OK, I have a 2010 SCREW with the 5.4. I was all set on getting a magnaflow muffler for a better sound, SI/SO with the pipe exiting out the back. Never understood having a chrome tip behind the wheel to get sand/salt blasted.

I called a very reputable shop that does only exhaust for the last 25+ yrs and they said I will loose a bit of low end torque and maybe a mpg or two because of less back pressure, but gain a bit of hp. I'm not looking to gain any power but will not pay money to lose power and burn more gas just for some sound.

Also how will a new muffler that is less restrictive affect the engine, will this cause problems at all? running lean of something?

Ideally I would like a durable SS muffler that sounds better than stock but not loud or obnoxious. Up until now I was shying away from flowmaster cause I didn't want to go too loud... but if the flowmaster is similar to the original restriction wise, maybe one of there milder series will be the ticket.

What do u guys suggest?

 

The good old boys at your muffler shop are stuck in the '70... they're nice guys I'm sure but they don't know squat about Ford trucks or EFI motors.
All Ford exhaust systems are restrictive so anything you do to open them up improves both TQ and milage, shorty headers and a free flowing catback are good for a 2-3mpg improvement and a noticable power increase at the drivers seat. The catback alone won't make as big a difference but the sound will be improved. And none of this will ever cause any damage to the motor as long as the front O2 sensors remain in the exhaust and connected.

 

Might want to look at an aftermarket pre engineered cat-back exhaust for your truck. A single 3" catback has been proven on the dyno to work well on the 5.4l. The cat-back system may cost you a little more than the local exhaust shop but you will most often get a better quality system. As a bonus you avoid some of the people that occupy a lot of the exhaust shops. Catback exhaust systems are really easy to put on in your driveway with a minimal amount of tools.

Plowmaster makes a good muffler and a good cat-back but some of their mufflers are a little overpriced. Flowmaster makes many sizes of mufflers for many applications, not all of them are loud. Their 70 series and larger capacity 50 series are actually close to stock sounding.

 

The highest restriction is at the cats (which really isn't that bad). Wether the muffler is completely removed, modified or not, the same backpressure will still exists (or so close for oem stock/street operations the difference is minimal). While the slight flow difference does require the ecm to do some fine tuning, the truck will run the same in terms of no performance loss. Those who feel loss I think is

1. The ecm hasn't recalibrated the fuel mixture completely
2. the increased performance elsware in the power band leaves an impression that there is a loss elswhere (when in fact there has been no change)

 

Hmmm


I have been looking at the magnaflow kits just didn't like the fact that the single comes out behind the rear wheel.

He will do cat back magnaflow muff and custom piping all stainless if I want, single out the back for 550 canadian.

What is better weld or clamp? I asked he said he can do either...I was thinking clamp that way I could put the original system back on if need be.

Thanks

 

You want to have that welded. It is more secure, and you don't get water trapped up in the joints, which could otherwise cause problems. If the original flanges are maintained, you could still swap back if you needed to. And the guy ate the shop needs to run that on a dyno before he claims stuff like that. An oversized system will cause a lose of power, please read my other posts for the details on why. But 3" is not oversized, and a straight through muffler will not cause a power loss if it is the right size for the vehicle.

 

The catback on my super duty is clamped and tacked. Good clamps work fine, just check for leaks after you run the system through a few heat cycles. Putting a tack weld or two keeps the system from rotating or moving at all. The tacks can easily be cut and the clamp removed. Still better off with an aftermarket cat-back IMO, the exhaust shop will end up collapsing the 3" pipe a lot at the bend point.

This is a cross section of what a non mandrel bent 3" pipe looks like. The bend was around 20-30 degrees.