How do I predict when a car will blow up?

Using an explosive to blow up a car next to an enemy is a great way to get some extra damage in. This is especially useful with grenades. Sometimes I can get two enemies in the radius, but the third one is outside it. The car the third one is standing next to, however, is inside the radius. So, if I can reliably get the car to explode before the enemy moves, I can still damage all three with the one action. Or, sometimes, a large enemy will be next to a car. I can blow them up with an explosive, and then get more damage from the car going off.

However, I'm not always able to predict when the car is going to explode before damaging it, meaning that the enemy may move before it blows, meaning I wasted my explosive when I could have just shot them.

Sometimes, it explodes immediately after the explosive hits it, sometimes it blows up at the start of the next turn, and sometimes it takes all the way until the start of the turn after next.

How do I know how quickly the car will explode? Does it depend upon the explosive used, the positioning, or maybe the type of car?

The focus here is on being able to predict when it's going to blow up prior to doing any damage, in order to aid tactical decision making.

I don't think there's a way to consistently cause a car to explode sooner other than by doing more damage. Hitting a car twice with guns seems to work fairly well, or hitting with a powerful explosive, like a plasma grenade. Destructible objects have an invisible HP value and much like when damaging enemies there's a range of damage values it can take.

I believe in the ini files there's values for terrain HP and cover damage HP that you could tweak, or at least peruse to see what the thresholds are. I've seen a shot from a ballistic heavy cannon + ballistic assault rifle blow up a car (in a hilarious gif) so a 2 shot explosion should be at least as likely with mag or plasma weapons.