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Turbo Oiling Systems
Turbochargers are cooled by oil, and sometimes oil and water. Most aftermarket turbochargers are cooled by oil alone. Turbocharger systems must supply high pressure oil to the turbo and back to the engine. An oil feed line runs from the engine to the turbocharger’s oil inlet on the center housing, then back to the engine through the oil drain on the center housing.
Picking up a pressurized oil feed on most engines is very simple. An oil feed source can usually be picked up where the oil pressure sensor mounts. A Tee in the oil sending port can provide oil to the pressure sensor, and the turbo oil inlet. Some engines provide extra ports or locations that can be tapped for fittings.
The high pressure oil feed line runs to the turbocharger’s oil inlet flange. Most turbos use a 1/8” NPT fitting at the inlet.
The oil that is pumped through the turbocharger’s bearings needs to be routed back into the engine. The oil return port is opposite the oil feed on the center section of the turbo. In most applications, gravity feeds the oil from the turbocharger back into a fitting on the oil pan or timing chain cover.
In systems where the turbocharger sits lower than the oil pan, a scavenge pump can be used to pump oil back into the crank case. This is also the case with remote turbocharger systems such as the popular STS kits.
Tapping The Oil Pan
It is possible to drill and tap the oil pan while the pan is still on the engine. This however is not recommended, as shavings may enter the oil pan while drilling. If you must drill and tap the pan on the engine, use plenty of grease on the drill bit, and drill slowly, cleaning away shavings as you drill. After you have drilled and tapped the pan, drain the oil and add new oil. You may want to drain and refill several times. The safest method here is to remove the pan before drilling and tapping. Use at least a -10 AN line for the oil return.
Oil return fittings installed on the oil pan.
Shavings in the oil pan after drilling. Photo courtesy of Nick Nagrodsky aka ddnspider.
Returning Oil to the Timing Cover
An alternative to tapping the pan is to tap the timing chain cover for oil return. On some pushrod engines, the timing chain cover is easily accessible, and makes a convenient place to return oil into the engine. As with the oil pan, it is best to remove the timing chain cover prior to drilling and tapping. If you must leave the timing chain cover on, follow the same suggestions on changing the oil several times as with the oil pan.
Oil returns in the timing chain cover.
When the turbocharger is mounted below the engine, gravity will not return the oil back to the engine. A scavenge pump must be used to return the oil back into the crank case. When using a scavenge pump, oil can be returned to the oil pan, timing chain cover, valve covers or even through the oil filler cap.
Oil being returned through the oil filler cap using a scavenge pump.
A pump must be rated for high temperature and flow to support the tough demands of turbo scavenging. The Mocal 12 Volt oil cooler pump fits the bill for turbo oil scavenging. It is rated to 300° F, and can pump up to two gallons per minute.
Mocal oil cooler pump.
A scavenge pump can be placed anywhere it will fit. It should be wired to turn on when the key is turned on, and some type of warning system should be used if the pump fails.
A scavenge pump
located in the trunk of a Z28 on a rear
An oil pressure switch connected to a piezo type buzzer can be installed between the pump and the turbocharger. If the pump fails, pressure will build in return line in that area. The pressure switch can detect and warn you if this occurs. You will also notice a large plume of smoke billowing from the exhaust pipes if a pump fails.
Using a Sump
Some people utilize a sump when using a scavenge pump. A small container can be placed under the turbo’s oil return to catch oil as it drains from the turbo. The scavenge pump picks up the oil from this container and returns it to the engine. A system such as this will allow the pump to keep up under high demands as the sump takes time to fill, allowing the pump to catch up.
A turbo timer is a device that keeps your engine running for a specified amount of time after you turn off the ignition. The reason for this is that a turbocharger can continue to spin long after the engine, and oil supply have been turned off.
A turbo that spins without an adequate oil supply will eventually end up with worn bearings. A turbo timer cures this problem as it lets the turbine and compressor wheels spin down while oil is supplied to the bearings.
Some of the more popular turbo timers are manufactured by Greddy, Blitz, HKS and A’PEXi.
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