Superiority of Floating metal

GReddy turbochargers are committed to floating metal bearings. This is because it’s the bearing system with the least resistance ‘during actual use’. When disassembling a floating metal bearing, it may appear to have high frictional resistance as metal surfaces seem to be in contact. Also, when manually rotating the compressor wheel while the turbocharger is cold, it may feel heavier than a ball bearing system. So why are floating metal bearings superior? The answer lies in the presence of ‘engine oil’. When the engine starts and oil pressure builds up, with the engine oil warmed up, the shaft floats in the center of the bearing, surrounded by oil. This is the ‘fluid bearing system’ where the shaft is supported solely by oil. Hence the name ‘floating’ metal. In other words, when disassembling the bearing, we’re working without the most crucial component – ‘engine oil’ – so we’re essentially overlooking the most important device. During actual use, the space between the bearing and shaft is filled with oil, and the metal surfaces never touch. To put it simply, comparing the rotation resistance of the compressor wheel when the turbocharger is cold doesn’t reflect the true performance of floating metal bearings. What matters for a turbocharger is its performance during actual use, not when the engine is stopped. When the turbocharger reaches its operating temperature, which do you think has less resistance: a bearing system where metal surfaces are in contact (even if at points), or a fluid bearing where metal never touches? Moreover, the fact that fluid bearings don’t require coolant circulation like ball bearings indicates that there’s no frictional heat generated around the bearing. When pursuing performance and convenience at the actual operating temperatures of turbochargers, we inevitably arrive at the fluid bearing system of floating metal bearings.