jameslleary

Did the muffler guy say what size pipe they used? My general rule is to reduce pipe size if going dual from single. Most V8's I have had true duals on are quite happy and productive with 2" duals, which were either 2 1/2 or 2 3/4 from the factory.
My 99 4.2 really liked 2" duals with magnaflows, 2 on each side, because i prefer silence. Got a best of 24 mpg with that combo.

808Lari8

I wish I had read this thread before doing any changes to my exhaust system. It has been very informative and helpful in restoring the performance I lost. I thought that what worked on my 2003 5.4 F250 would work on my 2012 5.0 F150. Let me explain.

I did a muffler swap only from stock to a Borla Pro XS 3" SI/SO and left the stock resonator in place. After 4 months I decided to have the resonator removed and the exhaust shop recommended installing 3" pipe from the Y collector flange to the muffler so the motor could flow and breath better so I agreed.

What a mistake that was. It was very loud inside the cab, there was a buffeting sound like that of a helicopter, I lost mileage, low end torque and, compression braking. I drove my truck like this for a month until I couldn't take it.

Armed with information from this thread, I recently went to a different exhaust shop and explained what happened and expressed my concerns. The best thing that happened aside from the quality craftsmanship was that the Owner listened and then He recommended replacing the Borla with a Flowmaster 70 series muffler 3" SI/SO, installing a 2 1/2" mid-pipe from the Y collector flange to the muffler inlet (approx. 4ft), no resonator and I'd still be able to use the stock tail pipe and my concerns should all be addressed.

When the work was done he told me to drive my truck around the area and come back. Now my truck is a Truck again, what a difference. I got back all that I lost. I'm very happy and pleased. I then had a 4" tip welded on but, I'm going back to have a 3.5" tip welded on instead to tighten up the sound just a bit.

Sorry to be long winded but, Thank You to Otto457 for this information and to the other posters for all of their comments and contributions. Aloha from Hawaii.

curtk69

area of a circle = pi r squared

therefore
single systems;
1-2.25 " pipe =3.97 sq inches
1-2.5" pipe = 4.9 sq inches
1 -2.75 inch pipe =5.93 sq inches
1- 3" =7.06 sq inches

dual systems;
2- 2" = 6.28 sq inches
2-2.25 " =7.94 sq inches
2- 2.5 = 9.82 sq inches

so if my stock 5.4 litre system seems to be about 2 3/8 which is about 4.5 sq inches, wouldnt a slightly upsized set of duals have to be prettty small to avoid having too much flow and sacrifice low end tq for meager high end power gains?
even a 2" dual is gonna flow 40% more than stock....

fordracing63857

I've got an 02 f150 5.4 screw, the stock y pipe was removed and true duals with glasspacks was installed. I was wondering where I should put an x pipe at?

otto457

Where the two sides first come together, usually where the stock Y use to be, is the best place.

02FX4OFFROAD

I really like this thread,tons of good usefull info! Thanks otto

Maverick163

When we installed crossovers on our race cars we used a piece of white chaulk to find the hottest part of the H pipe. We marked a line down each side of the H pipe, ran the engine and noted where the line turned brown on both sides. That's where we installed the crossover. Worked like a charm.

Also, my flow bench guy said there was a lot to consider on head flow when for savenging. For example, a 302 or 5.0 head will drop horse power if you remove material from the bottom of the exhaust port. Those heads need the bump on the bottom of the head for proper scavenging.

We managed 400 plus HP on stock 5.0 heads using a flow bench. Not bad for stock heads.

mike2100

This is the best exhaust thread I've found on this site, but I don't think the answer for my situation has been spelled out exactly (unless I have reading comprehension problems).

My truck is stock with the 5.4 engine. All I want is to hear some of that V8 sound without sacrificing any low end power for towing purposes, because that's all I use my truck for is hauling and towing. I don't want shiny chrome, and I'm not particularly interested in dual pipes unless it will give me significantly more towing power.

I *think* the answer for me is to swap out the stock muffler with a similar length straight through muffler like from Magnaflow, keeping the stock pipe.

What do I get as I move up in price?

- swap muffler: good sound, more flow? (power/mpg)
- custom mandrel tubing (what size for low range towing power?): even more flow?
- pre-built catback exhaust: same as custom mandrel bent system?

jameslleary

Correct, for what you want, just swap out to the muffler of your choice.
You may get a 3-5 hp increase, maybe even lower, maybe a little more.
Try to find a shop that will clamp a few different ones on to hear, and gonfrom there. Yes the Best flow is from a straight through style muffler, you may Like a flowmaster chambered design better. There really is no bad choice.
General rule is, the longer the muffler the quieter. The oval type seem quieter than the round case styles.

mikewayne

Thanks for putting up such an informative post, as there seems to be very myths and other complicating things related to it.