Now don't spaz... but here is a VERY informative link - i love that I found it, and have been pouring over it for some time now - from a chevy site:

http://superchevy.com/technical/engi...xh/index1.html

Additional research I've done, via the web and a very knowledgeable Summit Racing tech guy (Thank you Wes!) has me up to snuff on muffler cfm-flow performance characteristics. Glad I took the time, as I had read last night that two online sources recommended Dynomax over Flowmaster, but I was apprehensive as so many people are choosing Flowmaster. Turns out the DynoMax Super-turbo actually does outflow a 40-series by about 100 cfm, which is just peachy for me. I'm back to a single exhaust system, which should be good for the scavenging effect.

I cancelled the Flowmaster 1-into-2 system I had ordered, and Summit made me a custom-priced single-in, single-out system (as Dynomax doesn't list one for the extended cab Long-bed trucks).

Life is good again.

Bought a Tonneau cover and some polyurethane end-links too. This truck will eventually run fine.

(insert obligatory geico commercial quote here)
"You can do it!!!!"

 

The major restriction in the exhaust is the cats, not the muffler. Dynomax makes a good muffler. It is quieter than a Flowmaster, but has a little rumble to it.

 

My F-150 with it's cat-back duals and Flowmaster doesnt get any better milage than the F-150 my father drives, which has completely stock exhaust.
Mine sounds a whole lot better though! LOL
Octane

 

well, i'm not sure why, but after a tune-up i'm still getting about 11 MPG here, so anything will help!

while those danged cats probably are the restriction, i'm betting that the muffler adds to the restriction somewhat. I haven't spent enough time under it, but how many cats, and what are our options for high-flow cats?

 

My '99 has 2 cats, one just after each exhaust manifold.
Im getting 18 mpg highway with my F-150: 4x4, reg cab, 8' bed, 5.4L with automatic and 3.73 gears.
Not sure why you are only getting 11 mpg, perhaps you have a heavy foot.
Octane

 

yeah, i have a heavy foot sometimes, but that was averaged out over a 1100 mile trip as well (where I wasn't flying).
Ext. Cab, long-bed, 4x4 w/ 3.55's, slightly bigger tires, 5-speed.

Not sure wha'ts going on, but my service engine soon light is now on (in addition to the ABS and brake lights for the ABS module it isn't going to get soon).

 

well, get the codes pulled. go from there.

 

Theres your problem: 3.55 with larger tires. If you want to run bigger tires, you should really regear it.
Octane

 

well, whats "slightly" bigger?

 

265/75/16's

they came with the truck, and I assumed they were slightly larger. Not sure they are 'it' for the problematic fuel mileage though. I realy do nned to get the codes pulled.

 

Okay, I will weigh in with a few questions that I know have been asked a million times elsewhere on this board. I am asking again only because the posts that I have read (I did do a number of searches) either seem to conflict in their advice or not be exactly what I am looking for.

Right now I have a '97 F150 XLT with basically no modifications. I am considering putting in dual exhaust mainly for the look and sound. Before I get to far with anything, I have several questions:

1. What is the deal with the check engine light? Some posts indicate that putting in dual exhaust requires removal of oxygen sensors, resulting in permanent check engine light on. Is this the case? Is there any way around it?

2. What are the various configuration options? I have hear catback. I assume this means splitting the exhaust after the catalytic converters. Is that right? What other options are there?

3. How do I know what diameters to select? I have seen a number of posts that recommend different inlet and outlet diameters for the mufflers. Is this a model year specific thing or is it a preference thing for sound?

4. What is the difference between the various flavors of Flowmaster? I have seen people refer to 40-series, 50-series, etc. Again, is this just a preference thing or is there a right choice and a wrong choice for various model years.

5. What is a reasonable total cost to expect for my local shop (not Ford dealer) to take my truck from stock to the correct dual exhaust configuration. Am I looking at a couple of hundred bucks or a thousand bucks? I was thinking it was a pretty major deal, but some have refered to doing the work for just a few hundred bucks. I think I could convince the wife to go for it if is that cheap.

I am sorry to repeat questions that have already been asked, but I really have tried to find all of these answers by searching, but I am still quite confused. Thanks.

 

1. True duals, real ones, run back from each exhaust manifold. When doing this it takes some parts and fabrication to allow places for O2 sensors - most people skip the O2 sensors and thus get a warning light (and poorer fuel economy from what I've seen)

2. correct on cat-back. From a cat-back, you can do duals, or a single to a muffler which makes duals, or a single to a muffler to a single. None of these are true duals, and I'm critical of the true gains made by splitting the exhaust so (duals) post catalytics with the 4.6 as it is so small. I, personally, am going for a single-in, single-out free-er flowing exhaust. I can't tell you that I am any more right than anyone else though. (I don't want to do all the calcualtions)

3. It's a truck, not a sports car, so you'll probably want low-end torque. Bigger diameters flow more, but can lose that low-end torque due to the exhaust cooling and a loss of scavenging. THe problem I see is - just how small of dual-exhaust pipe diameter do these small V-8's really need to maintain a heated exhaust? I don't know, but I'm nt sure I'd want to see it. Maybe 2-inchers would work.

4. look to Flowamster's site, they have descriptions. Basically the 40 flows more than the 50, and is louder. I gave up on flowmaster based on my research though. They aren't bad, but people are buying them primarily for their sound.

5. first, i expect that if you really try, you'll get conflicting reports of what dual set-up is really 'right' for you. You need to do your own research and base your focus on where in the RPM range you want power, or if you really are just going for sound and looks (in which case you hi-jacked this thread). They sell Flowmaster kits (with 50-series) at Summit Racing. Call them up and ask for something that looks and sounds nice. If sound is a goal, you really ought to find a few similar trucks you like the sound of and ask what systems they have on theirs.

Best,

 

Why can't you fab up a Mustang exhaust to fit under your truck? It's a 4.6 and "true dual", from headers to tips. You could get an H-pipe with high flow cats and then straight pipe the rest of the way out. My brother had this set-up on his '95 GT and it sounded good. This way you would have your cats, so as to be legal (federally and morally), as well as somewhere to plug your o2 sensors in, and you'd have your low restriction exhaust that you think will increase your gas milage. Either way, the bottleneck is definately in the cats on this engine, so getting some high-flow cats and keeping the stock exhaust will get you better results than vice-versa. I am a recovering Mustang addict, so I know a thing or two about the 4.6l engine, albeit not so much in a truck, but it's still the same animal.

 

Onespeed, how much are high-flow cats, and are there brands you recommend?

I live in a state that doesn't check for -anything- ... -ever- , so I feel I could get away with losing the cats altogether as long as I had a place for the O2 sensor(s?). But at this stage i'm not sure I want to pollute the environment that much, thus if high-flows work I would consider them. (I would think that in this day and age the auto manufacturers would already be using high(er)-flow cats.)

 

Thanks for the info, and sorry for the hi-jack. You are right, that is what I did.