On many boosted cars fuel pressure needs to be raised as boost is added to compensate for extra air. The 3800 FWD supercharged engines use several methods to control fueling, which render an AFPR worthless in many cases. The MAF sensor reads the airflow and tells the PCM how much air is coming in and therefore how much fuel to deliver. The MAP sensor monitors manifold pressure (vacuum or boost) and fueling is adjusted by the PCM. The ECT sensor monitors engine coolant temperature and also has some effect on fueling. And then the front oxygen sensor (B1S1) monitors overall air/fuel performance and tells the PCM how well the actual air/fuel matches the desired air/fuel.
As you begin to mod and increase the overall airflow of your engine, the MAF and MAP sensors detect the increased airflow and/or boost, and the PCM automatically lengthens your fuel injector pulsewidths to compensate. The stock fuel pressure regulator (FPR) changes fuel pressure with vacuum or boost. As your boost increases so does your fuel pressure. By changing this function by replacing the factory regulator you run the risk of making your car more difficult to tune. Using an AFPR to increase static fuel pressure may not change the maximum pressure available because the stock L67/L32 fuel pump usually can't reach 70 psi on most vehicles. So even if you might add five psi of fuel pressure at idle and cruising, you may only be adding a pound or two at WOT. And this loss of linearity can make tuning the car a nightmare.
Scott
As you begin to mod and increase the overall airflow of your engine, the MAF and MAP sensors detect the increased airflow and/or boost, and the PCM automatically lengthens your fuel injector pulsewidths to compensate. The stock fuel pressure regulator (FPR) changes fuel pressure with vacuum or boost. As your boost increases so does your fuel pressure. By changing this function by replacing the factory regulator you run the risk of making your car more difficult to tune. Using an AFPR to increase static fuel pressure may not change the maximum pressure available because the stock L67/L32 fuel pump usually can't reach 70 psi on most vehicles. So even if you might add five psi of fuel pressure at idle and cruising, you may only be adding a pound or two at WOT. And this loss of linearity can make tuning the car a nightmare.
Scott