B1209 - Injector Correction MAP/Vac Selection

[EngineCalibrations]

"This calibration selects between MAP or Vac depending upon whether the fuel system is referenced to MAP or atmospheric pressure."
This wording is confusing to me.

You have two choices: MAP or Vacuum. Does this mean you select whether the fuel system is referenced to MAP or Vacuum? Vacuum and atmospheric reference is NOT the same thing!

What setting do we pick for fuel pressure regulator that has NO vacuum line that's run to it? We are using this regulator :
http://img3.imageshack.us/img3/2152/mycamaro0632ol.jpg

[joecar]

"This calibration selects between MAP or Vac depending upon whether the fuel system is referenced to MAP or atmospheric pressure."
This wording is confusing to me.

You have two choices: MAP or Vacuum. Does this mean you select whether the fuel system is referenced to MAP or Vacuum? Vacuum and atmospheric reference is NOT the same thing!That setting selects the axis parameter of the IFR table and the voltage correction table...

VAC = BARO - MAP

that parameter selects whether the pressure axis is MAP or VAC (which is reverse of MAP)...

in most E38/E67 calibrations, when selecting MAP for the axis, it is not true MAP, but it is FPR base pressure offset by MAP (i.e. BASEP + MAP)...

so for example, with a 4-bar FPR (400 kPa, 58 psi), actual manifold MAP range 0-100 kPa corresponds to FPR range 400-500 kPa (and this corresponds to VAC range 100-0 kPa)... the axis range shows 400-500 kPa somewhere in the middle of the axis, anything below 400 kPa is boost.



For MAP-referenced (aka vacuum-referenced, manifold-referenced) FPR, the IFR will be flat, and the voltage table will have the same column everywhere.

For un-referenced (atmospheric-referenced) FPR, the IFR will be sloped (with a squareroot gradient), and so will the voltage table.



What setting do we pick for fuel pressure regulator that has NO vacuum line that's run to it? We are using this regulator :


That is an un-referenced FPR integral with the inline filter (as used by Corvette)... so the IFR will be sloped.