At what point is it advantageous to shut the engine off while driving?

[TestDrive]

Originally Posted by Mazda_2.3

I based my decision on the fact that the lower grill was so large and with the OEM belly pan (extends from the front bumper to just past the axles) it seems that a lot of air would be getting trapped in the engine bay. Could you possibly elaborate on why it would be better to block the top grill? Oh, and I have a picture of the grills on my profile.

Seeing the hatch work lower grill (nice looking Mazda3s), I'll change my mind and like leaving the upper grill open better. If the lower grill wasn't such a mess, I'd have suggested partially blocking it in addition to fully blocking the upper. You could probably fully block the lower and still partially block the upper. Take a look at the tiny opening (picture) on basjoos' aerocivic (ugly as sin, but insanely good mileage) which has a full belly pan.

The engine compartment must be designed to vent excess air somewhere. Maybe the front wheel wells??? In any case if you block either grill, there's going to be less air to vent.

Normally it's better to block the upper grill because most cars don't have any sort of belly pan - muffler, mud flaps, oil pan, transmission, steering linkage, struts, ... hanging in the wind, making lots of turbulence. Better to send more of the air over the top where there are fewer obstructions.

[PaleMelanesian]

This is from Phil Knox's photo galleries, book illustrations category. Notice how the lowest nose has the lowest drag. Based on this, I'd go for a smooth upper block first, then block the lower as needed. Even if the car has a fairly smooth bottom, there's the car-ground interaction to deal with, which is more draggy than the free air above the car.

[Mazda_2.3]

I will agree that is one ugly civic. Though it's cool that such a small opening is enough to prevent overheating.

I am actually considering doing the uppergrill too but I'll probably get an aftermarket grill first w/o the big bold Mazda emblem.

Originally Posted by TestDrive

Seeing the hatch work lower grill (nice looking Mazda3s), I'll change my mind and like leaving the upper grill open better. If the lower grill wasn't such a mess, I'd have suggested partially blocking it in addition to fully blocking the upper. You could probably fully block the lower and still partially block the upper.

[Mazda_2.3]

Originally Posted by PaleMelanesian

Notice how the lowest nose has the lowest drag. Based on this, I'd go for a smooth upper block first, then block the lower as needed. Even if the car has a fairly smooth bottom, there's the car-ground interaction to deal with, which is more draggy than the free air above the car.

I can kinda see the image going both ways. Yes, less drag with a lower nose but when that low nose has such a huge opening I could see that benifit being cancelled out. This did give me a great idea though.

http://ecomodder.com/forum/member-ma...ibilities.html

just that small opening between the two and perhaps two parallel openings on the lower grill about 1/2" tall each running the length of it. . . hmm...

[Wonderboy]

You may also want to work out some kind of plexiglass covering for the fog light sockets.

[Mazda_2.3]

Definately agree but my goal is for any mod to be removable without
knowing it was ever there. Primarily if I intend to sell it someday but also cause I'm lame and told my girl that nothing would be perminant. Any ideas on how I might go about doing that. I've thought about trying to get lucky at a upullit or on craigslist and finding a bumper that was the same color for cheap but that's not likely. Though if I could, there would be no foglights and no lower grill opening at all. . . . SIGH

Originally Posted by Wonderboy

You may also want to work out some kind of plexiglass covering for the fog light sockets.

[taco]

i have had my grill blocked fromt he inside for a few months now, i uses doubloe sided 3m tape(think vent visor tape) it has lasted through 3 snow storms. and is not one bit weak. easy to remove even harder to see. well that is if i painted my coroplast.

i usually get 27-30 mpg, when i was running well like i am now.!!
new wires at 260k miles then a tranny at 155kish miles.



another question what is your drive like, please explain.

[Wonderboy]

@mazda:

I feel the same way about my car even though theres probably no way id be able to sell it at like 190k mi. I havent done any aeromods yet but grilleblocks are definitely easy/effective/temporary enough. As for your fog lights, your regular headlights are probably plenty bright, so if you took the fog light bulbs out, you could either make something that fits in that socket, or hopefully you could take the socket out to put something you're willing to screw into back there. As taco said, some good tape is probably your friend here.

Also, take notice of places where existing screws/bolts are and use those - when i had my corolla and deleted its mudflaps, i was poised to make rear wheel skirts because of the existing holes i could bolt into. There mmay be options like that up front on that mazda you could take advantage of w/o drilling any holes.

[PaleMelanesian]

Wonderboy, take a look at what I've done on my car: Aero mods - new grill block and wheel covers - CleanMPG Forums Plexiglass upper block, and foam mat press-fit into the lower.

[Mazda_2.3]

Definately need to look into the 3M tape option, probably a lot easier than what I'm trying to do now w/ sheet metal and vinyl. My drive is about 11 or 12 miles at 6:30AM so pretty cold (frost on windows and wet roads). It's about 3/4 freeway and there are . . . 7 stoplights (engine off at most) and a MAX (passenger train) crossing on the other 1/4. Few gradual hills here and there but nothing that isn't compensated for by coasting down after. Oh, Highway speed is 55 and I keep to the slow lane.

Originally Posted by taco

i have had my grill blocked fromt he inside for a few months now, i uses double sided 3m tape.

question: what is your drive like, please explain.