Grill Blocking Caution

Remember that the boiling point of liquid goes UP with pressure. That is why (one reason) modern cars have pressurized cooling systems. Your in no danger of boiling over at 212-220f assuming you have a proper coolant mix. Higher with pressure, lower with altitude.

Having said that, my intuition is that running ~200F the engine really isn't more stressed than ~190F, but running consistently ~220F would get me worried. I suspect that there are some gearheads out there who would really know. My problem is more with -40F!

Icarus

 

Is my blocking method safe/effective?

I blocked my grille a few weeks ago. I commute about 40 miles each way, hilly highway driving, running between 65-75mph. Outside temps have occasionally gotten above 50F during that time, and your post now makes me worry I may have been pushing the limits of the Prius' operating temps, with the hilly terrain of my commute. I currently have no way to measure temps. I'd hoped to get a CAN-view at some point, but now I wonder, if I'm going to use grille blocking, should I invest in a scanguage asap and get the CAN-view later? (I hate to spend the extra money -- I'd prefer to just use the CAN-view.)

How I Blocked My Grille:

For the upper grille, I blocked each slat individually with it's own, single piece of pipe insulation foam (meaning I didn't use the foam to span across any slats). Each grille slat is itself visible, but the spaces between are completely blocked from end to end.

(I presed the foam tightly into place, and of course got a wavy effect from the vertical cross-supports attached to the grille's back side at regular spaces. To create a more even look, I pressed the foam very firmly into place, then pulled it out. There were clear indentations in the back side foam where they had been pressed against the vertical supports, so I made a simple slice partway into the foam at those points, then pressed the foam back into place. The supports slipped nicely into the newly cut notches in the foam, allowing for a nice, even look for the upper grille.)

For the lower grille, I did span the foam pieces across slats. I used three pieces of foam altogether. The top piece tucked into the first and second spaces, covering one slat. The middle (slightly thicker) piece tucked into the second and fourth spaces, covering two slats. The third piece tucked into the fourth and fifth spaces, covering one slat. However, although the lower grille is blocked from top to bottom, it is not completely blocked from end-to-end. The lower grille has the same cross-support pieces spaced regularly across the backside of the grille, effectively dividing it into sections, and the sections on the very ends are not blocked. I haven't measured it, but I'd estimate that my blocking method leaves about four inches unblocked on each side of the lower grille.

This makes me wonder whether 1) I've blocked enough of the grille to be effective, or 2) I've blocked TOO MUCH of the grille to be safe given the driving conditions of my daily commute to work (hilly highway driving).

Also, I'll be driving home to the rocky mountain region for the holidays -- a two day drive one-way -- and I wonder if, with no way to monitor temps, my grille as currently blocked is safe for such a drive. It'll tend to be colder in the rockies, with temps rarely above freezing and probably never even into the 40s.

Can anyone offer wisdom as to which areas of the grille cool which components? I'm also curious where the outside temp sensor is located and whether my grille blocking is giving me inaccurate (high) outside temp readings.

Bryan

 

that would be an extremely tough call because i dont think water temps are the issue here. any radiator has built in safeguards so i wouldnt concern myself with that.

what is of more concern is the temps inside the MG's. if you are going to be in the mountains doing a lot of elevation changes, remove one of the lower blocks. that should cover you against overheating there.

 

Wouldn't it be cool if one of those genius' out there would build an after market shutter kit like I had on my transport trucks. It would open the slats when all the temps got above the optimum and closed them when it was below. Pretty simple to do in this day and age.

I run with all the grill blocked except the bottom until the temp is ~50F or above. I have ordered a scan gauge, once I get it going I will consider blocking the final slat.

 

Bryan, I keep the upper grill blocked all year and it improves the FE. I have yet to have the fan turn on even in warmer temps with both grills blocked. The usual route is around 35 miles highway driving zoned 40-55mph.

Sign me up for thermostat controlled slats.

 

Great Thread

Evan,
Thanks for the write-up. I was sure before now that 90C to 95C (203F) was all good, but I'll start getting a little more worried above 85C. In Texas we routinely get 30F swings in temperature. This week alone we've seen the temps swing from 82F to 45F.

When I first started blocking my grill I though that I would surely get my summer MPG, but running blocked with Winter Gas (bad RFG in Houston) I'm consistently 5-10 MPG down from my summer averages.

May need to get that SG II+XGauge if there is any way to peel MG2 temps (searching PC in a separate tab already)

11011011

 

Heres a question: Instead of removing an entire lower bar, why not remove a bar's worth of blocking on the right side of the car (in front of inverter).


That way the inverter gets air, and if needed, it can also provide some cooling to the radiator. Then the people with a SG can monitor the ICE WT directly to check if it is overheating.

 

Evan, do you still have the fiberglass insulation in your engine compartment?

If yes, do you think that could be effecting inverter, MG1 and MG2 temps?

 

longer warmup times is only part of the drop in winter gas... changes in the formulation will take 1-4 mpg depending on your location. summer gas freezes at a very high temperature, so winter gas has additives that lower it to prevent gas line freezeups and such. the additives take up space but dont burn, so your winter gallon of gas is actually not a whole gallon. there is only three small areas in the country that dont change their formulation for winter...mostly southern florida and whatnot.

also, colder air is more dense, so air friction is higher as well.

tire pressures drop in colder weather, so real important to adjust. definitely check your tires in the morning to insure that your pressures are still where you want them to be.

 

Regarding the 190 temps, I remember some cars (at least in the 1970's) had factory thermostats in the 220's for emissions purposes. Seems as though if engines are meant to run that high (just for minimum operation), then it wouldn't really be an issue, would it? I really don't know, but mabe some motorhead might bring up what temp is safe, on the high end.

 

still no info on the max safe temps for the MG's? that would help a lot.

 

Would be intersting to see what temps hit without any grill blocking and ambient temps of 100*F+. Throw in some mountain passes, too. That ought to tell you what reasonable max temps are that you should be sure to keep temps under.

 

Pardon my confusion here,,,

I just installed a scan gauge today. I have been running with all but the bottom slit covered for several months. Temps in the 30's-50's F. I have always suspected that the car was running cold even with that much of the grill blocked and the heat on. My first test drive confirmed that. Freeway driving @ 70mph and the temp struggled to stay near 175f (O.A.T. ~45f)

I blocked the final bottom slit. The car warmed up quicker, and got to about 190f with no heat on. After I turned the heat on, it stayed ~180f. 50mph up a 2 mile hill brought the coolant temp to 200-205f. It is nice to be able to see quickly what is happening.

My question is this: We are going on a trip next week through the intermountain west, E. OR, Central NV, AZ, NM, UT. If I were to unblock some section of the grill to cool the inverter? Drivers side top top, slit, top bottom slit, bottom top slit, or bottom bottom slit?

I don't have a great concern that it is going to over heat, but since we will be in the mountains alot, with no way of knowing I think perhaps I should unblock part of one.

Any ideas would be appreciated. Thanks in advance

Icarus

 

I'll restate my thoughts.

First, I don't think we are in any danger of overheating the engine/coolant. The reason is the fans aren't even running. Once you get the thermostat fully open you are just -starting- to get the rad in use. Worry when both fans are running at full speed.

I worry only about the inverter temp. Saying this, however, I DO NOT worry if the inverter temp is below 150F. Ambient can (and does) get over 110F in the southwest US (and probably parts of Australia as well - the north east from what I've been told). If the ambient temp can get that high, and we don't have refrigeration to cool the inverter, then the inverter is designed to be safe at those temps and a fair bit above.

I think many of you are overreacting. But keep watching, because sooner or later, somebody WILL overheat the car.

More information is always a good thing, as long as we all remember to "DON'T PANIC!!"

 

with temps in mid 30's to high 40's, i block EVERYTHING and have done so for past 3 winters...