Boost Gauge

The stock Boost Gauge signal is PWM based signal sent across a single wire from the ECU. At 100% the gauge points to the top, 0% it’s at the bottom. The ECU calculates the Boost Gauge Duty Cycle (BGDC) from a single 2D table in the ECU.

The axis is just engine load which is calculated from air flow, then compensated for temperature and then is stored in a location in memory. The look up values you see in the table are where the needle physically points on the gauge itself (-8 = bottom, 14 = top). There’s really no rhyme or reason to how mitsu setup the gauge. One would think that 100 engine load = 0psi but the engineers probably knew better. After flash tuning a couple cars with the EVOX map sensor, I’ve been noticing 0psi is actually closer to 75-80 Load which almost matches the table. Who knows…

In either case, this data is pretty useless. The gauge really just serves as a fuel mileage calculator if anything…