Advanced Wastegate Control for New Generation 3-Cylinder Gasoline Engines
With tightening fuel economy and CO2 emissions standards, carmakers around the world are resorting to turbocharged, downsized and down-sped engines that are beginning to see a shift from 4 to 3 cylinder architecture.
This, in turn, is driving demand for new generations of turbochargers that come with custom aerodynamics and ultra low loss bearings. However, 3 cylinder engines pose new challenges to the wastegate.
The issue is maintaining precise control. At small openings, a classic flat valve behaves in a non-linear manner. The aerodynamic load reaches a peak as it opens and then falls as the opening continues. The higher pulsation in the exhaust from a 3 cylinder engine can excite the valve system and make precise control difficult.
“The Garrett solution is a brand new valve design thanks to a deeper insight into the system behavior by combining multiple simulation codes,” says Gary Agnew, Director of Gasoline Applications at Garrett Turbo Technologies.
First, the new valve has a toroidal profile that self-centers in a conical seat. Second, the opening is far more symmetrical and progressive than a regular valve and the sealing is very close to the outside diameter.
These two features, in combination, provide an almost linear load profile which is perfect for control. The profiled seat provides a superior seal while the flow symmetry and the zero clearance design significantly reduce pulsation and vibration. This helps improve durability and leads to much quieter operation.
Garrett is the only turbo manufacturer to provide a one-piece or mono-block wastegate valve. “Our new wastegate turbo for 3-cylinder engines has incorporated new bearing and aerodynamic designs that offer performance upgrade from a system perspective,” says Peter Davies, Director of Performance and Systems Engineering at Garrett Motion.