tony1963 said:
The speed of the coolant going through the circuit has nothing to do with the heat transfer abilities.
Keep in mind that if it runs "too fast to lose heat" in the radiator, it consequently runs too fast to pick up heat in the engine.
Speed of running coolant is not relevant.
uuhhh.....wrong.
tony and NODIH....I hate to break the news to you but the speed of the coolant flow DOES have something to do with the cooling efficiency. Basically...the faster the better. Any engine cooling engineer in the world can verify this for you.
Trust me, the coolant has plenty of time to "give up heat in the radiator" and "pick up heat in the engine" no matter how fast it is moving.
It really is an old wives tale (that is totally false) that slowing down the coolant helps the cooling system. I think that got started eons ago when hot rodders started revving stock engines past where they (or their water pumps) were designed to operate. As a result the water pumps cavitated, stopped pumping and the engine overheated. Someone got the idea to slow down the water pump with a larger pulley on the water pump and the engine quit overheating. So....they invented this idea of "slowing down the coolant so it has time to pick up the heat and give up the heat". Trouble is, the reason the engine no longer overheated was because the water pump was pumping again and not cavitating like before....it had nothing to do with speeding up the or slowing down the flow rate.
Theoretically, it is easy to argue that the mass flow rate of the coolant doesn't matter. Trouble is, that doesn't take into account the efficiency of the radiator and the "scrubbing" effect of the high velocity coolant inside the engine.
The greater the temperature differential across the radiator (the radiator fin temp to the air temp) the more efficient the heat exchanger is. The faster you move the coolant the higher the temp of the fins on the cold side so the rad efficiency goes up and the system cools better.
Inside the engine, at the hottest spots, bubbles can form on the hot surface...called nucleat boiling. Those microscopic bubbles on the hot surface tend to isolate the coolant from the surface and reduce heat transfer. Faster flowing coolant scrubs the bubbles away and promotes more heat transfer to the coolant thus reducing engine temperature. High flow is good.
Modern engines move the coolant at a very high rate. The higher the output of an engine the faster the coolant flow. The coolant pumps are designed for very high flow rates at high efficiency so as to not sap too much power from the engine.
It is not desirable to run without the stat in general because of warmup and such. With the Northstar engine, in particular, the stat is an integral part of the flow control of the system and the sytem will NOT work correctly without the stat in it and it will NOT have the maximum cooling efficiency.
Having said that....with the 4.9 engine the stat is a fairly simply device that simply controls to a temp and it is NOT part of the integral flow control of the system. Removing the stat will usually help the cooling of the system due to the increased flow in a 4.9. This is true only for a maximum effort cooling situation where the stat is fully open anyway. Removing the restriction from the system will help slightly if that were the only situation the engine had to deal with.
NODIH, the problem with your reasoning is that you forgot to include the part where a much greater volume of coolant would go thru the radiator in the same time period. True, per your example, on a single pass an individual slug of coolant would give up less heat in the radiator but without a given time interval more slugs of coolant would pass thru the radiator with a faster flowing system thus the total heat transfer would be the same in that simplistic example.
As I indicated earlier, that slug of coolant would pass thru faster and would give up less heat and would exit hotter....so the end fins would be hotter in this case than in the slower moving coolant case. THAT would improve the heat transfer capability of the radiator by increasing the delta in temperature between the fins and the air coming thru it....thus the overall cooling efficient DOES get better with faster flow.
Trust me, I have done lots of engine cooling development and have seen it proven over and over that the more flow the better. It isn't even up for debate. Slowing down the coolant or orificing the system is NOT the correct thing to do for cooling efficiency. If someone makes a mod like that and it "improves" the cooling of the system then they had something terribly wrong elsewhere and they are not fixing the problem by slowing down the coolant..!!