Independent Wastegates & Integral Wastegate Actuators
Turbocharged engines allow automotive designers the freedom to create vehicles that offer impressive power output ratios from more compact engines, enabling a reduction in weight and volume, as well as decreased fuel consumption, and cleaner exhaust gases. Lower engine noise also generally results from the achievement of a target power output at lower engine speeds. In order to maximise the response times of the turbocharger, the size of the unit is kept deliberately small, by matching it to the lower end of the engine's speed range. However, this strategy generates the problem of potential over-speed of the turbocharger's rotor at higher engine speeds.
Independent external wastegates were traditionally used but as packaging requirements have become more of an issue, wastegate valves are integrally incorporated into the turbine housing of the turbocharger and so a separate device is required to operate it. The actuator resolves this problem by forcing the wastegate valve to open at a pre-set boost pressure, so allowing some engine exhaust gas to bypass the turbine and thus preventing over-speeding. As the engine speed decreases, the waste-gate valve is closed, and the actuator piston movement is completed. In addition, by preventing excessive airflow into the engine, the emission of oxides of nitrogen pollutant into the atmosphere is reduced.
The traditional turbocharger actuator is a mechanical pneumatic device that senses boost pressure and opens the wastegate valve once a predetermined pressure is reached. The air pressure is sensed typically from either the inlet manifold or the compressor housing of the turbocharger. Inside the canister of the actuator the main components are a diaphragm, retaining cup and spring. The spring is designed to compress below the diaphragm. These two components are separated by the cup, attached to which is a rod that links to the pivoting wastegate.
Failures are extremely rare within the normal service life of the component but occasionally it can happen. The diaphragm can split and occasionally the rod or spring can fracture. The most common problem is the spring 'going weak' generally due to excessive heat and thus the wastegate is opened prematurely causing a drop in boost pressure. In service conditions the actuator's opening pressure can be easily checked against original tolerance by using one of the pieces of workshop equipment we can provide.
Standard 'genuine' replacement actuators are available for most applications. When not available as a separate component Turbo Dynamics will usually have a solution for you using one of our large range of exclusively built units or by accessing our bespoke database of interchangeable turbocharger parts. Turbo Dynamics also offers an exclusive range of uprated wastegate actuators to replace the standard item. These are constructed from the same quality components used by Garrett with the exception of the spring. The same high grade material and design techniques are used but the spring tensions are increased. This allows us to offer a huge range of opening pressures to suit high output applications.