Tuner
Senior Member
Joined: Dec 2008
Posts: 1,650
Likes: 2
From: The Bayou State
I'm afraid MGDfan is right. If you put a MAF sensor in a different (larger) tube or body with different bends, and it's going to alter how it that sensor interprets air flow and communicates that information to the PCM. Unless the manufacturer of the CAI has painstakingly developed that unit to read air flow similar to the stock air intake, you may and likely need a tune. Adaptive learning may compensate for some adjustment that is out of range, but unless you know a particular CAI is within the learning range, you could encounter a dangerous lean condition. The purpose for adaptive learning is to change for minor variation between vehicles and poor vehicle maintenance (dirty MAF, air filter, etc.). It is not intended to compensate for changes to the mass air flow sensor's housing.
Ford used to use a MAF sensor inside it's own tube. Changes to the air intake between the MAF and the throttle body, didn't change the air flow around the sensor all that much, so changing the intake wasn't that big a deal. That all changed when the sensors were place in the air intake (04+). Change the intake you will change the way air flows around the sensor.
The MAF sensor is a heated wire that interprets air flow (cooling of the wire) in terms of voltage output between .7 - 5 volts. There are 30+ data points in the PCM calibration that is called a transfer function that is used by the PCM to interpret voltage readings as air flow. It's a table that has volts and air flow. Increase the diameter of the tube around that sensor and less air, or rather less air flow volume, is going around that sensor to cool the wire. With enough deviation, it is sending bad data to the PCM with which to make calculations. That's not to say that a different transfer function can't be developed and entered into the PCM so that it can properly compute the data, but that will require a custom tune.
My advice would be to talk to a tuner before you install a particular CAI and ask him if he's had any experience with that unit. He should be able to tell you whether he has worked with that unit and has a transfer function developed for it. If he does, I would only install a CAI after I have the tune in hand that will accommodate that CAI. If the tuner tells you that CAI is within the range of adaptive learning, proceed at your own risk.
Just because someone without an understanding of the concepts has been able to do something and not blow up his engine, is not a reason for you to do the same. I'm sure not all CAIs are the same, so I would take some of this discussion with a grain of salt. I hope I've been able to clarify why the opinions are so different in this thread and why a CAI can cause a lean condition. I'm not saying all will, but unless you datalog the vehicle to determine variations in short term fuel trim, you simply just don't know.
Why believe me? I've been tuning my own stuff for about 10 years now. I have a good understanding how all this stuff interrelates. I doubt any tuner can read what I've posted above and disagree with it.
Ford used to use a MAF sensor inside it's own tube. Changes to the air intake between the MAF and the throttle body, didn't change the air flow around the sensor all that much, so changing the intake wasn't that big a deal. That all changed when the sensors were place in the air intake (04+). Change the intake you will change the way air flows around the sensor.
The MAF sensor is a heated wire that interprets air flow (cooling of the wire) in terms of voltage output between .7 - 5 volts. There are 30+ data points in the PCM calibration that is called a transfer function that is used by the PCM to interpret voltage readings as air flow. It's a table that has volts and air flow. Increase the diameter of the tube around that sensor and less air, or rather less air flow volume, is going around that sensor to cool the wire. With enough deviation, it is sending bad data to the PCM with which to make calculations. That's not to say that a different transfer function can't be developed and entered into the PCM so that it can properly compute the data, but that will require a custom tune.
My advice would be to talk to a tuner before you install a particular CAI and ask him if he's had any experience with that unit. He should be able to tell you whether he has worked with that unit and has a transfer function developed for it. If he does, I would only install a CAI after I have the tune in hand that will accommodate that CAI. If the tuner tells you that CAI is within the range of adaptive learning, proceed at your own risk.
Just because someone without an understanding of the concepts has been able to do something and not blow up his engine, is not a reason for you to do the same. I'm sure not all CAIs are the same, so I would take some of this discussion with a grain of salt. I hope I've been able to clarify why the opinions are so different in this thread and why a CAI can cause a lean condition. I'm not saying all will, but unless you datalog the vehicle to determine variations in short term fuel trim, you simply just don't know.
Why believe me? I've been tuning my own stuff for about 10 years now. I have a good understanding how all this stuff interrelates. I doubt any tuner can read what I've posted above and disagree with it.