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V6 Mustang Exhaust FAQ

Discussion in 'V6 Mustang Articles' started by Justang, Feb 5, 2004.

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  1. Justang

    Justang ɹoʇɐɹǝpoɯ-ɹǝdns

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    Everything you wanted to know about exhaust systems and more…​

    By Justang​
    All the V6 Mustangs come with a single exhaust. Not only does this look bad, but it doesn’t get any rave reviews in the performance world. One of the first modifications done to the V6 Mustang is converting the weak single exhaust system to a good looking and powerful dual exhaust system. There have been many questions asked on the exhaust system of the V6 Mustang, and we are going to try and cover them all in this article.

    Engine Basics
    Let’s start with how your exhaust system works. First thing we need to know is that the engine is nothing more than an air pump. Sucks in clean air, and pushes it out dirty. The more air you can pass through the engine the more power it has. For this article we are going to focus on how much the exhaust can effectively push out.

    Exhaust basics
    The engines in modern cars have 4 strokes: intake, compression, combustion, exhaust. After combustion the cylinder must evacuate all the burnt gases into the exhaust. This is done by the exhaust valve opening and the piston pushing the gas out of the cylinder and into the exhaust system. The exhaust system has some resistance to the exhaust gases being pushed in because of the diameter of the tubing. This is called backpressure. With significant amounts of backpressure the piston will have to push harder against the outgoing exhaust, and horsepower will be lost. Conversely if the piston doesn’t have to push as hard to get the same amount of exhaust gases out of the cylinder, you will gain horsepower. Backpressure is decreased. How do we decrease backpressure to take advantage of this horsepower? By making our exhaust systems flow more. We can achieve this by bolting on headers, changing our catalytic converters to high flowing catalytic converters, increasing the diameter of our exhaust tubing, and putting on high flow mufflers. In essence we would be increasing the volume of flow, or Flow Volume. But if we increase the flow volume too much, we will start to lose power. Why? Because when you increase Flow Volume you lose Flow Velocity. We want Flow Volume for midrange to top end power. But if we flow too much, we will sacrifice low-end torque. An increase in Flow Velocity will increase low-end torque, but at the sacrifice of midrange and top end power. Thus the main problem of exhaust flow dynamics is revealed.

    Before you decide on any exhaust components, you need to decide what you want out of your car. If you are looking for all out performance, then you will head in one direction. If you are looking for just a couple of bolt ons for a fun daily driver you will want to head in a different direction. Let’s start with what’s available.

    Headers
    Sound is nothing more than alternating high and low pressure waves. In an engine, when the exhaust valve is opened and the cylinder contents are expelled, there is a high-pressure wave introduced to the exhaust system. The high pressure moves at a nominal speed of 1300 to 1700 feet per second. At the same instant the wave of pressure is being expelled the exhaust gases are being pushed out as well. But the exhaust gases are being pushed out at a slower nominal speed of 150-300 feet per second. The shock wave, moving 5 times as fast as the exhaust gases, will pass the exhaust gases and when they hit the first low pressure area, most likely the collector of the header, the shockwave will reverse itself and start heading back toward the exhaust valve at almost the same speed as which it came. The reversed shock wave is called the reversion wave. The reversion wave will then pass through the slower exhaust gases head on, and both will continue in their respective directions. Now, two things can happen. One, the reversion wave will reach the exhaust valve when it is closed and simply bounce off the exhaust valve back toward the collector and it’s energy is simply dissipated in that valve to collector reverberation. Second the shock wave will reach the exhaust valve when it is open. Now two things can happen here depending on which part of the reversion wave hits the open exhaust valve first. If the high-pressure part of the wave (called the Node) hits the open exhaust valve the next exhaust pulse coming out of the combustion chamber will be inhibited and you will lose flow and thus horsepower. But, if the low pressure part of the wave (called the Anti-Node) reaches the open exhaust valve first it will actually help suck out the exhaust from the combustion chamber and subsequently help fill the combustion chamber with fresh air and fuel. This results in added horsepower. What has just been described is resonating frequency. This is what you would call a “tuned” exhaust system. You can obviously see that the length of the primary tube on the headers is of great value. Too short or too long and you’ll hit the closed exhaust valve, or inhibit flow out of the combustion chamber. But if the primaries are the right length, you’ll make some HP! What is the proper primary length for a V6 Mustang? 30” is probably the ideal size, and 22- 24” for people that want to rev their engines really high. This site will give you a rough estimate on what your primary length should be for a given primary diameter and engine size: http://www.bgsoflex.com/bestheader.html

    With all that said there are 2 types of headers that can be put on the V6 Mustang: Short Tube or Long Tube headers. If you ask some people, Short tube headers are never a good idea and Long tubes are the only way to go. But some people don’t want the “hardcore” Long Tube headers and would rather settle with Short tube headers. On a side note, the stock exhaust manifolds will handle up to 300bhp so it is not wise to “upgrade” to short tubes until you reach that goal.
    Short Tube Headers
    Short tube headers are nothing more than stock replacement with a larger diameter primary tube. This will increase flow volume, but will not change the resonating frequency. The only time Short tube headers should be used is when you have to maintain a car that is smog legal or you reach 300hp and don’t want to put on Long tube headers. Some would rather stick with Short tubes because they say Long tube headers sound too aggressive for a daily driver. Some would disagree. ​
    Long Tube headers
    Long tube headers are just what they describe. The primaries are longer than stock and extend below the engine. Mac is the only company that makes Long tube headers for the V6 Mustang. The primary length on the Mac Long tube header is on average 26”. For the person with all out performance in mind Long tube headers are the only way to go. With the Long tube headers you will have to buy the Mac LT catted H-pipe, the Mac LT off road H-pipe, or modify your existing intermediate pipe to fit the LT’s. Either way you will have to delete two of your cats. On a side note, Long Tube headers are not legal for street use in California and some other states.
    For more information about Long Tube Headers, GreenSteeda has made an excelent writeup, which can be found here
    Intermediate Pipes
    The intermediate pipe is the piping from the headers to the cat back system, which includes the catalytic converters. The intermediate pipe can also contain the crossover. A crossover being an H-pipe or an X-pipe. On a V6 Mustang there is no need for a crossover due to the even firing engine. Although there is no need for a crossover on a V6 mustang, it has been shown that having one mellows out the raspy “ricer” sound that occurs above 3000rpm. And a crossover placed in the correct spot may also help with exhaust scavenging. There are only two companies that I know of that make crossovers at this time for the V6 Mustang: Mac and Spintech.
    Mac H-pipes:
    Mac makes a total of 4 versions of their H-pipe. Mac makes a Catted H-pipe (has catalytic converters) for the stock exhaust manifolds or stock replacement headers (Mac or JBA Headers). They also make an O/R (Off Road) catted H-pipe for the stock manifolds or stock replacement headers (Mac or JBA Headers). Next Mac makes a Catted H-pipe (has catalytic converters) for their Long Tube headers. They also make an O/R (Off Road) catted H-pipe for their long tube headers.
    It should be noted that running without cats on your car is illegal. It will only free up a couple top end horsepower, and may result in some lost torque. If you do decide to run without catalytic converters you will need to get mil eliminators or have a chip that will turn off your O2 sensors. I highly recommend against not using catalytic converters. Not only will it hurt the environment, but it also makes a V6 sound like trash!
    When using any of the Mac intermediate pipes you will need to extend the wires on your back two O2 sensors. There are a couple ways you can go about this, you can cut and splice your wires and make extensions yourself for very cheap. Or you could Pay about $40 and but a set of BBK O2 extenders that are plug and play. BBK part number 1676. This kit will work on 1986-2003 models.​
    Spintech X-Pipe:
    Spintech makes a Catted X-pipe (has catalytic converters) specifically for the V6 mustang. They only make this part for stock exhaust manifolds, and/or stock header replacements (Mac or JBA headers). ​
    ** Note GT Intermediate pipes will not fit our cars without modifications.

    Y-pipe kits
    What is a Y-pipe? The Y-pipe on your car is the intermediate pipe on the stock V6 Mustang. It consists of the flanges that connect it to the headers, catalytic convertors on each side, and where the two tubes meet up in an offset center position to form the “Y”. Here is a picture of the stock exhaust system on the V6 Mustang.

    There are a couple companies that make a y-pipe adapter kit for the V6 Mustang. What a y-pipe adapter does is adapt a dual exhaust system to your single exhaust “Y-pipe.” The kit splits up the one tube into two. You get two mufflers and two tail pipes and 2.5” diameter tubing. This sounds really great because no welding or cutting is required for a y-pipe system. The down side to this system is that you have to run all your exhaust through the single tube before you get to the dual exhaust. This is not favorable for the high performance modder. This kit is only good if you want a fun daily driver that isn’t going to be pushing big horsepower.

    GT Take-offs
    The next step up above the Y-pipe kit is GT take-offs. GT take offs come from, you guessed it, a GT. Many GT owners get aftermarket exhaust systems and have nothing to do with their stock exhaust systems. So they sell it to us. It’s a good system. The GT take offs will give you a “true” dual exhaust system. True, meaning that it isn’t just dual mufflers and tail pipes like the y-pipe kits. This system comes with 2.25” diameter tubing and your y-pipe must be cut for this system to work on your car. The down side to this system is that you must cut and weld to make it fit your V6. The up side of this system is that it is a dual exhaust system and you will be increasing your flow volume thus giving you more horsepower, and/or more potential to build horsepower.
    With the GT take off system, you are not limited to the GT mufflers. Any high performance muffler can be bought and adapted to your GT take off system. Muffler tubing size: 2.25". Dimensions: 4"x9"x14" with an offset/offset inlet/outlet style.
    Take offs from any 94-04 GT will require the same modifications to fit a 94-04 V6. The only difference between the years is the hanger style.

    Bullitt, Mach1, and Cobra (1994-1998) Take-offs
    The Bullitt, Mach1, and pre99 Cobras also share the same live axle setup as the GT, so their tailpipes are routed the same way and are no different to adapt to a V6 than a regular set of GT take-offs.

    Cobra (1999+) Take-offs
    The 1999+ Cobras use an Independent Rear Suspension (IRS) setup. The routing of their tailpipes goes under the suspension and gas tank. Thus, a set cannot work on a live axle (V6,GT,Bullitt,Mach1,pre99 Cobra) without modification for clearance or swapping an IRS onto the car as well.

    GT Cat-Back Exhaust
    For the person with big horsepower in mind the GT cat-back exhaust system might be for you. It the same style as the GT takes offs, but comes with 2.5” mandrel bent tubing and high flow mufflers. Mandrel bending is a process where the tubing is bent without changing the diameter of the tubing in the bend. So if the tubing is 2.5” in a straight part, then it’s going be the same 2.5” in the bends. Most muffler shops don’t use this type of bending, and neither do the GT take offs, they use a bend press. Bend pressed tubing is not a consistent diameter through the bends. The tubing diameter will decrease in size depending on the angle of the bend. Since the mandrel bent tubing is the same in the straight parts and the bends, you get better flow. This system gives you all the room to grow that you need. This large tubing is not needed if you are going with just bolt ons, but if you plan on a Supercharger or an Extreme NA system, then this might be the choice for you. Once again, you’ll have to cut and weld this system into place if you still have your y-pipe.

    Mufflers
    There is no one muffler that sounds the best. It’s all a matter of opinion. If you ask anybody which muffler is best, they will most likely tell you that whatever exhaust they have is the best. If you need a place to listen to the most popular mufflers, visit the 3.8mustang multimedia section. http://www.3.8mustang.com/multimedia There really is no reason to have other people give you their opinion, you may like something totally different.
    GT Muffler size is:
    Dimension: 4"x9"x14"
    Tubing: 2.25"
    Inlet/outlet: offset/offset

    Difference in sound between the years:
    There is NO difference in the way any exhaust system will sound between a pre99 and a 99+ V6 Mustang. The firing order is the same. The cam may be a little more “wild” on the pre99’s, but that does not make even the slightest difference. If you think you can tell a difference, then you are kidding yourself.

    Tubing Size
    - 2.25” is good for most people that just want bolt ons and don’t want a y-pipe kit, or for the person that will have a mild NA setup.
    - 2.5” from a y-pipe kit is good for bolt ons and a better exhaust note.
    - 2.5” is for the people that want superchargers, or extreme NA applications. For people that plan on making big power from the V6 Mustangs.

    Here's a list in order of least to greatest in terms of flow rates:
    Single 2.50"
    Dual 2"
    Single 3"
    Dual 2.25"
    Single 3.25"
    Dual 2.50"

    [​IMG]


    Chrome exhaust tips
    These will not increase flow, they will not make your car louder, they will do nothing more than make your car look a little better.

    Exhaust Hangers
    You can have a muffler shop put in custom hangers if you have them do the installation. Or you can go to Ford and get the hangers from a GT of the same year as your V6.

    Average Horsepower Gains
    If you are just converting your car to dual exhaust or getting a y-pipe, you can look to gain anywhere from 6-10rwhp. Results may vary. Headers and Catted H-pipes may vary your Horsepower levels depending on the modifications that you have. Long tube headers will always produce more horsepower than stock or after market Short tube headers.

    Sounding like a V8
    No matter what muffler, tubing, cat, or header configuration you have, it will never sound like a GT. The GT has two more cylinders and has an odd style firing order that gives it its exhaust note. An odd firing engine will fire two cylinders on the same bank (A bank is one side of the engine) in succession. The V6 has an even style firing order. An even firing engine will fire one cylinder on one bank then another cylinder on the opposite bank.

    Exhaust and Warranty
    A new exhaust will not void your entire warranty. But it will void your exhaust warranty.

    No dual exhaust on a V6 Mustang?
    If any shop tells you that dual exhaust won't work on a V6 then take your car some place else. They do not know what they are talking about, or what they are doing. Wether they say the passenger tail pipe is too close to a brake line, or a fuel line, or anything else, they are wrong. Thousands of V6 Mustangs have dual exhaust with no problems.

    Price of Installation
    If you supply all the parts you should never pay over $200. Most places you will find will charge $100-$150 to install parts. If you have them make your own system, then the sky is really the limit. I would suggest buying your parts and having them installed. There are many great kits that are available for the Mustang. And if you have a Y-pipe, install it yourself. It’s a simple bolt on if you have a jack and some jack stands.
     
    pacbelt likes this.
  2. greensteeda

    greensteeda Retired Speed Racer Mod. Suck It!

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    Lots of people have questions about Long Tube headers. I have had some experience with them, to say the least, so I thought this post could clear up some questions and be a point of reference so the same questions don’t keep popping up. We are not angry at questions but it does get redundant answering the same questions over and over again.

    What are Long Tubes?

    Long Tube headers are just that. Headers that have long primary tubes. To be more specific, the primary tubes are the pipes that come directly off the engine before coming together in the exhaust pipes. Here is a picture of Mac long tubes.
    [​IMG]




    Why do I need them?

    Well as you may already know, and if you don’t here ya go, the better your engine can breath the more horsepower you make. Its like a big air pump. The long tubes help your engine exhale better than stock headers. Most people don’t NEED long tubes until they have done all the basic bolt-on’s and even some mild engine work. A lot of people will use 300 hp as a benchmark to upgrade your headers. Stock headers on the V-6 flow very well for stockers, and replacing them on a nearly stock engine will not net a lot of power. Dyno’s have seen gains from 5-10 hp on stock engines and will show more gains with the more engine work that is done.

    How do they work?

    Here is the best way to explain it, this is in the exhaust sticky that has been written already by Justang.

    “Sound is nothing more than alternating high and low pressure waves. In an engine, when the exhaust valve is opened and the cylinder contents are expelled, there is a high-pressure wave introduced to the exhaust system. The high pressure moves at a nominal speed of 1300 to 1700 feet per second. At the same instant the wave of pressure is being expelled the exhaust gases are being pushed out as well. But the exhaust gases are being pushed out at a slower nominal speed of 150-300 feet per second. The shock wave, moving 5 times as fast as the exhaust gases, will pass the exhaust gases and when they hit the first low pressure area, most likely the collector of the header, the shockwave will reverse itself and start heading back toward the exhaust valve at almost the same speed as which it came. The reversed shock wave is called the reversion wave. The reversion wave will then pass through the slower exhaust gases head on, and both will continue in their respective directions. Now, two things can happen. One, the reversion wave will reach the exhaust valve when it is closed and simply bounce off the exhaust valve back toward the collector and it’s energy is simply dissipated in that valve to collector reverberation. Second the shock wave will reach the exhaust valve when it is open. Now two things can happen here depending on which part of the reversion wave hits the open exhaust valve first. If the high-pressure part of the wave (called the Node) hits the open exhaust valve the next exhaust pulse coming out of the combustion chamber will be inhibited and you will lose flow and thus horsepower. But, if the low pressure part of the wave (called the Anti-Node) reaches the open exhaust valve first it will actually help suck out the exhaust from the combustion chamber and subsequently help fill the combustion chamber with fresh air and fuel. This results in added horsepower. What has just been described is resonating frequency. This is what you would call a “tuned” exhaust system. You can obviously see that the length of the primary tube on the headers is of great value. Too short or too long and you’ll hit the closed exhaust valve, or inhibit flow out of the combustion chamber. But if the primaries are the right length, you’ll make some HP! What is the proper primary length for a V6 Mustang? 30” is probably the ideal size, and 22- 24” for people that want to rev their engines really high. This site will give you a rough estimate on what your primary length should be for a given primary diameter and engine size.’’ – Justang


    Fitment?

    The headers are made for years 94-97, 99-00, and 01-03. These are the years that you can order specifically for. Now, you might wonder to yourself “But I have a 98/04, what do I do?”. Well this is a common question and has a simple answer. The 04s will fit on the 01-03 and the 98s will fit the 94-97 but you will have to bend and modify the EGR tube or just delete it all together. So if you have a V-6 you can get long tubes.

    Installation:

    I will first start by saying that it is not that hard, just time consuming. To start off jack the front of the car up as high as you can and put on jack stands or have some roll on ramps if you can get on them. Then for safety chock the rear wheels and unplug the positive on the battery.

    Drivers side – On my 2002 the EGR tube is on the passenger side but if yours is on the drivers side then just scroll down and look what to do when I go over it on the passenger side. First unbolt the dipstick holder, then using masking tape label the spark plug wires and where they go (its very bad to cross your wires). Remove the spark plug wires and unbolt the distributor box, I took mine off completely so I could get them out of the way. Then unbolt the headers. Space is tight so do yourself a favor and get some ratcheting closed-end wrenches. To get the old headers out, I recommend cutting the old pipes right after the secondary cats and sliding headers and cats out from the bottom.

    Passenger side – Take off the air intake from the throttle body to the filter and put a bundle of paper towels in the throttle body to keep crap out of there. Treat the sparkplug wires the same as you did the drivers side. Remember to label the wires. On this side I had to disconnect the EGR tube, I first unbolted the pipe from the EGR solenoid. Then unscrew the tube from the old headers. Unbolt the headers and slide out from the bottom.

    To install the long tubes simply slide them from the bottom of the car and re-install everything that you took off

    Important note: When installing new headers always use new exhaust gaskets. The old ones will fit but you don’t want to have to redo everything because of a leaking gasket.

    What else do I need?

    You will need some sort of mid-pipe to connect to a dual exhaust cat-back system. You can either get an H or X pipe, catted or not. You can even get an exhaust shop to make you something custom but most shops wont work on cars that don’t have cats and I recommend that nothing ever be welded to your headers because you most likely will need some sort of transmission work at some point in the cars life. You will need to get the midpipe made specificaly for long tube headers. This midpipe will act as an addapter so that you can use any exhaust made for your year GT

    FAQ’s:

    Q: Are they legal?
    A: Yes and No. It all depends on if you need emissions testing and how strict the testing is. If you live in California, don’t even think about long tubes. Anywhere else you can usually get by with having some high flow cats on your mid-pipes. If you don’t have testing then your good to go.

    Q: How low do they hang?
    A: They hang a little lower than your stock cats do right now. If you have a lowered car then you will need to be careful going over speed bumps. I have scraped them rather hard and nothing had happened to the headers. Look at picture below

    [​IMG]
    [​IMG]



    Q: Do they delete my cats?
    A: Yes, all four, but you can get cats on the mid-pipe.

    Q: How do they sound?
    A: Look at the sound clips in my signature for a sample. I have Mac LT headers, Off Road H-pipe and Mac 2.5 inch exhaust

    Q: Do they rust?
    A: They can rust but with some header paint it should be no problem. They may surface rust but that’s as deep as it goes, it will actually prevent further rusting so once it starts to rust do not keep removing the rust.

    Q: Are there any Heat Issues?
    A: Less than stock headers actualy. You will run no more risk of burning plug wires than you would if you stayed with your stock headers. The have the same amount of heat at the top of the primaries (right off the block) and by the time the gas gets to the collectors it is actualy cooler than it would be with your stock setup due to more surface area for the heat to disapait.

    Q: Do I have to extend the O2 sensors?
    A: Yes, you will have to for all four sensors. Just splice the wires and you will be good to go.


    Q: Will I get a Check Engine Light?

    A: If you go with no cats at all yes you will have a CEL. If you have cats then most likely you will not. To turn off the CEL just get some MIL elliminators or get a tuner/chip that turns off the rear O2 sensors


    Q: Where can I get them?
    A: Several places carry them, just google Mac Exhaust


    If there are any more FAQs just let me know and i will keep adding them untill i get them all. hope this helps
     
    pacbelt and GreyHorse like this.
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