Originally Posted by
B2N2
Carburators are (were) made of pot metal so very conducive to temp changes.
Start with a hot carburetor body and within seconds after applying power you’d have a cold carb again. I would put that one to bed.
My back-of-the-envelope calculations told me so too, but it's one of those things that you do as told by the instructor/examiner at the time but you don't really start thinking about it until later. As mentioned before, the temp increase from carb heat isn't all that much, so it is not as if you are heating up that carb with a blowtorch. Once you switch the carb heat off and go to full power, you've got the original -20C air going through it again and at a higher mass flow. As you say, it's not going to stay warm for long. If someone has a carb temp indicator and wants to try this on a cold day, I would be interested in the numbers.