Blocking the grill

[New2Prius2008]

Hey guys -

I've read several times on this forum that blocking the grill is a way to keep the engine from running so much in the winter to keep the engine warm. Great advice. I'm just wondering how you guys actually accomplish this and have something that is easy to put in and take out depending on the temp and something that doesn't look like crap?

[F8L]

Crap appearance is relative. If I saw human crap I would be repulsed; however, if I saw the crap of a Tasmanian Wolf (Thylacinus cynocephalus) I would be overjoyed and find it beautiful!

The best looking method would be to take apart the plastic facia over the radiator area and put some kind of flat plastic-like panel to block air coming through the openings from hitting the radiator. There are numerous threads in here that show a pic of someone using a yellow panel for such a purpose.

In on the of the newer threads someone used thinner pipe insulation and tucked it in nice and neat. I thought it looked good myself. I would recommend doing a search and finding the latest thread on the subject. It was only posted about a month ago.

This is the thread:

Looks good IMO.

[john1701a]

<div class='quotetop'>QUOTE(New2Prius2008 @ Nov 18 2007, 03:16 PM) [snapback]541272[/snapback]</div>

I've read several times on this forum that blocking the grill is a way to keep the engine from running so much in the winter to keep the engine warm. Great advice.[/b]

Misunderstood advice, but still very good.

Realistically, unless the temperature is well below freezing, you aren't really gaining warmth from blocking. I certainly haven't from my first month's of data... and I've got 4 years to compare back to. When it gets a lot colder, observations from lower-grill blocking may be revealing. But we're talking 20 F at the very warmest.

At above freezing temperatures, the blocking benefit mostly comes in the form of improved aerodynamics. The sealing of the upper-grill section definitely contributes to higher MPG, especially at highway speeds.

So regardless of the whys, it is indeed a good thing to do.

[Rangerdavid]

We use the simple pipe insulation that one can purchase at any home improvement type store. it comes in about 4 ft. lengths. cut is one lengthwise opposite that existing cut so you end up with two long pieces. then you just tuck it in and trim it to fit.

Its one of the cheapest and effective and safe additions for wintertime. Good Luck!!

[efusco]

<div class='quotetop'>QUOTE(john1701a @ Nov 18 2007, 04:16 PM) [snapback]541289[/snapback]</div>

Misunderstood advice, but still very good.

Realistically, unless the temperature is well below freezing, you aren't really gaining warmth from blocking. I certainly haven't from my first month's of data... and I've got 4 years to compare back to. When it gets a lot colder, observations from lower-grill blocking may be revealing. But we're talking 20 F at the very warmest.

At above freezing temperatures, the blocking benefit mostly comes in the form of improved aerodynamics. The sealing of the upper-grill section definitely contributes to higher MPG, especially at highway speeds.

So regardless of the whys, it is indeed a good thing to do. [/b]

Just to counter-point this, I disagree with essentially every point.
1)Even above freezing reducing the cold air-flow through the engine compartment reduces the conductive heat loss. I, too, have 4 years of exerience and at least 2 full winters where I've had mostly moderate tempertures to compare to as well as additional monitoring equipment to observe engine temp. I can tell you that unequivocably that Engine temps are higher, ICE run times are lower, time to peak temp is shorter, and overall FE is much better.
2)The aerodynamics statement is pure bunk, and undefensible by any objective data.
3)The more of the grill you block the less air flow through the engine compartment. In warmer weather it may be advisable, when you can monitor the inverter temp and the ICE temp, to block just the upper grill in order to assure that the radiator for the Inverter gets adequate air flow. Note that grill blocking has nothing to do with the radiators (other than noted above) because the thermostat will stop the coolant flow through the radiators when the ICE is cool...it is all about keeping as much cold air as possible out of the engine compartment itself.

I do agree that it's a good thing to do.

[john1701a]

<div class='quotetop'>QUOTE(efusco @ Nov 18 2007, 04:41 PM) [snapback]541301[/snapback]</div>

2)The aerodynamics statement is pure bunk, and undefensible by any objective data.
[/b]

This has taken a weird turn.

How could improving airflow not make a difference?

I live 3 blocks from a 70 MPH highway with an uphill ramp. Only the upper-grill is blocked and the 2 lights are usually green. The first 5-minute segment shows a definite MPG increase.

[efusco]

<div class='quotetop'>QUOTE(john1701a @ Nov 18 2007, 06:28 PM) [snapback]541331[/snapback]</div>

This has taken a weird turn.

How could improving airflow not make a difference?

[/b]

Improving airflow, by definition, will make a difference...but my point is that I'm not convinced that blocking the upper grill improves air flow...maybe it makes it worse by not allowing the air that hits that area to pass freely through the grill, radiator and out the engine compartment? Maybe it's a zero affect issue? The point is that that is not the reason for blocking the upper grill.

I live 3 blocks from a 70 MPH highway with an uphill ramp. Only the upper-grill is blocked and the 2 lights are usually green. The first 5-minute segment shows a definite MPG increase.[/b]

I don't know what you're trying to tell us with this sentence.

[john1701a]

<div class='quotetop'>QUOTE(efusco @ Nov 18 2007, 08:48 PM) [snapback]541390[/snapback]</div>

I don't know what you're trying to tell us with this sentence.[/b]

You seem to be forgetting that my driving style, situation, and fuel is the quite different from yours... I haul ass onto the highway. I never, ever pulse & glide. I don't have an EV button. Maximizing engine-off means little to me. My efficency aim is simply keeping the current MPG over 50...

So our basis of measure have little in common. You are that guiding-light for aspiring enthusiasts. I am the representative of joe-consumer-never-participate-online. That's a huge difference.

I blocked the upper-grill. I didn't witness any temperature difference on the ScanGauge, just very stable as usual. Yet, MPG climbed. Preventing the pass-through/entry of sure makes a heck of a lot of sense as the major influence at temperatures above freezing, since the warmth isn't needed yet. With the upper sealed, the pressure pocket reduces input from the bottom.

If it was warmth, how does that factor in at 70 MPH? My engine stays at a happy 186^F quite consistently, like before upper blocking. What's different if it isn't aerodynamics?

[efusco]

<div class='quotetop'>QUOTE(john1701a @ Nov 18 2007, 09:29 PM) [snapback]541402[/snapback]</div>

You seem to be forgetting that my driving style, situation, and fuel is the quite different from yours... I haul ass onto the highway. I never, ever pulse & glide. I don't have an EV button. Maximizing engine-off means little to me. My efficency aim is simply keeping the current MPG over 50...

So our basis of measure have little in common. You are that guiding-light for aspiring enthusiasts. I am the representative of joe-consumer-never-participate-online. That's a huge difference.

I blocked the upper-grill. I didn't witness any temperature difference on the ScanGauge, just very stable as usual. Yet, MPG climbed. Preventing the pass-through/entry of sure makes a heck of a lot of sense as the major influence at temperatures above freezing, since the warmth isn't needed yet. With the upper sealed, the pressure pocket reduces input from the bottom.

If it was warmth, how does that factor in at 70 MPH? My engine stays at a happy 186^F quite consistently, like before upper blocking. What's different if it isn't aerodynamics?
[/b]

I'm forgetting nothing, I just didn't understand what you were trying to say with the sentence (2 green lights?)...but I think I know what you were getting at now.

I drive in a lot of conditions. While my usual commute does, indeed, permit some great P&G/hypermiling opportunity I have many thousands of miles under my belt in highway steady speed conditions as well. And my observations are much different than yours. Just b/c you're seeing a constant engine temp doesn't mean that the ICE isn't running harder to maintain that heat even if you are experiencing 100% ICE-on time. If your fuel flow is .1gal/hr more to keep your temp up then your MPG will be impacted.

My "evidence", poor as it is, that it's not an aerodynamic affect is that my first year of radiator blocking I actually didn't block the outer grill, I used an old piece of one of those windshield sun screens inserted just in front of the radiator but well behind the grill--thus the grill slats were wide open. And yet I jumped my mpg from about 45mpg the prev. winter to 50 my second winter. My 3rd winter I went to the blocking of both upper and lower grills from the outside and experienced an even greater jump...I attribute that to the fact that the airflow via the lower grill was stopped and the air flow from the upper was more effectively stopped.

Look, maybe you're right, maybe there's some way to wind-tunnel test and find out... but when I look at my blocked grill I can't imagine that that tiny piece of insulation is having a measurable affect on FE... A 5% improvement in FE based upon aerodynamics alone would require a drop in Cd from the base 0.26 to approximately 0.23 (using Wayne Brown's simulator) at 60mph. Ain't no way you're getting that much from a piece of foam.

[David Beale]

I notice a difference with my blocked grill. The car warms up faster and stays warm longer without the engine running. At an ambient temp close to freezing, so far (hasn't gotten cold here yet), in city driving at 50-70 km/hr (30-45 MPH) the car will not warm up. With the blocking the coolant will reach 70-80C. It gets to 50C in just a few minutes, and will blow nice warm air inside.

Here's what mine looks like, with 3/4" pipe insulation in the top grill and 1 1/2" to 2" in the lower grill. Bonus, it also protects the grills from winter crud and makes it easier to clean the front.
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