Logging coolant temps on OBD2 in stop and go traffic the coolant temp reaches 213f before the fans come on and then comes down to 203f. If I run the AC, because the fans are always on, coolant temp never gets above 193f. Does this mean its better to drive with the AC on in stop and go traffic and AC off when you're moving? With the car moving even pushing it, the car never goes over 200f, even in 95f ambient.

Coolant temps measured at the radiator are not the same as the coolant measured at the cylinder head. I understand thats why the fans come on at 213 not 195.

 

Have you measured the coolant temp in stop-&-go traffic with the top down and the heater at full max? No A/C.

Thanks!

 

When you first open the heater the temp drops by like 6 degrees until the heater core is saturated. Then the temp goes back to normal maybe like 1 or 2 degrees cooler.

 

Thanks, I always wonder what the temp drop was, as I sweat to death in an overheating car.

So I guess it's better to turn the A/C on in an overheating S2000? At least you are comfortable.

 

Ideal gasoline engine operating temperature is roughly 195°F–220°F. Colder is ineffective combustion, warmer carries risk of boiling out. As far as I can tell there's no benefit at any specific temperature within this range. The car doesn't care! 213° is neither better nor worse than 193° or 223° they're all within the normal range. The car will run the fans when needed.

Historically cars had their radiator fans permanently bolted to the front of the crankshaft and ran 100% of the time and we still had overheating. Electric fans are much more flexible at cooling when needed and don't use power when it isn't.

-- Chuck

 

Which, it's kind of funny...most cars these days are engineered to disable A/C when over-heating is detected. I'm sure the saturation level and cooling ability is vastly different on modern vehicles or even from model to model but still...humorous.