When to remove grill blocking?

The rule of thumb has been when the daytime high hits the 50's.

Benefit comes mostly from when the temperatures are below freezing.

Sadly, that's been quite useful this particular winter. We've seen lots of days in the negatives.

 

in your particular area, grille blocking is probably not that effective. and temps swinging back and forth in the 40's and 50's make it diificult due to the pain of constant re applicarion. this is where active shutters would be useful.

 

Depending on the mixture of water to antifreeze, the boiling point would be over 212F. It's probably closer to 230F in the factory setup. I've seen posters here leave the grill block on above 60F. A Scangauge/Torque app would display the coolant temperature if you're worried.

 

Coolant temperature constantly over 200F would be an issue for me. Mine stays between 180F and 190F when it's warmed up but the engine hasn't run since early December as all of my miles have been in EV.

 

I'm doing 50 % of lower between 5 and 10 centigrade. If temps are consistently under 5 I'll go to 100% block. I never block upper. If we're going up sustained uphill grade (ski hill) I'll pull it all out, regardless of temps.

 

With the grill block in place, were your coolant temp to remain above 200F for extended periods of time, I'd be worried. That 199F peak doesn't seem to be too worrisome. If you can keep the coolant below 200-210F when climbing, I don't think I'd worry about it. As soon as you start the descent, the temps will drop well below 200F.

 

I was thinking that the electric radiator fan doesn't even turn on until 202 or 204F. That significantly increases the cooling, usually quickly dropping the temperature below 200. If the temperature goes above that, I'll take the first stop and remove another strip or two of the blocking. If it never shows excursions below 200, I'll also remove more.

 

Here's a nice article on grill blocking.
http://www.cleanmpg.com/forums/showthread.php?t=17560

 

The answers on how much grill blocking is appropriate for each temp range is included in this 2009 post:

2010 Prius Grill Blocking strategy by Ken @ Japan:

Celsius|Fahrenheit|lower blocking %|upper blocking %
below 5|below 41|100|50
5 - 18|41 - 64|75|50
18 - 30|64 - 86|75|0
above 30|above 86|50|0

Sorry I cannot provide the link - not enough posts but you can find the thread using search

 

Here's that link, with thanks to CeeJayNorth for finding it:

2010 Prius Grill Blocking strategy | PriusChat

 

I never had an issue with full upper block. Never removed it. Radiator has plenty of flow. I'm using A coro body kit from Japan