Hallelujah. Praise Honda for stepping up to the plate and finally bringing us a car worthy to succeed the ever-popular EG6 (1992-'95) and EK4/9 (1996-'00) platforms. Let's put it out there that the EM2 coupe (2001-'05) and EP3 hatch (2002-'05) were half-hearted efforts by Honda to try and recapture the magic they had a decade prior. While the EP hatch registered some interest on the radar screen, the 160-horsepower, 2.0-liter engine put a stake in the coffin as many were left on the dealership floor.
Unlike the EP3 hatch, the 2006 Civic Si (FA) is equipped with an incredibly potent 197-horsepower K20Z3 powerplant that has brought back a glimmer of hope to the Honda faithful. No longer are we left wondering what the true potential could have been.
The biggest difference in the K20Z3 engine is the drive-by-wire throttle, which some enthusiasts already are complaining about. Between shifts the throttle body butterfly is kept open for a split second before closing. This causes the engine to rev up when you push in the clutch pedal and release the accelerator. It has been a trend for car manufacturers to move towards a drive-by-wire system for better transient emissions between shifts and also a smoother drive during cruising.
The downside of a drive-by-wire system for performance enthusiasts like us is now we are at the mercy of the factory ECU until the aftermarket gets up to speed to develop an engine management system for the vehicle. We know from previous experience with the K20 powerplant there is a lot of power to be generated from a stand-alone system. Alas, for now we just have to cross our fingers and hope that the performance products we install will work with the new drive-by-wire system.
Luckily, companies such as AEM/DC Sports, Skunk2, GReddy, HKS, and K&N already offer performance upgrades for the '06 Civic Si so the tuning can begin. Although not officially released until December 2005 as an '06 model, Honda took the initiative and gave out a number of vehicles to aftermarket performance manufacturers so they could start building products for the vehicle. One of the companies to receive a vehicle was AEM. Wasting no time at all, AEM developed an intake, exhaust, and race header, and had the products on the shelves ready to ship before the Civic Si was even released to the public.
Fortunately for us, we were able to locate our test vehicle from a friend who was pounding on the local Honda dealer's window the day the new Sis came in. With only 250 miles on the odometer we strapped the Honda onto a Dynojet chassis dyno. Who needs to break in their engine? We say driving below 5000 rpm for 1,500 miles is a load of crap.
On XS Engineering's Dynojet, the K20Z3 engine performed like a champ. The 197-horsepower and 139 lb-ft of torque at the flywheel factory ratings translated to 179.1 horsepower and 129.1 lb-ft of torque to the wheels on out run. The most remarkable part of the dyno run was the power curve. The engine redlines at 8200 rpm but it is clear to see that if the engine was allowed to rev out to 8500 or 8600 rpm it would continue to generate power. From reviewing the dyno graph we estimate the engine would make an additional 3 to 4 horsepower with a higher redline. Considering the fact that the engine is rated at 197 horsepower at the flywheel, the power loss to the wheels is only about 9 percent. That is an extremely low drivetrain loss percentage, so either Honda is underrating the power output of the engine or the drivetrain is barely soaking up any power.
With an established baseline reading under the Civic's belt it was time to move on to the first modification for the Si by adding a cold-air intake from AEM. The AEM system was designed and tested for maximum overall power and comes with the company's new Dryflow air filter.
Unlike the previous design that utilized an oil-soaked cotton-gauze filter element, the AEM Dryflow filter is constructed from completely synthetic microfibers. The synthetic fibers are extremely durable and can even withstand the harshest chemicals, including our personal favorites: brake cleaner and gasoline (not that we recommend cleaning the filter with either of these chemicals). With today's highly sensitive vehicle equipment, excess oil on the filter can be pulled along the intake tract and foul the MAF (mass air flow) sensor, which then affects engine performance.
The AEM cold-air intake is constructed from lightweight aluminum piping that is mandrel bent for superior flow. AEM supplies all the necessary hardware. The best part of all is that the system is 50-state legal and will not void thw factory warranty.
On the dyno, the AEM intake-equipped Civic Si generated 183.3 horsepower and 133.1 lb-ft of torque to the wheels, an increase of 4.2 horsepower and 4.0 lb-ft of torque. More importantly, the K20Z3 engine responded extremely well from 4500 to 5200 rpm where the AEM intake increased power output by 5 to 8 horsepower.
With the intake tract free-flowing to our liking we then concentrated on maximizing exhaust flow. Up to the task was a DC Sports single-canister after-cat exhaust system. During initial testing with the system DC Sports found that the factory Civic Si exhaust system is extremely efficient. DC Sports concluded there would only be minimal gains if solely an exhaust system were added to the Civic Si. Therefore, the only way to extract maximum power from the exhaust system is to also utilize the DC Sports race header. Since Greg Nakano of AEM did not mention this tidbit of information to us before our dyno session we had went ahead and tested the exhaust system without the race header. On the Dynojet, the exhaust system still produced more power than the stock exhaust but the gains were not as high as we originally expected, and of course what AEM already knew to be true. The DC Sports exhaust increased the power output of the Civic by 3.1 horsepower and 3.2 lb-ft of torque. The Si now registered 186.4 horsepower and 136.3 lb-ft of torque.
The last of the modifications was the addition of the race header from DC Sports. The race header is only meant to be used off road and is not street legal. Nonetheless, for curiosity sake we wanted to see what this baby is capable of. The ceramic-coated 4-2-1 race header is tuned specifically for the Si engine. The equal-length, CNC mandrel-bent piping is properly sized for more power across the entire rpm range.
Removing the factory header and cat, however, was a much harder task than we anticipated. Although the catalytic converter was easy enough to remove, the factory header was considerably more difficult. Unlike the RSX, which has the same engine and similar platform design, where you can access the header bolts from the engine bay, the Si's layout puts the engine underneath the cowl section of the firewall. This makes it impossible to reach the bolts from up top and thus requires removing the bolts from underneath. Unless you have a lift at your disposal it is almost impossible to get to them.
After spending nearly an hour to remove the five 14mm bolts we now had a second problem. On the RSX we were able to remove the header from the top of the engine compartment, but that is not even an option with the Si. As such, the only way out is from the bottom. Needless to say, because the engine is situated further back than in the RSX, there is much less room to remove it. After some gentle persuasion, and a bit of cursing, and some bloodied arms and fingers we were able to come out victorious.
Thankfully, installing the DC Sports race header was much easier than removing the stock header. In the end, the hard work paid off and the race header generated an additional 10.8 horsepower and 5.6 lb-ft of torque to the wheels. The Civic Si now peaks out at 197.2 horsepower and 141.9 lb-ft of torque to the wheels. Overall, with the three modifications we saw an increase of 18.1 horsepower and 12.8 lb-ft of torque, which are pretty impressive numbers considering the engine is already generating more power in stock form than we expected at the beginning.
Finally, Honda has put forth the effort to give Americans what they have been requesting for the past two decades. Will the new Civic Si be the savior for Honda? Only time will tell, but for now we think the Si will fit in just fine with the right tuning mods.