Just trying to show how surface area, material, and air flow IMO have as much or more to do with engine cooling than flow rates and radiator cores. I've raced air cooled motorcycle engines for a long time and in the late '70's early '80's high performance motocross and off-road motorcycle engines became liquid cooled and we dealt with the overheating issues and mostly (but not exclusively) the problems were caused by lack or reduced air flow. On air cooled engines it relied on the surface area of the cylinder fins, the material (aluminum) and the air flow across and around the cylinder and cylinder head fins. When we went to liquid cooled engines all we were basically doing was using the coolant as a medium to take the primary source of heat engine combustion and taking it to one or two aluminum radiators and dissipating that heat to air. No real rocket science except in air flow with radiator side panels as scoops and our engineers even came with side panel or radiator "shrouds" that had opening that created a "chimney effect" that would help remove hot radiator air from behind the radiators at slow speeds or even at a standstill. Engines are still air cooled in my opinion they just use coolant to take that heat to a radiator or air cooling area. That's why I feel or know that air flow, surface area and material are most important. Check out this air cooled, 500cc single, hemi head, twin spark plug 60+ HP motocross bike from the early '80's. Lots of aluminum cooling fin area with lots of space for air flow. BTW most liquid cooled motocross bike still use the same basic size aluminum radiators to this day. Only a few things have changed like special radiator coating rather than black paint to better dissipate heat or small electric fans on the backside of the radiators for extreme slow moving conditions. AIR FLOW IMO is a key element.

The battle rages on because of the myths perpetuated that will not die.

Think about it.

The longer the coolant stays in the radiator, it’s also staying in the block longer. Where it picks up more heat. That means the radiator has to dump more heat. So staying in the radiator is adding to the heat load the radiator has to eliminate.

We are working with limited temperature differentials. On a 100 degree day, the difference between that ambient temperature and your coolant temperature is less than it is if the ambient is say…60 degrees. That temperature differential is what makes cooling possible.

What your temperature gauge is telling you is the AVERAGE coolant temperature at the intake manifold. You can (and probably will) have localized coolant temperatures much higher than what the gauge says.

Getting the coolant out of the block quicker (more flow) will reduce local hot spot temperatures because the coolant is moving out of those areas so it’s not allowing the temperature to build up in those places.

You can always tell when a cooling system is inadequate. When the temperature on the gauge is higher than the rated temperature of the thermostat you’ve got issues. If you have a 180 thermostat then your gauge should stay between 180-185 in ANY weather conditions you may incur. On a very hot day, you may see an additional 10 degrees of temperature sitting at a LONG stop light or (alike happens to me if I’m not paying attention) if you get caught waiting for a long train to get out of the way. But as soon as you start moving the temperature should go back to where it normally runs.

If you have a 180 thermostat and your normal operating temperature is say…195 then your cooling system is inadequate. That then is a coolant and air flow issue. Too slow of coolant speed or not enough airflow or both.

The thermostat sets the MINIMUM operating temperature. That’s all it’s job is. It’s a restriction and that’s BAD, but it’s necessary. I have to run a thermostat. If I don’t, even on a 90 degree day my coolant temperature won’t go over 120 degrees or so. On a 50 degree day it won’t go over about 90 degrees. That’s because my cooling system is fully capable of controlling coolant temperature like it should so the thermostat does exactly what it should do, and that’s set the minimum temperature.

There is a reason why guys can go from a 190 to a 160 thermostat and the engine doesn’t stay any cooler. The cooling system is inadequate to deal with the heat load it has to deal with.

I run my water pump at 6% overdriven and if I could I’d double that or a bit more. We had some 108 degree days several years back and my engine temperature was at 160 even in that heat. At stop lights it would get to 175ish and then it would drop back down to 160 once I got moving again.

The backwards thinking that the coolant has to stay in the radiator longer to dump more heat is a fallacy, because the coolant stays in the block longer picking up more heat that the system has to deal with.

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