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1. Distilled water is safe to drink
only use distilled water until the engine has been fully tested
-for many reasons: so it can be spilled anywhere (very useful), so it is cheap to replace, so you can see how filthy it really is, many tracks require 100% water only also
2. Coolant temps:
Cruising Coolant near 200-215*F with oil temp 200-215* is optimal fuel economy
Tracking/racing with coolant near 178*F with oil temp ~205-212*F is for fuel safety
Idle in traffic 210*F coolant with 140*F oil Is helping warm the oil up
Idle in traffic 175-185*F coolant with 205-215*F oil temp is ideal for headroom
-notice the goal is to move oil temp to 200-215*F as quickly as possible (to thin the oil out properly before racing) And then drop the coolant down to ~180*F for cooler intake air pathway parts and increased headroom for temp rise.
The rate of coolant temperature increase/rise is dependent on:
-amount of power the engine is making (at that moment)
-efficiency of radiator/fan to reject heat
-capacity of cooling system
So,
If engine makes alot of power, the temp will rise faster, at that instant, especially if low capacity system
e.g. 'lots' of 180*F water has more heat capacity than 'a small amount' of 180*F water, to resist temperature change when energy is input
If have a poor fan/radiator/shroud setup, the temp will rise faster, all the time, it may even uncontrollably increase.
The way to test system is firstly at idle,
Run the engine idle and see how long it takes to warm the entire contents of radiator up with no fan running.
SR20 with typical aluminum radiator should take at least 10-20 minutes to do this when started from 80*F.
The way the system works is,
1. the thermostat initially shut is constantly checking the temp of the water in the engine.
2. The engine water does not flow into the radiator while the thermostat is shut. So it warms up very fast.
3. After just ~1 minute or so, the engine water should be nearly hot enough to cause thermostat to open (180*F?) Fans are set 188-195 so they are still off when the thermostat opens.
4. Thermostat opens now 180*F for example, and some water is exchanged between the thermostat and radiator.
5. Because the water taken into the engine from the radiator is only 80*F, it cools the thermostat/engine rapidly and the thermostat shuts again.
6. Only a little bit of hot water was ejected into the radiator from #5. When this happens, the top of aluminum radiator will suddenly get hot. If you have been standing there for the entire minute waiting for this event, feeling the sudden change in temp of upper radiator tank is a sure sign the thermostat has opened a little and pushed some hot water out of the engine.
7. Now the process repeats for ~10 minutes. A little 80*F water flows into the engine, shutting the thermostat again. A little 180*F water flows out of the engine and into the radiator. Gradually the radiator's temperature increases. Soon 90*F water is going into the engine. Then 100*F. Then 150*F. Eventually 169*F water is going into the engine from the radiator, and 179*F water is coming out of the engine, instead of 80*F in and 179*F out.
Note that the higher the water temp is in the radiator, the more often the thermostat is letting water flow into the engine. Until eventually its just open constantly and water is flowing non stop. This same sort of theme takes place in the oil pan where oil in the pan is initially only 80*F and as it flows through the engine might hit 100*F before falling back into the 80*F pan and starting over. The two systems are both cooling the engine and have reservoir capacity which influences the rate of temperature change. High capacity oil systems can keep an engine cold for too long, they require thermostats which just like for coolant, allow the engine's initial supply of oil to warm up without being mixed with a high capacity heat exchanger until necessary.
8. Once the radiator water is thermostat set point and water is flowing non stop, it will continue to rise because the fans are not on yet. If the cooling system is sufficiently large, and engine output is very low (at idle it is) some engines can idle indefinitely with no fan running because heat rejection from the radiator even while just sitting still is enough. So expect that while the engine isn't doing much that the system won't be heating up very fast. Once the fans turn on, they should run for a bit then shut off. The first time they start, then stop, is going to be the easiest. So if they have trouble turning off from the start, the system is in big trouble. Once the entire car is hot, the engine bay, the metal of the car itself, the hood, insulations all around, the hot exhaust and hot intake and hot everything, the hot radiator that if you touch burns your skin right away. All of that heat is bring thrown around in there, and it needs a really really good fan, and a well thought out pathway for airflow, if the engine is going to make some serious power.
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