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.
Oil Feed
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.
|
Oil block-off plate drilled and tapped for
oil feed. |
Oil feed flange
and AN fitting on a turbocharger. |
Oil Return
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.
See more of Nick’s Trans Am build at http://my.fit.edu/~nnagrods/mp/
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.
Scavenge Pumps
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.
Turbo Timers
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.