As a grill blocker, what is temp max for efficiency

[gillis-t]

Does anyone know, when blocking and unblocking grill, how to strike a balance for efficiency, between maintaining warm ICE temps and power used while occasionally kicking radiator fans on and off. Also does anyone know a scangauge code for inverter temp?

[David Beale]

You can't get the inverter temp from a Scangauge.

The hotter the engine coolant, the more efficient the engine. As long as you don't boil the coolant of course. The Prius coolant shouldn't boil until it gets well above about 120C (50% glycol under 7 PSI pressure).

I've found Pearl is just fine even when ambient temps. are about 20C (about 70F). In fact, Pearl was fine even at 30C (about 80F) and even on the highway (the Prius runs hottest on the highway - higher the speed, hotter the coolant). I wouldn't -plan- on running her above 20C however. I remove the blocking when the ambient gets to 20C.

[nerfer]

You can get the battery temperature and engine temperature, but I don't know if anybody has found a way to get the inverter temperature. This thread at CleanMPG has more info.

With short trips, cold weather, and a balky thermos, I've been concentrating on getting the engine coolant temp above 120'F, haven't worried about hitting a max yet, but I seem to recall the radiator kicks in at about 180'F, so there's no point in blocking the grill if you're hitting that regularly.

[beach247]

David, howdy from Toronto!

I've completely blocked my upper and lower grills. I don't have a scangauge. With the cold winters here in Ontario, I think I'll be all right without a scangauge. I've seen a tremendous increase in fuel efficiency (MPG) from mid-20s to mid-40s even with below freezing temperatures.

I've read some of the posts on here and I'm confused as to what to remove first when spring arrives. From what I've gathered, it's best to completely remove the blocks on the lower grill at 10C. Then, to completely remove the blocks on the upper grills at 20C. Although, there are some people who leave the upper grills completely blocked all year round. Without a scangauge, I don't want to take that risk just to save a few bucks on gas.

What's your opinion on the matter?

TIA

Originally Posted by David Beale

You can't get the inverter temp from a Scangauge.

The hotter the engine coolant, the more efficient the engine. As long as you don't boil the coolant of course. The Prius coolant shouldn't boil until it gets well above about 120C (50% glycol under 7 PSI pressure).

I've found Pearl is just fine even when ambient temps. are about 20C (about 70F). In fact, Pearl was fine even at 30C (about 80F) and even on the highway (the Prius runs hottest on the highway - higher the speed, hotter the coolant). I wouldn't -plan- on running her above 20C however. I remove the blocking when the ambient gets to 20C.

[donee]

Hi All,

I try to get my car in the high 80's C. I will run the heater to drop it down to about 82 C, then turn it off. If I time things right, I can keep it between 85 and 90 based on the stop and go, and hills, with only a little bit of heater, even as cold as 10 F (with a 90 % grill block).

I base this on the summer time driving when I have a full top grill block , and a 1/3 lower grill block. The engine never gets above 92 C (no heater used in the summer). So, that is how I try to run the car in the winter too.

Keeping the engine temps above 80 C, once you get into Stage 4, will allow most of the hybrid functionality. There is actually an advantage in cold weather, in that the car will not go into the idle mode at speed at any temp above 70 C. Once you get above 70 C, you can go into glides anytime over 35 mph, and many times it will get into a mode where it will let you do that at slower speeds. If you want to glide, you just have to plan to not use the engine till you can be sure you can safely reach 35 mph.

This is unlike warmer weather operation, where the car will not go into glide above about 76 C until you get past 80 C. That happened for the first time this winter just today, with temps at 42 F (ran 80 % grill block on the way home in a 30 to 40 mph suburban slow and go). This may be battery related, as this was the first day the battery has been warmer than 20C all winter.

[tochatihu]

The electric fan on the radiator turns on at 90 oC and goes to full speed when the ICE coolant is 95 oC. So to avoid that energy loss I think that 90 oC should be the upper target. Previous post mentioned 80 oC as a minimum for stage IV so there's your desired range.

In the NHW11 any use of A/C also spins the fans, so we would not want to puch the A/C button with grille blocking in place.

[bobjeri]

I understand the importance of operating the car so that it does not over heat BUT

As a backup and failsafe to the great info provided on optimum temp and fan operation in this thread would like to get one more piece of info if possible.

At approx what temp does the Idiot Light come on to indicate coolant temp is approaching the danger range.

This is wife's car and she is not interested in engineering or mechanics or the reasons why ... A scanguage is not going to happen. She does however respond well in the Pavlovian sense to lights and noises like fans...she doesn't drool tho. We will of course block in a conservative fashion. Ave high temp here is only 69F(20C) in summer so 80F(25C) is a very hot day. I was hoping to keep the upper grill mostly blocked to a conservative 80F (25C) except for trips.

Yesterday was our first experiment with grill blocking ... wildly successful on a 180 mi drive. Got 49.4mpg and wife says was very happy ... she usually only gets 40-43mpg and the heater was great. ... She drove 80%. Upper full block and lower 1/2 block 33 to 46 deg F.

Blocked the upper grill in our Subaru Wagon today for a 50 mi run ... higher operating temp than normal for 5C (40f) but still below midrange ... it is nice to at least have an analog temp guage.

[patsparks]

As a rule of thumb, as you only blocked half the grill, if you turn the heater off because it's warm enough without it, unblock your lower grill. That should keep your head gasket safe. When the heater is on you have some cooling through the heater. You might consider unblocking at lower temps if you are driving high speed on hilly roads. I don't know if there is a temperature warning?

I wonder how hard it would be to install an analog temperature gauge? There is plenty of room for one.

[DaveinOlyWA]

i have seen temps above 90ºC with no fan... even had temps hit 206 F with no fan. i will have to check that again.

i had the fan on my 2004 come on one time but did not have anything to monitor it. this was on a trip to Montana, the OAT was 101º and i was averaging 75 mph with A/C set to 72º. the fan kicked on about 30 secs after i parked because i had gotten out of the car and was walking to grab a drink when it kicked in and it was pretty loud so i was a bit startled.

so i went back, popped the hood, but by the time i got it open, it had kicked off after running maybe 90 seconds or so. so i closed the hood and as i was walking away, it kicked on again, ran about 30-45 secs and kicked off again. when i came back out, the fan was off and stayed off

[bobjeri]

[QUOTE=patsparks;791417 I don't know if there is a temperature warning?

I wonder how hard it would be to install an analog temperature gauge? There is plenty of room for one.[/QUOTE]

According to the Owners' Guide there is a dash located warning symbol-light that comes on when engine coolant approaches the danger zone.

Analog- I'm afraid sweetie would ignor an analog gage.

Dave -- thanks for your comments, esp those on another threaad a few years ago about AC and defrost.