Civic grill block, front undertray, tire deflectors

[daqcivic]

Originally Posted by wwkayaker

I agree with binarycortex on the GB. Your current block will create a ram air effect (or increased pressure) on the radiator.

wwkayaker, a ram air effects is exactly what is desired for the radiator inlet, since it will mean more air going in per square-inch of opening, reducing the size of opening required for sufficient cooling and thus allowing more of the airflow over the nose to be undisturbed.

The concern with having the grill block recessed is that it may create (or increase) a static, high-pressure pocket of air at front edge nose where the grill is covered up, slowing and/or detaching the airflow across the nose. I do not think it actually does this to any significant degree, as so many very aerodynamic cars seem to have recessed false-grill sections, as well as recessed pockets for fog lights or faux cooling ducts (which should be even worse)--see the new E-class coupe with its .24 cD.

On the ducting I am trying to make for the cooling inlet, my inspiration comes from the smooth, inward-curving inlet of the Tesla Roaster (see attachment). Any thoughts about this?

[lunarhighway]

The McLaren SLR has front aero-shaped deflectors that exhibit this design strategy.

Given all this, why are factory deflectors always flat, forward-facing tabs? My guess is that these are cheap, require less fine-tuning in the windtunnel, and allow air to be diverted to either side of them equally so that a car will be more stable in crosswinds or when traveling through the wake of semis.

i think it's because anything low in front of the car will be ripped apart by curbs.

it's amazing how many torn wheel and air dams i see on cars and even complete dragging undertrays...

however some carmakers are aware of the ideal situation. more and more carmakers in europe are introduceing "eco" models wich are tuned vehicles to use less fuel and be more "green"

for example the standard vw polo with conventional wheeldams

vs
the bluemotion


the little polo has many faces from a mom's shopping trolley to boy racer but in many cases it's used by people who just want something small and practical to throw around in the city.

the bluemotions fairings wouldn't live a day with some people and at the same time wouldn't save much gas there's not a lot of high speed driving

just for fun and comparison here's the boy-racer gti

and don't-i-look-tough cross polo... not sure who buys that, but than again, it's got all the suv look, and lets face it, most of these never see any mud either


same car different audience... but it does prove a little change can make any car more fuel efficient

[vtec-e]

Originally Posted by daqcivic

The concern with having the grill block recessed is that it may create (or increase) a static, high-pressure pocket of air at front edge nose where the grill is covered up, slowing and/or detaching the airflow across the nose. I do not think it actually does this to any significant degree, as so many very aerodynamic cars seem to have recessed false-grill sections, as well as recessed pockets for fog lights or faux cooling ducts (which should be even worse)--see the new E-class coupe with its .24 cD.

I've recently trialled a flush mounted lower grille block instead of the recessed one that just replaced the original grille. I've left the opening the same and temps have gone from 82 deg c to 88 deg c. What you've just said is exactly what i was thinking! The pocket of air must be getting compressed and going through the opening with more pressure. I might flush off the fog light blanks to see what mpg improvement i see.

ollie

[daqcivic]

LH, that's the McLaren pic I was looking for--thanks. And your Polo montage is very pertinent, as it of limited benefit to ponder why a given model like the new E-class is aerodynamic, but far more instructive for DIYers to see how a manufacturer goes about improving cD with slight modifications. The chin spoiler on the Polo BM definitely seems designed to divert air around the front tires and wheel wells in a more aero-optimized manner than the standard tabs. I notice also that the upper grill is much smaller than the standard Polo, but it is interesting to see that the BM wheels look less aero than either the standard or the GTI wheels--perhaps they are quite a bit lighter?


Ollie, interesting that you show such clear results with your GB change. It would seem there is significantly more pressure build-up in recessed areas. How much was your original GB recessed?

I wonder if you would see the temp drop back down if you slightly enlarged your outer GB opening and curved it inward so that the final aperture was the same as your original GB.--how much was your original grill block recessed?

It remains to be seen, however, whether and how much recessed zones at the leading edge actually affect the airflow and increase drag overall.

[vtec-e]

Originally Posted by daqcivic

Ollie, interesting that you show such clear results with your GB change. It would seem there is significantly more pressure build-up in recessed areas. How much was your original GB recessed?

I wonder if you would see the temp drop back down if you slightly enlarged your outer GB opening and curved it inward so that the final aperture was the same as your original GB.--how much was your original grill block recessed?

It remains to be seen, however, whether and how much recessed zones at the leading edge actually affect the airflow and increase drag overall.

It was about 2 inches deep. I might leave it like that for now but if i have to do any daytime driving in any kind of heat i'll have to dump heat in the cabin! I need someone to make me an automatic grille block. ......now who could i get?.......

ollie