KJ Jones
February 4, 2014
Photos By: KJ Jones

The continuous research we do with '11-'14 Mustang GTs has proven that Coyote engines thrive on airflow. Yes, we've seen mild-to-wild performance gains when air to these new bullets is improved with intake systems, power adders, and freer-flowing exhaust systems.

The exhaust side of Mustang performance is our focus this month, and with the help of Ricardo Topete of GTR High Performance, we're installing MBRP Performance Exhaust's all-new, 3-inch Street Series after-cat exhaust for '11-'14 5.0s (PN S7258409; $719.04). We will evaluate the bolt-on system's sound, and of course, the impact its 3-inch tubes and high-flow mufflers have on performance. MBRP claims this system adds approximately 3-5 horses at the feet. When you consider the fact that the MBRP after-cat system flows an additional 100 cfm over the 2.5-inch, resonator-choked, bend-heavy OEM tubing (604 to 502), a gain of some sort certainly is anticipated.

Freddy Contreras provided his ridiculously fresh '13 GT for this experiment. The Pony was completely void of any other mods, and weighed-in with baseline peak power (366.07) directly in line with the rear-wheel steam of other stock Coyotes we've worked with.

Check out the photos and captions for the details on MBRP's updated Coyote exhaust pieces, and a few quick highlights of the after-cat R&R procedure. The effort does qualify as a 1.5-hour DIY. However, as Ricardo demonstrates, that's only if you have the facilities and equipment necessary for this type of under-car operation.

GTR High Performance’s Ricardo Topete hangs one of two MBRP Performance Exhaust mufflers on the tail end of Freddy Contreras’ ’13 Mustang GT. The new-design cans highlight MBRP’s 3-inch Street Series after-cat exhaust system for ’11-’14 Mustang GTs.
Exhaust efficiency is largely based on gasses traveling as smooth and straight as possible. These comparisons clearly show the differences in the factory tubing design and MBRP’s direct approach to exhaust ventilation. Of course, the restrictive factory resonators are eliminated from the new pipes.
Exhaust efficiency is largely based on gasses traveling as smooth and straight as possible. These comparisons clearly show the differences in the factory tubing design and MBRP’s direct approach to exhaust ventilation. Of course, the restrictive factory resonators are eliminated from the new pipes.
This look at the new muffler’s innards highlights its race-oriented, straight-through design. While these Street Series cans are made with considerably less baffling than their first-gen siblings—which we worked with during the header install (PN S7224304)—they’re still not as raspy as MBRP’s Race Series mufflers.
The system’s big, mandrel-bent tubes clear all potential conflict points on the chassis with no problem (with the exception of the area between the frame and Panhard bar bracket on the driver side). MBRP includes 3-inch clamps for securing slip-fit unions at the H-pipe and mufflers.
MBRP provides two M10x50 bolts and steel spacers with the kit to ensure there’s sufficient clearance for the driver-side extention pipe in the aforementioned chassis/Panhard area.
The install is closes with a slick pair of dual-walled, T204 stainless-steel exhaust tips measuring 4 inches in diameter. Ricardo confirms the tips are centered in the rear bumper cover, double-checks the fasteners and clamps, and it’s time to hit GTR’s Dynojet chassis dyno.

On the Dyno

Having performed baseline dyno tests on Freddy Contreras' new '13 Mustang GT at the outset of our project (and logging the 'Stang's anticipated 365-367 horsepower in stock trim), we closed the evaluation with another round of laps on the Dynojet's rollers to compare performance and exhaust-sound differences with MBRP's 3-inch Street Series after-cat exhaust for '11-'14 5.0s (PN S7258409; $719.04) installed.

First we have to say, the aural change this setup makes on a Coyote's exhaust note is awesome. At the crack of the ignition, the Street Series high-flow mufflers sound great—mellow, but also pleasingly aggressive, and (in our opinion, as well as others who were present at the dyno session) indicative of the way '11-up GTs should sound from the factory.

As for power-at-the-wheels, the exhaust upgrade feted us with nearly 6 extra horses at the feet of Freddy's Pony, in accord with MBRP's claim (a little better, actually) and without PCM manipulation via custom tuning.

RPM Power Torque Power Torque Power Torque
2,500 137.57 289.01 135.14 283.93 -2.43 -5.08
2,600 141.20 285.25 138.62 280.02 -2.58 -5.23
2,700 147.49 286.9 144.27 280.62 -3.22 -6.28
2,800 154.65 290.09 152.15 285.40 -2.50 -4.69
2,900 160.47 290.62 160.34 290.37 -0.13 -0.25
3,000 168.54 295.05 168.15 294.37 -0.39 -0.68
3,100 177.19 300.18 176.92 299.74 -0.27 -0.44
3,200 185.29 304.11 184.87 303.41 -0.42 -0.70
3,300 194.31 309.23 193.16 307.39 -1.15 -1.84
RPM Power Torque Power Torque Power Torque
3,400 204.41 315.75 204.69 316.19 0.28 0.44
3,500 213.43 320.26 213.53 320.40 0.10 0.14
3,600 222.48 324.56 224.05 326.88 1.57 2.32
3,700 230.13 326.67 231.24 328.24 1.11 1.57
3,800 235.72 325.80 238.01 328.97 2.29 3.17
3,900 245.27 330.30 245.44 330.52 0.17 0.22
4,000 252.98 332.16 254.68 334.39 1.70 2.23
4,100 263.56 337.60 265.58 340.19 2.02 2.59
4,200 275.38 344.35 277.41 346.88 2.03 2.53
4,300 285.93 349.22 287.97 351.73 2.04 2.51
4,400 293.48 350.32 295.44 352.66 1.96 2.34
4,500 295.64 345.06 299.08 349.07 3.44 4.01
4,600 299.21 341.63 303.25 346.25 4.04 4.62
4,700 304.20 339.94 307.18 343.28 2.98 3.34
4,800 310.08 339.28 310.37 339.61 0.29 0.33
4,900 315.23 337.89 317.64 340.46 2.41 2.57
5,000 322.97 339.25 325.59 342.00 2.62 2.75
5,100 331.21 341.09 333.48 343.43 2.27 2.34
5,200 337.32 340.69 340.69 344.11 3.37 3.42
5,300 342.57 339.48 345.24 342.13 2.67 2.65
5,400 344.02 334.61 348.02 338.50 4.00 3.89
5,500 346.00 330.41 350.02 334.25 4.02 3.84
5,600 349.19 327.50 352.24 330.37 3.05 2.87
5,700 349.82 322.34 353.66 325.88 3.84 3.54
5,800 350.55 317.45 355.31 321.75 4.76 4.30
5,900 352.64 313.92 356.77 317.60 4.13 3.68
6,000 354.64 310.43 360.51 315.59 5.87 5.16
6,100 358.39 308.58 360.93 310.76 2.54 2.18
6,200 362.01 306.67 365.75 309.84 3.74 3.17
6,300 363.78 303.28 366.83 305.82 3.05 2.54
6,400 365.41 299.88 371.39 304.78 5.98 4.90
6,500 366.07 295.8 371.79 300.41 5.72 4.61
6,600 363.85 289.55 371.07 295.29 7.22 5.74
6,700 361.06 283.04 368.96 289.23 7.90 6.19
6,800 357.01 275.75 367.18 283.61 10.17 7.86