Leaderboard

Hal, here is a list of Hitachi MAF sensor flow rates GM assigned the MAF sensor output frequency in a stock 3800 vin C chip... MAF Vs. Output Frequency Table 1 kHz gm/sec 2.00 3.19 2.13 3.53 2.26 3.94 2.39 4.38 2.52 4.81 2.66 5.31 2.79 5.88 2.92 6.41 3.05 6.97 MAF Vs. Output Frequency Table 2 kHz gm/sec 3.05 7.44 3.18 8.06 3.31 8.81 3.44 9.56 3.58 10.31 3.71 11.31 3.83 12.50 3.97 13.69 4.10 14.88 MAF Vs. Output Frequency Table 3 kHz gm/sec 4.10 13.9 4.23 15.1 4.36 16.5 4.49 17.9 4.63 19.3 4.76 20.8 4.89 22.4 5.02 23.9 5.15 25.4 MAF Vs. Output Frequency Table 4 kHz gm/sec 5.15 25.43 5.28 27.07 5.41 28.55 5.54 30.19 5.68 32.16 5.81 34.13 5.94 36.09 6.07 38.23 6.20 40.20 MAF Vs. Output Frequency Table 5 kHz gm/sec. 6.20 41.00 6.33 43.25 6.46 45.75 6.59 48.25 6.73 50.75 6.86 53.75 6.99 56.50 7.12 59.50 7.25 62.75 MAF Vs. Output Frequency Table 6 kHz gm/sec 7.25 62.5 7.38 65.8 7.51 69.4 7.64 72.7 7.78 76.3 7.91 79.6 8.04 83.2 8.17 87.2 8.30 91.2 MAF Vs. Output Frequency Table 7 kHz gm/sec 8.30 91.2 8.43 95.2 8.56 99.3 8.69 103.3 8.83 107.8 8.96 112.4 9.09 117.4 9.22 121.9 9.35 127.0 MAF Vs. Output Frequency Table 8 kHz gm/sec 9.35 126.3 9.48 131.0 9.61 136.4 9.74 141.8 9.88 147.1 10.00 153.2 10.14 158.6 10.27 164.6 10.40 170.0 As you can see they are "close" to your test readings. Sorry you couldn't find any 3.0" MAF sensors at your junkyard but I do have one sitting here I can send you if you want it. -ryan

This is the MAF chart I received from GM Tuners many years ago. You can decide if it is discrete enough to require it to be pre calibrated. I can only speak personally about replacing MAF sensors, but I do not know of anyone that changes that entire assembly, despite what it says in the FSM. If you take apart the TB and MAF assemblies, there is almost no machining done after casting and the passages are as cast. I have run a couple dozen sensors on my flowbench just to get a sense of the range and if they are operational. The calibration, if there is any, consists of the sensor, the passageways, the laminar flow over the sensor and the ECM. This is the way I understand the system: The sensor has a heating element and a thermistor to read the temperature. The ECM sends a pulsed signal (probably ground) to maintain the target temperature to infer that actual mass of the air. The frequency listed in the chart is the pulse I am referring to. I am pretty sure the air temperature sensor in the air box is needed to precondition the required heating range. The MAF reading is used in combination with other inputs for the PROM to generate the LV8, or engine load figure, which is one axis of the main spark timing chart. It looks like this old chart won't open, darn it LN3 MAF chart.pdf