two-stage turbocharger (bi-turbo) Cutaway are: both turbochargers, control flaps and the fresh-air valve. The turbines and throttle valves can be moved. Exhaust air, fresh air and oil channels are accentuated in colour. description ordernumber 1327 see also: amshafts model case switch-over induction system cylinder head four-valve mechanism Electric turbocharger (e-booster)