Indeed; you would almost never leave the fuel pressure regulator open to fresh air since - as far as I know - all ECUs make the basic assumption that the fuel delivery is directly proportional to the time the injector is open. This is only the case when the fuel pressure is a constant pressure above the manifold pressure; hence that link.
While it's possible to map a normally aspirated engine with a constant atmospheric reference to the fuel pressure regulator, the effect is that at small throttle openings, the fuel pressure would be approximately 1 bar (depending on weather and altitude) higher than at wide open. This means that you would have to have smaller injection periods at idle and cruise - exactly where you need the best precision for good idling and economy - and injectors become less precise with short openings. You'd also be subject to mixture changes with weather and altitude changes. As Jim says, you *can* map an engine that way, but it's a very unusual way of doing it. Neil On Apr 18, 11:16 am, "Jim Hearne" <[email protected]> wrote: > As long as the ecu has a map sensor it wouldn't really matter if it was > connected or not as long as it was the same setup as was when the ecu was > mapped. > The vacuum connection changes the fuel pressure according the the inlet > manifold pressure. > > Jim > > -------------------------------------------------- > From: "xtreme brian" <[email protected]> > Sent: Monday, April 18, 2011 11:11 AM > To: "Quantum Owners Group" <[email protected]> > Subject: [Quantum Owners] xtreme zetec > > > > > > > > > Hi All,Ihave read somewhere that when running an injected zetec on an > > omex ecu you leave the vaccum inlet on the fuel regulator open to > > atmosphere.Can anybody shed any light why this is as mine is > > connected?. Regards Brian. > > > -- > > You received this message because you are subscribed to the Google Groups > > "Quantum Owners Group" group. > > To post to this group, send email to [email protected] > > To unsubscribe from this group, send email to > > [email protected] > > For more options, visit this group at > >http://groups.google.com/group/quantumowners?hl=en > > > IMPORTANT NOTE: All information presented herewith is provided on an "As > > Is" basis, without warranty or the implication thereof. Neither the > > Quantum Owners Club nor the individuals associated with the Quantum Owners > > Club or in the preparation of the above information shall have any > > liability to any person or entity with respect to liability, loss, or > > damage caused or alleged to be caused directly or indirectly by the > > instructions contained within this or related message(s). -- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/quantumowners?hl=en IMPORTANT NOTE: All information presented herewith is provided on an "As Is" basis, without warranty or the implication thereof. Neither the Quantum Owners Club nor the individuals associated with the Quantum Owners Club or in the preparation of the above information shall have any liability to any person or entity with respect to liability, loss, or damage caused or alleged to be caused directly or indirectly by the instructions contained within this or related message(s).
