The 2012-and-up, ninth-generation Civic is a great platform for performance modifications. Some of the haters will be quick to point out that this era Civic will never be the tuning sensation that the fifth-generation (1992-1995) EG Civics were, but that’s an unfair comparison. What you need to do is compare the current Civic to the rest of the current platforms in the tuning scene. In this light, the Honda stacks up well. Anything with a Honda badge has a strong legion of enthusiasts behind it, and among Honda fans in America the Si model is the top dog. We’re going to take a 2013 FB6 Civic Si four-door sedan and drop in some basic bolt-ons to see how the 2.4-liter K24Z73 i-VTEC engine responds on the dyno.

The art of making power has changed since the days of the EG Civic. You can no longer bolt on and blast away. Nearly every change you make must be accompanied by a corresponding ECU flash to optimize the new combination. Heck, looking at the current model there isn’t even a header to swap. In the design of the K24Z7, which was new in thwe Si in 2013,the component formerly called a header is known as a downpipe. It is basically the collector portion of a traditional header. The ‘runners’ are incorporated into the cylinder head.

Our plan is to take the first logical steps that any enthusiast looking for some extra punch will take and provide you with the added benefit of back-to-back dyno pulls to chronicle the gains. Our game plan calls for the addition of a cold air intake and full exhaust system accompanied by a proper flash tune. We raided the parts bins at Skunk2 Racing and enlisted KTuner to handle the software side.

KTuner founder James Holy was quick to point out that newer cars are dramatically different from the OBD1 platforms. “I started by creating the NepTune Engine Management for OBD1 Hondas,” Holy says. “Ultimately, the next step in development was to support the OBD2 Honda/Acura applications, as well. Enter KTuner. While most of the vehicles now are MAF, and we generally put out an initial platform release with factory MAF support, we have been developing speed density support starting with some of the most popular codebases like the Civic. We ended up using a beta of the speed density fueling on the 2013 Civic Si and it proved the importance software plays in the success of performance hardware.”

Before busting out the wrenches the first task at hand was establishing a baseline. The Si was strapped to the Power Automedia Dynojet chassis dynamometer where it belted out 180.92 horsepower. It should be noted that the K24Z7 is factory rated at 205 horsepower at the flywheel so the Honda’s driveline is quite efficient as there is only a nine percent parasitic loss. Torque checks in at 164.85 lb-ft.


Skunk2 Cold Air Intake

This Skunk2 intake is the trickle-down theory in action. This theory describes how the technology of racing finds its way into street-going vehicles. Skunk2’s intake for the 2012 to 2013 Civic Si was developed via the company’s technical partnership with the championship-winning Compass360 Racing team. The cold air intake is made from molded polymer plastic and Skunk2 says this construction provides superior intake air insulation compared to aluminum. Intake piping in the kit consists of a 3.5-inch internal diameter lower tube and a tapered, 3.5-inch to 3.0-inch internal diameter upper tube that connects to the factory throttle assembly.

The days of loosen one hose clamp, unplug one sensor intake installs are long gone. Today you gotta want it. The Skunk2 kit requires the use of a battery relocation tray to open up some room under the hood. The tray drops in and bolts to existing points. With the battery in place the upper hose connector can be installed on the throttle body.

Then the driver's side wheel is removed to gain access to the inner bumper area. The lower pipe and element are installed. At this point, the upper and lower hose connectors are staring each other in the eye. The hard pipe bridges the gap between them. It is positioned and tightened to spec.

With the Skunk2 intake connected and all the clamps and bolts sufficiently tightened it is wise to check one last time for possible leaks or loose fittings. It is also advisable to jog the car on the dyno so you can listen for air leaks before letting loose with the power runs.


With the intake installed the Civic lost power, illustrating the need for ECU tuning.

On the dyno and spinning the rollers for real, the importance of ECU tuning in modern vehicles became readily apparent, as our Civic dropped 8.02 horsepower, to 172.90. We believe the tapered pipe changed the characteristics of the charge air by creating backpressure and rendering the MAF unable to properly read the flow. The dyno charts revealed a big drop in air/fuel ratio, falling from a power-friendly 12:1 to a rich, power-robbing 10:1. Torque increased slightly to 165.71 lb-ft. The flow to the MAF was unaffected at lower engine speeds so some gains were possible. But once substantial flow was introduced power and torque both suffered the consequences.

Flash Tune To The Rescue

The KTuner Flash Tuning package we used on the Civic is basically a hardware device that is paired with single user licensed software, all matched and locked to a single ECU, so it can only program the matched ECU. The unit connects to the OBD2 port under the dash. Users can access ignition, fuel, cam angle, and additional supporting parameters and the system is capable of datalogging. KTuner uses direct USB connectivity for fast data transfers.

Kenny Sampson of handled the remote tuning session for our Civic on the speed density platform. Sampson tuned the car from his home base in Florida. Remote tuning is when a tuner, using remote access software, takes control of a computer and controls the tuning of the ECU directly. Data is received from the car’s ECU onto the host laptop, tunes are made, and the program is reflashed into the ECU from the remote host laptop. PAM’s Kyle Kitchen controlled the dyno on site. “I did the tuning based off the data received from KTuner and dyno sheets from the dyno,” says Sampson. “Most of the data, outside of the output of the engine, is from the KTuner. Fueling, ignition, knock control, road speed, engine speed, and other parameters are directly recorded by KTuner. It allows everything to be reviewed in one place. That makes for very efficient tuning.”

The results very well demonstrate the necessity for ECU tuning on these newer platforms. Sampson concurred with our suspicions, telling us upgraded intakes can lose power with newer cars because most use MAF-based fueling. “With a change of pipe size, the fueling is affected, and the factory ECU is calibrated to the stock size… the ECU knows the constants… pipe size, injector size, and engine size. Once you change that, you can bet it will change the performance and need tuning.”

“With newer ECUs, knock control, MAF fueling, cam angles, and timing need to be adjusted for most mods,” says Sampson. “With a change of intake piping, intake plenum, and cam swaps MAF tuning is very important to dial in. Remember, I’m tuning the engine for what was added to it. I am reviewing data and changing the ECU to make the most, safe power that the car can make. Being in California, the fuel is octane-limited, so it is very important to tune the timing and knock control perfectly. This optimizes power and keeps the engine stable and safe.”

With the KTuner re-working the ECU, output jumped to 191.06 wheel horsepower, a 10.1- horse improvement over stock.

Back on the dyno, the Civic was tuned and re-run many times. After dialing in the all the pertinent tables, Sampson tipped the power scale back in our favor, ultimately spinning the rollers to the tune of 191.06 wheel horsepower. The air/fuel ratio was wrangled into a more power-efficient range between 12.5:1 and 13:1 and output jumped to a 10.14 wheel horsepower improvement over stock. Torque rebounded as well to 170.80 lb-ft.

Skunk2 MegaPower RR Exhaust/Downpipe

A properly designed exhaust system is critical to engine performance because it relieves backpressure produced by the restrictive stock set-up. This reduces pumping losses, or the power or effort it takes for the engine to move exhaust through the stock system. A higher flowing, bigger tube exhaust frees up that power and puts it to the pavement.

Installing the Skunk2 exhaust system was quite straight forward. It's refreshing working on such a new car because the bolts come off so easily. Tech Tip: Always hand tighten the pipe segments as you install an exhaust system. This allows you to adjust it as you go and properly tuck the pipes and muffler. Also check all the joints and ensure each one has a gasket. There is nothing more annoying than hearing exhaust leaks coming from your freshly installed system.

Skunk2’s 76mm MegaPower RR exhaust system for the 2012 Civic Si was developed to optimize engine airflow and volume through carefully selected, application-specific tubing lengths and diameters. The system is constructed of T-304 stainless steel, is robotically TIG welded, and features CNC mandrel bends. CNC mandrel bending allows for a constant tubing diameter throughout the bend, which results in precise fitment as well as improved exhaust gas flow. Each system is fitted with a resonator, includes stainless steel flanges, and is finished off with a straight-through, low-restriction racing muffler for uninterrupted flow.

Brandon McCray, media specialist for Skunk2, was quick to point out that in usual OEM fashion, Honda equipped the Civic Si with a restrictive header/downpipe and exhaust. Improving the OEM exhaust came easy. The factory design was simply not conducive to great flow due to the dual catalytic converters and 90-degree transitions. The plan was simple: increase the diameter to what the K20 prefers and eliminate the restrictive nature of the stock system.

The Skunk2 Alpha Header is a remove and replace procedure. Be patient and precise when removing the four mounting bolts. Since they heat cycle more intensely the bolts can be difficult. If you meet resistance bust out the WD-40. The middle image shows the 'collector' portion of the header. We are so used to seeing dedicated runners here we may never get our head around this setup. What will the new Civic turbo motors look like in this area?

The MegaPower RR for the ninth-generation Civic Si was installed in conjunction with the Skunk2 Alpha Header. As mentioned, this iteration of the Civic doesn’t have a traditional header with runners, a collector, and so on. “The downpipe/header on the 2012-and-up Civic Si is not an ideal setup and creates some issues with performance,” says Jeff Giovino, deputy general manager at Skunk2. “The first issue is the short and long ports in the head, the second is limited area for airflow, and the third is limited performance. While we have to deal with these issues, we strive to maximize the airflow by creating a smooth path with a large cross section area. We are unable to change the runner length or diameter, so everyone is on the same playing field when it comes to manufacturing a downpipe/header for these engines. The Skunk2 design uses a large, heavy duty cast elbow with factory position sensor, and high quality three-inch mandrel bent stainless tubing terminating to a three-bolt flange so you can connect factory and aftermarket exhaust systems without needing any adapters.”

The Skunk2 Alpha Series header for the ninth generation Civic Si also fits Acura ILX as a direct bolt-on unit. McCray says, “You should be able to see a clear difference in size between stock and Skunk2 bell-mouths. Our engineers went with this one-piece design using a three foot long, .065-inch wall, mandrel bent stainless-steel tube with a flex joint and OE mounting location for factory sensors because we wanted installation to be simple for the user. We know lot of our customers like to install things themselves, often times in the driveway or garage at home.”

In the final analysis our efforts bumped the Civic’s bottom line 20.6 horsepower and 8.7 lb-ft of torque at the wheels.

As advertised, the system bolted up like a dream. On the Dynojet the dream continued as the K24Z7 broke 200 horsepower, dropping 201.5 horsepower on the Dynojet’s rollers. The Skunk2 system delivered 10.4 horsepower above our intake numbers. The final tally shows a total gain of 20.6 horsepower to the wheels, as our Honda went from 180.9 to 201.5. On the torque side we saw a 8.76 lb-ft increase from 164.85 to 173.61. That’s a significant wake-up call for the already-sporty Civic Si.

Beyond the power, the revelation of this dyno session was the critical importance of ECU tuning in the latest sport compact platforms. If you drive a current-generation import you need to think software when bolting on hardware. And with every generation of car, engine, or ECU, that software may need to evolve so due diligence is in order. The bottom line is power is still possible you just need to understand how your engine and ECU will react to the aftermarket parts you throw at it.