First Grill block design a failue.
 

So I tested a partial upper grill block yesterday. I'm not sure why but I actually got to watch my fuel gauge drop. One positive was my engine warmed up in less time, but it felt like it was working harder.

I compared the drive to my normal drive. Including coasting down hill and cruise control on flat roads.

It felt like my car was being held back the entire time. I'm not sure what happened. I thought a grill block was suppose to have a positive effect, however minute, on driving.


Any Ideas?

Odd. Where dose the engine pull its air from? Did you inadvertently block the engine intake or cause it to pull hot air (not all cars like hot air mods).

Make another one, cover the entire grille/bow tie. It's winter, you shouldn't have any problems with overheating.

As far as I am aware the intake hoses down to the bumper infront of the driver side tire. I'm going to dismantle it and find where the inlet is and block accordingly.

From how it appears in the photo, you don't even have the entire grille blocked. I'd suggest you first remove it completely and see if there is any improvement. (I think it might be just coincidental about the performance. So I doubt this is cause and effect.) If there is no improvement, then it's an unrelated problem. You don't even have the whole grille blocked, let alone having a full radiator block. Usually, at worst, the fan will come on more often once it reaches 210+, but overheating is unlikely.

How many cylinders? Manual or automatic? How long does it usually take to warm up? Are you using a Scan Gauge?

1.5 %
 

spydyr,you're looking for maybe a 1.5 % change in fuel economy tops.If you weren't extremely careful just in filling your tank,this difference could be lost.
A fully-warmed car in mild weather with no wind over the exact same route would be required just to see this change through all the environmental 'bandwidth/signal-to-noise ratio.
I suspect that you've reduced your drag a little,you just can't 'see' it.

4 cycliner. 2.2 L. Automatic 4 speed. Typically 5-10 minutes in winter 3-7 in summer. No.

When i drove the car with the grille block the temp stablized at 195 where it typically stays. No fans came on.

I'll try it without the block and see if anything changes.

I'd suggest not looking to the grill block as a panacea. Some people seem to think that a grill block will make obvious improvements immediately, and that's a lot to ask of a little cardboard and tape. And basing "failure" on one day's driving just doesn't make sense.

Understand that it's not about "blocking the grill", it's about "improving aerodynamics". Cover the entire grill, and make it as smooth as possible, but know that modifying your driving habits will have a much bigger effect on fuel economy than a cardboard grill block, and you need to sustain any changes you make for longer than a day.

That grille block looks sound, but as the other poster mentioned, you should probably block the entire upper section. No matter what, it certainly does not look like it's increasing drag.

Is there more grille below the bumper, too? If so, block 100% of the upper and a portion of the lower.

I regularly see +/-10% variations in my fuel log for no reason that is immediately apparent. If you do coast-down testing including taking a video of your speedometer, you may be able to discern the effect of the grille block.

Is there an opening below the bumper? If so, then I'd block off the entire upper grill.

Did you have a different wind on the test day? Was it colder? Maybe the handbrake was dragging, or a tire was low on air pressure?