Quote:
Originally Posted by Tremelune
Whoa, where's that thread?? I haven't seen anyone put a water-cooled motor in an air-cooled 911.
If I had a 912 that needed motor work, the Porsche lump would get pulled so fast...
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Here's that build thread with the 911:
http://forums.pelicanparts.com/porsche-911-technical-forum/518231-pvx-build-thread-one-view-slope.html
Interesting that his 911 is also running radiators in series, possibly because it's simpler to plumb. I've worked out the math, and parallel radiators are more efficient, likely why new Porsches all run their multiple radiators in parallel.
The challenge with parallel radiators is ensuring even coolant flow, and there's a possibility of stagnant coolant locations (where the coolant just sits, does not flow, hence does not cool).
The challenge with serial is ensuring the pressure drop is not too high. Think about, what happens if you put your hand in front of a hair dryer? It stops blowing air, the fan will just spin. Your water pump is just like this, it's designed to operate with a minimal pressure drop, it will pump a large amount of fluid if there is not a lot of pressure difference. As you start increasing the pressure drop, the efficiency and hence the amount of fluid it pumps rapidly drops.
In summary, regarding the serial/parallel radiator discussion:
Radiators in series:
- easier NOT to screw up (you're guaranteed to have the same amount of coolant through each radiator).
- easier to plumb
- produces a higher pressure drop -- this means that the water pump is working against a higher pressure load, which means that loses efficiency if the pressure drop is too high, the pump will not work at all. need to be really careful here.
Radiators in parallel:
- higher efficiency and cooling capacity than series
- there's a reason why all factory multiple-radiator cars run them in parallel
- easier to screw up -- if the flow is not balanced, parallel is much worse than serial.
- more complicated plumbing, somewhat heavier because of extra plumbing.
- lower pressure drop -- the water pump will operate in the range it was designed to.