BenArtM80
10-08-2012, 07:10 AM
So I was reading through the s14 FSM and saw this little section about the absolute pressure sensor. It states that it is not used for engine control, only diagnostics and emissions stuff.
I'm not smart on ECU programming, but for those who are, this sensor is effectively be a MAP sensor, with a linear correlation between manifold pressure (from 3.94 inHg to 31.5 inHg) and output voltage (from 0.5 to 4.5 V). Bear with me here, but since the MAF sensor uses a similar voltage reading (less than 1.0V to more than 4.0V), it seems theoretically possible to swap the absolute pressure sensor wire for the MAF sensor wire at the ECU so the ECU is receiving the voltage from the absolute pressure sensor instead of the MAF. Now I realize that it would take re-writing the ECU fuel maps because the voltages between the sensors wouldn't correlate to the same fuel requirements for the different sensors obviously. Additionally, you would have to take into account TPS, engine RPM, etc. so it might even require completely making your fuel maps from scratch. However, for those folks who have the knowledge and equipment to adjust their own maps, it seems like a possibility to retain the stock ECU and have a more reliable way to schedule fuel delivery for forced induction applications.
I searched through zilvia for a bit and haven't found much about this idea. Has anyone ever attempted this or have any thoughts along these lines? Again, I don't know how to re-write ECU fuel maps or anything, but for those who can, it seems reasonably possible and I'm mainly just asking for my own curiosity.
EDIT: well I re-read the FSM and I misinterpreted the voltage chart. It actually is only measuring vacuum and doesn't read positive pressure. So, I'm an idiot, but the idea may still work albeit with another sensor.
I'm not smart on ECU programming, but for those who are, this sensor is effectively be a MAP sensor, with a linear correlation between manifold pressure (from 3.94 inHg to 31.5 inHg) and output voltage (from 0.5 to 4.5 V). Bear with me here, but since the MAF sensor uses a similar voltage reading (less than 1.0V to more than 4.0V), it seems theoretically possible to swap the absolute pressure sensor wire for the MAF sensor wire at the ECU so the ECU is receiving the voltage from the absolute pressure sensor instead of the MAF. Now I realize that it would take re-writing the ECU fuel maps because the voltages between the sensors wouldn't correlate to the same fuel requirements for the different sensors obviously. Additionally, you would have to take into account TPS, engine RPM, etc. so it might even require completely making your fuel maps from scratch. However, for those folks who have the knowledge and equipment to adjust their own maps, it seems like a possibility to retain the stock ECU and have a more reliable way to schedule fuel delivery for forced induction applications.
I searched through zilvia for a bit and haven't found much about this idea. Has anyone ever attempted this or have any thoughts along these lines? Again, I don't know how to re-write ECU fuel maps or anything, but for those who can, it seems reasonably possible and I'm mainly just asking for my own curiosity.
EDIT: well I re-read the FSM and I misinterpreted the voltage chart. It actually is only measuring vacuum and doesn't read positive pressure. So, I'm an idiot, but the idea may still work albeit with another sensor.