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Old 02-03-2009, 05:12 PM   #1
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Coolant temp

I have been playing with a radiator block on my Insight, and a thought came to me.

Cooling systems are designed with a reserve capacity to cover all situations, especially when it's very hot and you are running AC.

However in very cold temperatures, the cooling system has too much capacity for heat removal, and other than blocking the flow to the radiator, there is not much you can do to control the temperature of the coolant when it is entering the engine after going through the radiator.

The colder it gets the less coolant the thermostat allows to flow through the radiator, but that has the disadvantage of making the coolant much colder when it reenters the engine. By blocking 50% of the radiator surface area on my Insight my mileage average has climbed from 58 to 65 MPG, a significant difference.

What is really needed is a temperature sensor in the bottom (cooler) radiator hose that controls the available surface area of the radiator to keep the return coolant around 120 degrees, which is about the same temperature it would be in ambient temperatures of 90 degrees. By restricting the heat losses through the radiator you would avoid the much colder coolant entering the engine and robbing it of heat energy.

It was done this way in the old days with the adjustable louvers in front of the radiator itself. It would be neat to rig a set of adjustable louvers that were controlled by a thermostat in the return coolant hose to maintain a certain temperature in the return coolant, probably about 120 degrees. This would also reduce the work of driving the water pump against the restriction of the thermostat itself, but that savings would be minor compared to the significantly lower heat losses to the much colder return coolant in the winter.

regards
gary
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Old 02-03-2009, 05:25 PM   #2
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Very Insightful. Pardon the pun.
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Old 02-03-2009, 07:30 PM   #3
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As long as the louvers don't freeze shut or open everything you say will work just great. If thermostats would close better it would be great too but they don't really work that well. I guess the next thing is a variable electric water pump or two - one for the block and one for the radiator.
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Old 02-03-2009, 07:50 PM   #4
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Another possibility would be a thermostatically controlled bypass circuit, that allowed hot water to bypass the radiator and mix with colder radiator coolant to maintain a 120 degree inlet (coolant into engine) temperature. Two thermostats, one 180 degree and the other 120 degree.

The 180 degree would act normally, while the 120 degree would allow coolant to bypass the radiator and mix with coolant through the radiator to maintain 120 degree temp. the 120 degree thermostat would close off the bypass when combined coolant temp exceeded the desired 120 degrees.

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Old 02-04-2009, 04:08 AM   #5
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Quote:
Originally Posted by R.I.D.E. View Post
Another possibility would be a thermostatically controlled bypass circuit, that allowed hot water to bypass the radiator and mix with colder radiator coolant to maintain a 120 degree inlet (coolant into engine) temperature. Two thermostats, one 180 degree and the other 120 degree.

The 180 degree would act normally, while the 120 degree would allow coolant to bypass the radiator and mix with coolant through the radiator to maintain 120 degree temp. the 120 degree thermostat would close off the bypass when combined coolant temp exceeded the desired 120 degrees.

regards
gary
Don't engines have a bypass channel built into the block/head? So far as I know that's the path the coolant takes when the thermostat is closed. Goes back to the pump which cycles it back through the engine.

I know my rear-drive Volvo has it.
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Old 02-04-2009, 04:51 AM   #6
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Yeah the coolant might be re-entering the engine at 10 degrees F or so, but the volume of coolant flow is so small that it doesn't really pull the engine temp down...

On the engines I'm familiar with, the water pump has two outlets and two inlets - one of each goes to the engine, and one of each goes to the radiator. Therefore there is essentially a built-in bypass already, in the water pump. The little bit of coolant that makes it through the radiator is mixed in with the hot coolant being circulated through the engine.

Maybe there are other engine designs, but all of the ones I've seen work that way...

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Old 02-04-2009, 10:03 AM   #7
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Yeah, they usually bypass though the heater core and/or a bypass hose to the other end of the block again.

Careful about using a thermostat on the radiator return. The tracker was setup like that and it was a huge pain. In the summer coolant temps hung around 201-203 no problem even at idle but when winter came around i was idling around 219 and cruising at 214. The thermostat sat in the cold return line with the bypass hose flowing past it at a right angle. When the thermostat would open a little because it was getting hot the cold water would cause it to shut.

Also, unlike a thermostat in the radiator inlet, in the return position the thermostat can get sucked open. In temps under 40 I could floor the car while fully hot and drop coolant temps from 219 to 140 easily and then it would slowly climb back up to full temp. Not good for the engine to shift temps like that!
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Old 02-04-2009, 10:49 PM   #8
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My old protege had 1 water pump output, to the radiator. But it had a bypass that went around the front of the block to an inlet into the block with 2 T's, one for the IAC (warmed up the intake faster) and one for the heater core. It was a very nice setup and worked flawlessly. Neither my GP or Sonoma has the same. The Sonoma is similar, as it does heat the heater core while warming up, but the GP seems to have no such heater core bypass; I wait till the thermostat opens, anywhere from 180-230 (its broken yes, haven't had time to fix it in the winter) and then the HC gets hot coolant. Sucks, cause while the engine has reached closed loop running, the rest of the car is still freezing and a pain to drive. AND since my transmission is cooled/warmed by the radiator, it runs poorly till it runs for a while or I get hot coolant to warm its oil.

I hate the Grand Prix's coolant setup. It just sucks. I'm thinking when I replace the coolant and 'stat I'll create a HC bypass, mostly just so it defrosts/de-ices the windshield faster. Driving with the window down and my head out at -20 or when snowing: not so good option.
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Old 02-05-2009, 09:03 AM   #9
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i'm still toying with the idea of an automated grill block. i just havnt gotten the materials together to build it yet. stays closed when the engine is cold and then opens once it warms up.
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Old 02-05-2009, 09:25 AM   #10
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To make sure you don't end up with a block that is frozen shut you might look into doing it behind the radiator, but I honestly don't remember what kind of room you guys have behind the radiator.

I have a question though. Does the significantly colder water even make a difference? The point of this is to make the cooling system as a whole warmer but what advantage does that give you? If the temp falls below thermostat temp it'll just close again, no big deal. You could increase your isolation from the radiator by plugging the air bleed on the thermostat so during warm-up you have less water flowing through the radiator but I can't think of a benefit of blocking the radiator.
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