WG

BMW M106 technical document states following: “Bypass valve with less spring force (65 N instead of 200 N) so that it opens in low load range with 0.2 bar already.” M102 document says: “The charge pressure must not exceed approx. 0.7 bar (10 psi), so that it must be controlled.”

Wastegate valve face diameter is 35mm and diaphgram opening in base about 65mm. As we know spring forces (65N and 200N), surface area is calculated to know pressure needed to overcome spring:

Area for valve is (0,0175m*0,0175m)*pii = 0,00096 m2
Area for diaphgram is (0,0325m*0,0325m)*pii = 0,00331 m2

Motronic WG:

Exhaust pressure P = F/A = 65N/0,00096 m2 = 67708 Pascals = 0,68 bar
Diaphgram pressure P = 65N/0,00331 m2 = 19 637 Pascals = 0,20 bar

L-jetronic WG:

Exhaust pressure P = F/A = 200N/0,00096 m3 = 208333 Pascals = 2,08 bar
Diaphgram pressure P = 200N/0,00331 m2 = 60422 Pascals = 0,60 bar

Note: 1 bar is 100000 Pascals