2010 Prius Grill Blocking strategy

Prius engine is very efficient. It does not produce much waste heat. Sometimes (when its cold outside) it does not produce enough heat to reach normal operating temperature for thermostat to open . Then the grill blocking is helpful. It reduces the air flow that cools the engine from outside, which allows it to warm up to normal temperatures faster.

- Alex

 

The grill opening has to big enough to suit ALL scenarios. That's basically why grill blocking's effective in winter: the opening size is overkill in that situation, the engine takes too long warming up, if ever.

 

Sooooo Im new to the gen3 grill block game... with my gen2, I'd block 100% of BOTH grills starting in November and lasting through April. What Ive done so far on my Gen3 is block the entire lower grill and I blocked on 2 slats on the upper (leaving 2 slats open). However, it is anywhere from 0f to -10f degrees here in Michigan lately.

Is it safe to do the same with my Gen3? I tried to read through this thread but its 24 pages long. Can somebody give me a cliffnotes version? lol

 

Why do you think the thermostat needs replacement?

It's not advisable to run any amount of grill blocking without monitoring the temperatures. If the electric cooling fans kick on, then it defeats the fuel saving benefit of grill blocking.

Safe, yes. You still want to have some method of monitoring the engine coolant temps to make sure you aren't over-running the cooling system. I'd say any temps over 210 F would indicate excessive grill blocking.

 

Ok then, when I get the car back from the tinting shop I will finish blocking the rest of the upper grill completely

 

I would not block upper more than 50%. Ever. Invertor coolant rad is exclusively in that zone.

I do pretty conservative block: 50% of lower from 15C to 0C, 100% of lower below 0C. Never block upper. Also, no blocking if doing something like a run up a ski hill.

 

Thanks for the input, as I wasn't sure if I should have blocked my upper grill also. I'll be leaving it open I guess.

I currently have my lower grill i'd say about 90-95% blocked. There is a half inch gap by about a foot under my front license plate holder thatI can't fit any more pipe insulator into. I guess that gap is fine then as it allows some cold air to enter..

 

I think this is the Rosetta Stone of 3rd gen grill block:

2010 Prius Grill Blocking strategy | PriusChat

Hang on, I'm linking this thread, lol. Just check out the table at the top of page one.

 

I did the Grill Blocking this time on our Christmas trip, Engine did heat up faster this time.

 

do you guys remove the block material in the summer? i lived in the mid west, right now it's around 50-70F, i think it's still ok to block 100% lower grill, but my upper grill is 0% ( unblocked). I am thinking if i should reduce down to 50% in the summer on the lower grill.

Any opinion?

 

Unless it's below freezing, I block 50% of lower. In your range (50-70F) I don't block at all.

If there's any possibility of using AC for cooling, it makes no sense to use blocking: you're blocking the AC radiator, basically.

 

I too live in the midwest. I run EngineLink with a wi-fi adapter that let's me know what the water temperature is. I would be leary of grille blocking in temperatures above 50 as others have stated. This puts a tremendous strain on the cooling system it wasn't designed for.

 

The cooling system was designed for to provide adequate cooling for cars going long uphills at 70 mph and with full load and AC running at ambient 100F. Therefore its perfectly happy (which is indicated by increased gas mileage) at partial loads AND partial grille blocking at lower temperatures than 100F.
I run 50% blocking till the time I need to use AC (if im not going up the Pikes peak), and I have never seen engine coolant temp above 85 C. This is for Gen 2 though, but I'm sure Gen 3 would be comparable.

- Alex

 

	temp in Celsius	temp in Fahrenheit	lower blocking %	upper blocking %
1	below 5	below 41	100	50
2	5 - 18	41 - 64	75	50
3	18 - 30	64 - 86	75	0
4	above 30	above 86	50	0

It kills me that people will post questions about temps vs blocking when the first post says exactly what you need to know.

I'm quoting it here for those that aren't able to click to go back to the first page of the thread (maybe their cell phone won't do that for them?)

 

and if you want the Gen II chart it was in a post a few pages later

 

I did look at this table before posting the question, however it seems like people have different opinions than what's posted on page 1 in the table. It clearly said when between 41-86F, block the lower grill at 75%. And the above people are saying it's too risky to even block the lower grill when the temp is above 50F.

That's why i am confused.

 

The object of grill block is to warm the engine up more and faster. But, next to the engine's coolant radiator, the biggest component is the air conditioning condenser, roughly 2' wide by 1.5' high. Once you need AC cooling, driving around with grill block seems to me akin to driving around with the parking brake on.

I do not know that it's risky. What I do figure is that the warmer temps get, the more you're approaching engineering design conditions.

 

If you'll note in the table for the Gen III he suggests 0% grill block on the upper half above 64F / 30C. That is to allow the air conditioning system plenty of air.

 

One of the reasons the thread is confusing is we are in the Gen III forum (2010 to 2015 cars) and some of us are talking about the Gen II (2004 - 2009).

Ken did quite of bit of research before sharing that data with us. If you read all of his posts specifically you'll see he has discussed every possible reason why to do it and why not and I trust his data.

Seriously do you run your AC when it is 60F outside or do you run heat? If you aren't sure how warm or cold it will be you are fine to err on the side of caution and just use the recommendation for the next warmer line on the table.

 

Behind the diminutive upper grill is the hybrid system's inverter radiator. The AC condenser (it's radiator) is the much bigger piece, starting at the bottom of the inverter rad, and going all the way to the bottom. Behind both of them is the engine's radiator.

The upper grill should be never blocked more than 50%, and only at low temps (if at all). Unblocking it does next to nothing for AC performance.

I've circled in red the hybrid rad, the yellow highlight is the AC condenser: