Learn how to safeguard your turbocharger and enjoy its benefits for years to come.
It wasn’t too long ago that turbochargers were reserved for exotics and high-performance sports cars. There were experiments on more mundane cars here and there, but for the most part, you had to make a concerted effort to buy a car with forced induction.
Things have certainly changed. Now, enthusiasts have to go out of their way to find a naturally aspirated car because manufacturers have found there actually is a replacement for displacement.
Back when turbos were more of a novelty, a big part of the reasoning was that turbos were considered unreliable. While that may have been true in the early days of the technology, it certainly isn’t now. Most turbos can easily go 100,000 miles or more.
But there are still turbo failures -- even more so in enthusiast circles. So, what are the causes, how can you prevent them, and is it safe to try and get more performance out of your turbocharged car?
What is a turbo and how does it work?
A turbocharger is a positive pressure air pump. It has two sides:
The “hot” side is a turbine spun by the engine's exhaust gasses as they exit the head, spin the turbine wheel, and then pass through the rest of the car’s exhaust. The turbine wheel is attached to a shaft that is connected to the cold, or “compressor” side of the turbo’s compressor wheel.
The “compressor” side pulls in air, compresses it, and blows it into the car’s intake. Generally, there’s cooling involved in there also, since compressing air increases the temperature.
Forcing more air into the engine effectively increases the engine’s displacement. The more air you force in, the more exhaust gas is produced to spin the turbo, and you can see how this creates a lot of horsepower.
A valve called a wastegate can allow exhaust gasses to bypass the turbo, which controls the amount of boost pressure created. If an engine is running at or near zero-boost, then the engine will not only produce normal levels of power for its displacement, but also achieve the normal fuel economy of a like-sized engine.
Why do turbochargers fail?
Turbos work hard. Not raking leaves in fall hard; I mean roofers in Phoenix in the middle of summer hard. Turbochargers can spin at up to 300,000 RPM and see temperatures over 1500 degrees Fahrenheit in the turbine. With those RPM and temperatures, oil and sometimes coolant are critically important. They are also the source of most turbo failures (oil being, by far, the most common).
Oil Issues
Dirty, contaminated, or broken-down oil is just as bad for your turbo as it is for the bearing surfaces in your engine. Even ball-bearing turbos need a constant supply of oil for lubrication and cooling. At this point, most turbochargers have water-cooling also, but this is as much for cooling after the engine is shut off as it is during normal operation.
Contaminated oil can clog oil passages and act as an abrasive wearing out bearing surfaces. Old, broken-down oil won’t provide the level of lubrication the bearings require. It should also be noted that using the wrong oil for your car can be just as bad for your turbo as old oil. Always follow the manufacturers recommendations.
Imbalance
Oil-related problems may be the most common sources of turbo failure, but they aren’t the only source. At the insane speeds that turbochargers spin, a slight imbalance of either the turbine or compressor wheel can create a large force on the turbo’s shaft causing a catastrophic mechanical failure. Imbalance can be caused by manufacturing defects (though this is rare), damage from foreign objects, or wear and tear over time.
Over-Revving
Likewise, spinning a turbocharger beyond its intended RPM redline, can have the same result. Over-revving a turbo can be caused by a wastegate failure or – more commonly – an overly ambitious tuner getting a little too optimistic with the safety factor built into the turbo’s specs.
When the engine is revved beyond its safe operating limits, it puts excessive stress on turbo components, especially the turbine and compressor wheels. The high rotational speeds can cause these wheels to experience forces beyond their design limits, leading to damage, warping, or even complete failure.
Foreign Debris
Lastly, foreign debris is a not uncommon cause of failure. When dirt, dust, or other contaminants enter the intake system, they can be drawn into the turbocharger. This can cause damage, usually to either wheel, which leads to the aforementioned imbalance.
How can I prevent turbo failure?
Oil, it’s all about oil – change your oil at or before factory recommended intervals. If you drive your car hard, changing your oil more often is (relatively) cheap insurance for preventing a turbo failure from contaminated or degraded oil.
Next, and this shouldn’t need to be said, but check your oil. As the car’s oil level drops, the chances of oil starvation rise. It takes two minutes.
And lastly on the subject, use the correct oil. The easiest way to find what oil your car requires is to check the owner’s manual. Some car manufacturers still give you the choice, but for turbocharged vehicles, a synthetic is going to be the better option due to its higher temperature-handling abilities. This can’t be stressed enough. In most situations, nothing is more important in preventing turbo failure than making sure it receives a constant supply of the proper oil.
With that out of the way, here are a few other things to keep in mind for making sure your turbocharger has a long healthy life:
Make sure your wastegate functions properly. They do fail, and occasionally a car’s ECU won’t react quick enough to save it.
Only use aftermarket software from tuners you trust. Trying to wrangle those few extra horses out of the engine might be an expensive mistake.
Let the engine cool down. Although some people have fond memories of Turbo Timers from the ‘80s and ‘90s that kept your car running for a set amount of time after you turned off the ignition, modern water-cooled turbos have mostly made them redundant. But, after hard use, you shouldn’t turn the car off immediately. Ideally, if you’ve been driving the car hard, give it at least five minutes of normal driving before turning it off.
Avoid cold starts. Do your best to stay out of the boost when the car is cold, as it can put excessive stress on the turbo. Allow the engine to warm up before any spirited driving.
Practice good maintenance. Finally, keep the rest of the car in good running order. Watch for oil leaks, pay attention to Check Engine lights, and your turbo will last well past the 100,000-mile mark.
How can I add performance to my turbocharged engine, and is it safe?
Turbocharging has changed the tuning industry. When most cars were naturally aspirated, bolt-on performance modifications were lucky to net gains of even 10% more power. Now, bolt-on mods are still common and do offer real gains, but none of them can match a simple software flash on a turbocharged car. It is not uncommon to see increases of 50 hp or more on turbocharged four-cylinder engines -- even more, if owners are willing to switch over to e85 fuel.
For the most part, software flashes are safe for both the turbo and the engine as a whole. Supporting modifications are often recommended by tuners, but from a functionality standpoint, intercoolers are really the only thing will supply bigger gains while also adding a level of reliability.
There are always questions about how modifications will impact a car’s warranty. Yes, the Magnuson-Moss Warranty Act does protect owners of modified vehicles from being denied warranty service, provided the aftermarket part didn’t cause the failure. But it is pretty easy to claim that adding a large amount of power or torque to your vehicle could cause failures of anything driveline-related. Some software tuners do provide supplemental warranties to provide coverage for claims denied by OEMs. Also, some dealerships are sympathetic to enthusiasts, and will treat the car like any other, as long as modifications aren’t too flagrant and didn’t obviously cause the failure.