Question about radiator blocking

Air flow through the engine compartment cools the engine itself. Further, do remember, even with a thermostat closed some coolant flows through the radiator. There is a coolant bypass, as all engines require some coolant flow regardless of temperature. The main effect of blocking though is to hasten warmup.

Even with the lower grill completely blocked Pearl S struggles to get the coolant up to 60C in the city. It gets close, then the engine is shut down and it drops. Good for fuel economy, not so good for getting nice and warm. Interior heat is fine though. I use the seat heat to help, and it is wonderful.

Of course all this is at "non-California" temps, such as today, just above 5F, at -15C.

 

Electric water pump, heater valve and a lot of hose. Just because ICE is off doesn't mean the coolant fluid stop. Plus with the heater valve the system can route the coolant from the heater core first before it switches to the radiator system to cool the engine.
1st heater core, then coolant system from what I can see.

 

Besides the faster warm-up mentioned above, grill blocking improves aerodynamics. Smoothly directing airflow around the vehicle is more efficient than forcing it through a radiator, engine compartment, and out the bottom of the engine bay.

 

My take is the behaviour of the thermostat, the grill and radiator areas and so on, are designed for worst case: hottest summer temps, hill climbing, stuck in traffic with charge depleted, and so on. And in winter you can definitely close things up some.

 

At least up here, a huge benefit of blocking is it helps keep the road grime out of the engine compartment.

 

FYI- I partially grill block my TSX even in the summer. Efficient driving means you are getting better than average fuel economy, which means you are generating less heat per mile than the typical driver. Since less heat is being generated, the cooling system is less burdened. This excess cooling capacity can be circumvented by grill blocking as long as one is careful to always maintain proper engine operating temperatures. I do this by setting an engine coolant temperature alarm on my UltraGauge.

With a full upper grill block and an open lower grill, I never reach my alarm temperature of 200 degrees, even during the summer. One thing I have noticed is that 1 cooling fan always runs if I have the climate control turned on. This has the effect of cooling the engine, even when it is stopped in traffic.

 

^ I can't see grill blocking when using AC for cooling. Seems similar to driving with a foot on the brakes.

 

True, that is a consideration, and AC efficiency will be reduced by grill blocking. For my driving pattern and AC usage, I have noticed a significant increase in fuel economy by blocking half of my grill area during the summer. Apparently running the AC a little harder in Portland, Oregon is more than offset by a faster warm up time and reduced aero drag.

Also note that there is a gap between your radiator and the grill opening of the car. With a fan running, air can still be drawn through radiators even when fully blocked. Since my a fan always runs when my climate control is on, air is always cooling the AC and engine coolant. Note that I drive a TSX; YMMV with a Prius, different climate, and different driving pattern.

 

Err uhmm, you do also track the MG temps as well.?

 

I don't own a Prius, and I don't believe the UltraGauge has the capability of monitoring this. At least, I don't know how to set it up to do so. I'm in the market for a gen III though, so I'll be monitoring the MG temps when I get one.

 

Oh OK.