An electronic engine control system has a pressure sensor communicating both to the intake manifold and the ambient air via a valve means selectively introducing either the intake vacuum or the ambient air into the pressure sensor. The control system further includes a valve control means for controlling...http://www.google.com/patents/US4416239?utm_source=gb-gplus-sharePatent US4416239 - Electronic control system for an internal combustion engine with correction means for correcting value determined by the control system with reference to atmospheric air pressure
