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Top 10 Modifcations for the 8th Gen 06-11 Honda Civic Si

Posted by michael stiren on

8th Gen Civic Performance Guide
Top 10 Modifcations you can do to your FA5 / FG2 Chassis!


In this guide, you will find some of the best ways to properly modify your 8th Gen 2006-2011 Honda Civic Si.

To start off with this vehicle comes with one of the most popular performance Honda engines of today, The K-Series platform. This platform has been at the fore front of power gains and engine swaps. Currently this is the goto swap into nearly every Honda applicable and for good reason. This specific powerplant in the 8th gen is the K20Z3, very similiar to the K20A, this system utlizes a DBW (Drive By Wire) electronic throttle body to allow the car to operate its VSA (vehicle stability assist), which modulates throttle to help maintain a stable vehicle and keep traction under normal power ranges in check. This is how all new Hondas are the real only limitation is you cant easily run a individual throttle body setup.

The Basics about the Platform

Here we will have a look at each various section of the vehicle, how it performs, what it needs to work better, thoughts and ideas to get yourself up to speed and in the know of the 8th Generation Civic Si. Lets begin!

The chassis is solid, but can use some assistance. Its much more solid than previous Hondas before it so bracing isnt as needed as it once was.

The transmission is decent, with capability of handling 500-600hp. But beyond that you will be looking at building that up with some stronger gears to handle the power. The transmission also comes standard with a gear based LSD. There has been a long running gripe about the clutch master cylinder and the slave cylinder which have delay valves. Which can cause lock-outs and gear grinds in shifts from 1-2nd mainly at high rpm or racing type situations. That can be address by modifying (removing delay valves) or purchasing kits which do not have the valves. As well the vehicle is getting older and most cmc and slave systems fail to work over time or completely loose all hydraulic pressure and a replacement will have to be done. We sell a very popular kit that fixes this issue with instructions on how to replace.

Handling, from the factory the Si is a pleasure to drive, but the slightly open fenders and possibly a little too soft of a suspension makes for a good choice of just going with a performance orientated coilover suspension which can help dial down the ride height to sit on the tires better and allow you to play with damper settings to really dial in your comfort level as well have some play for track days.

Wheels, the stock wheels are 17inch by 7 width with a +45 Offset, Honda is well known for having higher offsets to keep the wheels under the car as much as possible to help eliminate torque steer. The Mugen Si took it to what is more known as its sweet spot in the handling department by going with an 18inch by 7.5 width and a+42 offset wheel that weighs 16lbs and was built by volk. With proven increases in handling by going to the 18inch, due to less tire squish at higher loads. It is certainly an upgrade to keep in mind when picking your next wheel for this vehicle.

The ECU & Tuning, as far as this vehicle its pretty forgiving with basic modifications, but if you want to take it further, using a tool like Hondata or Ktuner for your vehicle tuning can really unlock its potential. For example the Hybrid Racing Intake is a 3.5inch in diameter, the piping is too large for the MAF to properly read (mass air flow sensor). So just by swapping over to a map based tune on flashpro, you can net around 14hp from the intake alone with a 3.5inch for this car. Which is exceptionally large for a 4cyl, but time and time again its been proven that this K-Series motor likes efficient air. The other part is Rev Hang, Rev hang was something a lot of people just do not enjoy. So Flashpro got rid of it all together and can now even be directly tuned to your exact tastes. Rev hang is quite simply where the revs just hang, versus the more normal quicker drop as soon as you left off the gas. Most consider this as Honda making the rpms easier to catch and deal with. But performance minded people want things to be more responsive and this product addresses that. Also flashpro can be invaluable with datalogs, knock counts, timing and increases all by itself. Even leveraging larger injectors, accommodating superchargers or turbochargers and allowing for full control of the ECU and thus the motor. We have several customers pushing over 500-600-700hp in their vehicles and are running flashpro. Ktuner can do this as well, but it is a newer product and they are always getting better and trading off between each other. Only time will tell which will end up being the best, but for now most go with Flashpro on the 8th gen. But be sure to look into both products and we sell those currently on the site.

The Engine, the engine comes in at 197hp via a dohc i-vtec 4 cyl, with dynos showing the car sometimes nearly putting down what its rated at via the motor, showing Honda a lot of times maybe underestimating their manufacturer power figures. The engines are good for 500-600hp. But at those levels it may go from ok, to not ok pretty fast. Just really depends on the tune and how quick the torque comes in, what sort of turbo or supercharger is being used.

Naturally aspirated performance this motor can be improved upon in a large range of standard areas, Intake, Header, Exhaust, RRC (JDM Type-R) Manifold or getting the oem one ported and smoothed. Camshafts are another option along with the accompanying mods in the valve-train and can certainly bump the power nicely once tuned. Even adding E85 to the fuel mixture along with an upgraded fuel system and fuel injectors to handle the increased fuel requirements. Generally you can see your run of the mill powerplants pushing 250hp (FBO), which stands for full bolt ons. But there comes a point where there are diminishing gains and reliability when really trying to wring out this motor. Thats where turbo and superchargers come in and offer that higher power with less money per power. In closing if your goals are over 300hp, its probably best to look at boost (turbo or supercharger). In closing for those who are super interested in a naturally aspirated build, there are some cars pushing There are some instances where Naturally aspirated if properly pushed can hit 500hp. Which is nearly jaw dropping, but these types of builds have become pretty famous. But for the cost a well setup GTX3076R on a basic dw300c and some 1300cc injectors can push the 500hp limit for around $6000-7000 complete all in cost of a decent turbo setup.

Time to go Turbo or Supercharged? This has become a very popular platform to turbo or supercharger, with a huge plethora of already completed builds basically making an almost guide-book to follow. There are some popular turbo and supercharger setups that can push you from the modest 200hp platform into a 500-600-700hp and beyond monster of VTEC. Generally starting at around 4000+ for the turbo or supercharger setup. We sell a multitude of systems and each one has its own pros and cons. But to make it simple safe and short. These systems have proven themselves to be great power additions. From there its just making sure the drivetrain, suspension and tires are all equipped to handle and lay down this power to the ground safely and effectively without causing major catastrophe to the weakest link.

The shifter, some like it, some hate it. But the good thing, we all have different tastes and there are several options to fill the needs of each buyer. From full metal caged adjustable short shifter kits, to nearly oem plastic and very affordable setups, to even shifter adapters on the low end to get this car to shift quicker and with a shorter more sporty throw. As well there are shift cables to beef up that area, metal bushings and bearings to make a more crisp shifting response. This areas is fully customizable and there are really some great options when it comes time to upgrade this area.

Intake, Header & Exhaust, the big three that everyone always has a look at right away when they first embark on modifying the car. The good news is each area provides some solid gains for a 200hp 4cyl car. With the intake netting a possible 14hp, the header 12-15hp and exhaust 7-12hp depending on the brand, piping size, quality and flow and we will be going over all that in this 8th Civic Si Performance guide.

The parts (what to get & what not)

1. Intake

When starting out we generally suggest to get an intake. That is of course if your goal is to go naturally aspirated, you dont want to spend too much, want a little more performance and enjoy a good running car thats simple. Another thing to keep in mind you can sell off the parts you dont need if naturally aspirated doesnt fit your power goals down the road.

The basics of the intake is pretty simple in our eyes, get a 3.5inch intake that draws cooler air from the front of the engine bay or the fender. Your going to net around 14hp with flashpro. So, Which intakes are 3.5inch? Well we have the list right here.

Top 3 Intakes to get for the 06-11 Civic Si

- Hybrid Racing Cold Air Intake 06-11 Civic Si
- Skunk2 Cold Air Intake 06-11 Civic Si
- K-Tuned Cold Air Intake 06-11 Civic Si

These intakes require: Hondata Flashpro

Sold out
Sold out

2. Header

Next on our list is which is the best header to get? This is another subject we can give thanks to dyno submitted by customers and committed enthusiasts of a digital age who also provide this info online through research / discussion boards. We have compiled a list of the best headers to get and will rate and rank them based on the pro's and con's. Generally all designs stick to the 4-2-1 setup.

For this one we will go over 4 main headers.

1. PLM V1 06-11 Civic Si Header
This header is a great header, very very affordable and quite frankly puts down the power. At $350 and the fact that this production header puts out top power is great. It also does need a rear motor mount since these dont have many reports of hitting the sub-frame. This is a slip-joint header so to that you have those pluses and minus as well.

2. Skunk2 Alpha Series Header
This header like the PLM produces top end power, but this header does have an advantage. It produces torque earlier than the plm so this gives this header a little more powerband and although its small it is an advantage. The cost of these at the time of writing is $483.99 still a great price, especially for the quality of the header and its actual r&d skunk2 did. We find this to be a top choice. Keep in mind it is recommended to get a rear motor mount, possibly upper torque mount and you may need to buy the extra 02 extension as this header moves the bung down a tad further.

3. Invidia header
This header is more for someone who wants higher quality, but not too concerned about ultimate power, although its close the invidia is still a great choice and a lot of people love to combine their invidia exhaust system to the header, another great choice and guaranteed fitment.

4. K-Tuned Header
As much as we want to love this header, and how popular it is, the power gains arent that high on this one. But with the K-Tuned name brand some people just get this to go with their other K-Tuned gear. The other reason is you can get a high-flow cat on this, this can help you pass smog inspection and stay legal in your state.

In the end these products are all great, we would highly suggest the top #1-2 choice. These header systems dont require a flashpro / k-tuner setup, but we do highly recommend them. Also the o2 bypass, cel bypass adapters are only used for those who dont have flashpro. A CEL light will appear on the dash of the vehicle, but this is just an exhaust warning and it doesnt effect the performance of the vehicle. Flashpro has a switch to turn off this warning (essentially removing the annoying light from drivers view).

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