BP CMD Lower Than TCMPR, BP, & MAP

[arnoldod]

Hi,

I identified BP CMD is lower compare to TCMPR, BP, and MAP pressure sensor reading in 1 of my datalogs.

I understand this is ECU limiting boost. My TCMPR set at 2.4 bar at 5500 RPM and other turbocharger limiting factor TC limit IAT & TC limit PA is set at 3.0 bar. Thus, turbocharger pressure limit is set at the correct amount and should allow turbocharger to command 2.4 (20.5 PSI) bar of boost at 5500 RPM.

BP and MAP reading show I hit TCMPR target with occasional boost spike up to 21.9 PSI. However, BP CMD maxed at 20.1 PSI.

Torque limit is set at 250 Nm at 5500 RPM. Given the difference between my calibration with +6 PSI is low (0.05 bar), 250 nm should be sufficient for BP CMD to command the set TCMPR at 5500 RPM.

I checked "MAP to determine WOT" option under close loop. Does this cause ECU limiting BP CMD & limit power?

Attached is the datalog for your review.

[Hondata]

Pressure ratio is the difference between the pressure on the inlet of the compressor to the discharge. The compressor inlet pressure is not the same as the assumed atmospheric pressure and not the same as the actual atmospheric pressure either due to a pressure drop on the inlet side. And the same applies on the compressor discharge side. The discharge pressure is not the same as MAP and may be higher than BP due to the intercooler.

It probably is best to look at the readings in absolute pressure, factor in the PA, and then adjust for a pressure drop on the inlet and outlet sides.

[arnoldod]

Pressure ratio is the difference between the pressure on the inlet of the compressor to the discharge. The compressor inlet pressure is not the same as the assumed atmospheric pressure and not the same as the actual atmospheric pressure either due to a pressure drop on the inlet side. And the same applies on the compressor discharge side. The discharge pressure is not the same as MAP and may be higher than BP due to the intercooler.

It probably is best to look at the readings in absolute pressure, factor in the PA, and then adjust for a pressure drop on the inlet and outlet sides.

Noted & thanks for the explanation. I changed the sensor reading to absolute pressure and notice BP CMD does meet TCMPR value. The pressure is spot on as per tuning objective. Thank you very much.