This was a very cool feature in ACE 2 that was an improvement on how vehicles blew up. Basically, some vehicles, when critically damaged and about to blow, would spew fire from the engine. The explosions from vehicles were also much cooler to watch. After blowing up, secondary explosions would occur inside the vehicles. There would be a large number of secondaries as the ammunition for the crew serves cooked off making it dangerous to go within about 20m of a blown up vehicle for some time. This was a really cool feature and created much more immersion. I'd love to see it in vanilla Arma 3.
You can see a demonstration of it here: