Intake, Header, HFC, CBE = Too Lean?

Originally Posted by F.I. Inc.

No you do not. If you run the HFC's and CBE your car will not become too lean. The ECU will correct and do it's job. Here is why the intakes change the A/F ratio's so much more than the exhaust system.

Inside your stock intake tube is a MAF (Mass Air Meter) As the air rushes by it, it samples that air. It works directly with the ECU and is calibrated specifically for the car. If you change altitude your cars A/F ratio will change. Meaning being at sea level opposed to driving in the mountains. In the higher altitude your car will actually be richer. Here is why, the air is thinner up there, your car naturally will take in less air. It naturally wants to lean out due to this and in most cases the ECU will compensate by dumping too much fuel and make the car rich. The MAF and ECU are designed from the factory to do this. However, they only work to a certain extent being that the elements from one place to the next are too different. If it worked perfectly your A/F would be optimum wherever you drove.

Now if you put an aftermarket CAI on the car that changes the location of the MAF or the tubing diameter it will change everything. The car is not calibrated for it. In the case of the Stillen Gen III intakes with exhaust & headers the intakes are causing the car to run way too lean. This is why you need a re tune so at the least amount you can bring the A/F ratios back to where they need to be. I know this how you may ask, over the past two days I dynoed a car that had Stillen Gen III intakes with our exhaust components and the car was borderline unsafe in terms of A/F. We re tuned the car, picked up alot of mid range power and low end torque just be getting the A/F back in the 12's. To be continued I am sure...

Thanks, Tony