Sorry Ian but I still don't understand the logic.
Although the question was in relation to the TKM, and we both agree that there is no need to choke a TKM, particularly when running 2+ turns on the low jet, if you want newcomers to understand why we do choke engines surely we should explain the logic properly, which I thought was the stated purpose of your post.
As an aside, we do actually still race old 100 "screamers" in Natska and we will be taking our selection of Ital MV21 Rotary Valves up to Rowrah next weekend. My driver will be using the procedure I have outlined because, when you are on the edge, 0.5 seconds without fuel - and OIL is enough to seize the engine. I know we have done it!
Your argument that the engine will not be producing any more heat with the throttle closed may be true, but when the lubrication is removed at 20000 rpm in the 0.5 seconds you say it takes between closing the throttle and applying the "choke" the piston ring will have will have scraped against its oil film protection over 160 times! Add to that the delay before you reopen the throttle as you recommend and there is plenty of opportunity to seize. If there is a reason to close the throttle BEFORE applying the "choke" then fine, please explain it, if not then why do it? If there is no justification, at best it adds complexity and at worst it risks defeating the object of choking in the first place?
Like I said I am happy to learn, but in order to do that, both I, and a newcomer, needs to have a rational explanation for the advice which they receive.
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