Skunk2 Racing 412-05-1930 Alpha Series Header for Honda Civic Si

Dyno video:[...]I included my dyno chart, 226 whp & 161 wtq.Skunk2 3.5-inch Cold-Air Intake (Part# 343-05-0100)Skunk2 Alpha Header (Part# 412-05-1930)Invidia Q300 70mm Cat-back Exhaust (Part# HS06HC4G3S)Hondata FlashPro (13.0 A/F ratio, dyno tuned by DB Performance in MN)93 Octane, everything else was OEM Honda.ProsLooks decent.Very inexpensive for a K20Z3 header.Great power output for such a low price.ConsNo cat, kind of loud after installation.Very difficult to install, a lot of steps required (but I'm sure every header for this car is hard to install).CommentsOverall I think this is the best bang for the buck. I personally prefer headers with a cat so my only regret was not getting the Vibrant Racing header that comes with a high flow cat. I miss how the stock system was so quiet, but that's just me. This header does come with a hanger relocation bracket, I added pictures for your reference. If you don't want to splice your wires you can buy an OEM Honda O2 Sensor Extension (Part# 06320-SNA-315), this helps you connect the first O2 sensor since it sits so far back on this header. This header comes with a defouler meant to be used only for the second O2 sensor, I accidently used it for the first O2 sensor thinking that's what it was for but a friend corrected me on this. No check engine light if done right, good luck!

I have this installed on my 2009 FG2 with the Megapower RR exhaust.DIFFICULTIES: As the other reviews have mentioned, it is very difficult to install on the Si chassis and engine. The stock exhaust, cat., and exhaust manifold are difficult to remove especially if the bolts are rusted and/or seized from winter exposure. It would be more convenient to install it at a muffler shop; the mechanics may remove the subframe for more access.Another difficulty is that the stock secondary oxygen sensor is not long enough to screw into the secondary bung/hole. Honda and Skunk2 feature a clip-on extension wire. The Skunk2 one is: 201-05-0614. This one is cheaper; the Honda OEM one is $90~. I highly recommend my fellow Si owners to not neglect this. Otherwise, the malfunction warning indicator will turn on. The engine will also produce a constant rattling or screech; it had done this on my Si without the secondary oxygen sensor.About a couple months after installing this, the header would vibrate and knock if I drove over deep puddles of water. However, this would not happened in dry weather.QUALITY: Since this header does NOT have a catalytic converter, the exhaust emits bitter, pungent, and unrefined emissions. When the car is stopped and idling with windows open, I can smell the odor.SOUND: The stock exhaust manifold produces a high pitched sound. The Alpha header with the Megapower RR is much more aggressive and louder. At low rpms (1000-3500), the Alpha header changes the exhaust flows to a rumbling, growling, and low pitched sound. At 4000-5500rpm, the exhaust sounds like a nagging, exaggerated fart. When VTEC kicks in at 5800rpm, there is still the distinct change in tone. And at redline, the sound is roaring VTEC. I must warn you that this setup is much louder and annoying than the stock exhaust manifold. This is especially true when cruising on the highway 55 mph at 2500rpm. Even with the windows closed, the exhaust sound makes it difficult to listen to music via the auxiliary. Overall, I must warn others that the cost of installing this header is reduced comfort and much greater noise in exchange for improved horsepower throughout the powerband and top end. It is VERY LOUD just to warn you. If you love VTEC and driving a more aggressive sounding Honda, then you should buy this header.PERFORMANCE: I have not tuned or dynoed my Si, so I do not know the specific improvements in horsepower. The only other engine mod installed is the K&N Typhoon air intake. With the intake, header, & exhaust setup, I only feel a marginal improvement in acceleration because the engine is still tuned to the factory valve timing of a low, straight line torque band. However, acceleration past 4500 rpm is certainly improved. Maximum horsepower at redline vibrate throughout the car.

In terms of quality this is an excellent header. The install is very tricky requiring a lot of under car yoga and you will need to be sure to pick up hardware, manifold spring bolts, and gaskets as they are not included. The O2 sensor wires will also need to be extended or an extension harness is needed to make the install work. There is a donut on the back of the header that attaches to the mid-pipe that will leak a little bit though the leak will improve as the car is driven and the donut "bakes in." This makes really good top end power and improves the response of the car though does not seem to generate low-mid range power the same way the vibrant header does. I love the way it sounds coupled with the 3" Full Race exhaust I have on my car though it is really loud.

great addition to my kraftwerks 08 si. replaced a 1320 2 piece header. better build quality, bigger piping, and 1 piece long tube style. got it on a warehouse deal so even better.

One of the pipes broke...simply don't know how it happened.

Great I have a coupe with a wire harness and fugita intake and vibrant exhaust my 2008 put down 224hp

is a great product but if u have a honda civic si 2008 4dr make sure u buy the extenion wire for the o2 senssor

If you want your car to sound like it has more power than it really does than this is the header for you! And it's not as loud as people make it our to be.

Very good product exactly the same as if i would of bought it on skunk2 site came alote quicker then the skunk2 exhaust i bought from the skunk2 site