JS...with open loop tuning, the computer still uses all the sensors to calibrate for the weather and changes. With Open Loop tuning, you eliminate the 02 sensors...and the inaccuracies that they cause. When I tune this way, I install a wideband sensor and calibrate each table to acheive the perfect A/F for different loads, temps, ect. The maf is still used, which detects more or less airflow...the iat to compensate for air temp, ect. The only thing you really lose is the inaccuracies of the stock 02's!!! Now, if you change something drastic, the car needs to be tweaked, since you don't have the compensating factor built in(02's). The nice thing is, I can program the A/F to be differant at certain points...such as 15:1-15:5 for a lean cruise, 13:8 under moderate throttle, and 13:0 under full throttle. Its just complete control!
Chris