Max physics delta time relationship with GetTimeSeconds

Hi,

I am new to Unreal so please feel free to correct any misinterpretations in the following:

I am trying to run a car simulation (AirSim) on Unreal 4.18. I want the simulated sensors in the vehicle to update at a high frequency so as to be more precise. The computer I’m running the simulation on can manage about 20fps, which is far too low for my desired sensor frequency (100Hz would be great), so I have set the Max Physics Delta Time to a very low value of 0.0013s. I hope I’m right in thinking that this time is now the maximum amount of game time which can pass per physics tick, which as far as I can tell happens at frame rate, so the game becomes very slow (but still at 20 fps); this is fine because it doesn’t need to be realtime, just an accurate simulation. The problem I have now is that I need to get the sensor timestamps in game time, but when I use GetTimeSeconds() or GetDeltaSeconds(), the result is clearly still in system time ie I can just time 10 seconds or so myself and see that the log also shows a 10 second interval even when 10 seconds in-game time has clearly not passed (the car takes about 20 seconds just to fall about 50cm). So how can I get this in-game time? I guess changing the max delta time does not count as time dilation?

TLDR: how do I get amount of time passed in game when max delta time is very small?