What Causes Turbo Flutter And Can It Damage Your Engine?
Getting the right power train soundtrack from a car can often make a huge difference in how much you enjoy driving it. For example, the curvaceous Ferrari 857 Monza might look fantastic, but its four-cylinder engine sounds like a lawnmower. Modern turbocharged cars, on the other hand, have an ear-catching sound of their own that some enthusiasts love – even though that noise, often referred to as turbo flutter, actually signals a harmful situation caused by too much back pressure in the system.
It's oddly similar to the popping and crackling exhaust sounds that get some gearheads going. They may sound cool to many, but the noise is the result of unburnt fuel getting into the exhaust system and combusting from heat on its way out. It's notably different from the unmistakable rumble of a traditional V8, which comes from the uneven firing order of its pistons. (That, in turn, leads to one of the reasons flat-plane crank V8 engines sound so distinctive: They use an even firing order.)
Turbo flutter is generally noticed when you get the turbocharged spooled up near its limits and then suddenly take your foot off the gas pedal. It's a kind of stuttering, choppy mechanical sound sometimes described as "stu-tu-tu," and it's the noise of air being forced back into the turbocharger in the wrong direction. If that sounds like it could be a problem, well, you're right. It might not necessarily cause any immediate physical damage, but it's something you should avoid if you want your engine to be as healthy as possible.
We're not going to go too deep into explaining the four strokes of an engine here, but you do need to know some basics of engine operation to understand turbo flutter. For starters, keep in mind that engines get their power from burning fuel and air, and a turbocharger sucks in outside air and force more of it into the cylinder than you'd get with natural aspiration. This provides more effective and powerful combustion.
The turbo does this with a two-sided fan arrangement. The blades on the turbine side are spun by the engine's exhaust gases, causing the blades on the compressor side to blow the air into the cylinder. Revving your engine causes it to emit more exhaust gas, which then spins the turbo quicker. If you suddenly take your foot off of the gas, though, the intake valve closes and the compressed air can't get into the cylinder. It's supposed instead to exit the system through a blow-off valve, but if the air can't get out via that valve, it forces itself back through the compressor and turbine, going the wrong way. The actual fluttering sound is the sound of the air going through the fan blades.
True, there are people who will tell you that turbo flutter won't hurt your engine, but you probably shouldn't listen to them. The sound, also called compressor surge, is the noise of the turbo building up and suddenly discharging pressure, first in one direction then another, over and over again. And that can indeed damage bearings and increase wear.
