Ryland3210 Posted April 29, 2008 Posted April 29, 2008 Bikes with the fuel pressure regulator mounted external to the tank have a reference port. This is not connected on some bikes, raising the question, of what it is for. This port allows the regulator to vary its output pressure with the intake manifold vacuum when connected to the throttle body intake manifold ports. At wide open throttle, when intake manifold pressure is nearly atmospheric, it has no appreciable effect. At part throttle, it lowers fuel pressure to lean the mixture. My '04 Cafe Sport and other models provide no access to the regulator, as it is internal to the tank. Bikes with external regulators that have the port disconnected raise the question of whether to connect it, and whether the mapping takes the disconnected port into account. Caution: a concern has been expressed that connecting it may lead to early fatigue failure of the regulator because of the pulsating nature of the vacuum signal. For a thorough discussion and connection diagrams, see the following thread: http://www.v11lemans.com/forums/index.php?...0Port&st=30
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