A couple weeks ago, we completed our turbo Viper here at Calvo Motorsports. We have a number of different ECU options we're considering for the final product, but figured we'd test out HPT before changing things drastically. We fitted the 3 bar MAP sensor from the Caliber, and had a hell of a time scaling it. It seems that the units are off for the slope AND offset. The scale for the sensor is supposed to be around 61kPa per volt slope and 6.8kPa offset, however, looking at the values for the stock MAP sensor, you can quickly see that the units in HPT for the Viper are off, being 15.561psi per volt and 0.704volts offset. This would mean that, being a 5 volt sensor, it would really be around a 4.5 bar sensor (since most sensors read 0.5 volts to 5.0 volts). I thought at first that perhaps the unit labels were just off and maybe that was actually in kPa, which COULD make sense (it would give a range of around 70kPa, which is about the range the motor will see, from 30kPa to 100kPa), but the offset would need to be 30kPa. Again, something is weird here.
I ended up just modifying the slope and offset until I got approximately 100kPa with key on and engine off, and 30kPa with the engine idling, as I read with the stock sensor. I ended up with values of 46.683psi per volt and -0.200 offset. It's obvious that this is not ACTUALLY in units of psi, and the offset is certainly not units of pressure. I'm thinking perhaps the background computation of the number inserted into the ECU is off, and the offset scale is either off, or it's an offset on the x-axis instead of the y-axis, so an offset of volts.
Has anyone else fitted a different MAP sensor successfully?
Reply With Quote
