Still new to this site not sure if this is in the right place. I bought my first F-150 this summer. 05 Super crew. It was getting poor mileage. So I put in a K&N air filter in place of the stock, I might have alittle more pep. I was still looking for better mileage so I went with a single in dual out Magnaflow. I might have gotten alittle better mileage. I was going to be some heavy dust and dirt so I put my stock air filter back in, and the computer is showing better mileage with it than the K&N. I'll check the figures after I burn a tank of gas has anyone else had this happen I thought that the K&N would get me better mileage. Thanks for any help
Eric

 

When you put inyour K&N disconnect the battery cable. This will earse the memory of the air intake settings. Then reconnect and start and let it idle for about three minutes to recalibrate to the new air flow. Lew

 

Wouldn't the computer automatically adjust for the newer air to fuel mixture?? Granted, it may take a tank or two to fully adjust to the new mixture ratio but the computer should make all the adjustment that are necessary. I could be wrong but this is what I have found out over the years with using K&N air filters on vehicles equipped with an ECU or computer.

 

Yes, it will learn by itself.

 

You may have learned something a lot of guys don't like to admit. That being... the expensive filter system they put on their intake didn't do squat. Tests we did on trucks at the speedway showed a pitiful 1-2 HP increase at the rear wheels, though the trucks did sound better. Fuel economy often got worse with the "novelty" intakes.

Ford already uses a monster muffler on the full sized trucks. You're not gaining much, if any, flow by changing out the exhaust. If you want better sound, sure, change out the muffler. More horse power? Better fuel economy? Probably not gonna help.

Case in point. My buddy has the exact same FX4 I do. He has a K&N intake, super chip and an awesome sounding Magnaflow dual exhaust. On the rack, he has 8 more HP at the rear wheels than I do. My stock engine gets 3 MPG more than he does and I'm dead even with him in the quarter mile.

Diesel engines are a whole different story, though...

 

Sounds like your buddy needs some custom tunig. I made over 43 hP on the dyno at the rear wheels with a good set of custom tunes and and AF1 intake on my 04 Supercrew two weeks ago.. My truck is a 4 x 4 with 3:73 gears and weighs in at a little over 6200#. I got over 18.5 mpg on the 380 mile return trip home with it after the tuning session..
Just a little curious if you don't mind telling us, or me, how did you test the trucks at the speedway? And what devices did you use to perform these tests?? Your stated results don't all up unless you were using a set of generic tunes...

 

"I got over 18.5 mpg on the 380 mile return trip home with it after the tuning session.. "

Marc, just out of curiosty, what kind of mpg are you getting now in stop-n-go driving?

Joey