As a grill blocker, what is temp max for efficiency

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.

 

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.

 

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

 

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.

 

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.

 

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.

 

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.

 

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

 

Oh I wasn't thinking about your SO, I was thinking about me. (Selfish little bugga eh?)

 

problems with dash warning or "idiot" lights is that they dont actually warn you until its frequently too late.

high temps are one of the worst as well. seeing an increasing temp beyond the norm would prevent me from jumping on the freeway or passing that "last gas for 32 miles" sign. i wish i could monitor inverter temps or for that matter know what temp i need to be concerned about since i dont remember reading a consensus on that figure either.

i use scangauge which only does water granted, but hopefully that would be enough

 

Thermostat starts to open at 80C, fully open at 88C, fans kick on between 98-100C. The warning light, don't worry about it.

Wayne

 

ok fan on at 98C is what i probably have seen. like i said, have seen 207F plenty of times but no fan that would be like 97ish... to be honest with ya, if OAT is like 45 or lower, the highest i ever see is 200 and its usually 185 and under.

i dont like to use heat until i hit 175

 

My interest in the Idiot Coolant Temp Light is a desire to have a simplistic 'Belt AND Suspenders' approach to monitoring engine temp while blocked.

Idiots Lights can be worthless .. spouse ruined the engine of an early 80's Toyota just after the oil change folks didn't tighten the drain plug. Light came on just AS IT WAS OBVIOUSLY knocking, wheezing and screaming in the final throes of cooking.

Then there's me ... I've seized two 2-cycle motorcycle engines while racing in the CA desert quite a few decades ago, with no excuse except youthful excess and ignorance.

In a little over a week we're driving from WA to CA for a few weeks ... thanks for the info. Will look into an analog or maybe scangage for MY mental health.

 

There's a fan?

 

I just had a thought, a light connected to the fan, just a simple LED on the dash to warn that temps are on the rise and the fan has come on. Only problem is the AC switches the fan on too. Hmmm.

 

+1

One other variable: Driving speed. Are you pulling a grade (say leaving Vegas) during 100+ degree summer temps? Or are you hyper mileing at 30mph when it's 90 degrees. The ICE isn't going to overheat at lower loads, even if it's 90 degrees, if it's only running for 30 second intervals. From other's experience on PC I've learned that lower speed driving, even when it's warm (90f and under), the ICE won't get too hot ... even with 100% grill block. If I'm going to jump on the freeway on a hot day though, I'll pull half the foam out. (caveat) Your results may vary.

 

If I wasn't running with a Scangauge I'd remove the lower rad. blocking when the ambient temps got above 20C consistently. An odd day here or there up to 30C wouldn't make me remove it.

I'd remove the upper grill blocking when temps were consistently above 25C.

Both my grills are fully blocked, though there is an opening in each end, as the pipe insulation forms a hole at each end which I haven't bothered to block. I access the block heater plug through one of those holes.

All this after two years of observation with the Scangauge of course.

This is a "cold car". I'd be VERY surprised if anyone in Canada or the Northern US ever boiled the coolant (other than if something failed).

Because I use one piece of foam pipe insulation for each grill, with two zip ties each, it only takes a minute to install or remove the blocking. So doing that on trips is practical.