Question about Metra engines and sounds...

Trains Magazine General Discussion
1

I have a question about Metra engines and the sounds that they make…I live near Metra’s southwest corridor line and there is a train with 2 engines that pass by around 3:30pm or so…Why does it seem that they growl or have this deep moan to them when there are two engines hooked together instead of the regular muffled sound with one engine?

Cway

2

Two thoughts here to offer:

  1. Are the sounds you are hearing different because some engines are F40’s and the others MP units?
  2. The difference in sounds could be from having two sets of dynamics rather than one?
3

One engine is supplying the HEP (head-end-power) that supplies power to the lights and other utilities on the train. The Metra engine that has the HEP unit turned on has the diesel engine running at full rpm constantly when set to high idle (there is also a low idle). The throttle posistion will determine how much electricity is sent to the traction motors.When there two Metra engines mu’d together both engines don’t needed to have the HEP turned on. The engine without the HEP turned on works and sounds like a traditional freight engine - you hear the engine throttle up and down. Metra assigns two engines to certain trains as protection power during the morning or evening rush periods,

I hope that this helps. If anybody has anything to add, please feel free to do so,

CC