Blocking Grill - safe operating tems

Do a search for "grill blocking" on this site. There are tons of threads ont he subject. Save the bandwith and read what is already posted. (It seems that we have to keep reinventing the wheel, rather than searching.

Icarus

 

1) At least 70c.
2) If you start going at or above 95c, then consider removing a slit. If you hit 110, start worrying and perhaps slow down a bit... If you hit 130c, the coolant is probably boiling at this point... You should really stop and unblock your grill at this point, as both your cooling fans are probably at full blast.

 

130c is ~260f. I think that is too hot to run consistently. 110c is about the max that I would like to see on an ongoing basis.

Not withstanding my above comment that we have been there done that: The best mileage seems to come ~190f, with not much gain above that. The thermostat BEGINS to open ~185 and is FULLY open ~205.

When I see temps above 205f for a bit, I turn on the heat climbing a hill, or if it stays that warm, I'll pull a grill plug.

Icarus

Another issue to consider is inverter/electric motor temp, that is NOT displayed on a scan gauge! Once again, a search will give you some additional information on that subject.

 

You would want to keep the coolant below the temp at which the cooling fan comes on. The increased electrical draw would pretty much cancel out any gains from a warmer engine.

 

Kaibz,

I'm sorry if I got your dander up. My point is thus. With no malice towards the moderators who do it all on a gratis basis: This site suffers from our own laziness. I do indeed include myself in that group. It is often easier to post important question and rely on the kindness of member to answer it, than it is to do at least a quick search to find out if the answer already exists on this forum. I co-moderate a site much like this one, and we strive to keep the number of duplicate posts to a minimum so that it is easier for all to use. It takes time and effort, but that effort is rewarded by making the site very good at getting the information out without having to wade through many, many duplicate and semi-duplicate posts.

I know for a fact that often I won't respond to a question, EVEN if I think I can add useful information because I know that the answer (probably answered by someone more knowlegable than me!) already exists on some other thread(s)

I am just a member here, and as such I have little or no say in how it is run. What I do know is that the good Danny pays for band width and storage, so filling it up with redundancy doesn't make sense, especially when there are often better answers posted elsewhere.

As to not doing the search for you,,, Sometimes I too have time constraints. I would always like to lead people in the proper direction by I can't always.

As for being called names,,,call me anything you like, just don't call me late for dinner!

Icarus

Ps. thanks Evan for doing what I know is a thankless job!

 

I think the good Doctor has steered you in the right direction, as he is the most "senior" (No offense Evan!) poster, I will follow his advice.

I don't think there is any "real" answer. The design of the car gives us the clues however. Since the T-stat starts to open ~185f, and is fully open ~205f I would logically assume that Toyota's engineers base their design on those specs. Since the car is designed to be a high efficiency car, I would therefore assume that that is the range that give it the best balance between efficiency and longevity.

Thats my story and I'm stickin' to it.

Icarus

 

You'll find that in cold weather (below 40f) it is very hard to GET 185f if you are on short hauls. It takes us almost 20 miles, 6 @ 50mph, 12 @ 60mph to get there from a starting temp of ~75f.

Icarus

 

From the above, it can be said that the most efficient temp range is 70c to 95c.

70c (158f) because this is the temp where your able to enter "stage 4" mode of prius operation.

95c (203f) because your radiator fans will probably start turning on once you go above it, based on ken's post.

110c (230f) is probably the "Better unblock your grill or start slowing down" point since I THINK the radiator fans start to turn on full blast around this temp or at 104c (220f).

130c (266f) is probably the "Holy smoking engine! It's about to blow! I gotta stop and unblock NOW!!" point, but I have no basis for this conclusion other then coolant starting to boil at this temp.

Either way, I'd rather not tempt fate and stress the limits of the prius by running above 100c for any continuous period of time.

 

and you do not use the gril block yet or is this with the gril block installed?

 

Also, note that the ICE will restart if coolant drops to 63C and run until 73C reached again, thus hurting mileage. I believe these temps are needed more on the emissions side than for mileage, but the Prius looks to control emissions #1, so Prius mileage is linked to emissions criteria.

 

Grille-blocking is an important tool in the mpg toolbox. Sythetic oil and tire pressure are two others. Learning new driving styles also helps.

 

There is lots of misunderstanding on this topic.

First, in general, best MPG or most efficient operation is at the highest temp the engine will run without damage. It's a heat engine. They work best at the highest temps they can reliably operate at. I haven't calculated the temp at which the "stock" coolant boils, but it should be around 130C. I would start to worry at 115C. With both grills blocked I have seen 110C at 20C ambient on the highway (worst case). In the city at 20C ambient the coolant was running around 95C.

Second, once the thermostat is fully open (around 85C) you are still no where near the max. capability of the cooling system. The two rad fans don't even start running until the coolant gets over 100C. Energy transport out of the rad is directly proportional to the temp difference between the coolant and ambient. Until the fans start. Then you can transport a lot more energy out of the coolant. I would start to worry when both fans are running at full speed.

With both grills blocked and ambient at -30C Pearl's coolant will not get over 70C, meaning the rad is not really being used (though there is some flow through it via the bypass).

Remember the car is designed to operate without overheating in Texas/Arizona/Nevada in summer, where ambient temps can reach 50C and you would also be dumping the energy from the interior via the A/C into the coolant (radiatively/convectively as the A/C rad is just in front of the coolant rad).

I think there is a lot of "headroom" in the cooling system.

There is, however, one area I WOULD be worried about. That is the inverter coolant. As posted above, we can't see the inverter coolant temps with the Scangauge. The inverter is built with solid state devices, and they don't like high temps (their power handling capability drops linearly with temp increase). So it would be "good practice" to be conservative with the cooling of the inverter. Remove the upper grill blocking before you would normally remove grill blocking for the engine coolant.

My grill blocking will be removed when ambient temps are above 10C.