With operating temperatures that shoot up to 1,500 degrees Fahrenheit and internal speeds that wind past 100,000 r.p.m., the stresses that a turbocharger must withstand seem like a recipe for certain mechanical disaster.
And sure enough, disaster struck regularly in earlier bursts of turbo popularity. Now, as cars with turbocharged engines have grown to nearly 20 percent of new sales, according to Honeywell, a large parts supplier, consumers may wonder whether they need to be concerned about the reliability of these devices.
The automotive turbocharger is simply a pump designed to push more air into an engine, using a small turbine driven by the engine’s exhaust that spins a compressor section. The technology lets carmakers install smaller engines that deliver better fuel economy – yet produce the horsepower needed to keep up with traffic. For that reason, turbo engines have become increasingly popular as new models are introduced.
The turbo failures of past decades have been traced to inadequate materials and insufficient lubrication. Either way, the repairs are expensive and the breakdowns can ruin a carmaker’s reputation. So automakers utilizing the technology can’t afford mistakes.
In years past, they made mistakes. The turbos in some 1980s cars proved troublesome. Turbine bearings were lubricated when the engine was running, but after shutdown they overheated and the lubricating oil cooked into hardened ash deposits. Consumers became wary of turbos.
Judging by the number of turbocharged cars arriving, one might conclude that the problems have been solved. Mike Katerberg, a senior powertrain engineer at General Motors, said that improvements have madr\e turbos reliable, noting that the warranty rate on GM turbos is very low and they don’t appear in a Top 15 list of failed engine parts. Lubrication circuits for bearings and cooling that continues after shutdown have reduced problems; internal parts better tolerate high speeds, and the turbo housings are made of more durable alloys.
Still, the jury is out in terms of real-world longevity. Consumer Reports magazine, which surveys a large number of owners, has seen some issues.
“Traditional turbos from Audi, Volkswagen and BMW have been reliable when they are relatively new but developed problems as they aged,” Douglas Love, a magazine spokesman, wrote in an email. “Newer turbo engines, such as the EcoBoost from Ford, have not always been reliable, even from the start.”
Ford owners complained to NHTSA about problems while accelerating, a condition caused by condensation, but failures of the turbo itself don’t appear common. NHTSA does report complaints of turbo failures on the BMW 535is and the Volkswagen Passat TDI (which uses a turbodiesel engine). And in August, an Audi service bulletin notified mechanics of turbo failures in 2015 A3 models.
Turbo longevity isn’t the only issue. In a Feb. 5, 2013, article, Consumer Reports wrote, “Small turbocharged engines aren’t delivering on the fuel-efficiency claims by the manufacturers.”
Katerberg, the GM engineer, explained that under light loads at steady cruise speed, the turbo will outperform the larger naturally aspirated engine because it operates without boost, and the advantages of smaller displacement come into play.