Is it OK to do? At approximately what outdoor temp should one start unblocking the grille? Obviously won't be doing this until next fall, but just curious.
Yes it's OK to do. Would remove at least one lower block at 50, all lower at 60+ and all blocking at 70+ for generic and safe margins of error. This has been covered a lot in several other posts...look for one by me ...search efusco caution grill block
Why do you suggest removing the lower block first? Is it related to the oil cooler, or is it simply because those blocks are easier to remove? Also, doesn't this relate to engine temp more than exterior temp? In other words, if you have short drives, then you should not need to remove blocking until the ambient temps are a bit higher than you've suggested - non?
The lower segment is the primary intake for the inverter coolant circuit...the more temp critical area (IMO) and from my observations tends to get near potentially more dangerous temps sooner. It also still allows some air flow to the upper radiator so there's some cooling of the ICE as well. This probably is not a critical decision (upper vs lower), but it seems logical from my observations. FWIW even in 70 degree temps here, with just one lower slot unblocked inverter and ICE temps were just creaping to a range I was starting to pay close attention to with local driving. My original numbers are intentionally conservative for those who have no means of monitoring the temps where protection from damage is the first priority.
I blocked my upper grille with pipe insulation couple days ago, and I can not believe how much improvement I got. On the same route and same conservative driving style it went from ~45-47 mpg to ~50-52 mpg (city driving). The temperatures here in Atlanta are in 40-ies in the morning and 60-65 F during the day now. I do not have a Scangauge, but I checked the engine and converter temparatures immediately after the drive several times. Converter does not even feel warm, and engine is pretty cold - I can touch the block with no pain. IR thermometer shows 26C converter and 41 C engine, which might be incorrect for engine. As far as I know metals do not scan very good with IR thermometers. Anyway, I assume nothing in danger of overheating (the lower grille is not blocked). Is this right? Now, why did I get such an improvement? The car is 2005, 112 000 miles. Maybe my thermostat is stuck partially open and engine was never warming up properly? Maybe upper part of the radiator exchanges fluid with engine even with thermostat closed? Any ideas or thoughts from priuschatters? Thanks, - Alex
that's pretty impressive. my mileage drops from 65 to 60 as the fall weather cools and 60 to 55 in winter. i definately need to try grill blocking!
i am going on a 100 mile trip this week for thanksgiving, all highway, avg speed 65 to 70. avg temp is predicted to be 47F - 52F. i have no scanguage, 4 adults will be in car. all my grills currently blocked. for an extended trip at this temp, i am thinking unblock 1/3 of lower grill only. currenly i have 3 strips of pipe insulation down there, so remove one strip. does that sound safe? PS since i added the blocking this week noticed major improvement in mileage, first 5 minutes was NEVER above 25 mph, now its consistantly 35-40, also noticing bars are higher across the length of my trip, usually about 25 minutes. old avg was 45 mpg, now seeing 53... this mod helps not just for cold winter temps, but for short commutes of 10-20 miles, 20-30 minutes in 40-70 degree weather too. cold startup and slow engine warming at normal speeds, coupled with ICE shutting down alot, really hurts mileage. this mod would help the daiy commuter increase mileage year round.
I wish I had a means of monitoring MG1, MG2 and inverter temps with Scangauge. My digging around turned up nothing. Maybe my Google-fu isn't good enough? I can definitely monitor coolant (fWT, Fahrenheit Water Temp) and engine temp w/SG...
You should be fine. With temperatures like those, I generally leave only the bottom-most grille slit open on highway trips, and block everything for my everyday around-town driving.
+1 on what Jimbo said. There are actually 5 horizontal openings in the lower grill. There are 3 full openings, with half-size openings at top and bottom. Most folks just block the center three openings. As a result, a small volume of outside air is still able to pass through the grill and radiator and into the engine bay. This is not wholly a bad thing because the lowest opening is allowing air to pass over the radiator for the MGs/inverter at the bottom of the ICE coolant radiator. (See diagram on pg 2-15 here.) In temps consistently below 40 degF, I block it nonetheless. I think that leaving the top half-size opening unblocked is counterproductive because... Blocking the grills has benefits beyond keeping the ICE warm. Any air that goes through the grills and radiator ends up in the engine bay. From there, it has only one way to go... down and under the car. This is the least desirable place for it. * It exits the engine bay in a turbulent fashion slowing the passage of air from front to back. *Air under the front of the car is moving at an angle out towards the sides of the car. Any air that gets passes through the wheel wells and then the spinning wheels pushes into the air passing down the side of the car and adds unwanted turbulence... drag... reduced MPGs. For this reason, some of us block the upper grill year 'round. There seems to be no real effect on ICE coolant temps read by SG, no matter the outside air temps. (Caveat: But there might be when pulling fully loaded up a mountain in mid summer.) I too would say that, yes, you can fully grill block without a ScanGauge if temps are below 50 degF. But why would you? It is a very good thing to be able to verify that temps are staying below ~200 degF when you're at speed, going up a long, steep hill, or caught in traffic. Driving a Prius without a SG is kind of like driving without any rear view mirrors. You're only getting half the picture. What you don't know/see can hurt you/the car/MPGs. In addition to the numerous ICE condition readouts that can help maximize MPGs, with the SC you can also keep tabs on the weak-sister 12V battery, and read trouble codes... saving you $$$. Get a ScanGauge, it's the only 'mod' that will pay for itself. Hope this helps.
Pictures would help me tremendously and specifically what are you using to block the grill (size of product) as I am going to this mod asap!!!
priusevo, You asked for it! You got it! Picture by Green Hokie, from this thread. This picture shows plastic pipe insulation. It comes in at least 1/2" and 3/4" sizes. Either will work, although the 1/2" is easier to insert in the grill(s). They are are made of two types of plastic: * dark black, open cell, more expensive, tends to break down over time. The picture appears to be this type and is very neatly done. * a little grayer, closed cell, lasts longer, recommended. A search using "grill block" will turn up lots of other threads if more info is needed. Be mindful of being conservative/cautious by letting some air go through the bottom of the lower grill to keep the inverter cooled in all but the coldest temps. While it's not the subject of this thread, did you know that there is a recall/free replacement of the inverter coolant pump for '04-'07 cars? See: http://priuschat.com/forums/gen-ii-...call-alert-2004-2007-inverter-water-pump.html
