Quick answer: No on both counts. increasing primary pressure increases fuelling, but the lambda system will fight you proportionally so until you get outside the lambda system's "band of adjustment", it won't do anything. Without going into massive detail, pressures in the system are set with a spring loaded valve that bleeds fuel back to the tank. By setting the pretension on the spring, you set the pressure where the system reaches an equilibrium. As the engine requires more fuel, the pressure will start to drop, the valve closes a bit, reducing the flow back to the tank, the pressure remains stable. The control pressure is fed from the primary pressure through its own regulator valve (Control Pressure Regulator anyone?), but is ALWAYS lower, so regardless of how you set the primary pressure, the control presure will remain constant, unless the primary pressure drops below control pressure, which it will only ever do if the pump fails, and by the time it does the engine will have stalled anyway. One of the "cheats" on an EFI system to run more fuel on a stock ECU is achieved by upping the primary fuel pressure using an adjustable valve. Widely available, often with a gauge attached. I love hydraulics, you can do so much off the back of a few very simple principles. Yes, I am currently single... Martin Marc Levy wrote: > I have been told by a number of people that INCREASING > the fuel pressure on these fuel systems will LEAN the > mixture. Yes, I know it does not make sense.. But > when it was explained to me, it made sense at the > time... I forget the reason now!! > > Also, if you increase the pressure, then wont you also > increase the resistance on the plunger?? if so, you > will be making it harder to open the the meter flap > and it will cause additional restriction in the intake > path. > > > [Non-text portions of this message have been removed] To address comments privately to the moderating team, please address: moderators@xxxxxxxxxxx For more info on the list, tech articles, cars for sale see www.dmcnews.com To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/dmcnews/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/dmcnews/join (Yahoo! ID required) <*> To change settings via email: mailto:dmcnews-digest@xxxxxxxxxxxxxxx mailto:dmcnews-fullfeatured@xxxxxxxxxxxxxxx <*> To unsubscribe from this group, send an email to: dmcnews-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/