ok, i've looked at the code and my last comment is irrelevant (re: angular velocity).
i understand that you want "more gravity" but doubling it (Set3DPhysicsGravity(0,
-20, 0)) combined with your deviation from the default scale seems to be the issue without "reining it in" somehow.
if i SetObject3DPhysicsDamping(e.car.id,
0.7,0.5) before setting the car's mass, i get no tunneling. without it, i fall through @ 300 every time (& never at the other 2 heights).
@ 200, speed = 526 at impact.
@ 300 & 400 = 600.0 (odd that they are both identical. see below)
adding the above dampening while leaving your doubled gravity but returning the scale to
default produces:
509, 565 & 600(-603) speeds from respective drop heights with
no tunneling for me. so, results similar to what you're looking for?
if i set the linear dampening to 0.4, the tunneling comes right back but, now, only @ a height of 400 (@ 800+ speed)
0.5 seems fine: 606, 710-715, 775-786. aka, definitely not a balloon.
0.6 and i'm ok @ 200 & 400 but 300 and i'm falling thru every time (speed ~650)
some of that seems "bug" to me and doesn't offer much light but, maybe, a place to further explore?
i don't know the bigger project for you, but for this i'd return to default scale, run 1000 tests at a a dampening you're content with and find a sweet spot?
hope that helps, blink. and, trust me when i say that i feel your pain re:
agk's current state of 3dphysics trying to figure this stuff out (i want to be fair. i just don't "get it" like i want to
).