|
I'll try to explain this. If it is unclear don't be afraid to ask questions.
When GM designed their intake they didn't just go create plastic prototypes and hoped it all worked out. They did a lot of modeling well before a prototype was ever produced. One of the most critical items is to keep the airflow over the MAF sensing element as smooth as possible. If the airflow is turbulent you will not be able to get accurate mass air flow measurements. Ultimately once they decided on a design they had to create a mass air transfer function (i.e. Lookup table) that converts the frequency output of the MAF to a flow rate (i.e. grams/second). If everything is calibrated properly the O2 sensors will add the final minor tweaks necessary to keep the air/fuel ratio where it needs to be.
So on to an aftermarket CAI...
Anything an aftermarket CAI changes from the stock intake can have the potential to upset the airflow behavior over the MAF sensing element across the RPM range and load range. A very slight deflection in the air path or a larger diameter tube can wreak havoc on the MAF output. This will lead to an inaccurate reporting of the actual mass air flow at that moment.
When your fuel trims change in this scenario you can't assume it is because of more airflow. It is likely it is not more airflow. It is likely it is a misreporting of airflow causing the change. How much one CAI changes the trims versus another is irrelevant to determining the performance value. A CAI if designed properly should have minimal changes on the fuel trims. If the air flow is being reported accurately the trims shouldn't change even if more air is truly coming in. Thats the whole point of the MAF. More air less air. It should all calculate out to the proper fueling regardless. If it doesn't something has upset the calibration.
Under WOT you don't have the benefit of the O2 sensors to keep the fueling on track if the calibration gets upset. So a CAI that causes a significant error in MAF output will have a significant error in AFR. This may show up as a power advantage if things lean out a bit but it is not correct. The CAI guys should be providing a recalibrated MAF table for their unit. But they don't because they hide behind the O2 sensors and fuel trims. If you are going to get a CAI you really should have the MAF table recalibrated.
When I get the Roto fab unit I will provide the properly calibrated MAF table on the forum. It really doesn't take that long to do.
|