How does this look in terms of a list of mods for my '04 3.9L v6

Krazy_NR

New Member
Jul 2, 2020
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Charlotte, North Carolina
I recently bought a 2004 3.9L as my first car and want to slowly begin to mod it. With some research, this is what I've come up with so far, thoughts?

-K&N 57 Series Cold Air Intake
-BBK 65mm throttle body
-Magnaflow dual exhaust conversion kit with 3" tips (not sure whether or not catback kits for a gt or smth would work or not so this is all I could find on cjponyparts)
-JBA 1619-4 Titanium Ceramic Exhaust Headers (These said they were for a 3.8L but i couldn't find any for a 3.9L?)
-Ford Performance "G" Lowering Springs

I was also thinking of getting a SCT x4 at some point but I have absolutely no idea where to start in terms of tuning.

Any help or advice y'all could give would be awesome, thanks!
 
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Warhorse Racing

Active Member
Feb 10, 2019
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It's always a good idea to plan mods for what you ultimately intend to do with your car. Are you looking to make your V6 a fun daily-driver, or use it for performance driving? Is it going to end up as a street car, drag car, autocross car, or track car? Knowing that will help us help you.

The intake/exhaust mods you've chosen will give the car a little more power and better throttle response. But, the Magnaflow dual exhaust still uses the OEM Y-pipe and cats. To get the biggest improvement, you would want to use an X-pipe that mates up to a GT cat-back exhaust. I have had a good experience with the Trubendz X-pipe on my 2004 V6. I sent you a link to some of my videos in your Welcome Wagon post. The Trubendz X-pipe is covered in the "Mustang ST PART 2" video.

A Trubendz X-pipe and GT cat-back exhaust would cost a little more than the Magnaflow system, but it will perform better.

The Ford Racing "G" Springs are a progressive spring designed for convertibles. They lower the car 1.2 inches. Depending on how you plan on using the car, you might want linear rate springs that don't lower the car as much. Going too low can make these cars handle worse for performance driving. I prefer the Ford Racing "C" Springs for my autocross cars, but they sit higher than most people would consider cool looking.

As for the tune... There are plenty of places that will send you a "canned" tune, or even a "customized" tune based on your mods. And, there's always the option of having it dyno-tuned at a local shop. But, again, it all depends on what you plan on doing with the car. A tune will wake the car up a little. But, in my opinion, the money you will spend on a tuner/tuning would be better spent on 1.8 roller rockers. They add power and strengthen the valvetrain, two improvements V6 Mustangs really need.

Many people will disagree with me about waiting to install a tune. My approach to modding my V6 has always been to solve the weak links first.

I hope this info helps. If you have any other questions, please ask.
 

Krazy_NR

New Member
Jul 2, 2020
7
0
1
18
Charlotte, North Carolina
It's always a good idea to plan mods for what you ultimately intend to do with your car. Are you looking to make your V6 a fun daily-driver, or use it for performance driving? Is it going to end up as a street car, drag car, autocross car, or track car? Knowing that will help us help you.

The intake/exhaust mods you've chosen will give the car a little more power and better throttle response. But, the Magnaflow dual exhaust still uses the OEM Y-pipe and cats. To get the biggest improvement, you would want to use an X-pipe that mates up to a GT cat-back exhaust. I have had a good experience with the Trubendz X-pipe on my 2004 V6. I sent you a link to some of my videos in your Welcome Wagon post. The Trubendz X-pipe is covered in the "Mustang ST PART 2" video.

A Trubendz X-pipe and GT cat-back exhaust would cost a little more than the Magnaflow system, but it will perform better.

The Ford Racing "G" Springs are a progressive spring designed for convertibles. They lower the car 1.2 inches. Depending on how you plan on using the car, you might want linear rate springs that don't lower the car as much. Going too low can make these cars handle worse for performance driving. I prefer the Ford Racing "C" Springs for my autocross cars, but they sit higher than most people would consider cool looking.

As for the tune... There are plenty of places that will send you a "canned" tune, or even a "customized" tune based on your mods. And, there's always the option of having it dyno-tuned at a local shop. But, again, it all depends on what you plan on doing with the car. A tune will wake the car up a little. But, in my opinion, the money you will spend on a tuner/tuning would be better spent on 1.8 roller rockers. They add power and strengthen the valvetrain, two improvements V6 Mustangs really need.

Many people will disagree with me about waiting to install a tune. My approach to modding my V6 has always been to solve the weak links first.

I hope this info helps. If you have any other questions, please ask.

I ultimately intend for the car to mainly be used as a daily driver, MAYBE track days up at the speedway here in Charlotte so I wasn't sure if some of your autocross-specific mods in your youtube series would benefit me any (for example the welded on chassis stiffening mods). I'm honestly just trying to mod the car to not be so sluggish when I hit the throttle and just make it ride smoother.

I'll look into the C springs, as the car already scrapes sometimes coming out of my driveway so I don't want to damage anything.
And as for the tune I was going to just buy a tuner and try to tinker with it myself, though you're probably right about getting it dyno tuned somewhere.
And I would need to get a GT bumper in order to incorporate a GT catback correct? The v6 bumper doesn't have dual cutouts.

Something I did want to look into was soundproofing the car a bit with dynamat at some point, the wind noise on the highway is pretty damn loud but i guess that's what comes with having a convertible though.
 

Warhorse Racing

Active Member
Feb 10, 2019
124
72
38
United States
I ultimately intend for the car to mainly be used as a daily driver, MAYBE track days up at the speedway here in Charlotte so I wasn't sure if some of your autocross-specific mods in your youtube series would benefit me any (for example the welded on chassis stiffening mods). I'm honestly just trying to mod the car to not be so sluggish when I hit the throttle and just make it ride smoother.

I'll look into the C springs, as the car already scrapes sometimes coming out of my driveway so I don't want to damage anything.
And as for the tune I was going to just buy a tuner and try to tinker with it myself, though you're probably right about getting it dyno tuned somewhere.
And I would need to get a GT bumper in order to incorporate a GT catback correct? The v6 bumper doesn't have dual cutouts.

Something I did want to look into was soundproofing the car a bit with dynamat at some point, the wind noise on the highway is pretty damn loud but i guess that's what comes with having a convertible though.

For daily driving, you wouldn't need to go as far as I have with mods. At a certain point, performance mods make the car worse for daily-driving. I only use my cars for autocross.

Your convertible has bolt-in bracing from the factory. It helps, but it's not ideal. If you plan on adding a ton of horsepower or doing a lot of track days, you will want to get some form of weld-in bracing. New Edge convertibles need more bracing if they are going to see a lot of punishment. Bracing makes them more responsive, but it can make the ride more harsh. You should also check the track requirements for convertibles. Many events/tracks require convertibles to have a roll bar. Generally, autocross doesn't require a roll bar for our cars.

You would have to find a GT rear bumper, or just cut the V6 bumper. I cut my V6 bumper with a Dremel and a plastic-cutting bit. Just remember to put tape over the paint to keep it from chipping when you're cutting.

The intake/exhaust mods will add some power, but they will mostly increase throttle response (which feels like more power). For better acceleration, consider rear gears (3.55 or 3.73). They make a big difference in how the car accelerates. Also, adding a Limited Slip Differential will help. A tuner will allow you to correct the speedo for the new rear gears. These cars are heavy and they don't have a lot of torque, so it takes a bit more than intake/exhaust bolt-ons to get them to feel more "present".

As for riding smoother... Most performance suspension mods will tighten the car up for racing. This can lead to increased noise, vibration and harshness. Smoothness can be a function of the shocks and struts. It's a good idea to check your shocks and struts to see how worn out they are. If you want to be able to take control of the ride quality, consider adjustable shocks and struts (they also help in performance settings). And, check your bushings; bad bushings will impact ride quality.

If the wind noise is coming from the convertible top, it's probably the weatherstripping or the top itself letting air in. I don't think sound deadening is going to help that.
 

Krazy_NR

New Member
Jul 2, 2020
7
0
1
18
Charlotte, North Carolina
For daily driving, you wouldn't need to go as far as I have with mods. At a certain point, performance mods make the car worse for daily-driving. I only use my cars for autocross.

Your convertible has bolt-in bracing from the factory. It helps, but it's not ideal. If you plan on adding a ton of horsepower or doing a lot of track days, you will want to get some form of weld-in bracing. New Edge convertibles need more bracing if they are going to see a lot of punishment. Bracing makes them more responsive, but it can make the ride more harsh. You should also check the track requirements for convertibles. Many events/tracks require convertibles to have a roll bar. Generally, autocross doesn't require a roll bar for our cars.

You would have to find a GT rear bumper, or just cut the V6 bumper. I cut my V6 bumper with a Dremel and a plastic-cutting bit. Just remember to put tape over the paint to keep it from chipping when you're cutting.

The intake/exhaust mods will add some power, but they will mostly increase throttle response (which feels like more power). For better acceleration, consider rear gears (3.55 or 3.73). They make a big difference in how the car accelerates. Also, adding a Limited Slip Differential will help. A tuner will allow you to correct the speedo for the new rear gears. These cars are heavy and they don't have a lot of torque, so it takes a bit more than intake/exhaust bolt-ons to get them to feel more "present".

As for riding smoother... Most performance suspension mods will tighten the car up for racing. This can lead to increased noise, vibration and harshness. Smoothness can be a function of the shocks and struts. It's a good idea to check your shocks and struts to see how worn out they are. If you want to be able to take control of the ride quality, consider adjustable shocks and struts (they also help in performance settings). And, check your bushings; bad bushings will impact ride quality.

If the wind noise is coming from the convertible top, it's probably the weatherstripping or the top itself letting air in. I don't think sound deadening is going to help that.
Alright, I think I've pretty much got my list reworked to your suggestions.
Although, a lot of parts that I've looked at say that they are for a 3.8L new edge, but would they still be compatible with my 3.9L?

I really appreciate your help with all of this.
 

Warhorse Racing

Active Member
Feb 10, 2019
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United States
I'm glad I could help.

It's worth mentioning that you might have to shorten one side of the cat-back exhaust to get it to fit with the X-pipe. It depends on the combination of X-pipe and cat-back system you choose. Sometimes they fit perfectly, sometimes they need to have some length taken out to fit correctly.

What specific parts are you concerned about working on the 3.9L?
 

Krazy_NR

New Member
Jul 2, 2020
7
0
1
18
Charlotte, North Carolina
I'm glad I could help.

It's worth mentioning that you might have to shorten one side of the cat-back exhaust to get it to fit with the X-pipe. It depends on the combination of X-pipe and cat-back system you choose. Sometimes they fit perfectly, sometimes they need to have some length taken out to fit correctly.

What specific parts are you concerned about working on the 3.9L?

Im likely going to be using the same flowmaster American thunder catback you used on your autocross mustang.

And the headers I chose and the roller rockers you mentioned in your video said they were for the 3.8L.
 

Warhorse Racing

Active Member
Feb 10, 2019
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United States
My 2004 is a 3.8L. I haven't worked on a 3.9, so I can't be 100% sure everything will fit your car.

It's probably a good idea to double check with JBA and Harland Sharp to make sure the parts will work on the 3.9. As far as I know there are only minor internal differences between the engines, but it's worth confirming that.

I've used Flowmasters on all my cars; some fit fine and others needed to be shortened. I remember needing to shorten the system on my V6 to clear the IRS subframe. There's more room with a Solid Rear Axle, but the exhaust still might need to be shortened.
 

Krazy_NR

New Member
Jul 2, 2020
7
0
1
18
Charlotte, North Carolina
My 2004 is a 3.8L. I haven't worked on a 3.9, so I can't be 100% sure everything will fit your car.

It's probably a good idea to double check with JBA and Harland Sharp to make sure the parts will work on the 3.9. As far as I know there are only minor internal differences between the engines, but it's worth confirming that.

I've used Flowmasters on all my cars; some fit fine and others needed to be shortened. I remember needing to shorten the system on my V6 to clear the IRS subframe. There's more room with a Solid Rear Axle, but the exhaust still might need to be shortened.

Alright, I will shoot both companies an email at some point then.

And if it needs to be shortened, I do have a tig welder and an acetylene torch so I could probably figure it out.
 

Warhorse Racing

Active Member
Feb 10, 2019
124
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United States
I had to cut about 1" out of ahead of the muffler. You might only have to do one side. Just use a piece of 1" tape around the pipe to define the cut and keep it straight. There's always a little bit of wiggle-room for adjusting these systems, so take some time to play around with the fitment before cutting it.