Lifetime Supporting Member
Join Date: Dec 2011
Location: Tallahassee FL
Bullitt Year: 08
Bullitt Color: HG
Bullitt Serialized Number: 4370
The changing to a KN or other reusable air filters do not need a tune. The air mass sensor in the intake tube "reads" the air flow just beyond the air filter, in the intake tube.
The air mass sensor reading is calibrated in the ECM for the diameter of the OEM intake tube and the diameter of the OEM throttle body. A tune is only needed if the diameter of the intake tube or throttle body is changed.
There is much debate on reusable air filters on their efficiency and oil effects. Most folks put too much oil on the reusable air filters, or neglect to clean them regular. I recommend a second filter, ready to go, cleaned and excess oil drained off.
Routine cleaning of the intake manifold-cylinder heads is necessary. Not so much from the oil from a reusable air filter but from the engine vapors (oil) recycled through the intake manifold, as the motor has a closed system with no PCV valve.
I use a JLT oil separator. On a 4.6 naturally aspirated, it is only needed on the driver's side, as the passenger side is the intake. It collects an ounce or so of oil vapors every 1-2 thousand miles. Depends on use of the go pedal, cause at a track day, an ounce in a day. That is oil that would have otherwise dirtied the intake manifold interior, the valves and spark plugs.
And for best underhood bling on a green Bullitt, a Green brand reusable air filter...
Last edited by tossass4370; 02-16-2018 at 02:53 AM.