Exploit of physics flaw or what?

I see what you mean. I still haven't managed to get the 200bx to climb that ramp to the extent that you did, or get the tires to spin while moving backwards, even at low speeds.

Is the code for idle specific to each car (I can't seem to find a value for max idle throttle in jbeam)? If not, I wonder if the developers have included realistic idling in the game yet. From what can be seen, the idle code simply seems to ensure that the RPM is kept at the idle value. There doesn't seem to be a max throttle value for idle.

 

Oh, now I understand confusion.

That BX200 in video has V8 engine from pickup (it can be heard in video).
I just wanted to test how higher torque engine behaves in BX200, it is very straight on swap and interesting bit is that it does not stall at all, torque without touching throttle is more than tires have grip.
You can see in video how that BX200 has 175Nm torque at idle and tires break traction roughly there.

There is variable maxIdleThrottle, which I believe is 0.15 by default (as not set in jbeam files of vanilla vehicles), I did test setting that to "maxIdleThrottle":0.035, which was pretty much smallest I could go, but it had no effect to actual idle throttle, but it had effect on throttle at idle without engine load, it does work bit weird way, imo.
You can put that code next to idle rpm line in yourengine.jbeam and test different values.
Also there is IdleTorque variable, but you can't set it in jbeam file, imo.
Also that is related to checking lockup condition and that part of lua goes beyond my capabilities really, however for me it has nothing to do with setting idle torque.

In combustionEngine.lua line 1278 maxIdleThrottle = jbeamData.maxIdleThrottle or 0.15,

Code is attempting to keep rpm to what is set in jbeam file of engine and uses 100% throttle if needed, despite what you set in that variable, which then leads to very strong idling characteristics, not sure if that is by design though as it does certainly help with controller users that don't use clutch assists.

It can also be that it is simulating idle compensation behavior of FI engines, especially modern ones that have throttle by wire can have automatic throttle opening if rpm decreases below idle, but not sure if it goes to 100%, older stuff that I'm more familiar don't have anything of such, carburettor equipped cars just stall super easy without throttle and when cold, they stall super easy without choke as there is adjustment to amount of throttle at idle.

Hopefully it is some use for you, it is quite little what I understand, but such curiosities I stumble upon might help you clever people to find ways to create more awesome, then world is slightly improved again