Examining water-cooling specifi cally, the water jacket inside the turbocharger’s center housing wraps around the ball bearing cartridge and is designed to keep ball bearing temperatures below the limits to prevent bearing failure. When water is not used or not plumbed correctly, bearing temperatures can easily go over the intended limits and result in increased bearing play, turbine and compressor wheels rubbing in their respective housings, and ultimately catastrophic turbo failure. In addition to this material degradation, high bearing temperatures cause the internal clearances to decrease in a steel ball bearing cartridge. If temperatures get too high and the turbocharger is run at higher than rated turbo speeds, a steel ball bearing cartridge can physically lock up or seize, causing catastrophic turbo failure. High speeds occur hand-in-hand with very high boost pressures, so turbo users running a high-boost system should be extremely conscious of the setup and condition of the turbo’s water-cooling lines. “High boost” varies from turbo to turbo, but can generally be considered anything above 25psig (1.7 bar).