Hidden grill block in the back of the grill, usefull or useless?
 

Hi,

grill blocks are very useful to get a higher mpg, but the look of these blocks lokks horrible to me.

Now i got an idea.

The german Opel Calibra was built with several different engines, but its body was always the same. The slowest engine (115hp) as a integrated upper grill block, hidden behind the grill. So it looks like normal, but ther cant get any air trough.

This smaller engined Calibra hat an cw of 0.26, all other engined Calibras had cw 0.28 to 0.29.

I´have no information if this car was sold in the usa, but you will find several pictures with google. Its upper grill goes deep in his front-bumper, so with a block at his end there is a deep hole. Does the air built a "filling" so that there are no turbulences, or is it a very bad aerodynamic idea?

Kind regards,

Benny

Its alright, but not as good as an outer grill block.

IMO if you're that stuck on looks make a nice looking grill block yourself. There are a few examples on the forum.

http://ecomodder.com/forum/showthrea...cho-15673.html

It takes more time and cost more, but you're the picky one. :)

it will help with warm up times and depending where your intake gets cool air it could help keep cool air away from the intake making it a bit warmer. It will not have the aerodynamic gains from an external block though

I have tried both in front of and on the back of the grill, there was no measurable difference between the two on the 2009 Corolla. It may be dependant the properties of the grill so your results may be different. However on the 2012 Ford Focus, Fiesta and other cars, they have active grill shutters and fake grill openings etc that all use the "in the back of the grill" construction. If it made a large enough of a difference they wouldn't have bothered to make it look the way they did.

I have mine behind the grill.

How about a piece of clear plastic in front of the grille? It's almost invisible, and has more aero advantage. In some cases the plastic may be black or in the chassis' color and still be barely visible.

I have a plexiglass block on my upper grille. It's visible, but not in your face.

It will still help.

The flow may not be quite a smooth as a well made external block, but it's still better, aerodynamically, than no block at all.

I had one on my truck inside the grill. The way I had it mounted, it would flex and allow air to flow past it and wasn't very effective. I noticed an improvement by moving to the front of my grill.

I think if you mount behind the grill, you need to make sure it will still prevent air from flowing around the block once the vehicle is moving.

Mounting in front of the grill makes this easy, since air pressure will keep the block in place.

I mostly disagree. "Buckets" in the front don't hurt aero much if at all.

I had the same experience as Darcane that the behind the grill block would flex at higher speeds and open up a little, leaking air. So it wasn't quite as good as my present external grill block. But it does help.

I also used clear plexiglass for the behind the grill block, so it was really invisible.

I doubt that putting the block behind the grillwork would make a big aero difference, for the following:

The front grill on an auto is at--or very near to--the stagnation point on the nose. Thus, the flow velocity near the vehicle is zero, or very close to that.

What happens is that the air upstream of the car "senses" the blockage...and the vast majority of the air flows AROUND the obstruction. This is true of all sub-mach flow. (Sometime look at the "grease streaks" you see on aircraft rivets...the airflow on the fuselage just ahead of the wing has a pronounced upward flow component, as the air tries to fill the low-pressure are on the top of the wing.)

So, keep it under 720 MPH, and it makes little difference. Above that, you want knife-edge leading edges anyways.

I'm not sure your cause and effect follow each other.

Correct that the grille is near the stagnation point. (more on some cars than others) A rear block will cause air to "pile up" in the blocked cavities. The rest of the air will flow mostly smoothly over those pockets of air. A rear block should work nearly as well as a smooth outer block.

You do have to get past that pesky problem of the air pushing it in and then leaking around the block. A front block doesn't have the problem.

Cool just fabricate it so you get just enough air,, thanks

see the grill block thread in my signature on a plexiglass front block

It depends on the vehicle if air can go around a behind the grill block. On my grandprix I used plexy for picture fraims and cut it to the grill insert installed and the air presses it tighter. The same is true for my Golf as the grill sits against a support and the air tightens the seal.

I have an inner block behind my grill which is only about 1/2in deep but I took the grill off used coroplast, black just like the grill. Then used Gorilla duct tape on the edges and it seals perfectly.

Now it's getting time for the lower block soon!