CP sd40-2's - why did they have louvered long hood doors?

[big train james]

The subject line pretty much says it all.  I don't think I've ever seen sd40-2's for other railroads with the louvered doors at the rear of the long hood.  What purpose did they serve?

Thanks,
Jim

[cpr4200]

The QNSL SD40-2's and EL SD45-2s's had them too. IIRC due to the large fuel tanks on these units, the air reservoirs and cooling coils were moved inside the hood under the radiators.

That said, I have no idea why CP units with normal size fuel tanks and the customary air reservoir location would have louvers back there. Some SD40-2's even had sets of four fiberglass filters added closer to mid-hood.

[big train james]

Thanks for the reply.

I saw some examples when I was looking around earlier, where the units had the fiberglass filters. It was suggested that they were added to address the heat under or around the dynamic brake resistors. But it didn't sound like that was an absolutely confident answer.

I also saw references to the louvered doors, but no explanation for their purpose. I agree that they don't make sense from the fuel tank capacity perspective. That arrangement seems pretty normal on the CP units.

Jim

[cemr5396]

the louvered hood doors on the CP SD40-2s WERE related to air compressor cooling. Not sure why they were that way, but they were. It was only on the early units, later units did not have them.

The intakes that were added to the hood doors under the DBs on some units were for snowplow service. The regular engine air intakes would be covered up and the air would be drawn through the intakes in the engine room instead. The idea was that by making the air go through the warm engine room first there would be less issues with snow (and water) in the intake air.

They did work to a degree, but they also caused other problems with dirt and grime being pulled into the clean air room.

[big train james]

Brad,
Don't know how I missed this earlier, but thanks for the extra information.

Jim