Can someone explain grill blocks to me?
 

I understand that they make your engine hotter quicker..

What I don't understand is it will not actually make your engine run hotter because of the radiator working right?

Your thermostat will tell the radiator that it is getting to the desired temperature (mine being 195) and then will just turn on the radiator on right? so the temp will actually just stay the same right? and wouldn't that just make the radiator turn on more often to keep the engine cool, making the car use more energy and making the MPG go down just a little right?

btw: I'm really thinking about doing the grill block for the 2 lower holes in the bumper and keeping the top one open, how much do grill blocks really help? it is really worth $5?

The thermostat and radiator regulate the max temperature unless they are under conditions in which they can't do so.

It's worth five dollars :p

My gauge stops at the half way mark every time, is this not the "max"
I was guessing that is just when the radiator/fans/thermostat or whatever kicks in and regulates it to stay there and not higher..

Well, it generally regulates to a maximum, it doesn't do extra to make it hotter once it's above around 140, I think. I don't have any graphs handy. If you grill block I would use a SG2 to monitor your ECTs

No SG2 but what is ECTs?
just a random guess... Engine current temperature?

Coolant temp, but yeah.

So if you had to make a super rough guess what would you say the benefit of the grill block would be? about 0.03 MPG? 0.30 MPG?

Sorry for the questions that are probably really stupid :p

It's going to be really hard to tell what the grille block will do for you until you actually test it out for a few tanks.

Here's how your thermostat/radiator works:

From dead cold, you start the engine. The tstat is closed, so coolant only circulates (via water pump) in the engine (and possibly heater core, depending on your setup). When your engine reaches (in your case) 195dF, the thermostat opens. This allows your (now hot) coolant to enter the radiator. For every action... Now, cold coolant enters the engine, via the other end of the radiator. When the colder coolant hits the tstat, it snaps shut, to allow that coolant to come up to temp inside the engine (195dF), then cycles open again, so on, so forth, until all the coolant reaches op-temp, and even then, the tstat still cycles open/closed periodically as the coolant cools down/heats up.

A grille block merely allows less direct airflow over the radiator, which affords less cooling capacity (not necessarily a bad thing) to the coolant, so that when it is able to re-enter the engine, it's warmer than it normally would be, takes less time to cycle back to 195dF, which means the engine warms up quicker than normal, with less heating/cooling cycles of the coolant before stabilizing.

The other thing it does, as a consequence of blocking airflow into the radiator, is push air up and around the car, as opposed to through the engine bay. This creates less of a parachute effect, at the expense of cooling capacity. Since cooling systems are designed on a worst-case scenario basis, you can afford to lose much of your cooling capacity without even breaking a sweat. Don't make anything permanent until you can verify that it's helping, though.

Also, check that your fan's thermoswitch is set to a temp higher than 195dF, else it will be coming on and defeating the warm up cycle anyway. It should come on at like 205dF.

Yeah I was not going to try to do anything permanent I was just going to tape some foam core poster board that is about a quarter inch thick in the bottom 2 holes and tape it in with packaging tape or duct tape.

Sound good, think the foam core board will be ok and not sog up too bad when it rains?

for me, the grill block hasnt increased operating temps despite completely blocking off an opening close to 2 sq ft. it gets all the air it needs and more from the air dam... so mines only getting me the aero effects right now. but i've been thinking about adding to the undertray from the air dam forward, and part of it would be to limit the opening up to the radiator.

i never did a decent a-b-a because of the massive amount of tape i used for my first grill block, my current stealthy grill block requires more work to remove and reinstall than i'd car to do for fun... but from my older fuel logs when i put it on i'd say somewhere between 0% to 5% improvement

metrompg tested one at 2.9% improvement Testing grille blocking & wheel skirts: +5.7% improvement - MetroMPG.com

It shouldn't get soggy at all... you can put shellac coating on it to waterproof it. (Shellac is environmentally friendly and edible when dry.. it's made from bug poop, though.)

I wouldn't do the lower ones, though... it might defeat the purpose, since your bottom grilles are presumably lower than the stagnation point. (Usually, you let the dirtiest areas stay dirty, and clean up the other areas.)

It might be in your best interest to start at the upper grille, then, once you're comfortable with it, block one part of the lower grille, etc.. until you start noticing the fan coming on more often, or noticing that your heater is hotter, blah blah blah..

You really should get an aftermarket temp gauge, at least. The OEM gauge isn't accurate at all, and will read normal in a range of ~160dF to 205dF before it changes position again.

Christ -

I thought that another purpose of the grille block was to keep the engine running hotter in general (maybe this is what you wrote). The idea is, we are "narrowing" the operating range temperature of the engine on purpose because hotter means more efficient (to a point). We can get away with this because we are running under reduced load and we are monitoring the engine at a higher degree of attention than regular drivers. Does this make sense?

CarloSW2

Oh ok.. I figured it would be better to block off the 2 lower ones since the top ones is so small anyways but I guess Ill do the top one first..

btw... If my results come out like metro-mpg and I get a 3.1% gain then I would be getting an extra 1 MPG which is pretty good... But that obviously is "IF"

Carlos -Sure, this is an added bonus, in some cases. The coup here is that many engines already run hotter now than they did in the past (generation-wise, not "my car used to run cooler than this") and are much closer to their optimal range.

Obviously, they're still not perfect, and a grille block can have a mixed effect to this. In most cases, though, you're right on the money here.

I didn't mean that it was the only purpose of the grille block, I meant that the other effects are a matter of circumstance, and the primary effect is reduced airflow over the cooling surface.

Christ -

Thanks for the clarification.

CarloSW2

I always thought the main reason for a grille block was aerodynamic. The faster heating a side benefit becoming greater in winter. I found these numbers recently. Someone posted them and I'm trying to find the original source.

sources of aero drag: from Toyota Nation Forums

Cooling package (including radiator, intercooler, oil cooler, etc) - 33.4%
Exterior - 31.7%
Front wheels - 13.1%
Rear wheels - 6.9%
Floor - 6.9%
Rear Axle - 3.1%
Engine - 3.1%
Front Suspension - 1.4%
Exhaust - 0.7%

Interesting numbers from Toyota.
I would suggest that anyone contemplating a grille block should also look at how you can make the air that you do let in do a better job of cooling, maybe some form of ducting to get the air to the radiator. This would potentially allow even more grille block. My 93 Trans Am has NO grille. All cooling air is ducted from below ahead of the air dam.

First things first, would be to make sure that any air that DOES get through the grille, will inevitably flow through the radiator, as well.

Some sheet metal roof flashing does the job very well of closing in gaps around the radiator, and can be done very tastefully.

Grille block can be for both aero gains and to get your engine up to temp faster.

Mine on either car makes little to no difference in engine temps, but that's in Michigan. Yours may help some.

Oh, another thing that's been brought to my attention a few times:

Adding a grille block can actually INCREASE the ability of your radiator to cool your engine.

It's a rare occasion, from what I can tell, but on some cars, the grilles are placed in such a way that the pressure at the upper grille circumvents the lower grille because of the stagnation point being where it is on those models. I have yet to actually see one in the wild that I could openly point this effect out with, but I'm sure it can happen, and might be something to look into. If you happen to have one of those cars, adding a grille block would force the air through the radiator, rather than it swirling around in front of it from one grille to the other, or out underneath the radiator.

Another aeromod that is often overlooked that doesn't affect cooling in any negative way is to shroud the radiator completely, so that all the air that does hit the radiator has to go through it, rather than around it, into the engine bay.

This creates sort of a parachute effect, but the excess air has nowhere to go, so instead of going around the radiator, like it normally would, it creates a (insert proper term here) that blocks further airflow until the air that's already being pressurized in the grille/radiator area is through the fins of the radiator.

In other words, it builds pressure there, so excess air is forced around the grille, rather than allowed through it.

Wouldn't that be most effective if you used to block more grill so because the air that gets through is more effective?

Also, as far as improvements, I showed a 6% improvement on my Jeep with an A-B-A test. This is probably more than I'll get in the real world, I'd prefer more test runs, but I only have so much time to run tests. When I put it back on soon, I'll see if it has a noticeable effect in daily driving. BTW, no overheating and I believe Wranglers are known for this problem.

Oh and as far as temperature gauges, if you have an SG it should be able to show water temp. I used that while testing my grill block.

RandomFact314, I think by this point you've maybe got this information sorted out, but from your first posts here it looked like some clarification might be in order. Sorry that a lot of what's below is sorta off topic but - if you're going to discuss modifications to the cooling system these basics need to be in your head first. In my humble opinion, of course.

The radiator is passive. Water (coolant) goes through it and and air passes over the fins, which cools the water. If there's absolutely no air flow (or no water flow), the water isn't cooled. Exactly how much cooling occurs depends mostly on air temperature and air flow speed.

The thermostat is also passive. In fact it's mechanical. When t'stat is cold it is fully closed, and water circulates through the engine and pump in a loop. Water flows through it and when it reaches a set temp the t'stat valve opens slightly, allowing some water to flow to the radiator. As the water gets warmer the t'stat gradually opens up further allowing more % flow to the radiator till it reaches a temp (maybe around 200-205 deg. F) where it's allowing full flow to the radiator, as much as it can open up the valve. Boiling is 212 deg. F so it's fully open before that point. Also, the cooling system is sealed so the boiling point is actually a bit higher than 212.

Under most conditions the t'stat and road speed airflow over the radiator are enough to keep the engine from getting too hot. Lengthy idling, heavy stop and go driving, or brutally hot days with a/c combined with idling or stop+go, can can set up conditions where the engine isn't sufficiently cooled. Enter the radiator fan. The fan increases air flow over the radiator fins so as long as everything else is in good working order, this will increase cooling capacity.

Assuming a 'modern' computer controlled car, the 'puter monitors the coolant temp and will start the (electric) radiator fan if coolant temp rises to some set limit. In my car it seems to kick in around 206 deg. F, which I can track on the ScanGauge.

Earlier cars, especially rear drive cars with in-line engines, had a mechanical fan run off engine belt pulleys, located right behind the radiator. Instead of computer controlled switching, it had a mechanical thermostat that increased the speed of the fan when the coolant got too hot. Otherwise the fan was nearly freewheeling; with the engine off you could spin it by hand.

The mpg gains are going to depend on where you drive, how you drive, what kind of car you drive, and how much air that you block. Let me explain.

if you only drive on the highway, you can block the whole grill and you'll get the best results, reason is, less air drag, faster warm up. now if you drive in the city in stop and go traffic less than 25mph, you won't get much, and will probably loose gas mileage, the reason is, grill block doesn't give you any advantage aerodynamic wise cause you're not going fast enough, and second there isn't enough air going through your radiator so your electric fan will run so much more using energy to keep the car from over heating.