In the first phase of our '17 Civic Hatchback Sport buildup, we added Hondata's user-friendly, C.A.R.B.-legal FlashPro system, and on the World Motorsports dyno, it produced more power and torque with no other changes. This time around, we're bolting on a few parts to see if opening the airflow in and out will net a positive gain. We'd heard a few rumblings about intake and exhaust upgrades actually robbing the 10th gen. Civic's turbocharged 1.5L of power but we wanted to test it ourselves.
We made a trip to Irvine, Calif., to visit Kenji Sumino and the crew at GReddy Performance Products, who were itching to get their hands on Honda's latest hatchback. With an extremely small window of time, GReddy got right to work, fabricating a new high-flow cat-back exhaust system and intercooler upgrade. In factory form, the 1.5L's small turbo doesn't need a massive front-mount intercooler for street driving and the occasional track day, however, there is room for improvement, and with the additional mods being added to our project, it made perfect sense to increase the car's cooling ability.
When placing the factory intercooler next to the GReddy version, the difference in size is obvious. Approximately the same thickness but almost twice as high and relying on a higher flowing design, the GReddy piece does away with the plastic end tanks and piping and retains a factory fitment behind the original bumper without issue. It's a straightforward install you can do in your driveway.
The Sport model's center-exit twin muffler exhaust system features the type of convoluted routing you'd expect from a factory exhaust. Intended to keep the noise level down, the OEM piece is all one unit, just like the S2000, and is much easier to take off with a second set of hands. The GReddy Supreme SP, however, is a multi-piece design based on a foundation of 3-inch piping that takes a straight path to a single muffler with dual finishers. The actual tips are about the same size as OEM but feature a slight angle cut and high-polished finish along with the GReddy logo, and they fill the factory bumper opening perfectly. Looking at the photos, we know what you're thinking, "no sub-muffler or additional resonator and 3-inch piping? This thing must be loud." The reality is that it's extremely quiet with a nice, deep rumble that comes alive at full-throttle and gives the hatchback a little bit of sound to match its increased performance. It's a much-needed component that, unless you were listening for it, will really surprise you when comparing the stock version to GReddy's upgraded system.
With the exhaust complete, we turned our attention toward the intake side. There are a number of intake kits already available for the 10th-generation Civic and not surprising, AEM was one of the first to develop its cold-air system that includes its familiar Dryflow synthetic filter that's both washable and reusable, as well as a free-flowing, mandrel-bent aluminum piping design. Best of all, your factory sensors plug right in so you won't have any issues with throwing codes.
With our bolt-ons installed and our Civic Sport's attitude audibly enhanced, we drove straight back to World Motorsports for another session on its wind tunnel dyno. With the new GReddy Supreme SP exhaust, AEM intake, and a re-tune with Hondata's FlashPro, our turbo hatch picked up an additional 24 lb-ft of torque and more than 35 whp! Still on standard 91-octane pump gas, using a C.A.R.B.-legal FlashPro, and retaining all of the original factory emissions bits, our final numbers are 212 whp/230 lb-ft of torque, compared to the stock 168 whp/169 lb-ft of torque we measured in the first installment.
On the road, throttle response is much sharper and midrange power, compared to stock, is a night-and-day difference. The intake and exhaust combo add a more aggressive note without being obnoxious—perfect for making our way through surface streets or the freeway. We also noted that pulling around traffic at speed is a breeze and no longer requires a downshift and, if we're being completely honest, we spend more time blasting through the gears than we probably should because the peppy 1.5L is a whole different animal with the changes.
Now that the power equation is out of the way, we're moving on to suspension changes along with a wheel and tire package as our Civic project continues.