The gearheads at Innovative Turbo have seen more than their share of turbo-related carnage and gave us the low-down on what causes turbo failures and how to avoid them. Most turbocharger damage can be traced back to just a few basic causes: lubrication problems, foreign object damage, temperature extremes, or poor materials and workmanship. While you have little control over the latter, the first three are within your grasp. Since turbos are lubricated and cooled by engine oil and, in some cases engine coolant as well, it's critical to maintain a strict oil/cooling system maintenance schedule when running a turbocharger.
If you're adding a turbo to your daily driver, then it's not a bad idea to make the switch to 100 percent pure synthetic motor oil, due to its high heat-handling capabilities. Installing dual, remote oil filters connected to an auxiliary oil cooler is also a good idea because after a hard run at full boost, the oil temp will rise, and it's important to get it cooled down to normal operating temperature quickly. The turbo's bearings are lubed with pressurized oil from the engine's oil pump, and since pressures are lowest at idle, a turbocharged car should not be idled after a hard run. Instead, slowly drive the car around in Low gear, maintaining high oil pressure, but opening the throttle as little as possible so there won't be much exhaust gas flowing to load the turbo.
Of course, the compressor side of the turbo is also subject to damage when its inlet is not properly maintained. The best defense against destroying a turbo on the intake side is a tightly sealed air intake using a high-quality filter.
As the OEMs and aftermarket continue to develop new and improved EFI systems and racers continue to push the envelope, better turbo systems will be the end result. We will all benefit from this new wave of turbo technology, so take advantage of it, and after you've read this story, consider yourself a graduate of: Turbogineering 101.
Anatomy Of A Turbo
The guys at Innovative Turbo explained turbos to us in full detail. We learned how a turbo is driven, where it gets its air from, where it sends it to, and some of the various control devices used with turbos. Here's the drive side of the turbo, called the Turbine Housing. It is usually made of cast iron due to the extremely high temperatures it must endure.
Hot exhaust gas enters the Turbine inlet here (1) and is routed directly into the housing's Volute. The Wastegate is typically mounted here, except in tight race car chassis. The gas then strikes the Turbine Diameter blades (2), which are connected to a common shaft driving the compressor's impeller. The gas then exits the housing (3) and goes straight out the tailpipe.
This photo shows the aluminum Compressor Housing with its impeller to the side. Normally the impeller would run inside the housing with its blades facing the radiused part of the housing.
Opposite this side of the housing is where filtered, outside air is introduced into the compressor (1). The air is then accelerated through the impeller wheel and across the radiused Contour (2). The Impeller discharges the air into the Diffuser (3), which slows the air down and increases its pressure, creating boost. The boosted air is recovered in the Volute (4) and is directed through the discharge nozzle (5) into the engine or intercooler. Turbos run "dry," boosting only inlet air. Fuel is mixed in downstream, usually just before the boosted air enters the cylinder head.
Compressor shaft speeds inside a turbo can exceed 100,000 rpm, so it must be precision-balanced to the extreme. This machine is made strictly for that purpose.
This photo shows the complicated exhaust routing involved with a typical race turbo. The Wastegate bypasses extra exhaust gasses from the header collector, allowing only the correct amount of exhaust into the turbo housing, which is wrapped in the heat blanket. The Compressor Housing outlet, welded to the intercooler tubing, can be seen to the right of the Wastegate with the pressurized oil line coming from the engine in the center. Try changing spark plugs in here!