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