2007 Civic Si Sedan - Project Si: Initial Bolt-ons

After engaging in a pretty good amount of research on the eighth gen (sixth-generation Si) and its K20, a few things became very apparent. First off, a solid exhaust and header upgrade will net some power you can actually feel. The numbers, of course, are all over the chart due to the fact that no two motors, or dynos, are exactly the same, but there are no doubt gains to be made. The other thing that kept popping up over and over again is how much of an improvement Hondata’s FlashPro can make to the Si. Inherent quirks like rev hang, and the downright annoying stutter that rears its ugly head when the car is still warming up, can be eliminated completely with the plug-and-play module. Of course, the FlashPro’s biggest attribute is its ability to allow fine-tuning of the vehicle and wring out every bit of power from those new bolt-ons.

Inhale
For the first round of initial testing, I contacted Vibrant Performance to try out its Cat-Back exhaust system and high-flow cat-equipped header. Doug MacMillan from Hondata was kind enough to ship me a FlashPro system, and as always, Elton Lo opened up the bay door to his dyno at Raceline so I could get some before and after numbers. The only modification to the car thus far is a Type One OEM-style intake. This kit uses a plastic snorkel that sits inside the front bumper and channels air through the factory ducting and into the airbox. Type One includes a high-flow panel filter and a carbon-fiber lid, along with an aluminum arm to replace the factory rubber version. This intake kit seems to be an improvement over the stock system, but is much better suited for an Si coupe or ’09+ sedan, as both chassis feature a foglight grille that can be cut out and direct air right to the snorkel. For the ’06–’08 sedan owners, the foglight openings are integrated into the main grille.

Exhale (Header)
While I won’t bore you with every step of the install, since this is simple stuff that can be done in your garage with basic hand tools, I will point out some of the areas that might look a little strange to newer-generation Si owners. If you’ve only had experience with, say, D, B, and H-series motors or perhaps a K-swapped Civic or Integra that has far more room under the hood than the eighth gen, you might not like working on this chassis too much. I fit into the above category as I’ve owned, worked on, and swapped a number of D and B-series motors and worked on K-swapped cars, but I’ve never dug into the ’06+ models. The first thing I noticed when popping the hood is that the majority of the valve cover is hidden by the car’s windshield wiper cowl and accessing the exhaust manifold bolts on the head is a bit of a pain. Removing the plastic cowl and metal support tray is necessary to get your hands, and your ratchet, somewhere near the intended target. The other issue with the header removal has to do with the game of Tetris that you have to play with the top portion of the cast manifold from behind the motor. There’s not enough room to go out the top, so you’ll need to remove a bracket or two underneath the car in order to squeeze it through. Fortunately, an aftermarket header is much slimmer and will snake through fairly easily.

The Vibrant Performance header that I requested is armed with a high-flow cat and a heavy-duty flex-pipe to compensate for engine torque and movement. The design is light-years superior to the factory manifold, and appearance-wise, the welds, flanges, and build construction are top-notch. The necessary bungs required to plug in the factory oxygen sensors are there, and every bit of hardware needed for installation is included.