Turbochargers Explained: Blow off valve

HKS S.SQV KIT BLOW OFF VALVE

The HKS Super Sequential Blow-Off Valve (SQV) is a dual stage pull type relief valve. Unlike other blow off valves that are push type, the SQV will not leak under high boost conditions or under vacuum at idle. Being of a pull type valve structure, the SQV cannot physically leak under any level of boost because boost pressure also keeps the valve closed against its seat. The SQV is actuated by pressure alterations only, not by the rate of pressure or vacuum in the line, which ensures a quick valve response and complete closure during idle. On typical blow-off valve designs, a large valve is utilized in order to accommodate high boost / high horsepower applications. However, these large valves tend to react slowly and require high activation pressure to open, therefore are not able to activate and prevent compressor surge at light-load conditions. On the other hand, smaller, fast reacting valves do not discharge the airflow capacity required for high horsepower applications and tend to creep open and leak as the boost pressure overpowers the spring on these push type valves. For maximum performance, the HKS SQV incorporates both a small primary valve for ultra quick activation, along with a larger secondary valve for additional discharge capacity. The SQV is engineered to initially open the small primary valve at light throttle and load conditions, then sequentially opens the secondary valve for additional relief capacity under high boost and load conditions. The SQV is constructed of polished billet aluminium, which ensures long-term durability and visual appeal. The mounting base utilizes a circular mounting flange that provides exception flow and complete secure mounting via a C-clip snap ring and O-ring gasket. The triple-fin discharge port design produces a powerful and unique aggressive blow-off sound along with added visual distinction. The HKS SQV is available as a universal unit for custom applications and also by vehicle specific kits for bolt-on applications. Vehicle specific HKS SQV kits come complete with all needed mounting flanges, brackets, and miscellaneous hardware for a bolt-on installation. For Universal SQV applications, weld-on flanges are available in steel and aluminium for custom installation.

HKS Super SQV 2(Super Sequential Blow Off Valve)

Uses a unique sequential valve structure and a differential pressure control system, which allows for a broad operation range from low boost to high boost. (Latest Model)

Blitz Blow Off Valve

Turbochargers Explained: The Wastegate

Without a wastegate, the amount of boost that a turbocharger creates varies with the pressure of the engine's exhaust. This happens because exhaust pressure varies with relation to the engine's speed (measured in RPM's). This implies that as an engine reaches higher RPM's, increasing amounts of boost will be created by the turbocharger. The problem with this is that an engine can only accomodate a given amount of boost. Most stock engines are only meant to take about 10 PSI if not less. In order to regulate the amount of boost that comes into the engine, a wastegate acts as a door only allowing a given amount of exhaust to hit the turbocharger's exhaust turbine. Once the engine starts producing more exhaust pressure then the wastegate system will allow, a flap is opened to redirect excess exhaust away from the turbine blades. In turn, this is where a wastegate gets it's name. It's a gate to carry away waste. In order to regulate when a wastegate opens, a boost conroller can be used.

There are two types of wastegates. The first one is an internal wastegate (right). An internal wastegate is a component on the turbo unit itself. The gate is opened via an actuator which is a diaphram type system (see left picture). Excess exhaust is then fed directly into the exhaust system. We also have what is called an external wastegate (left), unlike an internal wastegate, it is seperate from the turbo unit and does not require an actuator. Excess exhaust can either be fed into the exhaust system or it can be vented straight out and into the atmosphere. High performance set-ups typically follow the latter alternative. Most stock systems come with an internal wastegate as this set-up is better suited for low boost applications. However most aftermarket systems perform better with an seperate external wastegate assembly making it an ideal choice for those generating boost in the range of 20-30 PSI.