The first big wave of automotive turbocharging came to auto showrooms during the ‘80s. Everything from grocery-getting Chrysler K-car station wagons to high-end Porsche sports cars packed a turbocharger under the hood. It seemed a requirement that these turbocharged cars could not leave the factory without the word “TURBO” emblazoned somewhere, if not all over the car. The fact is that a turbocharger can add on-demand performance to an otherwise economy-minded engine. Turbocharged engines are again becoming more common as consumers demand more horsepower along with better fuel economy.
Simple in theory
The turbocharger sits in between the engine and exhaust and takes advantage of energy that usually runs out the tailpipe and puts it to better use. Inside the turbocharger are two finned wheels that spin together on a common shaft. The hot side turbine wheel captures the power of exhaust. The cold side compressor wheel takes the energy captured by the turbine wheel and uses it to force air back into the engine. The air is then mixed with fuel and presto – a smaller four-cylinder Chihuahua of an engine suddenly boasts the power of a Doberman V-8. Since the compressed air forced into the combustion chambers contains more oxygen, the engine can generate more power than it would by operating without the turbo. When the driver doesn’t need additional power, the turbo spins along for the ride, allowing the engine to function with improved fuel economy.
Care and lubrication
While the turbocharger itself is a relatively simple device, replacement can be an expensive reality. A new replacement turbocharger can run into the multiple thousands of dollars without counting installation and labor. The way to avoid premature turbo failure is to follow manufacturers’ motor oil and service recommendations to the letter. Turbo engines can be brutally tough on motor oil. The same exhaust that spins the turbine wheel gives the hot side its name. The hot side housing can visibly get red hot. Since the shaft can spin in the range of 100,000 rpm, using high-quality motor oil is key to turbocharger survival. Advances in both motor oil and water-cooled turbocharger housings have made turbocharged engines more consumer friendly than ever, but neglecting oil changes can still spell the end of a turbocharger before its time.
In the balance
The price of a new replacement turbocharger can be staggering. If the turbocharger failure is of the normal wear, then rebuilding may be an option. The bad news is that rebuilding a turbocharger is beyond the scope of most home do-it-yourselfers. Disassembly and inspection might be possible, but any machining and balancing require both specialized machinery and experience. The good news is that there are professionals to handle the job. A turbocharger rebuilt with fresh bearings and seals can live on to serve for many miles at considerably less cost than a new replacement unit.
Five-step turbocharger rebuild
Step 1: The turbocharger is disassembled. Oil can become so hot inside a turbocharger that it cooks and leaves carbon behind. The carbon then clogs oil passages and restricts oil flow. Restricted oil flow is bad news for the turbocharger.
Step 2: Parts are cleaned and inspected. Measuring of inside housing diameters and outside shaft diameters will determine which parts can be reused and which need replacement. Cracked exhaust housings will require replacement.
Step 3: Balance is everything. Even the slightest bit of imbalance can cause a turbocharger assembly to come apart. The compressor and turbine wheels are balanced individually and then the entire assembly is balanced.
Step 4: The turbocharger cartridge is assembled with new bearings and seals. The shaft spins on a thin layer of oil just like the crankshaft in an engine. Worn bearings cause excessive shaft play. Oil can escape past the seals. Clouds of blue smoke from the tailpipe on boost could explain where all that oil is going.
Step 5: The turbocharger cartridge is put back in between the hot and cold side housings. With assembly complete, the wastegate actuator is pressure checked to see if it opens the internal wastegate at the correct pressure.