Originally Posted by Tango
I find it odd, but according to the diesel gurus over at 4BTSwaps...Cummins engines run on the cool side compared to gas or most other motors. Many of them have made the conversion to electric fans and comment that even in hot weather they rarely switch on at all unless pulling a load up a hill.
That said, I do plan on trying to over build my cooling system and include a couple of temp sensors plus a manual on/off switch. The trans cooler will be completely separate and electric as well.
you are also running a smaller engine and a smaller bus too... your radiator size ratio to engine size will be high compared to an RE bus or esp the 'DT' conventional busses.. the 'DT' conventionals have half the grill area as the turbo cooler and half as the radiator as opposed to a stacked position like most turbo-charged vehicles.. the result is very low radiator area / engine size ratio so they rely on the fan to do a lot of the cooling esp in hard pull situations... at idle or around town my fan clutch's low-speed constant is pretty much enough to always cool the bus unless im doing a ton of stop / heavy accelerate, stop, etc.. like stop and go traffic where the traffic goes from 0 - 35 - 0 - 35 etc..
electric fans will easily cool a very ;arge bus when the speeds are constant at a low level.. or I should say engine loads not speeds...
but pull a mountain pass where your foot is to the floor and the engine is under full load slowed below governor RPM... thats where you make heat... lots of it.. if you have a Huge coolant volume that can absorb that heat then you would be fine as your fans can remain on high speed aftyer the engine loading has ceased.. the cooling system will dissipate more heat than is being produced until the temperature is back to normal.. but if your cooling system isnt large enough to absorb that load, it relies on the ability to dissipate all of the heat produced as it is produced..
I dont know what the engineers used for numbers and capacities when designing the RE busses from the factory... or the conventionals.. but I do know from having a bad fan clutch that always stayed at a constant 300 RPM on my DT360 conventional is that it stayed at 195 or below most of the time until I got it on the highway or in stop-go traffic then it warmed up.. It needed more cooling than it was achieving some of the time..
Tango's bus is custom and so the cooling system for it must be designed according to the custom design.. and I venture to say the radiator cvolume will be somewhat small just because of size restraints.. and then rely on fans to dissipate the heat as needed...
its my belief that cummins engines tend to run cooler because their torque curve is pretty extreme at lower RPM's allowing the engines to "unbury" themselves pretty easily from being Lugged.. Lugging any engine will make tons of heat... alas why gasoline engines detonate or "ping" at Lugged low RPM's.. the cylinder head temperature are quite high during that timeframe..
Im all about electric fans in general... ive used them in most every hotrod i ever built with great success.. but I also had nice big aluminum radiators where I had high radiator volume ratio compared to engine size..