Do I have a "D" turbo or a "C" turbo?

[martin]

Hi
I had a whistler which was very loud so we just cut the stack so it went up vertically and popped a flap on it.
This reduced cab volume dramatically.
Martin

 

[jimk]

The whistle may be caused but the turbine tips(or air vortices there) exceeding the speed of sound.

The C turbine has more angular compressor wheel.

The Mack I operate at work has a variable nozzle turbo. This has a ring of movable vanes in the housing (around the turbine) to contol output (turbine speed).The whistle changes as the servo motor does its thing.

Every turbo I have ever seen has whistled [under load]. The deuce has a lot of other noises coming from the engine. That may drown out the D. Mine M35A2 has a NAPA stack muffler and the turbo can occasionally be heard spooling up.

JimK
edited - got the photo's mixed up