[Kris]

I have just read this post on the FX forum:

installed a k&n airfilter to get better gas mileage for my fx45.....i was getting 12miles a gallon ....now i am getting 10.5 miles(only city driving)

and the reply:

Drop in or cone filter?

The MAF is calibrated for the [to match the] oem air box and filter.
Changing things in front of MAF can cause strange reactions, especially if oil gets on sensor elements, or hotter under hood air gets into the system, or just the shape of air flow changes creating strange vortices!

I have been using K&N for the last 25k miles and did not really notice any difference. Performance or milage wise. Anybody out there with different experience?

 

[Eric L.]

No significant mileage difference with either the K&N drop in or the JWT cone for me.

 

[Dalite]

This could be another case of "computer will".

The engine computer is programmed to the limits of the imagination of the programmer.

If the range of operation in the sensors that measure air flow, temperature, barometric pressure, ect.. only take into account a certain range of parameters, and if a change is made in one of the measured systems.....

In other words, if the data that the sensors send to the computer falls outside of the parameters the computer is programmed to accept, the computer can either de rate performance until the data returns within the programmed parameters or throw an error code.

One thing to consider in most modern engine control computers is to disconnect the negative battery lead and turn on the emergency flashers, hit the brakes (or energize any constant hot circuit) to drain any residual voltage on the computer. This will allow/force the computer to re-enter the "learning" stage, and may provide the quickest response to a change or modification by removing historical data from the computer.

I just left the world of Chrylser Turbo-Charged PT Cruisers, and Stage I Performance computers, torque-based turbo management and modified speed density look-up tables, so I am somewhat familar with results that aren't always what you expect; especially when you are fighting a stubborn computer with no sense of real-world data that extends beyond the programmers imagination, or familarity with reality in the real world.

Your mileage may vary

 

[Tyler_Canada]

My mileage went down about 1mpg after installing the pop charger. I installed the k&n so early that the engine might not have even been broken in (can't remember, long time ago).