was seeing cylinder temps as low as 215 degrees F.  I was flying not having installed my winterization kits yet in colder weather than I had forseen. Does anybody know if Lycoming cylinders have a low temperature operating limit?

[Raptor05121]

I think there was a too low limit, I'd try to keep them above 250. I usually just nose-over for descent and gradually reduce throttle every few thousand to keep it between 17-20

[carusoam]

There is a thread around here that discusses this detail...

The winterization kit for the IO550 consists of a blocker for the oil cooler... This keeps the oil from getting too cold.  

I don't think this has much to do with the CHTs.

There is a temperature that keeps the LL in the fuel from behaving as expected...

Best regards,

-a-

[1964-M20E]

When I begin my decent from cruise altitude I just nose it down for 500fpm and only start reducing MP to check it at 23".  If I need a faster decent I will reduce MP further and or nose down a little more.  This will keep CHTs in a normal range.  IMHO there is no real need to reduce MP to 15" until you are ready to slowdown to enter the pattern.

[kortopates]

Here is some thoughts on this topic from a few leading experts:

from Walt Atkinson --

"Lycoming publishes that min. operational CHT is 150dF. TCM does not publish
a number that I have been able to find, but reading between the lines
indicates that it is something in the 200dF range. TCM sets the
water-cooled engine with the same cylinders as the air-cooled engine to run
continuously at 240dF. These are data-based numbers, and not "opinions".
Forget about running too cool unless you're operating out of Barrow, AK, in
Feb."

 

Mike Busch's  article --

https://www.avweb.com/news/savvyaviator.savvy_aviator_59_egt_cht_and_leaning-198162-1.html

It's possible to run CHTs so cold that the tetraethyl lead (TEL) in the 100LL is not properly scavenged and starts creating metallic lead deposits in the combustion chamber and lead-fouling the spark plugs. However, in most engines, it takes verycool CHTs (down in the mid-200s °F or lower) for an extended period of time (hours) for this to cause a problem. We usually see this problem in airplanes used for fish spotting, pipeline patrol, search and rescue, and other "loiter-mode" operations. Unless you fly at very low power settings (e.g., 50 percent) and/or at very high altitudes and very cold OATs (e.g., FL240 and -30°C), it's not usually a problem.

My caveat -- 

This should only be a concern at both very low power settings (evidenced by low EGT) and low CHTs, and thirdly ROP. If the very cool operating temps are during LOP combustion it will keep things very clean making the engine less susceptible to lead deposit inn the combustion chamber and valve guides and lead fouling on spark plugs. However, for Turbo's though, I do add the caution to slowly increase power till CHT's get to 250-260F (per Continental) before going to full power.