shombre

1) The P20 row is accessed using the Apex'i 3Bar MAP sensor. Given that the default P value in this row is 24000, or around 19psi relative, and the voltage resolution of the 3Bar MAP sensor is 29 psi, this means that P20 potentially holds the fuel/timing value for a large range of boost values, i.e. 19 to 29 psi. Many posts have alluded to editing the P values to alter the resolution, but nobody's posted that they actually do this, or recommend this.

Therefore, Q1 is, do people use their software of choice to edit the P10 to 20 values to allow a greater spread of cells in which one can tune for boost (and, as is axiomatic, alter their injection/ignition values in those cells accordingly) ? Or do they accept that the skill in tuning is that of idle/part throttle/boost transition rather than WOT, and therefore accept the lower resolution under high boost ?

2) Chuck Westbrook and others have in the past convincingly alluded to the PFC's derivation of boost from the MAP sensor voltage being inaccurate. This has hitherto been ascribed to an internal calculation error. Muddying the waters somewhat are the other interesting threads about the voltage calibration of the MAP sensor (Wargasm et al) itself being off.

Was the derivation of boost an issue only with early model PFCs / MAP sensors, or is this a current issue ?

If the latter, can (or should) it be addressed by altering the calibration of the 3Bar sensor, i.e. by altering the offset and scale values whilst using a hand pump, boost gauge and datalogger to analyse voltage and pressure ?

Thanks in advance.

cewrx7r1

iTrader: (2)

Q1: do people use their software of choice to edit the P10 to 20 values to allow a greater spread of cells in which one can tune for boost (and, as is axiomatic, alter their injection/ignition values in those cells accordingly) ? Or do they accept that the skill in tuning is that of idle/part throttle/boost transition rather than WOT, and therefore accept the lower resolution under high boost ?
A1a: I do it with my stock map sensor and custom maps using the stock map sensor and corrected PIM ABS. For these I set P20 at 17.5PSI with 2 psi steps for 4-16psi above.
A1b: I just calibrated a 3bar map sensor for a customer who is not going to be running over 16psi for a while. We set P20 at 18PSI. Later if he goes water/alky injection, I will change the MAP REF table again for his new boost range.

Q2 Was the derivation of boost an issue only with early model PFCs / MAP sensors, or is this a current issue ?
A2: Still an issue with the stock and Apexi 3 bar!

Q3 If the latter, can (or should) it be addressed by altering the calibration of the 3Bar sensor, i.e. by altering the offset and scale values whilst using a hand pump, boost gauge and datalogger to analyse voltage and pressure ?
A3: I have calibrated a three bar as mentioned above, but it takes accuurate equipment.

shombre

Chuck, thanks for the succinct reply. I'm just wanting to clarify a couple of points
1) Was I correct in nominating 19-29psi as the boost range for which ignition/fuel are mapped in that one row P20, when the Apex'i 3Bar sensor is used ?

2) I will PM you about the second.

cewrx7r1

iTrader: (2)

P20 at 24000 PIM ABS, if accurate with any map sesnor would be 19.4PSI.
If used with a 3 bar, P20 would be use for any boost greater than about 19PSI.
That means P20 would be used from 19 to 28.8PSI.

If you wanted to boost to 28.8PSI with a decent resolution, then P20 as the max would be setup as 30591.
If you wanted P19 to be 27PSI, you would have to plug in 29325.