grill blocking, does it work from the back?

[2000mc]

i was thinking of doing some grill blocking. i was wondering if anyone had tried blocking air with panels held up to the back sides of grill openings? would this be just as good in some cases, or would smoothing the front side make much more of a difference?

[SVOboy]

Smoothing out the front would make more difference, but from the back is good if you're going for a radiator block without any sexy exterior mods.

[thisisntjared]

the difference would not be as great because of a parachuting effect. i wonder if recessed blocks would actually be worse...

[theclencher]

you shur about that?

[trebuchet03]

It should help -- you're going to create a high pressure zone inside the cavity, and if you could see it's shape, it should be "cone-like."

It would be better to be completely flush, but it's surely better than letting air impact a vertical "wall" of a radiator :p

Here's what an apple does -while it's no car, it does have a cavity that's blocked...


http://www.gassavers.org/attachment.php?attachmentid=988&stc=1&d=1192657327

[MnFocus]

the difference would not be as great because of a parachuting effect. i wonder if recessed blocks would actually be worse...

It may not be quite as good ...I don't think I'll notice the difference.

[thisisntjared]

thanks for the pic! now i definitely think it will be better than no block at all. i was recently thinking about doing the same thing today because i want anyone that sees my car to think it is completely unmodified(theft deterrent) but i still want to block the grill for the winter months. i do not want to sit for more than a minute to let my car warm up.

i think i want to go for a degree in aerodynamics.

[MnFocus]

my temporary test block :
http://www.gassavers.org/garage_images/pzmd6ed7k3mhlnuzxt9l.jpg
It was still in very good shape after a couple months ! Its now made of 1/8" lexan and painted satin black Krylon Fusion-I deleted the 1"x6" cut out as well as 90% of the lower grille .

[91CavGT]

I blocked off the back of my grill on my truck, but every time an 18 wheeler passed me the wind blew the duct tape off.

[Ryland]

well, the stock grill block that came on the civic VX sat behind the grill, it also helps by preventing air from entering that less then airodynamic engine compartment and going under the car.

[trebuchet03]

i think i want to go for a degree in aerodynamics.

The funny thing is... I'm not an aerospace major - I'm mechanical :p But I still got to play with a water tunnel, and now I'm developing a fairing for another human powered vehicle :thumbup:

I wanted to compare apples to oranges in the aerodynamic sense... I couldn't find an orange though :/

Just for fun.. I here's a few more pictures from my collection :p

I did the calculations awhile back, and IIRC the equivalent wind speed was something like 6mph for those car models... This tunnel is just for flow visualization ;)

Check out the pressure wave formed behind the shield - that's actually very significant (think sound pressure wave in some cars when only one window is open)
http://www.gassavers.org/attachment.php?attachmentid=991&stc=1&d=1192684955
Very Slippery Shuttle
http://www.gassavers.org/attachment.php?attachmentid=992&stc=1&d=1192685112
Toy Car (I brought a box of die cast Porsche cars)
http://www.gassavers.org/attachment.php?attachmentid=993&stc=1&d=1192685175

Here's the water tunnel
http://www.gassavers.org/attachment.php?attachmentid=994&stc=1&d=1192685360

Sorry to thread jack there :p

[bowtieguy]

I blocked off the back of my grill on my truck, but every time an 18 wheeler passed me the wind blew the duct tape off.

try foil tape. it seems to adhere better.

[lunarhighway]

many cars have (fake)fog lights palces in fake grills at the lower edge of the bumper... most likely this is only for looks to give the car more character as there's no reason why fog lights can't be perfectly flush with the rest with the bumper, but on the other these will quickly fill op with high pressure pockets so perhaps the increase in dragg is small (especially since they may give a little downforce wich might aid stability). not that i like this setup, but perhaps sealed of cavities like the grill are not as bad as they look.

also another advantage of a grill block might be that with an open grill the air usually has to find it's way out again, wich may disturb undercar airflow even further

[Hockey4mnhs]

I blocked off the back of my grill on my truck, but every time an 18 wheeler passed me the wind blew the duct tape off.

I would have been behind that truck drafting it so it would stay on ;)

[theclencher]

hard to draft 'em at a closing speed of 120 mph

[rh77]

I saw a Modern Marvels episode last night on "Sticky Stuff". They featured a powerful acrylic foam tape from 3M: the VHB Tape.

Apparently this stuff is weather resistant and is more structurally sound than rivets for impact and heat expansion.

Here's a link to the 3M product website. (http://solutions.3m.com/wps/portal/3M/en_US/VHB/Tapes/)

The cost may be the limiter: the cheapest is about $1.25/yd. for the 1/4-inch wide, 15-MIL application. It goes up from there in tensile strength width, color, and thickness. With a range of -40 to 200F, this might be a good applicator for grille blocking environs.

RH77