Damage of couched lances with RBM combat module equals joules of kinetic energy of such attack. According to following scientific paper, couched lances without lance rest (gadget on plate armor) can achieve up to 230 joules of KE, this is combination of ballistic properties of the lance and skill of the rider the can put some weight into the lance. This added energy seems to be in ballpark of up to 110 joules which in turn is in ballpark of 2.5 kilograms of added weight via the skill of the rider. With lance rest impact energy can go over 250 joules, however at 250-260 joules lances started to break. Tested lances were made of solid pine wood (presumably Scots Pine, since article was of British origin). Lances were relatively thin and long (details in the article), comparable to lances on these frescos. Riders were probably moving at roughly 10 metres per second.
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According to specs in the article (length of 360 centimetres, tapering diameter of 30-54 mm - some 42 mm on average) I calculated weight of tested lances to be 2.5 kilograms and ballistic KE of the lance to be roughly 125 Joules at 10 m/s (standard jousting speed). As a result both added body weight (based on the skill) and weight of the lance is taken into account in RBM until damage cap that scales with skill is reached (100 skill roughly equals performance of the riders in the article), after this point only the ballistic KE of the lance is taken into account.

However war lances were made of ash not pine, so weight of the lances and breaking point of the lance was adjusted accordingly. For example Scots Pine is very similiar to Red Pine and European Ash is very similiar to White Ash. I was able to find only impact bending (wood attribude that seems to represent potential lance breaking the most) values for RP (660mm) and WA (1090mm) so their values were used instead of SP and EA. Since 1090/660 = 1.65, I assumed that ash lance of same specs as pine lance is going to have +65% higher breaking point, breaking point of pine lance seems to be 260 joules according the article so breaking poin of ash lance should be 430 J. As a result raw damage (this includes only the piercing, not blunt part) of couched lances in RBM is capped at 430 damage. This is in ballpark of both sides mail penetration mentioned in some first crusade sources. For example wrought iron mail + gambeson should require some 140 joules to be penetrated by spear or lance, so 280 to penetrate both sides.