Cat-back vs muffler

[Inspector13]

Is a cat-back exhaust worth it as opposed to just replacing the muffler?? I'd like to get as much fuel economy out of the Ex as I can. I was looking at getting a 2.5 inch single exit cat-back for my 4.0 Ex but don't know if I wanna spend the money on one. I just replaced the mufflers on my '96 Mustang GT as the cat back that was on it (Flowmaster) was rubbing on the tires. So I have two 2.5 inch Flowmaster mufflers (that are in good condition) sitting in my garage. I'm not expecting a whole lot of MPG out of a cat-back but would it be more then just replacing the muffler???

 

[JoshMcMadMac]

Is a cat-back exhaust worth it as opposed to just replacing the muffler?? I'd like to get as much fuel economy out of the Ex as I can. I was looking at getting a 2.5 inch single exit cat-back for my 4.0 Ex but don't know if I wanna spend the money on one. I just replaced the mufflers on my '96 Mustang GT as the cat back that was on it (Flowmaster) was rubbing on the tires. So I have two 2.5 inch Flowmaster mufflers (that are in good condition) sitting in my garage. I'm not expecting a whole lot of MPG out of a cat-back but would it be more then just replacing the muffler???

A muffler will make no difference in fuel economy, and a cat-back exhaust will not make enough difference to pay for itself strictly on the merits of gas mileage. You would see more return on investment with under drive pulleys and an electric fan. A cat-back is nice for a little performance gain, though, and a great improvement in sound.

 

[Triton8273]

A muffler will make no difference in fuel economy, and a cat-back exhaust will not make enough difference to pay for itself strictly on the merits of gas mileage. You would see more return on investment with under drive pulleys and an electric fan. A cat-back is nice for a little performance gain, though, and a great improvement in sound.

What he said.

 

[Inspector13]

I'm doing an electric fan but I won't put an underdrive pulley on. They only make a crank pulley (from what I found) and I do not like the idea of straining my water pump and alternator. If they also offered a water pump and alternator pulley I would. Just wondering if a full cat back was that much better then just a muffler (they said that they are also going to remove the "resonator").

 

[skysthelymyt]

You won't see any mpg gains from a Flowmaster. All my friends that ran them got worse mpg and when they switched to a Magnaflow (with the same pipe setup just changed the muffler) they gained 2-3 mpg. Flowmaster mufflers to my knowledge don't offer anything but noise.
But like they said, the cost of the cat-back won't be enough to pay for itself in milage gains.

 

[therover1991]

honestly after I installed my magnaflow catback I saw no increase in mpgs. maybe its because I mostly do city driving where I live? however performance gains were noticeable. Nothing crazy, but its there.

 

[HiImBrian]

Nobody gets better mileage from upgrading their exhaust. Pedals hit the floor a lot faster when it sounds good.

 

[Inspector13]

Nobody gets better mileage from upgrading their exhaust. Pedals hit the floor a lot faster when it sounds good.

No worries. I have the old man driver mod. Part of the reason I am currently getting between 18.4 and 19.7 mpg city/highway on 87 octane. So far my best highway was 26.4 mpg.

I had a modded Silverado Z71 that used to get 21 mpg average with combined city/highway and on 31 inch mud tires and blowing through a Flowmaster. I'd like to best that at least.

 

[Sams01XplrSprt]

what series are your flowmasters

 

[Kazer]

I'm doing an electric fan but I won't put an underdrive pulley on. They only make a crank pulley (from what I found) and I do not like the idea of straining my water pump and alternator. If they also offered a water pump and alternator pulley I would.

I obtained this pulley from Underdog Performance ( http://underdog-performance.com/index.html ). The pulley cost $90.00 to my door, and was red anodized aluminum. Its aluminum construction allows for less rotational mass.

In an endeavor to resolve my charging voltage at idle quandary ( http://www.explorerforum.com/forums/showthread.php?t=152430&highlight=alternator ),
I ordered an overdrive alternator pulley from Underdog Performance ( http://underdog-performance.com/index.html ). Of course it had to be red to match my underdrive water pump pulley (http://www.explorerforum.com/forums/showthread.php?t=153779&highlight=underdrive ).

The pulley cost $40.00 delivered to my door.

For those who don’t understand underdrive/overdriving, let me reiterate; to underdrive the crankshaft, you use a smaller ( than stock ) diameter pulley, whereas to overdrive the alternator ( or any other accessory ), you also use a smaller diameter ( than stock ) pulley; a larger pulley on an accessory would underdrive it.

My Underdrive water pump pulley

 

[Inspector13]

I know very well how pulleys work. To under-drive (turn slower) the accessories you need to A) put on a smaller crank pulley or B) put on larger accessory pulleys, never both. The crank can not be under-driven or over-driven because it is always turning at a 1:1 ratio with itself. Unfortunately I have not found the corresponding pulleys for the water pump and alternator to go along with the crank pulley to keep up with the demand needed.

Say the crank pulley is 30% smaller then factory, thus under-driving (turning slower) the accessories by 30%. Now say the alternator can only be under-driven by 20% and the water pump can only be under-driven by 15%. The smaller crank pulley under-drives them to much and you don't get the amperage or cooling capacity needed to adequately run the vehicle. So to get the accessories over-driven (turning faster) to where they will put out an adequate amount to properly run the vehicle you put on smaller pulleys (which turns them faster), but not as small as the crank pulley. You would use a 10% smaller then factory alternator pulley (which would bring it up to being under-driven by 20%), and a 15% smaller then factory water pump pulley (which would under-drive it by 15%). Make sense???

BTW your links to the store don't work.

I was just wondering where the restriction was in the exhaust. The muffler or the piping. Apparently it is the piping as everybody says that the factory muffler flows just as good as any aftermarket muffler. As there are no power gains to be had by replacing the muffler.

 

[Inspector13]

After just the muffler on my Explorer on the 10th and running a few tanks through her, I am now averaging between 20.3 and 21.7 mpg (up from 18.4 to 19.7) and that is with true 30 inch tires too. Both tanks of which I spent a bit of time city driving and sitting in road construction. Sounds like crap but it gets the job done (really V6 sounding and I don't like it). Doesn't down shift as often or for a long as it used to. Ended up costing me about $10 bucks for clamps and **** and an hour of my time. Could squeeze some more mpg out of it if I made the piping bigger, but for $10 I won't complain. Thanks all. :mattmoon:

 

[JoshMcMadMac]

After just the muffler on my Explorer on the 10th and running a few tanks through her, I am now averaging between 20.3 and 21.7 mpg (up from 18.4 to 19.7) and that is with true 30 inch tires too. Both tanks of which I spent a bit of time city driving and sitting in road construction. Sounds like crap but it gets the job done (really V6 sounding and I don't like it). Doesn't down shift as often or for a long as it used to. Ended up costing me about $10 bucks for clamps and **** and an hour of my time. Could squeeze some more mpg out of it if I made the piping bigger, but for $10 I won't complain. Thanks all. :mattmoon:

Your mileage most likely went up do to the summer shift away from blended gasoline, as the muffler definitely is not the source.

 

[Inspector13]

Went up several weeks ago from the usual 16-17 I get in the winter up to it's normal 18-19 (as it has the past 2 years). I've never averaged over 20 with mixed driving, on the interstate yea but never mixed city/highway. Especially not 2 tanks in a row and doing more city driving then normal for me. Switching to a summer blend also wouldn't explain why it doesn't down shift as often going up hills or when it does down shift it doesn't stay in the lower gear for as long as it normally has for the last 2 years either.

 

[College Student]

Similar question so no need for a new thread/

I'm wondering how a cat-back can be beneficial compared to just a muffler when a cat-back exhaust is basically a new muffler and new piping. But the new piping is the same diameter as what is on the x already so no benefit there. Meaning the muffler is the only difference. So why is replacing the muffler with magnaflow or flowmaster or cherry bombs not act the same as buying a twice as expensive cat-back system from the same companies?

 

[JoshMcMadMac]

Similar question so no need for a new thread/

I'm wondering how a cat-back can be beneficial compared to just a muffler when a cat-back exhaust is basically a new muffler and new piping. But the new piping is the same diameter as what is on the x already so no benefit there. Meaning the muffler is the only difference. So why is replacing the muffler with magnaflow or flowmaster or cherry bombs not act the same as buying a twice as expensive cat-back system from the same companies?

The piping is not the same size as stock, it is larger.

 

[College Student]

The piping is not the same size as stock, it is larger.

According to magnaflow the cat-back is 2.5 in diameter pipe with 3.5 in tip. Then according to my car which is stock

Now forgive me for the fact that the pipe is round and that i cant get a true picture of it since I'm trying to do all this while laying in gravel. But I can assure you that it is 2.5 in in diameter. So I'm back to the only difference being a muffler...oh and a pretty tip.

Edit:
Here's the end, which is not just some tip that's larger than the rest of the pipe. Mine stays a continuous size the entire way. except the minuscule changes due to bends.

 

[JoshMcMadMac]

The factory exhaust is 2.25", not 2.5". Wrap a string around your round exhaust pipe, measure that distance, and divide by 3.14. Also keep in mind that is OD, not ID.

 

[College Student]

Alright, I understand didn't know which they were measuring. Now a few more questions.
Q1: How would the expel so much better if it is already being constricted by the manifold and cat. Without changing the diameter of the those by buying headers and high flow cats, wouldn't the larger cat-back be useless.

Q2: I keep being told by my father that the back pressure needs to be there or there is the potential to damage the engine. I searched here to find out the opinions. I read on one thread that there is no need for any back pressure, and that its only purpose is to basically set the exhaust to a rhythmic frequency to expel exhaust at the perfect rate. ???

Q3: If I never planned on upgrading the manifolds and cats then wouldn't a muffler with the same pressure rating be the best option?

Q4: Besides sounding like an odd idea. Would it be irresponsible or a bad idea to create a custom cat back exhaust by buying a new muffler with larger diameter outlet say 3 in. and then bend 3in. conduit to flow under the body like the stock system. In essence doing the same as a body shop?

 

[Kazer]

The factory exhaust is 2.25", not 2.5". Wrap a string around your round exhaust pipe, measure that distance, and divide by 3.14. Also keep in mind that is OD, not ID.

x2