First Morning with a Blocked Grill

[TonyPSchaefer]

I posted this in the Modifications forum. It's a simple modification, but a modification nonetheless. I know that some people do this on a regular basis but this is the first time I did it and I'm so impressed I want to dedicate a thread to it.

At the most recent Chicago Meetup, FireEngineer gave me some pipe insulation (I still owe him $2.00). He uses it to block his grill. Last year, he blocked only the two slits right under the hood but this year I noticed that he also blocked the very lowest slits under the front bumper.

Now F.E. or anyone else, correct me if I'm wrong, but if I remember correctly, he told me that multiple people have independently verified via the scan gauge that for temperatures lower than 40ºF there is no risk of overheating the engine with the grill completely blocked off - top and bottom.

Last night, I blocked off the grill with his insulation. I did both upper slits but - because I'm always a little overly cautious - I left a couple slits open on the bottom. The bottom has five slits I think.

This morning, I scraped thick frost off my windows. It was 25ºF and I do not have a block heater. When I left the house, my MFD tank average showed 49.3MPG with 77 miles on the tank. The first five-minute segment sucked as usual but it was all roses from there. When I arrived to work, 20 miles and 45 minutes later, the tank average was 51.1MPG. That's a bump of almost 2 full MPG at 25ºF! Now I know that with less than one hundred miles on the tank, the tank average is still prone to jumping around a bit. But if the rest of the mornings and evenings are anything like this, I'm going to be a lot happier this winter than I was the last two. Oh yeah, I even ran the heater today for the first time, I was so happy.

Needless to say, the insulation is staying on through the remainder of the winter except on those fluke days when the temps get above 40ºF.

Who else blocked their grills and what additional advice can you share?

[efusco]

Tony,
I've had both upper and lower grills blocked for over a month now. I leave it on with temps up to the low 60s. I did, briefly, remove the lower blocker when we had a few days of temps into the 70s.

With CAN-View I've not yet seen ICE temps over 195 degrees even when outside temps were in the upper 60s. The highest temp I've seen on MG2 Inverter is 120 degrees, but that was very brief and when going in reverse...under normal driving it hasn't risen over about 112 degrees.

Keep in mind, also, that I have packed fiberglass insulation around the ICE under the hood for additional heat retention.

My last two tanks have approached 60mpg in DECEMBER....I've never seen mpgs like this before...granting this has been an unseasonably warm December, but we did have a week of temps never getting over the low 20s.

I would concur that blocking both when outside temps are 40 or less is 100% safe...I'd even say up to 50 degrees is save under all driving conditions. Without the ability to monitor temps I would not risk blocking both at temps over 50, esp. in high stress driving (high speed interstate, mountain climbs, etc.), but even then blocking only the upper would be safe probably up to 70 degrees.

[FireEngineer]

Actually I had both upper and lower grills blocked off last year. If you hadn't been so worried about me tearing your back seat apart to show Parrot Lady you would have noticed.

And listen to the good Doctor. Block off everything and don't worry until May. And get yourself a block heater so the grill block has some real heat to protect in the first five minutes. Besides I need one more install to make it an even dozen block heater install's.

Wayne

[efusco]

I strongly second the block heater suggestion.

[JimboK]

I am using the same technique with good results. I first put the insulation in all slits in both the top and bottom grills in early November. I took a trip shortly afterward with ambient air temperatures in the 60s (IIRC) on the first leg of the trip. My ScanGauge showed coolant temps frequently creeping up above 200F on the highway, so I temporarily removed the piece in the bottom slit of the bottom grill. Coolant temps have since stayed at or below the mid-190s in all driving conditions. After winter temperatures are here to stay (we had record highs yesterday), I'll put the piece back in the lower grill.

I haven't done a precise before and after MPG comparison, but my per-trip results are similar to Tony's: After the predictably low first 5-minute segment, I routinely see segments above 50. My current tank average is around 52. (It actually was at 57 eight days ago. I've been on a business trip since then that requires 2 or 3 short drives per day of a 1/2 mile or less with cold starts.)

[TheForce]

Can anyone post some pics of your installation? Just wondering what it looks like and how everything is attached.

[TonyPSchaefer]

The bag is at home or I'd look it up specifically.

It looks like this:


Wayne showed me to cut it into halves creating two Cs out of each length of insulation. Oddly, the length he gave me was the perfect length for the Prius grill.

As for "attaching," there is none. I love the term "compression fitting" because it makes the process of "shoving it in" sound scientific. Basically, by folding the halves in half length-ways, you can "compression fit" each strip into the slits. The Cs become Vs and you shove it in with the points of the Vs pointing to the front. There are vertical bars that cause the insulation to not go in as far in some places giving a wavy look. If I'm up to it, I might make little notches in the insulation to remedy that. Key word: "if".

Someone will probably get pictures posted before I make it home to snap one for you.

By the way, on some colors, it's obvious that there's something shoved in your grill. On the Tideland and probably black you don't notice until you really look at it.

[c4]

I've got a Classic Prius which doesn't have the plastic top cover at the front of the hood, so I usually do two levels of blocking.. Instead of shoving pipe insulation in the grill, which I feel really looks bad, I insert a sheet of that foil-lined bubble-wrap insulation right in front of the radiator, but behind the small hybrid radiator. This blocks 90%+ of the air flow through the main radiator, but leaves the hybrid radiator exposed and at full cooling efficiency. This arrangement is good up to about +10C or so and down to about -5C.. For colder weather, I also insert an additional couple of sheets of coroplast (with cutouts to make it around the supports, etc) that further block air flow through the front.

I also have a hood liner made up of the same foil-lined bubble-wrap insulation to reduce engine heat loss through the hood. With this liner, you can drive the car for several hours and hood doesn't even feel warm afterwards.

With the full arrangement (hood liner, radiator insulation and coroplast shields), the car will overheat at any temperature above 0C (I've had the heat turned up full blast and windows open to keep the engine temperature down on warm days when I was too lazy to remove the blockers), but is great down to -30C.. I get full stealth and engine stop, and very good cabin heat. The engine itself runs better as it keeps warm, but additionally, the intake air temperature is now at least 4-10 degrees warmer than ambient, so fuel economy and power are also much better, and there's no obvious signs of blocks of foam, etc from the front of the car..

[john1701a]

I've been waiting for the real cold, when high's don't exceed freezing for a month. With 3 years of data now, I'm very well prepared to quantify the kind of improvement comes from blocking and I too see it as safe.

A few weeks ago, when the temperature was at 12 F, I played with pipe insulation to see how well it (the 3/4" size) would attach. That worked like a charm. Though the smaller (1/2" size) probably provides a better overall fit.

Since it is now warm again (30's) all is off for more collection of control data. In the meantime, I'm hoping to stumble across a more cosmetically appealing solution... something the masses will easily adopt, so easy installation in the cold is a must.

As for above when this is beneficial, I'm not recommending that another bother unless they routinely deal with sub 25 F tempertures. MPG and the heater have been quite good when it's warmer than that. There doesn't appear to be any real gain unless it's Minnesota cold.

[FireEngineer]

Tony, why do assume that the length I chose was random but correct. I spent many a minute in Menards that October day debating which package of pipe insulation was on sale for $.99 before making my choice of the "Prius-centric laser cut winter thermal management devices".

Wayne