Have a 2003 F-150 4X4 supercrew with a 5.4L engine. I want to soup it up a bit and have plans for an intake, exhaust and somekind of chip. Nothing more radical than that. With respect to the exhaust, can anybody comment on what kind of setup would be best? I'm wanting to keep it legal and the truck is still in warranty. Should I consider headers? True duals? Cat back? The considerations are confusing because of pre-igniters, catyletic converters, O2 sensors. What is the best route?

tx_eveready
Austin, TX

 

That's largely a matter of personal preference.
WRT the warranty, modifying the exhaust should only effect the exhaust portion of your warranty.

WRT legalities. Depending upon mileage (50,000?), replacing the stock cat may not be an option, unless it's "defective".

Headers: Yes. Shorty headers are easier than long tubes. Long tubes are better for torque production, but may not be as good for off-roading (ground clearance issues). Ceramic coated is best. Stainless won't rust. Painted headers are cheapest (in all senses of the word). Price doesn't always reflect quality, but with headers it's a close approximation.

True duals: Difficult to do on a 4x4. Even more difficult to find a shop willing to try. A properly designed single should give you everything you need.

Cat back: Yes. Better after headers, high flow cat, and high flow y-pipe.

O2 sensors: As long as you keep them in the same location as stock and don't remove any components, then that shouldn't be an issue. When going to a dual setup, most of the time it is only necessary to have O2 sensors on one bank of the engine. Again, the sensors go in the same location as stock, just some of the exhaust will be going down a different pipe.

Pre-igniters: What's that?

My preference is for duals. Long tube headers. X pipe.
I'd recommend headers first (even the short ones), then a high flow y-pipe (if remaining single), then cat-back, then high flow cat (I've found nothing to indicate that aftermarket "hi flow" cats flow any better than new late-model factory cats. But then I don't own anything that new so haven't been looking very hard.

 

Thanks for your response,

I'm told that the setup on the 03 F-150 have a pre-igniter (a second catylitic converter if you will) on each bank, then a catylitic converter before the Y pipe.

So what I hear you saying is that headers definitely, factory cats are probably OK, then a high flow y. Have you any recomendations on size? It seems to me that the larger the pipes the better the flow to a point. Should I be concerned about loss of back pressure?

And what about a muffler? And does the size of the tailpipe affect performance, or does it just affect the sound? Can you recommend something high flow, but not too loud?

Thanks,

tx_eveready
Austin, TX

 

Cat back first as I am pretty sure your dealer will try to get out of doing any warranty work if you put on headers and stuff, just guessing though hear about it alot with the Powerstrokes when people put AFE air filters on them.

 

Your pre cats (pre igniters) are usually a part of your exhaust manifolds. I say usually, because I have not seen the exhaust on the truck you have. Headers will not have them. However, I have not seen a single vehicle that did not pass an emission inspection without them.

Your warranty should not be affected with any mods done AFTER the main cat. Any decent dealership will not give you any grief about having a cat-back exhaust. Y pipes should be ok, too. A dealer has to prove that the mod you did caused the problem. Like I said, a DECENT dealer.

Never be concerned about loss of back pressure. The less the better. Exhaust velocity is your main concern. Magnaflow would be my choice of muffler. Tailpipes should not affect sound, unless you get a resonated one.

Hope this helps.

 

Many stock tailpipes are 1/4" smaller than the pipes going into and out of the cats. This is because exhaust gas cools and contracts as it travels down the pipes. The tailpipes are smaller to keep the gas velocity up and provide a scavenging effect. For this reason, don't go too big on the tailpipes, or low end torque will suffer.