A question about diesel engine idle noises.

[Owencr905]

Hopefully this is the appropriate place for this.

I’ve watched plenty of videos of trains like class 43’s, 50’s and 37’s and couldn’t help but notice that sometimes when the engine is idling you can hear the engine oscillating (if that’s the right word?), like the RPM is fluctuating. I was curious what exactly causes this/what it actually is. It also seems to be present a lot when a loco has just been started up.

Any insight would be much appreciated.

 

[Spagnoletti]

The English Electric CSVT engines used in Class 50 and Class 37 drive their camshafts via a chain. If the chain is worn or stretched, this, coupled with cam wear, can produce very obvious 'hunting' around the idle speed, especially as you say when cold. Not sure about the 43 engines as I've never worked on them.

 

[tomuk]

It is the engine governors they are hydraulic made by Woodward. In tip top condition with oil up to operating temperature they aren't brilliant, cold or lack of maintenance, dirty oil, leads to hunting.

 

[Owencr905]

The English Electric CSVT engines used in Class 50 and Class 37 drive their camshafts via a chain. If the chain is worn or stretched, this, coupled with cam wear, can produce very obvious 'hunting' around the idle speed, especially as you say when cold. Not sure about the 43 engines as I've never worked on them.

Interesting. Thank you