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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.
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.