Actually It's the 3rd. The first one was the simple light circuit controlled from the 3rd channel as you said and the sevond one was an entire analysis on the difference between nitro engines and electric motors (torque - rpm diagrams). Unfortunately the 2nd was a huge post in someone elses's thread...I think the initial topic was something about putting a 0.9 engine on a 1:10 car...or something like that...

I've also done many other calculations and simple formula applications at several threads.
Thank you for your words! I'm glad that the "scientific RC" club is getting bigger!!! [8D]