Have a 99' F150, 5.4. When I bought it, it had a single flowmaster muffler with two exhausts straight out the back. I didn't like the extra noise, so I had the muffler changed back to stock, but kept the dual straight out the back pipes. Question is this: Would going back to the single pipe out the rear side increase mpg, lose any performance, pros & cons? Does the engine need a certain amount of backpressure? Main question is will it increase mpg any? Thanks for help.

 

A friend just put dual exhaust on his 5.4L and said his MPG went from 16 to 23. I'm just lookin around to see if anyone else has had the same increase in MPG. If I see one, I'll let you know

 

There's nothing you can bolt-on to your truck that will give you a 40-50% increase in MPG (to go from 16 to 23 mpg).

Even the mild hybrid Chevy trucks only get 10% in city driving...

 

With the 5.4, id be surprised it'd get 16 with a intake/exhaust....23mpg out of a 5.4=

 

Don't laugh......

I drove from Glasgow, KY to Powell, TN recently. Topped off before I left and when I arrived. 195.8 miles, 8.33 gals.

 

Ok, I see the 23 there. I guess the change in MPG was 16 city before the exhaust then to 23 Hgy after. This would be poss, but otherwise I would waive the BS flag if we had one here

 

A) That's retarded !
B) Automotive engineers fight constantly to meet MPG requirements using all means possible.

 

Your biggest problem is the OEM muffler. I'd just find a quieter, but less restrictive muffler. A different Flowmaster, or larger Magnaflow, Spintech, etc will be better. If you like the look, keep the dual pipes. They affect performance (including fuel efficiency) very little.

 

flowmaster claims a 5-10% increase in HP and a 1-2MPG increase.

I imagine when you slapped your old stock exhaust back on, you pretty much shot any chance of increase in either of these.

http://www.flowmastermufflers.com/cg...aster/faq.html

qouted from the link above

"An "H" pipe added to a true dual exhaust will help equalize the pressure between both banks of the engine. This will give you a torque increases throughout the rpm range and also helps eliminate any "back-rap" and also mellows the tone both inside and outside of the vehicle."

from magnaflow http://www.magnaflow.com/07techtips/faq/question14.asp

"Question: Does a dual cat-back exhaust system perform better than a single?

Answer: In most cases a single exhaust will give you better torque and horsepower. The exception would be a heavily modified engine."

Hope this helps answer your questions!

--
KBL