Is Turbo Flutter Bad? (Turbo Surge)

November 15, 2024 Off By RICHARD

Is turbo flutter/turbo surge/compressor surge bad for the engine? Is it bad for the turbo?

If you want background information, this turbo flutter video has some examples of what it sounds like & this article details what is h appening.

Is Turbo Flutter Bad?

Will it damage a turbo?

Not immediately. Over time, and especially on journal bearing turbos, turbo flutter will reduce the life of a turbo.

Why?

Turbo flutter happens when the turbo reaches a surge condition. The surge condition happens when the difference in pressure in the intake versus the speed of the air passing through the turbo becomes too large.

As the turbo approaches the fluttering/surging condition it is compressing the air in the intake, when the turbo is pushing the air, force is applied to the turbo bearings and shaft. When the turbo starts fluttering the pressure in the intake is dropping and increasing rapidly.

As the pressure drops, the turbo goes out of surge and so builds pressure again, until the pressure is too high versus the speed of the air passing through the turbo and the turbo flutters (enters surge) again. And this process repeats until the air speed through the turbo is sufficient to maintain the target boost pressure (because the engine is at a higher RPM).

This process of building pressure & losing pressure is what causes the fluttering sound.

The damage/wear on the turbo is caused by the turbo bearings & shaft being subjected to load and then suddenly relieved of load and then subjected to load again, violently, rapidly and repeatedly.

So Yes..

Flutter is bad because it wears turbo bearings faster and puts stress on the turbo shaft. More of an issue with journal bearings turbos but it’s not ideal for ball bearing turbos either.

Full throttle flutter is worse than lift off (between gear changes) turbo flutter because the forces on the turbo are greater when pressure is higher and sustained (because vehicle is accelerating).

This article describes what we can do to reduce / eliminate turbo flutter.