A'PEXi VTEC AFC
By Robert Choo
Photography: Robert Choo
In the world of golf Tiger Woods is probably going down in the history books as the best golfer of his time maybe all-time, unless another 20-something-year-old comes along and blasts him out of the water.
Just like Tiger and his pure dominance on the links, the Honda VTEC engine dominates the performance aftermarket in its own right. No other internal combustion engine comes close to its cult-like following of small displacement power. Today, we see hundreds of manufacturers designing and developing performance products for Honda VTEC powerplants. Whether it is the 1.6-liter SOHC VTEC engine found in the 1992-2000 Civic or the 3.2-liter quad-cam Acura NSX engine, manufacturers have found ways in extracting more horsepower from the already potent powerplants.
Since, the company's introduction in 199? on U.S. soil, A'PEXi has unleashed a number of high-tech electronic products on the import scene. One such product was the original Super AFC that allowed the user to fine-tune the fuel curve at five preset rpm points. A more technological advanced unit superseded the original unit, but it was still dubbed the Super AFC. The new unit utilized a digital screen, allowed for more tuning points (nine user-selectable rpm points) and also featured monitoring capabilities (check out the November '99 issue for complete review).
A'PEXi has done it again with the release of the VTEC AFC (V-AFC), a piggyback fuel computer for VTEC engines. The V-AFC and the original Super AFC share similar fuel tuning capabilities with one big exception--changing the VTEC engagement point. The V-AFC is a very potent tuning weapon for enthusiasts utilizing performance camshafts in their VTEC engines. One of the common downfalls of VTEC performance camshafts is the dip in the powerband due to early engagement of the VTEC effect. By utilizing the V-AFC, you can eliminate the "dip" by engaging the VTEC later in the rpm, resulting in a smooth curve.
Like the Super AFC, the V-AFC incorporates three different modes: "Monitor," "Setting" and "Etc."
In the monitor mode, the user is allowed up to four data channels at once; intake pressure, throttle position, engine rpm, air correction rate, ECUs VTEC solenoid output and V-AFC VTEC solenoid output. The data channels can be viewed in three different ways: numerical, digital analog meter and graph display. Data-logging capabilities are also part of the monitoring mode. One channel can be recorded for 60 seconds, two channels for 30 seconds, three channels for 20 seconds and four channels for 15 seconds.
The most important of the three modes is the setting mode. The setting mode is where all fuel adjustments and VTEC engagement points are tuned. In the setting mode, the user has access to the seven different parameters. Fuel enrichment for wide open throttle, partial throttle, VTEC engagement point setting, VTEC unmatched (compensate for ECU and VAFC VTEC control difference), throttle position for wide and narrow settings, fuel correction for high camside and fuel correction for low camside.
The last of the three modes is the etc. mode. Before jumping headfirst into tuning the engine for more horsepower, the etc. mode must be accessed, so the engine being tuned corresponds with the V-AFC. The etc. mode has six different parameters to utilize; sensor type, car select, graph scale, sensor check, vacuum fluorescent display (VFD) brightness and initialize. Of the six parameters the sensor type, car select and graph scale has to be programmed before starting the vehicle or the engine might not run.
Many power-hungry enthusiasts have asked, "so does it make power?" As we mentioned earlier, the true potential of the V-AFC can't be fully realized unless the engine is moderately modified. A bone-stock VTEC engine with stock cams and factory exhaust will show little if any increase in power from tuning. Our candidate was an Acura Integra LS equipped with a Japan-spec B16A engine. The engine has been modified with an AEM cold-air intake, DC header, Tanabe Racing Medallion exhaust, SPW Civic Type R throttle body, SPW Integra Type R intake and exhaust cams and Hayame Adjustable cam gears. In its current fighting trim the engine pounded out 14x.x hp and 10x.x lbs-ft of torque to the wheels. From viewing the dyno curve we were able to establish the VTEC was engaging too early, causing a dip in the dyno curve. Hopefully by adjusting the VTEC engagement point and fine-tuning the fuel curve, we will not only eliminate the dip, but also extract more power for the 1.6-liter engine. Installing the V-AFC requires splicing the factory harness, so we recommend having a competent shop perform the installation. We went to XS Engineering for our installation and dyno tuning needs. Having tuned dozens of V-AFC units, XS plotted in a basic tuning program into the V-AFC. After a couple of dyno runs and more fine-tuning of the fuel curve, horsepower was increased to 14x.x hp and 10x.x lbs-ft of torque. More importantly, the dip we were experiencing at xxxx rpm was nearly eliminated by moving the VTEC engagement point to xxxx rpm.
When it comes to evaluating a performance product, there isn't a better measuring tool than the dyno. Its shiny exterior or a cool display screen can't impress a dyno, just pure power figures. Fortunately for A'PEXi, under V-AFC's cool blue fluorescent display screen lies the power to back its good looks. What more can you ask for, beauty and brawn in one complete package.