I have a 04 expedition with the 5.4. I am looking for better mpg like everybody else is. I have a open air box, free flow muffler and thinking on 2 more options. Electric fans? do they work well as everybody claims on mpg. Also I was told to remove the cats. I have heard from several sources if I do that the performance go up and mpg goes down. The other sources say performance goes up and mpg goes up too. if I install the dummy o2 sensors. Has anybody done this with the cats? Thanks in advance

 

This isn't 1984, modern cat's don't hamper performance enough to remove them while they are working. Even if they were bad, I'd replace them because of the performance gains(1-2hp) would not out weight the smell.

Efans are a decent option, but just because your not spinning the fan off the crank shaft, it still takes power from the motor to run. Efans create a larger draw on the electrical system and the alt. The Alt does take HP to spin, so you may not gain much, but it could be worth while if your looking for any and all possible gains.

Fuel mileage is function of your right foot. Keep your tires inflated, air filter and MAF clean, change your fuel filter and o2 sensors regularly and wax it monthly.

 

Here is real world results on e-fan results.https://www.ford-trucks.com/article/...c_Fan_Kit.html

Leave the cats.

 

I am not familiar with the 04 Expedition exhaust cat design, but on some earlier models the cats are extremely restrictive. Certainly exhaust restrictions will lower gas mileage as well as reduced torque and overall street performance. A good brand high flow Cat (Maganaflow, Pype...) replacement will certainly improve flow and consequently performance, mileage and emisions. Unfortunately the installation may be complicated and may be ilegal.
Electric fans may also be a good choice although a professional installation is necessary to keep the vehicle's cooling system reliable.

 

You can look for high flow cats here if you want to make a new y-pipe with only 2 converters. http://www.bearriverconverters.com/

 

LxMan1, thank you very much for the link to bearriverconverters.com, it has good products and information. Also you are very correct a new y-pipe will make a big diference to the exhaust of some of these vehicles.

 

There is a poll on the 97 – 03 F150 page you may like

 

the best way to get better miles per gallon is to use taller wheels/tires & lower gears (number lower). taking the cats off will help a little if you can keep your foot off the floor board but it will be a very very small gain in the real world . gears will help a good mile per gallon.

 

by putting taller tires on and giving the truck less gear you may actually lose fuel economy as the engine will have to work harder to perform the same function. It will require more throttle then before to do the same job. Also the taller tires will probably be heavier and thus make it that much harder to turn.

You would be best off going with the lightest tire (and wheel) that is rated for the job in the stock size, keep the stock gearing, and if you want to go for more fuel economy you could lower the truck and use a tonneau cover. Make sure there are no things to make it less aerodynamic (bug deflector, visor, etc.). You can also remove any un-needed weight E-fans and underdrive pulleys seem to work the best for improving fuel economy. Anything that can make the engine more efficient should help out.

Also ensuring that all fluids are changed regularly can help as well - engine oil, tranny fluid, front and rear diffs, transfer case, power steering and so on.

I would keep the cats for best fuel economy as well providing that they are still in good working condition. If not I would replace them with 2 high flow cats. You could remove them altogether but I do not think that it would help out too much unless the cats were not efficient anymore or if you were to dyno tune it to work without them for the most gains.

Alot of mods will move your powerband further up which may not help as you have to use more throttle to get the same power that you used to have at a lower rpm.

 

Yep, if I ever get the funds to put 4.10 gears in my truck, I'm sure it will get better mileage than the 3.55's do.

 

LxMan1 the 4.10s are lower gears then the 3.55s . Are you changing wheels to?

 

No, but it has the 17" 265/70r17's on it which are 31.7" tall. This makes my gear ratio more like a 3.08 and it takes more power to get it going. 4.10's will take load off of the engine and multiply the torque to the ground making it more efficient.
On the highway, I am only turning 2000rpm @ 80MPH. This would give me a calculated top speed of 200mph if the engine would pull to 5000rpm in OD. So it doesn't take much of an incline to unlock the converter and waste gas to keep the preset speed on cruise control.