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Discussion Starter #1
It’s in the 20s to high 30s here in the mid-Atlantic states so I fashioned a few block off plates for the oil coolers and radiator inlets. The oil coolers are completely blocked while the radiator is about 80% blocked.
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I understand blocking off the oil coolers, but that seems extreme for the radiator. with a functioning thermostat you shouldn't really have a need to do that at all.
 

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"Need" and "helps" are two different things. Use case also matters - if, as mine does, your drive cycle requires you to be going 50+ MPH less than two minutes after you start the car, then something to restrict airflow over the radiator in sub freezing weather really helps with warm up times. My winter beater Celica (which has a very similar cooling system to the 2ZZ-GE) warms up a lot faster when I put a cardboard air block over 2/3 of the radiator. I also have black duck tape (it's a black car) on the lower two slats of the intake grill in the bumper cover. This is as much to keep brine off the aluminum radiator as it is to restrict ram air into it, but it does help with overcooling as well. I watch the temp gauge carefully and note when the cooling fans is running. Temperature regulation is the same, but warm up time is reduced by about half. This means less oil dilution and better crankcase vapor removal. It also gets heat and defrost going sooner, which is welcome too.

The engine is designed to easily manage coolant return from the radiator at temperatures up to about 110 F, therefore it does fine with an 80 F delta-T (regulated to ambient temp) in most use cases. If it's 20 F outside, the car is above about 30 MPH (uncontrolled ambient ram air over the radiator), the delta T at the radiator return is going to be more like 170 F. The return coolant is so cold that (particularly if the engine is above 3000 RPM and so the water pump is doing a thorough job) the thermostat's jiggle valve is a significant cooling source at these temperatures if the engine is lightly loaded.

My own experiments with my Elise have also shown that you get a lot more cooling from the side scoops and belly scoops than you may want in cold weather as well. Oil pan temperature actually increases when the car is idling below freezing compared to what I see on the highway because of airflow through the engine compartment scoops. Great in July; not so desirable in January.

In short - if you are watching the temperature gauge and the engine coolant isn't over 200 F, why worry? If it's like my duck tape arrangement, it's pretty trivial to get out of the car and peel off a strip to get more airflow if the radiator fans have kicked up to high speed.

And yes, I do have about 2/3 of the radiator grille blocked on my Elise as well after about November 1 until about April 1. I don't block the oil cooler ducts because I'm using an oil to water cooler now.
 

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I'm a cold weather driver. In winter up here in Toronto we often are in the range 15 F to 40 F. I usually drive for about 5 minutes on smaller roads before I hit the highway. By that time my temperature gauge has reached its steady state value.
 

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Discussion Starter #5
I understand blocking off the oil coolers, but that seems extreme for the radiator. with a functioning thermostat you shouldn't really have a need to do that at all.
It’s just an experiment, totally reversible. My reasoning was to help the engine maintain safer engine oil temp in very cold weather. I don’t have an oil temp gauge, but the engine warms up faster and the coolant temp gauge is a few degrees higher now. Also, the car speeds up faster due to less air moving through the clam creating drag. The car accelerates more freely with less engine effort at speeds over 80mph with oil plate blocks and radiator partially blocked. I can remove the radiator block in a few seconds. The Exige is overcooled for street application so I’ll probably leave the oil cooler plates in situ for spring and summer too.
Blocking off the NACA ducts will help oil temps as well.
 

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My oil coolers have been disconnected and geez the engine heats up a lot more quickly now.
 
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