Ford Expedition Intake and exhaust [Archive] - Glock Talk


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walkin' trails
08-25-2005, 16:36
I've got an '03 Ford Expedition XLT 4X4 with the 5.4 (3.73 differentials). I've been considering the addition of an open element air filter and intake and some type of cat-back exhaust to open it up and make it breath a little better. Anybody have any experience with these mods, and if so, what kind of power and milege improvements have you noticed. I'm currently running a K&N filter in the stock air box, and Mobile One synthetic in the crankcase. I am hitting almost 17 on the highway. I'd consider everything successful if I increased to 18 or better on the highway. I've thought about trying to have a true dual exhaust with a crossover fabricated, but I don't know if there is enough clearance with the independent rear suspension unless I go with side exits.

08-26-2005, 06:31
No real need for a dual exhaust. Just a good single exhaust or even just a weld in muffler will help reduce backpressure.
You might not get any better fuel mileage but it will sound better:)

08-26-2005, 19:40
If you wheel it in the mud think twice about the open element filter. I bought a OE filter for my 98 F-150 4.6L 4x4 and learned quickly at the car wash. I went to one of the washes that has an underbody sprayer when you drive in and as soon as it started spraying the engine started missing. I looked under the hood and the filter was soaked in water. Being a frequent off roaded, I am working on fabricating a lower side shield out of sheet metal to shround the botton half of the filter.

As for performance, I too had the K&N in the factory airbox and I did not feel a seat o' the pants improvement with the new set-up; which also included a large metal pipe instead of the factory squished plastic tube.

Depending on how the fabrication goes, I may clean the K&N and put it back in the factory set up if I can use the big pipe with it. Oh well, looks like more fabrication for that one...

09-07-2005, 14:30
I replaced my factory muffler on my `99 F150 4x4 ext cab 5.4 V8 with a Flowmaster 40-series.
That and a K&N filter w/ a modified stock air box netted me a best of 18.7 mpg hwy and some city driving.

It sounded very nice; throaty and noticeable, but not too loud.

walkin' trails
09-08-2005, 19:05

What did you do to modify the airbox? Also, did you also go with a cat-back pipes with the Flowmaster 40?

Anyway, I noted in a magazine that AEM is coming out with a synthetic filter that takes no oil, and allegedly filters up to one micron. I'm tempted to take a look at that system. I ran Flowmaster two chambers on a 5.0 Mustang about ten years ago, and noted that it could get pretty decent milege when my foot wasn't in it. When the pipes rusted out, I replaced the system with a Dynomax system that touted to be more effecient. By that time I was looking for something that wasn't quite as loud and the Dynomax fit that bill. It just didn't seem like it made as much power with the new mufflers, however.

Anyway, thanks!


09-08-2005, 21:56
Boy, that was a long time ago and many other modified air boxes have wielded to my hand tools.;f

If I remember correctly, I simply drilled a bunch of 9/16" holes in the sides of the airbox below the filter level and away from the engine (heat issues)...I also smoothed out the drilled holes with sand paper and removed any silencers.

Here's a pic of the custom air intake I built for my `92 F250 with an EFI 460 for about $80:

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