2010 Prius Grill Blocking strategy

I have yet to have the ICE come on driving in EV without me wanting it to (for heat purposes). There have been many single digit days, with a few below zero.

 

OK

 

I'm in Nor. Calif. A few days ago I use a 72" piece of (1/2" pipe) insulation to fill most of the lower 3 of the 4 slots of the lower grill. So the lower grill is essentially 75% covered. On the flats driving in HV, coolant temp stayed around 195 F - 197 F (once going to 200 F briefly). Ambient temp was prob. 60 F. This morning, first test of Torque coolant temp. when climbing hills. Ambient was 48 F. Max temp reached climbing a few 2 minute long steep hills at 67-70 mph was 197.8 F.

From this I would assume that the amount of air surface still open (25% of lower and 100% of upper grills) allows more than enough air flow for the radiator to remove enough heat from the coolant at 48 F. I would guess that that this current open grill amount would also be plenty to maintain normal operating temps of 190 - 197 F during hill climbing even when ambient Spring temps got into the 65 F - 70 F range.

Anyone know if Torque is able to see when the thermostat is actually OPEN? If the Prius thermostat is like normal cars and controlled by the temp of the coolant (rather than some electronic sensor 'telling it' to open/close), I can't see how Torque could sense that. But it would be interesting to know if at a given 'blocking' % and a given ambient temp, how much of the time the T-stat was actually needed to be open to maintain it's designed sweet spot of coolant temp. If T-stat was opening <25% of the engine operating time, you'd have plenty of headroom for conditions that may need more cooling than normal (Like climbing the VERY Steep Priest Grade on way to Yosemite or Hwy 80 up to Donner Pass for long uphill grades*).

* Note: "I" would certainly be there closely monitoring via Torque for these fun experiments!!!

Though I feel very safe from this test, at least for these cooler (snow people can roll eyes here) winter temps, my wife, who is the daily driver of the PiP, fears there may be some catastrophic overheat issue (when she is driving), so I will probably just remove the blocking. Easing here mind is likely more value than any miniscule ICE heat loss reduction may save us in fuel costs. She is NOT likely to want to be bothered with turning on Torque, being sure it is connected, and watching it. (though I do not know why )

If there is any data available to assuage my wife's worries, I would gladly pass it on!

 

fwiw I've left the 55% grill blocking in on my 2005 year round for the last couple of years. I didn't have any concerns in the 80s or 70s and it never stayed hot enough to make me bother recording the temps from torque.

I suppose next summer when it gets hot again I'll pick a day and pull some temps from torque after my normal commute.

Knoxville is 0.97 on the Leaf battery aging model and San Fransisco is only 0.76. Depending on the length of your commute you might never need to worry about overheating in such a mild climate.

Maybe go down to 50% grill blocking in the summer just to be safe?

Battery Capacity Loss - MyNissanLeaf

See the link above for the climate comparison by city/state compiled for Leaf owners

 

Finally heading to Home Depot tonight to grab the insulation.
After the -18 we had here last week and averaging in the 20s lately, my mileage has taken a dump.

 

Here's a quick video that a sales woman made on this topic recently:

 

Has anybody used foam or other like material to slide down in front of the radiator? I used this on my 2008. Not visable from the outside as the pipe insulation is.

 

Hi. I did fully blocked the radiator with foam pannels (i.e. popping the hood open and radiator top cover to slide them).
I am using Torque Pro to monitor temperature.
Questions:
Does anyone know at what coolant temp the radiator fan kicks in?
At what temp the hot engine light would come up?
What is the maximum safe high coolant temp?

I have been reaching for a couple of minutes tops 200-203F on rare occasion and when driving on Freeway on a 70F ambient air temp.

On a different note, I converted my 2009 GenII prius to a 10KWatt plugin hybrid with Boulder Hybrid Conversion and have been getting 128MPG even with the cold snaps this past months. I am very happy with this gas mileage and look forward to toping this when it gets warmer, while staying clear to over heating the ICE in the mean time.

Thank you,
Donat

 

How am i suppose to know if it is 50% or 75% block?

Do you guys think now it will be a good time to start blocking it and in the spring, you take it off?

 

Tis the season.

Really depends on temps in your area and what your driving habits are like.

 

i am trying to get the best MPG of the prius, and i am not heavy footed at all. Like my location said, it's in Ohio, so right now around 50-60, then in the winter, it can be cold, maybe down to single digits.

 

If you aren't monitoring engine temps, then I would wait til a little colder temps until you block. There is tons of great info on this in this very thread.

 

I would never block the upper grill more than 50%, due to the small Inverter radiator being behind there.

What I do, on the temperate west coast:

1. Never block, when AC is being used for cooling. (for dehumidifying, ok)

2. Block lower 50% when temps are staying below 7 degrees C.

3. Block lower 100% when temps are staying below 0 degrees C. (freezing)

I use this plumbing pipe insulation like this:



And hold it on with this Velcro tape:

 

now, it's around 50-60F, and i can already tell my MPG is getting low.

I used to get 54-56 calculated MPG in summer. now the temp is slightly dropped, and i no longer getting that, i can only do around 50-51.

So u guys are saying, still not the best time to start blocking?

 

Prius programming that controls the ICE, includes it's need to run simply to warm itself.

If you want to block 50%, then have a ball and tell us what you experience.

I do not block so long as daily highs remain above freezing.

 

Thanks, when you block the grill in the winter, do you just leave it there during the entire winter? let's assume it's below freezing.

 

Where I live, we enjoy the full 'Four-Seasons' climate. Our winter will normally include a few months where it does not get above freezing, and anywhere from 2-3 days to as long as 2 weeks of -20F temps.

Once you notice the seasonal drop in MPG, install grill blocking. Leave it in place until spring.

 

I leave grill blocking in year round. I just figure the most I can get away with in the summer and leave that on all year long.

I could add more for winter but our winters aren't that bad. I could take some out on the hottest day of the year but I don't drive long trips at high speeds so the temps aren't that big of an issue for me in the summer.

In fact my normal trip length of 16 miles is why I grill block in the first place. I don't drive long distances so there is no downside. I suppose if I were ever going to start a road trip I'd pull some out and put it back after the trip.

 

Are you using AC with the grill block in? I mean for cooling the cabin? This would make no sense to me.

 

If you look at Ken's tables for Gen III you'll notice that at the warmest temps he is suggesting 50% and 0%, if both sections get the same airflow that averages out to 25% blocking of the total area even in the warmest conditions.

I can't find the thread but in the Gen II thread I think he had different percentages listed. Either way he did all the testing needed to make me feel comfortable with his recommendation and thus I leave part of my grill blocked all year round.

I'm not saying it is safe to block the entire grill year round, I'm saying you can pick a row based on your expected highest summer temp and block to that level and leave that in year round.

If you choose to you can adjust the grill blocking to block even more when it is cold but then you have to be sure to remove some when it warms up.

That is more work that I choose to avoid so I don't change the blocking level by season, I just pick a low blocking level and leave it year round.

It's probably worth noting I park in my homes garage overnight in winter so I don't need extreme grill blocking for winter nights. If I had to park outside at night I'd probably pick a 2nd grill blocking level for the worst winter months.