180 degree turn with NO E burned??? Please explain the physics and how to... please

This ticks me off every time and eventually log off

After 10 + years you would think that I should have the answer, instead

every time.
This usually occurs with a Spitfire or Ki84, but not limited to those airframes. I see a guy low near his runway heading towards me (I am tracking another target, so am watching out for his head on attempt, because once I pass him he should be no threat)>>>>>> WRONG.....

He is able to spring into the air climb and 180 degree turn and gain on my 6 o'clock from long range shot position.
How, and what kind of physics supports this?? Maybe I will be around for another 10+ years to exploit such a maneuver if available in any of my favorite aircraft (depending on my sight).