2010 Prius Grill Blocking strategy

I'd think Ken's research is for engine warm up, safe temperatures. But, if you're using AC for cabin cooling, isn't it paramount to keep that big front radiator clear? That's what provides the AC cooling. If you're blocking that the AC's going to be working harder, possibly wearing faster? Sorry, but it just seems to me Ken's research is focusing on engine performance, but missing something fundamental regarding AC.

 

My normal commute is 16 miles, in the worst case I run the AC for about 1/2 the trip in bursts of a few minutes on and as many or more off. Often I use the AC less or not at all.

I get 60 MPG a tank and often the gas engine isn't running.

I don't drive steady state above the speed limit on level ground or all uphill. I do go faster downhill but only when I can get the indicated MPG above 70MPG (preferably when it reads 99 MPG) and I'm trying to maintain speed for the next uphill.

I don't end up sitting in gridlock stop and go traffic soaking up sun in high temperatures.

The AC system is designed to work even in TX, AZ, NM, CA, etcetera where it is hotter than here.

So I figure between my states lower temps, my driving length, my driving style (low ICE usage in summer), my AC usage (I don't use AC continuously, I manually cycle it on and off), after all that taken into consideration I figure I could block more than half my grill in the summer and still not kill the AC system.

As is I'm not blocking the grill enough to cause an issue. My car has ~120K miles on it and I've been year round grill blocking for about 4 years now.

I fully understand that AC is affected by grill blocking, I'm just saying it isn't a concern for those of us doing short trips on uncongested roadways in the majority of the US. For sure if you are sitting in stop and go traffic in 90F, 100F, or warmer or even if you are driving at 70+ MPH in high temps like that, don't grill block as much or at all.

Feel free to vary your grill blocking for time of year, weather, traffic, any factor you can think of. I'm just saying there is a minimum amount of grill blocking that I feel applies for my use even in the hottest of summer.

 

if your stuck in traffic and stopped..... and it's hot.... grill blocking or not... the fans will come on and such air in from various gaps around engine bay......

if driving along with grill blocking the fans may come on also.... so extra energy will be used
so the loss may come on cruising .. but not stop start motoring

 

Last year I slipped two pieces of 1/4 inch blue plastic insulation board in front of the radiator to achieve grill blocking without the ugly foam pipe insulation. With temps in 60's my engine temps never rose over 200.
Anybody see a problem with this?? Although I plan on painting them black this year.

 

^Need more info. What percent are you blocking, and what ambient temp ranges? Are you blocking just engine coolant radiator, or the inverter coolant radiator as well? The latter is the smaller, maybe 5" high radiator behind the top grill opening, really should never be blocked more than 50%, even at very low ambient temps.

If you're blocking the whole area, year 'round, yeah, you might have a problem. Particularly the inverter circuit.

One time I'm inclined to do zero blocking is during sustained up hill climbs, say a ski hill. This is the extreme test for an engine, what the radiator areas are designed to handle.

Addendum: messed up a percentage, edited in red

 

Top 5" not blocked. As I said before Temp up to the mid 60's on the hi-way with no engine temp over 200. short trips engine temp's 130- 160.

 

Ok. I think over 205F is the problem zone, but really just going by what I've heard here. I prefer foamtube insulation, mainly 'cause it is more "leaky", and relatively to add/remove. I only block the bottom opening. If temps are below 7C I'll block 50% of lower (one tube of two), and if consistently below 0C I'll put in the second tube, completely block the lower.

I suppose I could be more aggressive, in winter I'll rarely see temps even hit 190F, on my ScanGauge. I'd rather err on side of caution.

 

First attempt at installing tube insulation (for 1/2" pipes) on my 2011 Prius II - I couldn't squeeze a single tube into each opening slot (too tight), and tried using the slit to cover two slots, but it was too loose. Suggestions? I'd like to get this done since winter weather has descended here in Minnesota...

 

The stuff I'm using has an outside diameter of 1.5", and the label says 3/4"x3', guess that means it's for 3/4" plumbing pipe. The 3' length is perfect to go full width of lower grill. I secure it with some Velcro tape I got from Lee Valley. I push the tube onto a slat, and it takes a couple to cover the full height of the opening.



People are using the smaller diameter, think they're pushing it in between slats. The bigger stuff works good for me though.

 

That's all I've ever done. Perhaps the problem is the type you purchased, too dense. Try the cheap foam kind for $2.35 from Menards.

 

$2.35? That's outrageous! I paid 97¢ (times two) for mine at Home Depot!

 

Was facing 34 degrees , snowy slush, rain and sleet today so bought the foam for $1.27 from Lowes for a 6-foot section that covered all the open slots in the lower air intake (100% lower block). Monitored ICE coolant temps driving through Pennsylvania mountains for 3 hours and observed min temp about 188, max temp 195 up a long slope, and modal temp was 190.
I think one advantage of blocking lower inlet in winter would be to reduce the intrusion of salt water and slush from the salted roads and thus reduce corrosion in the long term.

 

is blocking the grill even needed in CA weather? thanks

 

There is most definitely no CA need. In fact, you don't even "need" to here in Minnesota.

The benefit comes from heat retention. When you need to keep yourself warm, keeping the engine warm too helps improve efficiency.

In other words, when the temperature stays below freezing.

 

Thanks.. the few times I have turned on the heat when the gf gets cold I notice the ICE engine stays on a lot longer if not the whole time I have the heat on... whats more important.. keeping gf warm or getting better mpg.. hmm tough one!

 

I block my grill in CA. It helps, but not nearly as much as it does in colder states.

Of course, California is a big place. Your weather and mine may be quite different...

 

Here's another method/material to use for grill blocking. I was having trouble with the pipe insulation on my 14', I couldn't get it to fit in the openings, and was getting annoyed trying to weave Zip ties in there. So I picked up some material from a sign shop called coroplast, which is basically corrugated plastic sheet. An 18"x24" sheet was $5. Ideally you'd use a 48" strip, but I didn't really want to buy a 4'x8' sheet. The lower grill is 48"x4 3/8". I cut two strips and taped the back of the center seam with Gorilla tape. The ends are tapered to fit the shape of the grill. I fastened with two zip ties under the license plate, and one small screw at each end. I wasn't happy about screwing into the bumper, but two tiny holes in an out of the way location is okay with me.
I'll see if it makes any noise that would require more zip ties. It's a much cleaner look than the pipe insulation, and took about 30 min total and $5.










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Grille blocking data climbing mountains in 23-34 F temps:
Yesterday climbed slopes of at least 3-5 miles long in Appalachian mountains at 65 mph in 23-34 F temps. I watched coolant temp with ScangaugeII for 3 slopes with 100% lower grille blocked (no upper) and 3 with lower grille unblocked. Was surprised to see exactly the same temps on upslopes at 197-198 and temps on down slopes of 183-185. Does this correspond to experience of others?
My rule would be to consider 200-205 F to be a "yellow zone" where I would remove all grille blocking, and 205 F and above to be a "red zone" where I should take immediate actions to help the engine run cooler. Reasonable?
LOD measured by ScangaugeII was 89 and in low part of the PWR section of the Hybrid System Indicator on the upslopes, but do not have exact grade of slope.

 

I don't know at what point the engine cooling fans turn on for the Prius, but in my Acura TSX they turn on at 215 F and stay on until temps drop to 195 F.

I'm showing a normal operating temperature of 195 degrees in the Prius with no grill blocking, but it often dips lower when the cabin heater is on and the car is operating with the engine off.

I would consider any temperature increase of more than a couple degrees due to grill blocking to be inappropriate. There needs to be adequate cooling overhead for the car to regulate temperatures without frequently cycling the cooling fans. Running temps up to 200 or higher is an indication that the cooling system is under-performing due to grill blocking. My reaction to engine temps going 5 degrees above normal is to remove 1 slat of grill blocking from the highest positioned block and continue monitoring temps. Run the maximum amount of grill block that still allows the coolant temperatures to remain in normal territory.

Fortunately, the cooling fans provide a backup in the event we overuse grill blocking. Grill blocking isn't likely to cause harm to the engine, although under hood temps are important to monitor as well.

 

I am having trouble understanding why the grill needs to be blocked. It seems to me that the coolant thermostat should keep the engine at its most efficent operating temperature. What am I missing here? I have blocked the bottom grill of my 2011 Prius this winter and it seems to help my mileage. But, I keep thinking that the thermostat needs to be replaced. I don't have a scan guage so I really don't know what is going on with my engine temperature.