A radiator cap does more than close the filler neck: it seals the cooling system and holds the coolant under pressure, its rating being the pressure at which its relief valve lifts.

The governing physical principle is that the boiling point of a liquid rises as the pressure on it increases, because a higher external pressure suppresses vapour formation.

So a cooling system held at higher pressure lets the coolant climb to a higher temperature before it starts to boil.

Comparing caps rated 0.7 bar, 1.0 bar and 1.3 bar on identical engines, the difference between the three systems is purely the sealing pressure each maintains.

The 1.3 bar cap holds the greatest pressure, so it raises the boiling point the most and allows the coolant to reach the highest temperature before boiling.

The 0.7 bar and 1.0 bar caps release at lower pressures, giving lower boiling points, so their coolant boils sooner.

They cannot all boil at the same temperature, because the boiling point is set by the cap pressure and the three ratings differ.

Hence, the answer is System with the 1.3 bar radiator cap installed.