It's the same signal, different signals wouldn't make any sense. You can look into the code on my drive account.
I use a 1:10 buggy (TeamC TC02 evo) and my friend a traxxas slash (also 1:10 but with 1:8 tire, this car looks more like a 1:8 model), so unequal "partners", they won't hide the IR signal by "nature". I cannot say what are the "best results", because I would also need a laser line within the pillar for exact matching (cross checking) when the car is passing the line and compare the results with the incoming signal (Maybe I'll try this out in the future). It also depends on which place you fix the IR-receiver on the car avoiding any different angle than 90 degrees (lower angle: you get the signal too soon, higher angle: you get the signal too late). All I can say is that it works quiet good without any missing triggers. There is also one thing:
If a signal is delivered with delay, this won't be a problem only in the final lap in case of a "photo finish".
Reason:
If the car pass (lets say in lap 7/10) the line and there is a short delay sending the signal you'll have this missing milliseconds as "bonus" for the next lap, because physically the car is this missing milliseconds beyond the IR-line and this will be subtracted the next lap. So maybe bad because you'll cheat the "fastest lap" a little bit .
The height of the pillar is about 40 centimeters.
I know the system is far away from "perfect", but as a cheap "just for fun" solution more than comfortable. Keep in mind that professional time tracking systems costs beyond 200 Euros.
A far better solution would be a RFID system. But I'm not familiar with it: So I have no plan which transmission strength/length is needed, but I guess far more than the cheap RFID modules you can get on Ebay or Aliexpress.