When to remove grill blocking material???

I block 50% of the lower typically. 100% of the lower if it's consistently below freezing (which barely happened this last winter, on the west coast).

I leave the upper completely unblocked. I've read not to block upper more than 50%, at any time, due to inverter radiator being exclusively in that area. I just keep it simple, never block the upper.

Once temps are getting up around 14~15C I pulled it all out. If I'm going up a ski hill I pull it all out. If there's a chance I'm going to use AC I pull it all out.

I'm using foam pipe insulation, reused it for 4 years now.

 

I'll watch my engine coolant temps and remove some blocking only if temps go above about 205 F. I block 50% of the Acura TSX and Toyota Camry grill year-round and temps remain normal even in hot summer weather. I expect the Prius will respond similarly.

 

When engine coolant reaches 90C, time to take the grill off. Double check the radiator overflow tank and fill to line if low.

Bob Wilson

 

i plan to remove the upper when i need to use the ac more as someone mentioned above and remove it all when the temps are above 40 as the lows for more than a week. btw i just came back from a 200 mile trip with 100% blocking and ambient around 43f and the temps never got over 193f.

 

An open grill is paramount for AC performance. Maybe in winter it's ok, for dehumidifying. But: look through the grill: that big front radiator you see is the AC radiator.

 

I have GenIII since 2009 and I keep blocking lower part until A/C is needed which is about mid May .... for me in NYC area ...

But this may vary on road/load/driving style. I would not recommend the above without "somehow" monitoring at least ICE coolant temp if it regularly reaches and stays above 190F time to remove it...

 

BP, the bottom is blocked year round.

 

BP, I leave the bottom blocked all year because the tubes are secured with twist ties. Engine coolant temp seldom gets to 200F and is rather stable. Inverter coolant temp varies a great deal. It starts at the outside air temp and increases with use. I'm not running any hotter than those in the deep South.

One photo is from last April at the 21st century Automotive Challenge after the day's rally. You can see the top is blocked because that white spot in the grill is the sun bleached label on the pipe insulation. (I know it's tacky but the pieces aren't replaced in their original slots. I should have flipped it for the display but nobody else notices.) The indentation in the bottom tubes are from the twist ties.

The other photo was taken the next day at the track waiting for inspection before the autocross. The car had the 2nd best time just behind the biodiesel Jetta.

 

if you are driving over 60 mph for over 30 minutes and the driving temperature is over 50 F no grill blocking
If you are driving under 40 mph for and the driving temperature is over 60 F no grill blocking

If you are driving below 40 mph in a driving temperature drops under 40 mph put on grill blocking

 

I add and remove blocking based upon this post: 2010 Prius Grill Blocking strategy | PriusChat

 

I've taken off my grill blocking - the driving temperature in the Washington DC Metro Area is now about 60 degree Fahrenheit most of the time so my grill blocking is now 100% off. The reason to take it off is to avoid triggering the electric cooling fan for the coolant system (if the engine runs too hot the extra load on the cooling system will cause the MPG to drop a tad). The return to warmer weather also means my Prius' MPG naturally is going up too!. The HSI display says my mileage for the last +540 miles is about 60 mpg but it is more likely to be closer to 58 mpg

 

exactly. 37 yesterday, blocking still in.

 

Yeah if you're running AC for cooling the first interior, seems to me completely wrong to leave ANY grill block in. That big front rad is the AC's means of dissipating heat.

One thing I do leave in year 'round tho, are short sections of tube insulation where hood meets fender. They don't impede rad cooling, but hold in the heat a bit.

Also I suspect they reduce air flow through engine bay, it seems to be staying pretty clean.

 

We have such mixed weather here.
See attached.
What to do...

 

Similar conditions here, I'm use nothing' on the top (ever), 50% on the bottom, and the aforementioned block at hood/fender seam. IF it stays solidly below freezing, then I'll put a second tube in the bottom, ie: 100% block.



If I'm doing something like going up a ski hill, I'll take that one lower tube out.