Just curious, how much gain could I realize in mile per gallon if I installed dual exhaust? What is the max diameter exhaust I could install? If I did this would the restraint be the intake air, and would I need to install a K&N kit to maximize the benefit?

 

If your wanting to install dual exhaust on an expedition.....you cant! There is not enough room under the left side for an exhaust pipe!! Alot of us hear have installed the Gibson side swept exhaust. Its pretty quiet and it gave my expy a considerable amount of power!!!
Check one FamilyRides post, he has a pic and sound bite to listen to of the Gibson.


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2000 EB EXPY
5.4
3.55 LS
K&N
Gibson SS Exhaust
Moonroof
Superchip
Royal Purple 5w-30
01 lightning headlamps and corners
00 Lightning wheels with Michelin pilot LTX 285/55/18 The mod bug has bitten!!

 

Hi VettMeister,

You really can't expect to see much if any increase in gas mileage from installing a good cat-back aftermarket exhaust system. The factory exhaust system flows well enough that it's really not costing you mileage, and only a little bit in the way of performance.

Most cat-back systems for these vehicles gain about 12-14 hp on the 5.4 motor, and 10-12 hp on the 4.6 motor, just to give you an idea, and that is at the flywheel.

Also, you do not want to go "true duals" unless you are going to downsize the tubing diameter throughout the entire system, from downtubes to tailpipes, to no larger than 2.25", so you don't lose a lot of torque down at lower rpms on part-throttle, where you really need it in these heavy vehicles.

You'll get your best results using the Gibson "swept-Side" system for that vehicle, it's a single 3" system that works very well. You *might* see a .5 mpg gain at best, and if you do, it's icing on the cake, meaning you're lucky. They don't normally give noticeable mpg increases these days, like they used to years ago before the factory exhaust systems were improved over the past decade or so.

Just FYI, best of luck whatever you decide!

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Mike Troyer
Performance Products, Inc.
National Distributor of Superchips
(540) 862-9515
Email: mtroyer@compuserve.com
Performance Products F150Online Superchip ordering system: F150Online Superchip Ordering System
First National F-150 Online Rally Event Organizer

 

Mike's right- you won't gain any noticeable mileage from an exhaust system. If you want true duals, then 2.25" is MAX diameter. Our X has duals (nobody ever said you have to have one pipe down each side of the vehicle!) and I'm considering going back to a single-pipe setup. Not because of any performance or economy reasons, but because I'm a little tired of the noise. Even a "77 Series" Ravin is loud with duals!

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1997 4x4 Expedition- 4.6L, true dual exhaust w/Ravin DI/DO, K&N air filter, SuperChip, airbox mods, Edelbrock shocks, 285/75R16 BFG ATs, 2000 F150 "XLT" wheels, 4.10 gears, Auburn LS, Clarion In-dash CD player, Smitty Bilt push bars and nerf bars.

2001 4x4 F350 SD XLT CrewCab LWB- 6.8L, Offroad Pkg, HD Suspension Pkg, 3.73LS, TT mirrors, 6-disc CD changer, Remote Keyless Entry, Sliding back glass, tinted windows, GoRhino nerf bars.
NoMo's site

 

Here's me and my link/sound bite. Click the link at the bottom. I Agree with everyone else too. You'd be surprised at how the OEM flows. However, I do love the sound of the Gibson Swept Side!!!

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2000 EDDIE BAUER EXPEDITION 4x2

• Estate Green
• 5.4 ltr
• 3:55 LS rear
• Superchip!
• Airaid FIPK
• Gibson S/S Swept Side Cat Back Exhaust
• Hellwig Rear Anti-Sway Bar
• Edelbrock Performer IAS Shocks
• Xenon Super White Head and Driving Lights
• Clear Corners (installed then removed and reinstalled OEM's)
• Tow Package
• Rear Load Leveling
• Moonroof
• Century Child Seat!
• Front Polyurethane Anti-Sway Bar Bushings recieved, wrong part number

-->Come share my Addiction<--

 

Here are a couple pics of a MagnaFlow dual exhaust on my 1998 Expedition. The tubing had to be customed fabricated.

 

That looks *very* nice! I'd love to hear it.

------------------
Mike Troyer
Performance Products, Inc.
National Distributor of Superchips
(540) 862-9515
Email: mtroyer@compuserve.com
Performance Products F150Online Superchip ordering system: F150Online Superchip Ordering System
First National F-150 Online Rally Event Organizer