Michael Johnson
Technical Editor
January 4, 2014

When I purchased my 2001 Ford Mustang Bullitt, one of the first things needing attention was the exhaust. It was pretty obnoxious; it sounded more like a dump truck rather than a Mustang. It had a deep tone that really didn't change no matter what rpm I was at. It was like talking to someone with a monotone voice with no variation in pitch. It was rather annoying and loud.

What I noticed when my buddy Jeff Foster looked at the car was that the exhaust was void of an intermediate pipe. No X-shape crossover or H-pipe at all. There were just two straight pipes with catalytic converters, and then an after-cat exhaust. It didn't sound good at all and no one liked the sound ... not even a little bit. Of course, a Mustang's sound is its trademark, so an immediate fix was required.

Since Brothers Performance's Deland, Florida, location isn't far from our Tampa office, we decided to see how the company could help us with this malady. Together with Brothers Performance reps, we decided on a BBK Performance X-shape crossover pipe combined with a Flowmaster after-cat—a classic combination sure to cure our dump-truck blues.

Something that stood in our way when we first talked with Brothers about the install was our Bullitt's suspension upgrades. The car boasts a full Maximum Motorsports Grip In A Box with a torque arm, Panhard bar, K-member, and the like.

In talking to Maximum Motorsports and Brothers Performance, we weren't sure if BBK's X-shape crossover pipe would work in conjunction with the torque arm's mount at the transmission crossmember. Plus, we had to worry about whatever after-cat clangin' and bangin' on the Panhard bar.

Communicating with Maximum Motorsport's reps, we were told the X-shape crossover would be close, but they also told us a Flowmaster after-cat, which follows closely the factory exhaust's route, is a good choice.

We pondered removing the torque arm from the car, which would necessitate reinstalling upper control arms. We didn't really want to do that, but fixing the exhaust note was paramount. Thankfully, we didn't have to remove the torque arm or the Panhard bar in this case, which made me happy. Plus, I now have an exhaust that makes my Bullitt sound like a Mustang, which is cause for celebration.

We were hoping for 250 rwhp after the exhaust since the car made around 247 hp at the wheels back on the Dynojet at our Tampa office. Here’s our Bullitt project car up on the Dynojet as James Gordon of Tuning by James straps her down to the Dynojet. Brothers Performance uses this Dynojet to test its performance packages and for car shows at its Deland, Florida location. We were hoping for 250 rwhp after the exhaust since the car made around 247 hp at the wheels back on the Dynojet at our Tampa office. Would it make the number? James told us right off the bat that Brothers’ Dynojet was a tad bit stingy, which didn’t bode well for our Bullitt. It needs all the horsepower it can get.
Here’s what the car’s existing exhaust looked like. Notice the lack of an intermediate X-shape crossover or H-pipe. Evidently, the previous owner probably arranged the exhaust to work around the suspension. However, the lack of a crossover pipe with the catalytic converters contributed to our Bullitt sounding more like a dump truck.
The after-cat exhaust we chose for the Bullitt is Flowmaster’s Force II kit (PN 17267; $529.99). This kit is designed for ’99-’04 Mustang GT, Mach 1, and Bullitt models with a 4.6 engine. It’s a 21⁄2-inch system featuring Super 50 Series mufflers; mandrel-bent, 16-gauge, aluminized tubing; and 3-inch tips. This Force II kit is designed to provide a mild interior and exterior exhaust tone. Think of the Super 50 Series muffler like Flowmaster’s three-chamber offering from days gone by. Yeah, we know—we’re getting old.
To acccompany the Flowmaster after-cat, and to provide that trademark Mustang sound, we chose BBK Performance’s X-shape crossover pipe (PN 1669; $219.99). BBK calls this its ’99-’04 Mustang 4.6-liter full-length X-shape crossover pipe. It is a direct replacement designed to bolt up to the stock exhaust manifolds at the front, and a stock-style after-cat. The 21⁄2-inch BBK X features CNC-mandrel-bent aluminized tubing with BBK’s unique die-stamped performance Xtractor center X-section for maximum flow and horsepower. We chose the X-shape crossover pipe simply for the sound it would provide our Bullitt.
James gets started by removing the old exhaust system, which necessitated removing the gas tank, as well. We could’ve removed the exhaust by loosening the shocks and removing the rear springs. However, our Bullitt needed a new fuel-filler seal since it was causing an error code and Check Engine light. James would kill two birds with one stone by removing the gas tank. Doing so made it a lot easier to remove and install the tailpipes, and we’d get a new filler neck seal installed at the same time. It was a win-win. Here he lines up both front sections of the X-shape crossover pipe, loosely attaching them to the factory exhaust manifolds.
Once James is satisfied at the placement of the front sections, he brings the X-shape crossover pipe’s rear section into the equation. The system uses two clamps on each side for a slip-fit installation. This will allow you to tailor the X-shape crosssover pipe to your Mustang.
Before James and I got too caught up in the fact that the X-shape crossover might hit the torque arm mount, we retreated to the back of the car to get started on the tailpipes. Here you can see the space around the Maximum suspension for the tailpipes. The previous owner was building the car to beat a new Boss 302 around the track, but that plan went out the window when he test-drove a new Boss...
James snakes the driver-side tailpipe over the Bullitt’s 8.8 rear, and through the suspension components. The driver side is much easier than the passenger side, as there is less Panhard bar hardware in the way.
And here’s the passenger-side tailpipe going in. Notice the tailpipe must go over the Panhard bar and mount. Maximum Motorsports recommended the Flowmaster after-cat exhaust because it closely follows the factory exhaust routing. Maximum designed the bar and mount to work with factory exhaust.
With the tailpipes in place, James moves to the muffler portion of the installation. James uses a transmission jack to position the muffler/flow tube assembly. Doing so will allow you to position the muffler right where you want it, and tighten up when you’re ready. Of course, you don’t want to fully tighten the exhaust until it’s just right.
Once James was satisfied with the exhaust position, he used the supplied Flowmaster hardware to tighten its clamps. James used the aforementioned transmission jack to hold the exhaust in place while he tightened the nuts, bolts, and clamps.
Here’s a look at the tailpipe routing on the driver side, which is much better. You can see where the previous after-cat had rubbed on the plastic gas tank cover.
James cut off the tailpipe hangers since they interfered with the Maximum Motorsports swaybar end-links. After everything was tightened, we used factory hangers from a Ford dealer, which we also modified to work with the Flowmaster muffler hanger arrangement.
The moment you’ve all been waiting for—did the BBK Performance X-shape crossover pipe work with the Maximum Motorsports torque arm? Well, yes, it did. As you can see, it’s a tight fit, and some clearancing might be necessary should you decide to go the route we took with our Bullitt. At this stage of the game, it’s hard to say whether you will have the same fortune as we did. Some cars haven’t been treated as well as others, but as our car illustrates, it is possible.
Well there you have it. Save for factory muffler hangers, James has completed our exhaust install. Most of the time with an exhaust swap is taken up with making sure the tailpipes are aligned properly, and aren’t coming in contact with the rear axle housing, suspension, or rear valance. Then it’s muffler alignment, as well. You could spend two hours just on exhaust alignment alone so take your time, and don’t tighten anything down until it’s just right.

On The Dyno

Datalogging the dyno pulls, James discovered our Bullitt was almost out of fuel. Further research revealed the alternator output trailed off at high rpm. Could our Bullitt's lack of fuel be related to reduced alternator output? Of course. If the car's alternator isn't giving full power, every other electrical component, including the fuel pump, will not see full power either.

However, it could also be a clogged fuel filter contributing to the problem, as well. We didn't have a new fuel filter to try while at Brothers, so we'll have to address that later. We'll also try a new alternator to see if things improve.

With the tuning done, the Bullitt's sound, driveability, and increased low-end grunt were welcome additions, making the car more fun to drive. No, it doesn't make a lot of power, but at least now it sounds like a Mustang, which was the impetus for the revised exhaust.

RPM Power Torque Power Torque Power Torque
2,300 110.87 253.17 109.62 250.31 -1.25 -2.86
2,400 115.59 252.96 113.90 249.25 -1.69 -3.71
2,500 121.45 255.15 118.23 248.39 -3.22 -6.76
2,600 126.57 255.68 122.69 247.83 -3.88 -7.85
2,700 132.62 257.97 127.31 247.66 -5.31 -10.31
2,800 136.07 255.23 131.22 246.13 -4.85 -9.10
2,900 140.33 254.15 136.87 247.88 -3.46 -6.27
3,000 146.07 255.72 143.02 250.39 -3.05 -5.33
3,100 150.61 255.17 150.52 255.01 -0.09 -0.16
3,200 158.53 260.19 159.72 262.14 1.19 1.95
3,300 167.22 266.13 168.51 268.19 1.29 2.06
3,400 173.09 267.38 176.57 272.75 3.48 5.37
3,500 178.97 268.57 182.21 273.42 3.24 4.85
3,600 181.97 265.48 188.09 274.41 6.12 8.93
3,700 188.71 267.87 195.26 277.17 6.55 9.30
3,800 197.14 272.47 203.05 280.64 5.91 8.17
3,900 201.95 271.97 210.95 284.08 9.00 12.11
4,000 209.33 274.85 216.10 283.74 6.77 8.89
4,100 216.05 276.76 223.79 286.68 7.74 9.92
4,200 217.65 272.17 227.33 284.28 9.68 12.11
4,300 222.18 271.37 230.10 281.05 7.92 9.68
4,400 225.22 268.84 233.00 278.13 7.78 9.29
4,500 229.49 267.85 234.83 274.08 5.34 6.23
4,600 234.39 267.62 238.41 272.21 4.02 4.59
4,700 238.70 266.74 240.51 268.76 1.81 2.02
4,800 243.51 266.44 241.73 264.50 -1.78 -1.94
4,900 241.03 258.35 243.41 260.90 2.38 2.55
5,000 245.88 258.28 245.20 257.56 -0.68 -0.72
5,100 244.52 251.81 245.34 252.66 0.82 0.85
5,200 241.52 243.94 243.45 245.88 1.93 1.94
5,300 238.18 236.03 242.57 240.38 4.39 4.35
5,400 237.81 231.30 239.75 233.19 1.94 1.89
5,500 234.56 223.98 237.99 227.27 3.43 3.29
5,600 234.92 220.32 234.00 219.46 -0.92 -0.86
5,700 232.03 213.80 233.89 215.51 1.86 1.71
5,800 229.63 207.93 231.93 210.02 2.30 2.09
5,900 229.96 204.71 229.38 204.19 -0.58 -0.52
6,000 226.23 198.03 227.48 199.13 1.25 1.10

When it comes to exhaust on your Mustang, it’s all about sound. Unless you’re going with a long-tube system on a supercharged Two-Valve, you probably won’t pick up much power. That was the case with our Bullitt. James also tuned our Bullitt on Brothers’ Dynojet, and it was an eye-opening experience. We gained the trademark Mustang sound we were looking for, any horsepower gain would just be a bonus. Turns out, we didn’t really gain peak horsepower. However, we gained midrange horsepower and torque, as much as 9 hp and 12 lb-ft of torque.
James Gordon of Tuning by James handled both the exhaust installation and tune on our Bullitt with expert care and proficiency. James used SCT software, loading the tune into a SF3 Power Flash Ford Programmer. James, when not tuning cars across Central Florida or the Internet, also performs the dyno work at Brothers Performance car shows at its Deland, Florida, location.
Here’s the SCT SF3 Power Flash Ford Programmer James used to store the tune for future use. We’ll carry this with us for future performance upgrades and tuning changes. Not only will the SF3 hold up to 10 tunes, it can also datalog, and read/clear trouble codes.
Here is our baseline dyno pass before the exhaust, and our best run with the new BBK Performance/Flowmaster exhaust upgrades. You can see we really didn’t gain in the upper rpm range, but in the midrange we gained a welcome 12 lb-ft of torque.

Horse Sense: Flowmaster has changed the way it names its mufflers. The Super 50 Series we installed on our Bullitt were called three-chamber mufflers. Of course, three-chamber are the quieter Flowmaster muffler offering. When we were younger, we installed two-chamber mufflers, which are now called Super 40 Series mufflers. (I was old in my youth and went for three- chambers, er ... Super 50s. —Editor Turner)