|Modern ceramic turbines do wonders to reduce
turbo lag. The reduced weighr means less intertia which leads to less low down
exhaust gas being required to turn the wheel. However, if you raise boost beyond
14.5 to 15psi the ceramic wheel will shatter. The turbine wheel has to exert
great pressure on the common shaft to turn the compressor.
This places stress on the ceramic wheel where the blades are atteched and where the hub bonds to the shaft. Both areas have a low load limit.
Another way the turbo can be destroyed is by splash damage. Before
removing or modifying any splash guards make sure the turbo is sufficiently
protected from water.
- Even a small loss in lubrication will destroy the turbo.
- Major consideration when upgrading a NA car with a turbo.
Turbo lubrication is a major problem for turbo installations on a non-turbo car. Turbos cant be operated above 65psi oil pressure. A restrictor must be used to reduce the oil pressure without restricting the flow. At idle a flow of 0.5L per minute is required and at load you need 2L per minute. Ball bearing turbos require a bit less, around 1.5L maximum. Obviously each turbo has slightly different lube requirements. It is usually possible to tap into the engines oil circuit to get the requires oil supply. The oil return line is more critical. You are relying on gravity to move the oil from the turbo to the sump.
|After passing through the bearings, the
oil is whipped up into a foam. Therefore, you need a large bore return with
minor or no bends all the way to the sump. If the turbo is high enough it can
enter the sump via a redundant oil dip stick opening or a tapped opening.
If the turbo is mounted too low then an aerodyne turbo can be used which has its own sealed oil supply which is not connected to the engine oil supply. Otherwise an electric or belt driven pump can be used to return the oil to the sump.
Always use fully synthetic ester based oil and
you should keep your service intervals at 5000mls. However, this is just the
beginning of turbo care. Ideally the turbo should always be allowed to idle for
upto 3 minutes after a hard run. This also applies to water cooled turbos. A
better option is to run the engine at 1500-2000rpm for a while before engine
shutdown rather than idling. Idling sometimes provides insufficient oil flow for
the turbo. People who live down country lanes or who have to go through housing
estates to get to their home have the advantage of having time to let the turbo
cool down before shutdown. If you are in a situation where you can idle or
shutdown immediately after caning your engine then you should invest in a turbo
timer because you will eventually forget to allow cool down time and will
destroy your turbo.
Also, never rev your engine prior to shutting down Giving the throttle a quick blip before shutdown will spin the turbo to 30000rpm and shutting down at this point will starve the turbo of oil at just the wrong time and cause premature ware. A similar problem occurs at engine startup. It can take 30 sec for the oil to reach the turbo. You should wait this long before applying throttle.
Similarly, if the turbo is just fitted or a reconditioned or new unit is being fitted, then it must be primed with oil before the first startup. Also, if the car has been parked up for a few months, the turbo should be primed with oil if it can easily be accessed.
A turbo should only need servicing every 30000 to 50000mls. If the vehicle spends a lot of time at idle or at high speed, then this interval will be reduced.