i have a 97 f-150 with the 4.6 and the auto tranny with a flowmaster 2.5 in and dual 2.25 out (came on truck) exits out the rear with 3.5 inch tips. i want a loader exaust i was thinking of going with true dual 40 series flowmasters (not delta flow) with a X pipe and turndowns on them. i did a search and don't know if i should get 2.5 or 2.25 inch mufflers. which will have a better sound and power? is this even a good set up? when mounted how do the mufflers sit? if anyone has a picture of your mufflers please post it. i know this is a common question but i don't understand why the 2.25 will be better than the 2.25 please help!!!

 

If you want it loud, go with a Dynomax Super Turbo muffler; those things can get fairly loud. Stay with the 2.25" pipe for backpressure reasons; it'll help with down-low torque.

-Flea

 

If i put true dual straight pipes on my 4.6 would 2.25 be too small? Or should i go with 2.5. If i decide to weld in mufflers or glasspacks later on, which pipe size should i go with??

 

Green 98,
get 2.5 thats what i have on my 4.2l and lost no power, with 2.25 you would be restricting the air flow.....

 

With the 4.6L you need to be careful when doing exhaust upgrades to not open things up too much. When you put a high flow exhaust on you free up flow and increase your low and hgh end power. That is achieved by reducing how much the engine has to work to evacuate spent exhaust. If you install a high flow muffler and run larger pipes you run the risk of loosing too much back preasure. With that set up you gain high end power which is good for runnin at highyway speed and bad for all other driving situations. 2.25 is more than enough if you are going to run duals, 2.5 or three for single depending on the muffler. All this is for the 4.6L ,5.4L may be different.

 

Check this out.

Flatsman went to 2 1/2" pipe on his highly modded 4.6 and lost 17 HP. He eventually had some restrictors made up to regaing the power. I know it contradicts logic but bigger pipes can rob power from modular motors.

Good luck.

 

thanks for the info LE PEW
it looks like i am going to have more time to do research on exhaust systems. the money that was going to the exhaust is now going to school and some tools i need for school. being in school sucks at times.

 

I kept the piping stock at 2.5... no problems. I have the cat. back system, though. Not true duals.

 

restrictors?
How do they look like and where do you install them?

 

Here is the restrictor thread that shows the handiwork. If I recall correctly he had them custom made but there are other ways to achieve the same effect.



Here's the original thread that showed the HP loss backed with dyno runs. Enjoy, it's good reading.

Good luck.