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Power Pages: 2003 Honda Civic Si

By the time this issue hits the stands, you will probably have already seen your fair share of souped-up Civic Sis roaming the streets of your neighborhood. The car that started it all is finally being produced at the factory with an engine that U.S. consumers might actually keep. It's been a long and windy road for Civic hatchback owners that wanted great stuff straight from the factory. This isn't to say that any of the previously available powerplants were slush, but when Honda decides to put the DOHC VTEC motor in coupes and give up on the hatchback altogether, that's pretty much a slap in the face. Well, apologies are now in order and the car that everyone has always wanted is finally here.

The Engine
The K20A3 engine is part of Honda's new line of K-series powerplants. Taking its fair share of design from the Acura RSX engine, the K20A3 makes its name as a 2.0-liter dual overhead cam motor with a factory rated 160 hp coupled with 132 lb-ft of torque. Honda VTEC technology (that's Variable Valve Timing and Lift Electronic Control for you, Mr. Armando M.) benefits from a new proprietary technology that Honda dubs "VTC". It's not mini-VTEC--it actually stands for Variable Timing Control, a system that, in essence, acts like an electronic cam sprocket on the intake camshaft, continuously adjusting its phase to produce the maximum amount of power where it's needed. Numerologists, engine builders, and Honda nerds alike will find the following numbers useful: a total displacement of 1998cc, static compression ratio of 9.8:1, 16 valves, and 4 pistons whose 86mm bore diameters travel in a "square motor" configuration of 86mm stroke.

Performance Components
It may seem hard to imagine that a car so finely tuned from the factory could have any more room left for additional power extraction, but if you look at it from a different perspective--one in which the car is essentially "detuned" to meet new car and emissions regulations--it becomes apparent that any increase, no matter how small, is a good one, as it tends to bring you closer to what the engineers had in mind before they were buried underneath all of the bureaucratic restrictions.

With this in mind, the first OEM piece to go will be the intake system. In its stead, we choose an open element filter, produced by K&N, mated to an intake adapter produced by the Tuner Staff. K&N filters are world renowned for their performance and durability on and off the track. They have set the industry standard by which all other filters are measured. While the intake adapter may seem like a miniscule piece in the world of import performance, without it, one is doomed to the factory airbox or makeshift homemade remedies that tend to lessen performance rather than increase it.

With the intake in place, the next performance bolt-on goody would be the exhaust system. A'PEX Integration, another company on the forefront of today's technologies, was among the first to step up to the plate and introduce an exhaust system for the new car. Our test exhaust is of the N1 variety, featuring a polished SUS304 stainless steel canister, specially coated piping to inhibit rust and corrosion, and a 115mm (4.5-in.) tip. Designed with N1 endurance racing in mind, the exhausts are known for their maximum output efficiency, especially from high-horsepower motors.

The final piece of equipment for our test is the A'PEXi S-AFC Digital, the Wundertool of tuners everywhere. With this piece of electronic wizardry, you can fine tune RPM-specific fuel supplies and load-dependent ignition timing, in addition to monitoring some of the car's other functions. The cost of installation and tuning of the device is considerably less than comparable stand-alone units and, according to tuners everywhere, the unit does what it's supposed to do when it's supposed to do it, and that's what makes it a crowd favorite.

Dyno Testing
The tuning on the EP3 was performed at XS Engineering's dyno facility. Since the test car was a daily-driven street car, the mileage break-in period had come and gone before our hands started tinkering with things under the hood. With the car strapped on the Dynojet dynamometer, the rollers were spun to a base horsepower rating of 130.2, with torque checking in at 118.2 lb-ft.

Once the baseline numbers were established, the hood was popped open and work began on the intake. With plastic shields and covers scattered about the engine bay, installing the intake was slightly more than a bolt-on affair, although no major components had to be removed or relocated. Dyno testing showed that the factory airbox and resonator combo placed a rather large restrictive load on the engine; the K&N extracted a peak 8.6 hidden hp and 2.6 lb-ft of torque. Final peak output jumped to 130.8 hp with torque coming in at 138.8 lb-ft.

The A'PEXi N1 exhaust was next on the list. Using a design that minimizes re-direction of airflow and maximizes output volume, we expected good numbers from the unit. We were, however, factoring in the point that the Si is a natural performer and expecting that the OEM muffler would reflect Honda's desire to produce a great car straight out of the box. Still, the A'PEX exhaust managed to boost power in the mid- to upper RPM ranges, with torque increasing in the same areas. Peak output rose to 140.1 hp and 122.2 lb-ft of torque.

Because the Si is one of the newer VTEC models on the market, we were sure that people would be very interested in how well the factory fuel and ignition maps took to some "tuner tinkering." The car's new production year meant, however, that it's ECU would fall under OBD-II guidelines, making it more difficult to obtain accurate numbers. Because the O.E. ECU has the ability to relearn changes made by the AFC, it had to be reset after each fuel change. This doesn't mean that you have to reset the computer every time you tune the AFC; it just means that you don't want the computer to remap itself based off the old AFC settings. Dyno tuning the S-AFC meant that the car had to be precisely warmed-up to the same water temperature as the baseline run, eliminating some of the variables involved in different engine operating temperatures. Final tuning produced 143.5 peak horsepower, up 3.4, and 125.4 lb-ft of torque, up 3.2.

The new Si is back and has begun the quest to answer the call of thousands of Honda enthusiasts that want something more "straight off the showroom floor." And, because of its heritage, there should be a dramatic influx of available parts for the platform, especially given its striking similarity (engine-wise) to the equally popular Acura RSX platform. With that in mind, our tests are just the tip of the iceberg for this new kid on the block.

COMMON SWAPS: K20A2 (2002 Acura RSX Type-S
The Parts
K&N AIr filter $ 60
A'Pexi n1 exhaust $599
A'PEXi Super AFC $419

A'PEX Integration
(714) 685-5700

K&N Engineering
(909) 826-4000

XS Engineering
(Dyno/installation facility)
(714) 698-8300

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