Discussion Starter · #1 ·
I just finished a mixture control mod. for the Hemi, but am not absolutely sure it will work. It should work any time the fuel injection is in the open loop mode, but I am primarily interested in open loop at WOT. At WOT the fuel injection is in the open loop mode and the oxygen sensors in the exhaust are not monitoring the mixture. In the closed loop mode they do, and force maintain the mixture at 14.7:1, which is chemically perfect for combustion and near optimum for emissions. Between 12-13:1 is optimum for performance. My mod. is a linear potentiometer that is adjustable from 0-50,000 ohms(which is the approximate range of the IAT) and is hooked up in series with "signal lead" of the intake air sensor (IAT). When in the "0" position (and in normal driving) it reads the sensor at face value, which is true intake air temp. Crank it all the way on (or somewhere in between) just before you're going to do a WOT blast, and the PCM computer thinks the intake air temp. is around 10 degrees F, and should then richen the mixture at WOT.....hopefully to the 12-13:1 air-fuel ratio. Right after the WOT run, the pot. must be turned back to "0" or the PCM will start tracking the readings and begin its adaptive corrections. My "Holley Bible" says that there is about a 4% difference in mixture requirements for every 11 degrees F change. I think it will work better in hotter weather than when cool, because of the larger temperature difference. My preliminary figures indicate that it will have to be set 43 plus or minus 7 degrees of true ambient to get the correct mixture. I have taken resistance readings of the IAT at 32, 40, 60, 80 and 120 degrees, so I will have some idea what to set the resistance at. Any comments or input on whether members think it will work are appreciated.