In Part I of Boost it up/Fuel me up, we previewed A'PEXi's new Super AFC and covered the fundamental basics on the importance of a fuel computer. The importance of utilizing a fuel computer with upgraded performance products can not be stressed enough. The majority of factory turbocharged vehicles utilize a hot wire/flap door type of air flow or density metering system. Some vehicles equipped with flow meter type systems are able to compensate and modify the fuel curve when the vehicle is moderately modified with simple bolt ons. However, there is a limitation on how much the factory ECU can alter the preset fuel curve. If the engine is modified beyond the simple bolt-on stage, the factory ECU is not able to compensate for the extra air, resulting in a lean air/fuel mixture. To increase reliability and horsepower a fuel computer should be utilized.

In this installment we will preview A'PEXi's new AVC Type-R boost controller and display dyno-proven horsepower results when used in conjunction with the company's AFC fuel computer. The AVC Type-R is A'PEXi's newest line of boost controllers and supersedes last year's Super AVC-R. The new AVC Type-R hosts a number of new features making the new boost controller second to none. To better understand the purpose of a boost controller and its function we will briefly overview the types of boost controllers available in the market today-manual boost controllers and electronic boost controllers.

Manual Boost Controllers
Most manual boost controllers utilize a regulator valve or relief valve to control boost. When used as an in-line relief valve, some of the manifold pressure is bypassed to the atmosphere preventing the wastegate from opening until higher boost pressure is achieved. By regulating the amount of bypassed air, boost pressure can be raised or lowered. However, boost pressure can't be lowered below the preset actuator spring or wastegate spring setting. When used as a regulator valve the valve controls the amount of manifold pressure that reaches the wastegate/actuator. When run in-line between a pressure source and wastegate/actuator, the regulator valve can prohibit the amount of manifold pressure that reaches the wastegate/actuator. By preventing manifold pressure from reaching the wastegate/actuator, the tuner is able to prevent the opening of the wastegate valve until higher boost pressure is achieved. On external wastegate applications the regulator valve can also be used as a manifold bypass valve. The side-port of the wastegate is T'd to one side of the regulator valve while the other end of the valve is connected to the top-port of the wastegate. The regulator valve can bypass some of the boost pressure to the top-port of the wastegate restricting the opening of the wastegate. By doing so increased boost pressure is achieved.