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2007 Honda Civic Si - Power Pages

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The eighth-generation Civic has been argued as the best Civic Si to come out of the Honda factory. This model comes equipped with a 2.0L K20Z3 i-VTEC engine that produces 197 hp and 139 lb-ft of torque. Coupled to a six-speed manual transmission with a helical limited-slip differential, the Civic is anything but a practical four-door sedan, and handles more like a sports car than a daily commuter. The K-Series motor was a godsend for tuners across the world, showing potential for tuning applications, making it possible to reach gains over 230 hp with aftermarket bolt-on parts and tuning.

We noticed the factory ECU tuning on the 2.0L engine was less than impressive when spun on the dyno. The baseline graph showed a signif0icant drop in horsepower at 5,800 rpm. Torque figures were also adversely affected before the low cam to high cam transition of VTEC. A decline of more than 7.4 lb-ft of torque from 123.5 lb-ft to 116 lb-ft was recorded before the high cam engaged, increasing torque once again.

Prior to recording a baseline run, we should mention our K20Z3-powered Civic was already equipped with an AEM cold-air intake system. With the intake, the Civic netted baseline power figures of 188.3 hp and 131.0 lb-ft of torque.

Go Power Exhaust

Exhaust, mid-pipe, hardware, and gaskets

10, 12, 14, and 17mm socket, 10, 12, 14, and 17mm open-end ratchet, extension, crescent wrench, antiseize, and WD-40.

Installation time
60 minutes

Constructed of 304 stainless steel, the Go Power exhaust system was designed to offer improved exhaust flow and horsepower gains over the factory unit. The Go Power system features large 3-inch diameter piping and a built-in resonator to minimize droning, and comes in an optional stealth black powdercoated appearance for an additional $60.

The new exhaust was easy to install, and required a simple spray of WD-40 to all the exhaust hangers to help speed up the installation process. Don’t be overzealous and attempt to remove your factory exhaust system under scalding conditions or you might suffer the consequences.

The Go Power exhaust delivered an increase in horsepower and torque from 6,200 to redline, with a gain of 4 hp and 5 lb-ft of torque through the top end. You might consider the Go Power’s exhaust piping diameter excessive in size, but considering once you start diving into the internal engine work, such as larger cams and higher compression pistons, the exhaust flow demand increases greatly. Thus, benefiting your engine by using a larger exhaust system, even on an NA vehicle such as our Civic. Notice even with our 3-inch exhaust, the vehicle showed no loss in low to midrange power over our factory exhaust.

Skunk2 Alpha Header

Header, adapter flange, gasket, mounting bracket, hardware, stickers, and instructions

12, 14, 16, and 17mm sockets, swivels, ratchet, open-end wrenches, extensions, breaker bar, antiseize, WD-40, screwdriver, and pliers

Installation time
180 minutes

Skunk2 Alpha Series headers feature equal-length, sequentially paired, stepped primaries and a 4-2-1 tri-Y design that terminates into a collector with a 2.5-inch outlet. These features, paired with Skunk2’s unique design specs, provide an extremely broad powerband that’s applicable to a wide range of engine sizes and configurations. Alpha Series Headers also feature the smallest possible primary tubes required to achieve optimum overall and peak power. By minimizing the primary tubes’ diameter, Skunk2 is able to maintain the highest possible exhaust gas speed throughout the header, which improves midrange power and throttle response significantly. Skunk2 representatives claim their Alpha Series header provides the perfect combination of top end power without sacrificing midrange performance or throttle response.

The Alpha header should only be used for off-road purposes, as it replaces the factory catalytic converter. Removing the OEM two-piece header requires accessing numerous bolts from under the vehicle. A swivel socket and ratchet extensions helps speed up the removal and new header installation process. We found it easier to remove/install the header by unbolting the subframe, which lowers it a few inches to gain easier access.

Dyno testing the header revealed an increase in power and torque throughout the powerband, with peak gains of 13.5 hp and 8.3 lb-ft of torque. The Alpha header made an impressive 14 hp and 10 lb-ft of torque at 6,900 rpm over our previous run, with plenty of gains in the midrange to top end from 3,800 rpm to redline.

Hondata FlashPro

Hondata unit/ECU, USB cable, stickers, instructions, and CD-ROM

Laptop and tuning experience

Installation Time
140 minutes

Hondata’s FlashPro for the ’06-11 Civic Si offers comprehensive tuning solutions to late-model Hondas. The Hondata FlashPro enables the user to quickly and accurately tune the Civic’s engine computer parameters through the OBD-II diagnostic port for maximum performance and economy, whether naturally aspirated or with forced induction. Using the FlashPro manager software enables multiple features including 20 hours of onboard data logging capability, support for larger injectors, race vehicle sensor disabling, individual cylinder knock data logging, fuel trim and ignition trim tuning, along with a bevy of additional parameters.

Any time you alter/manipulate the ECU for additional fuel/timing or ignition, we advise contacting experienced Hondata dealers to create a custom tune for any bolt-ons—failure to do so could be catastrophic.

Jeff Giovino of Go Power lent us a helping hand in tuning the Civic using the FlashPro. Giovino quickly recalibrated the Hondata map by adding/removing fuel for low cam tuning, and then moved onto high cam tuning before focusing on fine-tuning the cam phasing. Giovino also altered the VTEC crossover point from 5,800 to 4,600 rpm and bumped up the Civic’s redline to 8,500 rpm to take full advantage of the new exhaust and header setup. Giovino says that Honda calibrated the factory ECU at a 12.5 to 12.6 to 1 air/fuel ratio in the low to midrange poweband, and an excessively rich power robbing 11.5 to 1 air/fuel ratio from 7,600 to redline as a means to protect the Honda’s K20Z3 engine. With tuning, we achieved a 12.8 to 13.0 air/fuel ratio. Our final dyno run showed a healthy gain of 25 hp and 22 lb-ft of torque in the midrange at 6,000 rpm over our previous run.


Just one day’s work installing two bolt-on parts, along with a Hondata FlashPro tune, improved output by 19.2 hp and 16.5 lb-ft of torque over our baseline numbers, as our K20Z3 now churns out an impressive 207.5 hp and 147.5 lb-ft of torque. With future modifications calling for a set of camshafts, intake manifold, larger diameter throttle body, and additional tuning, we’re betting this unassuming four-door “commuter” has what it takes to eclipse the 250hp marker.

Go Power Exhaust189.71.4133.62.6
Skunk2 Alpha Header203.213.5141.98.3
Hondata FlashPro207.54.3147.55.6

Go Power Exhaust$595.00
Skunk2 Alpha Header$449.99
Hondata FlashPro$695.00

2840 Columbia St.
CA  90503
Skunk2 Racing
2050 5th Street
CA  92860
Go Power Motorsports
17056 Hercules Street
CA  92345
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