I'm switching to a dual out the back on my Supercrew.(Probably a Flowmaster deltaflow 50
si/do rear's with 3.5" slash cut tip's.)
My main pipe off the cat's is 2.5".
Should I stay with that out the back or should I go with 2.25" out the back to help maintain my low end torque.

Any comment's or opinion's would help.
Thank's guy's

------------------
2001 Supercrew XLT 4X4
BLACK W/DARK GRAPHITE
5.4 EFI V8
17" 10 SPOKE'S
3.55 LIMITED SLIP
ENGINE BLOCK HEATER
SKID PLATE'S
POWER MOONROOF
SLIDING REAR WDW.
TRAILER TOW PKG.
BED EXTENDER
CLOTH CAPTAIN'S CHAIR'S
STAINLESS STEP BAR'S
GIBSON SWEPTSIDE
WINDOW TINT
VENT VISOR'S
LINE-X-BED LINER
FORD MOLDED MUD FLAP'S
K&N FILTER
HUSKY FLOOR LINER'S
HEADLIGHT/FOG SWITCH MOD.
BFG 265/70/17 AT/KO
STAMPEDE BUG SHIELD
WEATHERTEC WDW. VISOR'S

 

fallscrew,
my experience is with a 4.6 so i don't know how the pipe diameter would work with the 5.4. here are my observations: 1st time i ran dual straights off a y-pipe 2 1/2" out the back. lost tons of bottom. went back , had the guy ( a buddy of mine) replace with 2 1/4" pipe and got my bottom back. seems funny to me how that small a diameter can make so large a difference. but, in my case it really did. good luck, Rich

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-1999 F-150 4X4 XLT SC
-4.6, auto
-3.55LS
-Westin chrome nerf bars
-dual straight pipes
-goodyear mt/r 265/75/16
-hikerdadrich@aol.com

 

I agree with Hikerrich.

If you go with 2.5" pipes, you will lose low end torque in a noticeable amount, but the upside is that you will make it up (and then some) at the higher end.

This is fine if you do a lot of highway mileage.

Going with 2.25" out pipes sounds like a good remedy but I wonder if you will then lose the high end gain.

What has been your experience at the high end Hikerrich?.

Baj


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2001 EXCAB F 150 LARIAT
ORP
(BLACK & GOLD)
4.6L AUTOMATIC
PARCHMENT LEATHER INTERIOR
WOODDASH KIT
FORD BLACK TUBULAR SIDE STEPS
6 DISC CD CHANGER
MODS:
FLOWMASTER 40 (SI/DO)
BEPO GRILLGUARD
A.R.E LSII FIBERGLASS LID (WITH SPORTWING)
K&N AIR FILTER
AUTOVENTSHADE DEFLECTORS

 

I'd go with the 2 1/4" pipes. I did and I lost no low end, and I gained mid-to-high end power. I Y piped it off after the cats and ran dual pipes straight out that back, sounds bad A$$.

------------------
1999 Ford F-150 (5.4)
Extended cab
short box
Off Road Package
Nerf Bars
Straight pipes
Ford box bedliner
Captains Chairs
6 disc cd changer
Sliding Rear Window

 

bajanblack,
i have noticed a better pull in the middle and at the top with the straights. although, i rarely ever drive fast. i am usually pulling a trailer, or loaded down in the bed. a couple of times i have noticed a better kick when playing in the mud though. lol, Rich.

------------------
-1999 F-150 4X4 XLT SC
-4.6, auto
-3.55LS
-Westin chrome nerf bars
-dual straight pipes
-goodyear mt/r 265/75/16
-hikerdadrich@aol.com