Real basic noobie question here: How can a MAF tune be used in open loop? I thought the whole idea of using a MAF was to use data from o2 sensors in a closed loop based measure of airflow. Why would one keep the restriction of the MAF if they're gonna use an open loop system? Why not just lose the restriction, sell the MAF, and go to a SD open loop tune?

 

In open loop, the computer targets an a/f ratio. To do that calculation, it uses the MAF readings to measure how much air is coming in. Then it adds the targeted amount of fuel based off the MAF reading. There is no O2 feedback to see if the a/f is correct. If the MAF tables are off, the car could run a little rich or lean and noone would be the wiser.

Dan

 

The MAF system is more responsive to changes in air flow than speed-density. Every time you alter the "breathing" of the engine, you've got to alter the speed-density system's volumetric efficiency (VE) tables. The MAF can measure improvements in engine breathing directly. And, its not really much of a restriction, at least not the GM MAF sensor used in the 4th Gens. The old Bosch units used in the 3rd Gens were a major problem, but not the current ones.