If you were to surmise which vehicle is the most popular in the scene, the 1992-'95 Honda Civic would be very near the head of the class. When APEXi elected to develop a street turbo kit, the company did well to aim its efforts at this particular Civic. The car has many advantages beyond its popularity. These Civics can be found online between $5,500 and $10,000 and we are sure many can be had for less in traditional newspaper classifieds. These are OBD-I compliant powertrains, which are easier to deal with and tune than OBD-II, plus you can get a hatchback.
The D16Z engine is a gem. It's factory rated at 125 hp at 6600 rpm and 106 lb-ft of torque at 5200 rpm. The powerplant is a VTEC, single overhead cam design that has proven its mettle on the street and at the strip.
With its roots in Japan, the idea of a turbo kit is in no way alien to APEXi, but this kit was developed by APEXi USA in the United States. The prime-time player is an IHI AX53B60-P18 ball-bearing turbo that was selected because it provided the best combination of spool-up and top-end flow. The insurgence of ball bearing center sections has dramatically increased the versatility of modern turbos. With the reduction of friction provided by the ball bearing center section, turbos can run bigger housings/wheels and produce more flow at higher engine speeds without sacrificing as much responsiveness on the bottom end. The APEXi kit includes a cast-iron manifold that has superior durability than tubular manifolds. Fuel enrichment is handled by a high-capacity pump and adjustable regulator. A Power Intake filter kit, the appropriate plumbing and all necessary mounting hardware round out the kit. On the optional side, APEXi offers a GT intercooler and fuel system upgrades. For our testing purposes, we will evaluate the stock non-intercooled kit and the upgraded front-mount intercooled kit.
Off To The Dyno Cell
Our testing was performed on APEXi's Dynapack dyno and an APEXi V-AFC was used in the tuning process. Test sessions prior to the development of the turbo kit returned power readings of 110.4 hp and 92.6 lbs-ft of torque in stock trim. With the kit generating its prescribed 6 psi and running through the cat with stock injectors, the test mule was once again at the mercy of the Dynapack. Power jumped to 171.4 hp and peak torque increased to 132.0 lbs-ft. The kit allows the power-hungry to feed their needs to the tune of 61 hp and 39.4 lbs-ft of torque at the wheels. What would the kit produce with the addition of the optional front-mount intercooler? The APEXi GT-spec cooler was grafted in the system and nothing else was changed. There was a 1 psi drop in boost pressure across the intercooler, so the IHI hairdryer provided only 5 psi to the engine. But the test illustrated the power of intercooling because despite the boost drop, the colder charge air netted a 15.4 hp boost to 186.8 hp. Torque also saw an improvement to 141.7 lbs-ft. The logical thing to do would be to turn up the boost pressure and "rescue" that lost pound. This would add even more power to the bottom line. Theoretically, boost could be turned up past 6 psi without the risk of detonation, but this should not be attempted until the fuel system is deemed capable of handling the added demand. This is where the APEXi fuel system upgrade would come into play but this alters the kit to off-road status. We hope to test the all-out version in the future.
The APEXi Civic turbo kit is currently a CARB pending affair with optional components offered for off-road use only. While we are not sure when APEXi will complete the CARB testing procedures, we can report that the kit delivers the goods when you drop the hammer.
Power Tote Board
Test Power Torque Hp Gain Tq Gain
Baseline 110.4 92.6
APEXi Turbo Kit 171.4 132.0 61.0 39.4
APEXi Turbo w/intercooler 186.8 141.7 15.4 9.7
Total Power Increase 76.4 49.1