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Welcome to (or Ford 4L or Ford 4.0, whatever you want to call it.) I've been driving a 4.0 V6 OHV equipped Ranger for 10 years now and am very surprised at how little info there is on the net for this engine/vehicle combination. So I put up this site to let others know what I've learned. In those 10 years, I've also made some mods to my Ranger that would be good for any Ranger, Explorer or SportTrac with the 4L V6 engine, and I've included them as well.

Common problems and solutions:

  • Hesitation, sputtering, etc. - HOT!
  • Overheating
  • Bad Gas Mileage

  • Air Box Mod for 10hp - HOT!
  • CAI, Cold Air Intake- actual data
  • Mass Air Sensor
  • KN Air Filter
  • Exhaust
  • Headers
  • 160F-180F Thermostats
  • Stealth: Avoiding unplanned meetings with Officer Friendly.

    I bought the PVC fittings here.
    I bought some flex PVC pipe here.
    I bought my clone golf clubs here.
    I bought the headers & MAS here.
    I bought my truck tires here.

    What I believe & why:

    Disclaimer: This website is a Ford fansite. It is not authorized, nor endorsed by Ford Motor Company. No affiliatation or association exists between (aka and Ford Motor Company. All trademarks are property of their respective owner(s).

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    K&N Air Filter

    Just buy a K&N panel replacement filter and drop it in. Prices are around $40-50 but you'll only clean it once a year and it'll last for the life of the truck. Both power and fuel economy will go up. Don't waste your money on those "air intake systems" that pull air from behind the headlight. See my temperature findings here. Part numbers are:

    33-2002 K&N Filter Ford Ranger 1985-88 L4 2.3L, 1986-87 V6 2.9L
    33-2024 K&N Filter Ford Ranger 1989-94 2.9L, 3.0L, 4.0L
    33-2106-1 K&N Filter Ford Ranger 1998-2004 2.5L, 3.0L, 4.0L
    E-0995 K&N Filter Ford Ranger 1995-97 3.0L, 4.0L

    What about those cone air filters? I'm opposed to them for 2 reasons:

    1. According to K&N, their filters flow approximately. 6cfm/square inch. You can use the formula to calculate how big a filter you need:
    A = (CID * RPM)/20839


    A = Cross Sectional Area of the filter in square inches
    CID = Cubic Inch Displacement, for the 4.0L that's 245 cubic inches
    RPM = Highest RPM you'll run the engine to.
    20839 is a constant based on the various measuring methods and units.

    For me, 5,000 is about max for this engine. The valve train is not engineered for anything higher. In fact the factory rating for this engine in 1994 is at 4200rpm, other years show somewhat higher numbers, but not by a lot. So 5,000 is about all I'm willing to turn this engine. Compare this to the typical K&N filter that comes with those kits. 6" diameter, 6" tall, about 127 square inches surface area. Putting that number in the formula and solving for RPM get's you 10,800 rpm. So unless you are turning 10K on your 4.0, or running a turbo with 15 pounds of boost, it's a waste to use those filters.

    The factory filter is 6"x11" or 66 square inches. If I turn the formula around, I can calculate that a 66 square inch K&N flat panel filter is good to 5,600 rpm, so there is no use going to a bigger element. Incidently, if you use the forumula for the paper element you find that you'd need at least 71 square inches to flow air to the 4.0 to 5,000 RPM, and that's assuming a new, unused paper element. So you can see why just dropping in a K&N always boosts performance. The factory paper element is undersized, and that's not even considering it getting dirty.

    2. Cone filters pull air from the engine compartment. That air is very hot and kills horsepower. For more info, see my temperature findings here.

    Thanks for visiting

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