Junk on the front...

[aerohead]

In free air,the light bar would have a Cd of around 1.05.

[Grant-53]

Assuming it meets NJ DMV spec. I'd try some fine nylon screen mesh to fair into the grill. Test the pattern at night by observing the lights from another car head on.

[mpg_numbers_guy]

Originally Posted by freebeard

For why? Stick around and you'll find out about stagnation point and the beneficial effects of an upper grille block.

My [notional] money's on the mileage goes up.

Maybe I'm missing something, but wouldn't air go over the LED light bar and in through the still unblocked grille? And wouldn't it have the same effect as those headlights on older cars that popped up and caused unaerodynamic drag?

[freebeard]

[QUOTE-aerohead]You're probably placing it where it will do the least harm.
It's a full-separation structure,but the cars nose will be training behind its wake.[/QUOTE]

What aerohead said, plus maybe a little grille block action due to interference drag and vena contracta.

[mpg_numbers_guy]

Originally Posted by freebeard

What aerohead said, plus maybe a little grille block action due to interference drag and vena contracta.

Hm, maybe. Actual testing on this would probably clear up my confusion here. It seems to me to be a little counterintuitive, but I'll have to give way to you more experienced ecomodders. A grille block without the LED bar would still be better though for MPG, right?

[MeteorGray]

I don't think your mileage will drop a bit with the LED bar in the grill where you placed it.

I have installed a pair of round LEDs in about the same position on my '15 Mazda3. In that position on my car, the grill is solid and is designed as a place for installing a front license plate where such a thing is required. Since my state does not call for a front plate, I filled that "void" with a pair of bright lights each containing 9 LEDs.

My two round LEDs naturally are not as long as your 21.5-inch bar, but they are a little "taller," being about 4.5 inches in diameter. The effect on MPGs, noise or anything else is nonexistent, or at least non-noticeable and non-measurable to me.

I've got a similar pair of these LEDs on the Jeep I use for off-road hunting, and they come in handy for that. But my Mazda doesn't go off-road, and since the LEDs are probably illegal on public roads and would certainly hinder oncoming drivers at night, about the only use for my extra LEDs are as signal lights and as very noticeable DRLs.

For example, yesterday I was passed by a "speeding" 18 wheeler, and since the traffic was tight and I knew he was anxious to get back into the lane, when he safely cleared my car I flashed the LEDs several times to signal him he was clear to return to his lane. He immediately pulled in, and to show his appreciation, he cycled his rear lights, which is a customary "thank you" signal in such situations.

I also use them to signal on-coming cars on two-way roads to let them know they are getting too close while passing another car, and for signalling pedestrians who seem too close to the road, etc. I could use the Mazda's headlights for such signal flashing, but the LEDs do it with a little more class; or at least, it's different. Hey, I got 'em already.

Occasionally, I also use the LEDs as daylight running lights (DRLs) in some threatening circumstances, such as in high traffic congestion with shadows when my little grey Mazda could easily disappear in the hustle. My car has small (about 2 inch) LEDs in the lower fog light positions as full-time DRLs, but they are not nearly as noticeable as the bigger 4 inchers in the grill.

I installed a button to press when I use the center-grill LEDs for flash-signalling, along with a toggle switch for keeping the LEDs on longer term, such as when using them as DRLs.

They do come in handy for such things.