Why more passenger side turbos fail first.--->
09-03-2003, 01:03 PM
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Why more passenger side turbos fail first.--->
My passenger side turbo had bearing failure. The blades of the turbine and compressor wheels were undamaged, except for outside rubbing. Why the passenger side?
<img src="http://pictureposter.audiworld.com/12010/Turbo-center-section1.jpg">
<b>Fig. 1</b>
Fig.1 illustrates how oil is supplied to the turbo bearings via the inlet port into a small reservoir, and from there to the bearings through a small metering hole (yellow arrows). The metering hole controls the flow rate of oil to the bearings approximately to the rate it bleeds out through the bearings to the return.
From the size of the metering hole it can be seen that the flow rate is low enough to cause the oil in the relatively large cross section of the external supply line to move slowly (Fig 2, yellow arrow).
<img src="http://pictureposter.audiworld.com/12010/turbo_oil_inlet2.jpg">
<b>Fig. 2</b>
Unfortunately, on the passenger side, that supply line carries the slow moving oil past the cherry red glowing exhaust manifold (red arrow) at a distance of about 1/2", further heating it before it reaches the turbo.
On the track, we see oil temperatures in the engine as high as 275°F. Further heat added by radiation from the glowing exhaust to the slow moving oil in the passenger side supply line, may well elevate its temperature to prohibitive levels (Radiation heat transfer is proportional to the fourth power of temperature). Certainly, the oil reaching the passenger side turbo under load will be of lower viscosity than that on the driver side raising the probability of bearing failure on that side first.
This problem can be avoided by wrapping the oil supply line to the passenger side turbo with a couple of layers of exhaust wrap (Fig. 3, courtesy Mat@4induktion), or by placing a small piece of sheet metal as radiation shield between the exhaust and the supply line. All those whose engine is out of the car should do this.
<img src="http://pictureposter.audiworld.com/12010/turbo_oil_feed_line.jpg">
<b>Fig. 3</b>
Here's a solution from NAPA:
<img src="http://209.128.70.155/HeatSleeve.jpg">
<b>Fig. 4</b>
On installed engines, a makeshift solution is to stuff a lengthy wad of wrinkled heavy duty aluminum foil between the exhaust and supply line, and wrapping its end around the coolant return line (white arrow) to keep it in place. This can be done by reaching in with the left hand while standing under the car.
Happy Motoring.
<img src="http://pictureposter.audiworld.com/12010/Turbo-center-section1.jpg">
<b>Fig. 1</b>
Fig.1 illustrates how oil is supplied to the turbo bearings via the inlet port into a small reservoir, and from there to the bearings through a small metering hole (yellow arrows). The metering hole controls the flow rate of oil to the bearings approximately to the rate it bleeds out through the bearings to the return.
From the size of the metering hole it can be seen that the flow rate is low enough to cause the oil in the relatively large cross section of the external supply line to move slowly (Fig 2, yellow arrow).
<img src="http://pictureposter.audiworld.com/12010/turbo_oil_inlet2.jpg">
<b>Fig. 2</b>
Unfortunately, on the passenger side, that supply line carries the slow moving oil past the cherry red glowing exhaust manifold (red arrow) at a distance of about 1/2", further heating it before it reaches the turbo.
On the track, we see oil temperatures in the engine as high as 275°F. Further heat added by radiation from the glowing exhaust to the slow moving oil in the passenger side supply line, may well elevate its temperature to prohibitive levels (Radiation heat transfer is proportional to the fourth power of temperature). Certainly, the oil reaching the passenger side turbo under load will be of lower viscosity than that on the driver side raising the probability of bearing failure on that side first.
This problem can be avoided by wrapping the oil supply line to the passenger side turbo with a couple of layers of exhaust wrap (Fig. 3, courtesy Mat@4induktion), or by placing a small piece of sheet metal as radiation shield between the exhaust and the supply line. All those whose engine is out of the car should do this.
<img src="http://pictureposter.audiworld.com/12010/turbo_oil_feed_line.jpg">
<b>Fig. 3</b>
Here's a solution from NAPA:
<img src="http://209.128.70.155/HeatSleeve.jpg">
<b>Fig. 4</b>
On installed engines, a makeshift solution is to stuff a lengthy wad of wrinkled heavy duty aluminum foil between the exhaust and supply line, and wrapping its end around the coolant return line (white arrow) to keep it in place. This can be done by reaching in with the left hand while standing under the car.
Happy Motoring.
