| [GMCnet] OT - Looking for help/advice with low and hi pressure issues [message #258767] |
Wed, 13 August 2014 20:11  |
glwgmc
Messages: 1014
Registered: June 2004
Karma:
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Senior Member |
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Hi,
Watching the good responses you have received so far reminded me of the many past posts about the effectiveness - or not - of electrically driven fans and fan clutches. The GMC requires a seriously large engine driven fan that comes on any time the incoming air temp reaches the turn on temp of the fan clutch. The fan consumes a lot more HP than one could ever get from an electric fan. Divide the watt draw of your electric fans by 760 and that will give you a rough approximation of the HP. The engine driven fan likely pulls something over 15 HP when pulling a long grade. Electric fans would have to draw something around 11,400 watts (nearly 1000 amps at 12vdc to provide the same HP). Can you imagine how big the wire would need to be to provide 1000 amps at 12vdc to an electric fan?! Not to even think about where one could generate that kind of on board power.
The other factor in your situation is how to baffle the fan to direct as much air over the radiator as you experience with the front mounted radiator at highway speeds in a GMC. I am not trying to suggest your task is hopeless, just that it is not easy. Even with great engineering not many rear engine, water cooled applications have proven to be successful as many Flexible Flyer bus owners would likely confirm. Even water cooled VW buses with far less heat and HP had a tough time once they aged over time.
My suggestion would be to do what you can to move the radiator close enough to the fan side of the engine that you can instal the same fan, fan clutch, fan surround and baffles used in the late model GMCs. Then work on means for forcing as much air as possible through the radiator at speed. Hope this helps.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed & hand crafted
in the 1907 former Masonic Temple building
in historic Kerby, OR
http://jerrywork.com
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Jerry & Sharon Work
78 Royale
Kerby, OR
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