Honda’s 2006–11 Civic Si Is a Sport Compact Sweet Spot We Won’t See Again
I’m sure there were a good number of friends and colleagues who thought I had really jumped off the deep end. I mean, I spent most of my life beating my chest about how V-8 power was superior and how small-bore Japanese mills were annoying and worthless. But there I was in the summer of 2021, making a deal on 71,000-mile ’08 Honda Civic Si coupe. I’d really done it now, abandoning all my morals to buy the very thing I so loved to ridicule.
But wait, there’s more!
I sold my 1969 Pontiac Grand Prix to make room for my new Honda. Yet here’s the thing: Three years on, I maintain that buying an eighth-generation Civic Si was the best automotive purchase I’ve made.
Honda nuts get it, but for everyone else’s benefit, let’s take a detour to discuss the Si lineup. Introduced in 1984 during the third generation of the Japanese Domestic Market (JDM) Civic, the Si, or “Sport Injected,” variant offered a sportier platform for the small Honda, much like the Rabbit GTI did for Volkswagen the previous year. The U.S. would get its first Si Honda in the form of the Prelude Si in 1985, quickly followed by Si variants of the Civic and CRX. Honda’s Si badge today carries with it the legacy of tight-driving, high-revving Honda goodness, indicating a car that that does daily driver duties just as well as it is does weekend shenanigans down back roads.
The eighth-generation (2006–11) Civic Si is one of the last of the breed to perform how you expect a spunky Honda to perform. The brand, of course, is famous for its high-revving engines; that’s the real “Power of Dreams.” In fact, one of the main complaints of the previous generation of Civic Si (the EP3 of 2001–05) was the toned-down nature of the engine, both in output and its ability to rev. There was also the matter of the car’s polarizing looks and distinct lack of an aero kit, and speculation has long been that Honda made these changes to drive buyers to the Acura RSX Type-S.
The eighth-gen Si saw Honda bring to market a car that the public wanted. The 2.0-liter K20Z3 engine made a respectable 197 horsepower at 7800 rpm, with the ability to scream all the way up to 8300 rpm before fuel cut-off. The last Civic to offer that sort of spunkiness was the 1999–2000 model with its rev-happy B16A2.
Sliding in behind the wheel of a stock Civic Si, you’re greeted by the standard array of gauges from any other eighth-gen Civic—which simply means a giant analog tachometer in the center and that’s it. Mimicking a heads up display, the digital speedometer sits atop the dash with a line of sight right at the base of the windshield. Where the Si diverges from the standard model is the red backlighting to the dash and radio, and of course the giant “Si” logo in the center of the tach. The seats are moderately bolstered while remaining cushy enough to be comfortable during long drives. But overall, the interior is decidedly Honda, which is to say, there are no premium materials and no extra amenities.
Where the Si starts to make sense is when you drive it. In stock trim, the K20 is quiet and civilized at idle and at cruising speeds, although you do get a sense of the car’s sporty focus while shifting gears through the close-ratio six-speed gearbox. It is typically Honda-precise (not quite S2000 or Integra Type-R, but sportier than, say, a Mk 5 GTI), but you had better like rowing your own gears, because you’ll be doing it a lot in traffic.
Give the long pedal a good press and the revs climb quickly. VTEC engages at 5800 rpm, and you feel the car pull all the way to redline. With the helical limited-slip differential, the Si tracks straight under full throttle with minimal feel of torque steer, even when VTEC comes on. Handling is more or less precise; the steering is highly responsive and the stock suspension is stiff, with minimal body roll under hard cornering. Understeer will rear its head if you approach a corner too aggressively, however, it’s not significant.
Needless to say, the eighth-gen Si is an excellent car in stock form—satisfying enough that I refrained from modifying mine for an entire year. Then the little shortcomings started to creep into focus. Even the best-engineered cars have their compromises, and the Si’s biggest one has to be the engine programming. On the low profile cam, the car makes great economy, but dig the spurs in and that 5800-rpm VTEC engagement feels like it hits too high up in the rev range, like there’s a flat spot in the power band until that point. If you shift before redline and the rpms drop below VTEC engagement, the car falls on its nose until you’re back on the high profile cam again. And though the act of shifting itself is precise, the Si is equipped with rev hang, an emissions-reduction measure that keeps the throttle open for a moment when the clutch is engaged in order to efficiently burn off fuel in the intake runners. It’s a minor annoyance that can get in the way of quick shifts, and the overall driving experience. Finally, as with any car, overall performance can be improved by upgrading tires, brakes, and suspension for a more balanced driving experience.
And so, in the winter of 2022–23, I set about addressing these little pieces that I felt got in the way of the ideal Civic Si driving experience. Now, working on an eighth-gen Civic is not like playing with earlier generations—or that old Grand Prix. The engine compartment is cramped; they stuffed 10 pounds of equipment into a 5 pound bag. If you’ve worked on a fourth-generation Camaro or Trans Am, you’ll get it. Research led me to conclude that the best way to improve the power band of the K20 was to tune it, and while I was in there to do a few basic bolt-on modifications to maximize my investment in a tune.
Luckily, working with Hondas means parts are plentiful and reasonably priced. To free up incoming air, I bought a cold-air intake system from Skunk2. The intake pipe is significantly larger than stock and the filter draws air from behind the front bumper, well away from the engine compartment. It also eliminates a complicated baffling system inside the driver’s side fender used to mute induction noise, offering a more direct pathway to the intake manifold.
If you’re bringing air in more efficiently, it needs to exit more efficiently as well, and for that I installed a Skunk2 Alpha-series header, with its massive primaries and tri-y design. This was by far the most complicated install of the whole endeavor, as gaining access to the old manifold on the back of the engine requires a lot of parts to come off, before you can thread it through a tiny space between the firewall and subframe to get it out. Installation of the header was a breeze in comparison. And because I like my neighbors, I went with the quietest, readily available aftermarket exhaust I could find, which was the Invidia Q300 in 70 mm (2.75 inches). Not only did the polished stainless exhaust look incredible, but the exhaust tip has less of that “fart can” aesthetic with offering more of an OEM-plus look.
With any bolt-on modifications to a modern car, a tune is necessary to unlock their full potential and ensure the longevity of the engine. A Hondata tuner was just the ticket, as it offers reliable base maps along with the ability for a talented tuner to customize the tune. I went the custom-tune route, using Innovative Motor Works out of Pennsylvania to do data-logging and track revisions to achieve optimal performance. This process took several weeks of tuning and logging drives, as everything from basic fueling to timing both in and out of the VTEC range were honed. In the process, rev hang was eliminated and VTEC engagement was lowered to around 4200 rpm, making for a very linear power delivery. As tuning progressed, I set about working out some bugs related to the bolt-ons. The big header primaries would rattle against the sub frame, so I installed a set of Hasport polyurethane engine mounts, which I later found out is a necessary upgrade for anyone running the Skunk2 headers in this platform.
With power delivery sorted, handling and stopping were next. At the recommendation of my colleague (and amateur racer) Eddy Eckart, a sticky set of Michelin Pilot Sport 4S tires went on. To improve braking feel and initial bite, and to reduce heat fade, I installed a set of Hawk pads and rotors. I cured the understeer issue by replacing the 17-mm rear sway bar with a 22-mm unit.
Was the effort worth it, and did I achieve what I was going after? Honestly, it exceeded my expectations. The bolt-ons and tune made a night-and-day difference. The engine pulls strongly from idle to redline without any loss in economy. With the freed-up intake, the transition to VTEC is much more noticeable, with a great howl coming from under the hood when it kicks in. The exhaust sounds good without being too over the top, though there is a bit of unavoidable drone in the cabin while cruising. Handling is close to neutral and thus much improved, and the sticky tires and bigger sway bar ensure much more confidence when chucking the car into a corner. It’s not quite an Integra Type-R, but it’s just about the best version of an eighth-gen Si it can be without going wild.
The greatest thing I came to appreciate about Honda ownership is the bang-for-buck proposition the Civic Si offers. They are fairly ubiquitous, with plenty of stock sedans or coupes to choose from, and right now, a clean, sub-100,000-mile Si can be had for under $10,000. That’s Miata-beating performance for the same money as a clean Miata. A collector-grade, low-mile Si is closer to $20,000. Top of the heap is the Mugen Si offered in 2008, which is the sedan version done up with bits from the famous tuning house Mugen such as a body kit, sport exhaust and suspension tweaks. With 1000 produced, they’re fairly uncommon, and exceptional examples have sold for as much as $40,000.
There are plenty of owner-modified examples out there, too. The K-series engine’s responsiveness to upgrades means that they run the gambit of lightly warmed over, like mine, to supercharged and turbocharged cars easily making upwards of 400 horsepower. Perhaps the most popular major upgrades are K20/24 “frankenstein” builds. This is achieved by sourcing a cheap K24 (2.4-liter) and swapping the high-flowing cylinder head off of the Si’s K20. The upgrade boosts torque significantly though it sacrifices the ultra-high redline.
Looking back, the eighth-generation Civic Si was the peak of the traditional Honda sport compact car. The ninth-generation Si (2012–15) would receive a larger K24 engine, making nominally more horsepower with an appreciable bump in torque, though with a redline 1000 rpm lower than that of its predecessor. The tenth-generation Si (2016–2021) would see the engine size shrink and introduce turbocharging, with no real change to output from previous series.
The eighth-generation Civic Si has the right formula to become a sought-after collectible. It does Honda things incredibly well and punches above its weight in terms of performance. It’s a car you can drive at 10/10ths and not risk your life or license. And just like the 1999–2000 Civic Si, which saw an explosion of interest a few years back, it is a tight-handling, high-revving driving experience that’s hard to find anywhere else. For me, seeing the market go up means very little when this car is likely to remain stay in my garage a very long time.
