the new models are watercooled (coolant), as well, which helps keep some of the heat away from the oil, and prevent it from coking in the main bearing like the older turbos.. so it's less of an issue, but that said.. i still drive the last 500m-1k gently before I turn the ignition off. meh.. can't hurt. A turbo timer won't hurt, but it's not a necessity nowadays for the newer turbos. If you want one, fit one ..
Some info from Garrett:
Oil & Water Plumbing
The intake and exhaust plumbing often receives the focus leaving the oil and water plumbing neglected.
Garrett ball bearing turbochargers require less oil than journal bearing turbos. Therefore an oil inlet restrictor is recommended if you have oil pressure over about 60 psig. The oil outlet should be plumbed to the oil pan above the oil level (for wet sump systems). Since the oil drain is gravity fed, it is important that the oil outlet points downward, and that the drain tube does not become horizontal or go “uphill” at any point.
Following a hot shutdown of a turbocharger, heat soak begins. This means that the heat in the head, exhaust manifold, and turbine housing finds it way to the turbo’s center housing, raising its temperature. These extreme temperatures in the center housing can result in oil coking.
To minimize the effects of heat soak-back, water-cooled center housings were introduced. These use coolant from the engine to act as a heat sink after engine shutdown, preventing the oil from coking. The water lines utilize a thermal siphon effect to reduce the peak heat soak-back temperature after key-off. The layout of the pipes should minimize peaks and troughs with the (cool) water inlet on the low side. To help this along, it is advantageous to tilt the turbocharger about 25° about the axis of shaft rotation.
Many Garrett turbos are water-cooled for enhanced durability.
Posted: Wed Apr 09, 2008 3:32 pm
