Electric fans vs miter box?

[HB of CJ]

Excellent thread and thank you.  45 years ago the master mechanic told us youngsters that the two BIG matched special Vee Belts cooling our old Cummings 220 hp Crown Supercoach School Buses pulled well over 30 hp from the engine.  Now I believe it.

[lvmci]

hi John, yes they are wall to wall fans over the radiators, especially the English built buses, I  thought about using the 24volt squirrel fans from the air/heat blowers, which moves a lot of air, to cool the radiators, lvmci...

[LuckyChow]

The last transit system I worked for has transits with electric fans.  They don't have a problem cooling at any rate of travel including at sustained highway speeds.  They cool just fine.  All new Gillig buses with electric fans are driven from California to any east coast destination on the interstate, just like their hydraulic counterparts.  Highway speeds are typically 65 to 70 mph.  In addition, many of the fixed route transits operate on the interstate daily.  You couldn't operate a bus today that was limited to low speed operation.  You can also order an new MCI with electric fans.  I think they are switching from the EMP system to Modine now. 

Be aware that these fans are not simply on and off.  They have an electronic controller that gets input from the engine computer about temps and are variable speed.  Each fan is individually controlled.  As the engine cools down, the fan speed drops until it gets to a set point.  Consequently, you may get fans running quite a while at lower speeds before cutting off.  One thing that you may not realize is that the radiator is also part of the electric fan system.  They did not just add fans to the existing radiator used on the hydraulic fan system.  It's thickness is optimized for the cooling capacity of the fans and is matched to the BTU capacity of the system.             

[kyle4501]

. . . . .
One thing that you may not realize is that the radiator  . . . . is optimized for the cooling capacity of the fans and is matched to the BTU capacity of the system.             

Excellent point!
That optimization is key to ANY successful cooling system. It amazes me that people will upgrade to a higher hp engine, but they insist on reusing the old radiator. . . . Then worry about overheating . . .