Understanding failure clues is a requirement for maintaining turbo performance

News Lucas Deal October 17, 2013

DSCN1641A turbocharger is a vital component to maximizing the performance of a commercial truck engine. Turbochargers increase engine power, boost fuel economy, and are important components in emission systems.

When operating at peak levels, a turbocharger simply makes a truck run better.

Today’s factory-installed turbochargers are built to run effectively without maintenance for a very long time. But their long-life cycle does not make them indestructible, and just like any vehicle component, when they are damaged their performance wanes.

A service provider’s ability to identify and diagnose turbocharger damage can be an excellent selling point in the aftermarket. While most customers know how valuable turbochargers are to engine performance, few have the expertise and skill to identify when service is required.

For inexperienced service providers, the first step in adding that capability is mastering the component and its operational function.

You have to know how a turbocharger works to know when it’s not working.

Turbochargers perform two primary functions, says Mark Rodrigues, director of marketing and product management at Honeywell.

The first is to improve power density within the engine by forcing more air into the engine chamber. This allows the engine to intake more fuel and thus gives it more power, Rodrigues says.

Randall Funck, partner and owner at ZOR Turbochargers, describes the process as follows.

A turbocharger turbine wheel is driven by waste gases expelled from an engine combustion chamber. The gases are forced by design structures to be channeled across the turbine wheel, and the faster the gases are expelled the quicker it rotates, Funck says. The turbine also is connected by a shaft to the compressor wheel, which pulls air through the air filtration system, compressing it and increasing its oxygen density and therefore its power, he adds.

“It all works together as its own little ecosystem,” says Tim Stechschulte, national sales director – diesel at Flight Systems Electronics Group, a remanufacturing company that services the light- to heavy-duty markets. “The turbo uses the existing power source to provide fresh air and improve power capabilities.”

Rodrigues says this operation also provides the turbocharger’s second major benefit: improved fuel economy.

“The denser air when entering the combustion chamber creates a more violent explosion. This magnified explosion provides more power with less fuel,” says Funck.

In addition to these advantages, Rodrigues says turbochargers also can be used to work with electronic gas recirculation (EGR) systems to improve vehicle emissions.

With this many benefits, maintaining a turbo is an absolute necessity. But because of its location and engineering design, the turbocharger is not an easy component to test for performance and maintain.

To be able to service a turbo, technicians must know its failure warning signs.

The easiest sign to spot is audible clues, says Rodrigues.

“Sometimes people will here screeching noises, and that can be a sign of foreign impact damage,” he says.

A turbocharger is built to run using clear air, so any particulate pulled into the system can harm the compressor wheel and diminish performance.

Stechschulte says this is most commonly seen when any type of foreign debris, no matter how small makes its way into the turbocharger’s air supply.

As the particle wedges its way into the system, the compressor wheel becomes unbalanced within the turbocharger housing and starts to rub against the edge of the housing or the particulate itself. This constant interaction not only ruins the turbo, but also produces the audible screeching associated with the component failure.

Another sign a turbocharger is failing is black smoke and a sudden loss in engine power. When a turbocharger’s compressor wheels starts to slow, it is no longer able to perform its two main responsibilities in improving engine performance.

Having a clean and viscous oil supply is another necessity to maximizing turbocharger performance, says Funck.

“Oil starvation on the inlet or outlet from the turbocharger or general lubricity breakdown as in cases of not changing oil” can cause significant damage, he says. “Oil feed lines and return lines must be clear of sludge, kinks or other obstructions. Failure to do so can starve the turbo of lubrication or create unwanted pressures.”

Over pressurization can result in stress cracks and overheating, which not only will destroy the turbocharger but also can have a harmful effect on the engine.

And unlike the easy to spot warning signs above, identifying oil starvation requires knowledge of the truck’s PM intervals and the ability to recognize poor maintenance warning signs.

A particulate lodged in a turbocharger causes an immediate performance change; improper engine maintenance will diminish the turbo gradually over time.

Any of these warning signs should lead to a turbo replacement, Rodrigues says.

New turbos are built to last at least through the life of a powertrain warranty, he says, but that doesn’t mean a truck owner or service provider should ignore the component during that period.

A damaged or malfunctioning turbocharger should be fixed immediately.

“Unless the turbo is severely damaged repairing by installing a service kit is feasible,” says Funck, though he warns disassembling and repairing a turbocharger be very challenging.

Other options include new aftermarket and remanufactured replacement units. Funck says remanufacturers have the ability to remanufacturer the original unit if the core was not severely damaged during the failure.

Stechschulte says his company has a core criteria it relies on when accepting components for remanufacturing. Foreign object damage on compressor wheels is not a problem due to the parts’ replacement necessity, but cracked turbo housings cannot be remanufactured.

For service providers unsure of their service kit skills, Rodrigues recommends a simple replacement. Spotting and diagnosing turbocharger failure is an excellent skill for service providers to have; there’s no reason to minimize it with poor service techniques.

“The turbo is a precision-engineered component,” he says, “it’s not a component anyone can take apart and easily put back together.”