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Power & Sound: Dyno-Proven Bolt-Ons for the S550 Mustang GT

The first “fast” car that I ever owned was a 1990 Ford Mustang GT. It made 225hp from its 5.0L small block. Back then, I was a high-schooler, and to me it felt like one of the coolest cars around and also one of the quicker ones.

But oh how times have changed. Today, most modern minivans make more horsepower than that Mustang and would outrun my old stock 5.0 at the drags.

To put it in other words, my own sense of what a fast car is might be different from people who have gotten used to in modern performance cars. For example, the 435hp that my 2016 Mustang GT made from its 5.0 engine stock still feels like a lot of power to me, but you can always add more.

2016 Ford Mustang GT White on Nitto NT555 G2 tires

And while my goal with my S550 was never to build a horsepower monster, the multitude of ways in which you can reliably and affordably add power and torque to these cars is downright impressive.

Primary Power Plan

When talking with the team at Steeda about the plans for my car, I told them my primary mission wasn’t to go way faster in a straight line, but that it’d be nice to wake up that Coyote under the hood just a bit.

2016 Ford Mustang GT Engine Bay

That’s where the Steeda Ultimate Induction Pack comes in. It’s a cost effective and proven way to extract power and torque from the S550 Mustang GT without any downsides.

S550 Mustang GT Steeda ProFlow CAI

The pack includes two key parts, Steeda’s ProFlow cold air intake: First, an easy to install, less restrictive replacement for the factory closed airbox and disposable air filter. Second, it comes with an SCT X4 handheld tuner that’s used to reflash the car.

Steeda S550 Mustang GT ProFlow CAI

After the parts arrived I logged on to Steeda’s website where I filled out a form with the specifics on my car and what upgrades were done to it. Shortly after I received an email with a downloadable tune file which I easily loaded onto the SCT tuner.

From there it was straight to the garage where I plugged the tuner into my Mustang’s OBD2 port, followed the easy steps to load the tune onto the car and a less than 10 minutes later everything was good to go.

S550 Mustang GT SCT X4 Steeda Tune

Tailpipe Emissions

And while I was excited to see the power increase from the Steeda intake and tune, I was equally excited to install the Steeda three-inch cutback exhaust system that was sitting in the box ready to go.

The system is made out of 304 stainless steel and replaces everything form the catalytic converters on back to a pair of dual four-inch exhaust tips.

Steeda S550 Mustang GT Cat Back Exhaust

While not a hard install, I didn’t have access to a lift so I left the job to a trusted local muffler shop—and needless to say when I couldn’t wait to fire up the car to hear the new exhaust note.

I was impressed right off the bat. The sound was louder and more aggressive, but not nearly as wild or raspy as some of the modified Mustangs I've heard around town.

S550 Mustang GT Steeda Cat Back Exhaust

I actually didn’t mind how the car sounded stock, but it was just too quiet, and a high quality catback like the one Steeda makes is the perfect remedy for that. Of course it’s hard to describe how an exhaust sounds in words, so that’s why I’ve included both before and after sound clips in the build vlog that I recently put together about this car.

S550 Mustang GT Engine Bay 5.0 Engine

So, with the exhaust and intake installed and the Steeda tune loaded onto the car, there was a noticeable seat of the pants improvement, but I wanted to be sure this wasn’t just the placebo effect and me getting too excited about the new exhaust note.

Dyno Proof

This is where my friends at Caliber Customs here in Central California and their full-service dyno come in.

2016 Mustang GT on Dyno

Just prior to installing the new parts we dyno’d the car and in bone stock form with 43,000 miles on the odometer, the car put down 366 wheel horsepower and 335 pound feet of torque. With all of the dyno’s corrections, this was right on the money for the 435 horsepower and 400 pound feet factory crank rating.

Caliber Customs Dyno

Cutting right to the chase, with the new parts installed I came back a few weeks later and with all the computer corrections for ambient temperature, humidity etc. we got numbers of 389 rear wheel horsepower and 361 pound feet of torque - maximum gains of 23 horsepower and 26 pound feet of torque respectively.

2016 Mustang GT Dyno Graph

These numbers actually line up perfectly with my seat of the pants impressions. It’s not a night and day different in power, but it’s quite noticeable and the 5.0 just has that extra bit of life to it. Not bad at all for just an intake, tune and a catback.

2016 Ford Mustang GT on Dyno

As with the rest of my upgrades to this car, these bolt-on power upgrades fall right in line with the balanced approach we’ve taken to modifying this car.

With all of the work done to the suspension, chassis and brakes there’s no doubt my S550 could handle a lot more power, and that may happen in the future, but for now it feels just right.

Stay tuned for more build updates coming soon…

  • And here are some braking upgrades we did to help slow this Mustang down after its newfound power gains.
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