Grill block on an Aveo

[kopid03]

My aveo has a grill that looks just like this:



I was wondering what I should block. I was thinking the entire top opening behind the Chevy badge, then maybe 3/5 of the bottom grill. The bottom grill is divided into 10 rectangles, so would it be better to block the middle 6 and leave the ends open, or to put in a big block and cut holes in the middle?

There are also foglight openings on the ends of the bottom grill that I might cover up as well.

[MetroMPG]

I would block the top, plus the outside of the bottom (including the fog light holes) where there's no radiator behind.

Test any further coverage gradually. Monitor your coolant temps closely if you have a ScanGauge (the needle on the dash, if it has one, isn't precise enough). Or listen for the cooling fan. If it's coming on more than normal, you've gone too far!

[FastPlastic]

Originally Posted by MetroMPG

I would block the top, plus the outside of the bottom (including the fog light holes) where there's no radiator behind.

Test any further coverage gradually. Monitor your coolant temps closely if you have a ScanGauge (the needle on the dash, if it has one, isn't precise enough). Or listen for the cooling fan. If it's coming on more than normal, you've gone too far!

I agree. You'll see an aero improvement blocking the front and sides. Beyond that you start covering the radiator, and that can lead to some problems depending on temps and output of your cooling system. So definately take it slow if you do decide to start on the middle.

[lunarhighway]

make sure to test on hot days (may not be possible when you want to) and is slow moving/idle situations... and preferably a combination of both... the problem with grillblocks is while they're perfectly fine for normal driving, every once in a while you might get stuck in a que for 10 minuts or so where it's not possible to turn the engine off/on all the time... this is where grillblocks always give me problems.

another thing you might want to look at is where the airbox is connected to... likely the hose will disappear in the front bulkhead and get it's air from the pre grill cavity... blocking this completely might give you an unintentional warm air intake which could aslso decrease FE (if the car coasts longer, but FE is not better/worse, this could be the case)

[winkosmosis]

Isn't warm air intake supposed to give you better gas mileage because the air is less dense?

[lunarhighway]

Isn't warm air intake supposed to give you better gas mileage because the air is less dense?

the idea behind a WAI is that when you need a given ammount of oxygen to deliver a given ammount of power reducing the oxgen level in the air will call for a bigger throttle opening to deliver the same ammount of oxygen. a wider throttle setting will result in less flow restriction and thus less pumping losses, the downside is that once the throttle is virtually fully open there's still less oxigen comming in than without the WAI and so top performance will suffer.

because modern engines monitor all sorts of parameters the engine might react to the lost performance or changed emissions by injecting more fuel to compensate thus resulting in less FE

so i wouldn't automatically assume WAI will improve FE in an injection engine although it's quite possible it does on some engines (on a carbed engine it probably will have a more predictible effect) (also it depends on climate youre in etc)

[winkosmosis]

But people on this forum purposely build warm air intakes

[lunarhighway]

But people on this forum purposely build warm air intakes

yes, i've experimented with them too, and was quite surprised when i saw my FE go down... after tracing the air pickup to find it also basically gets its air from the grill i figured that what the reason a car that noticably coaster further drove worse and got worse FE.
(i have a semi urban commute so perhaps efficient acceleration has a bigger impact on my FE than top motch aero)

i've got nothing agains WAI's but i'm also sceptical how much their effect can be on modern engines. throttle restrictions are apparently i big loss factor (in fact i've just seen an article somewhere about a throttleless engine that worked by variable valve timing and got 15%-if i'm correct- better milage) and the theory behind a WAI is simple enough. in fact that might be the reason older carbed engines often had their air pickup inside the engine bay. but if warmer air only had benefits why don't carmakers fit a wai as a standard today, and compensate the loss of power with a bigger throttle?

but anyway, on the subject of grillblocks again. all i wanted to add to the discussion is that i found myself in the strange situation where a grillblock hurt my milage, but that that doesn't mean grillblock are not working (in theory... finding an alternate air pickup should allow me to run the GB)

[winkosmosis]

Interesting. That reminds me of something I've heard on Jeepforum or NAXJA.... Some people report a gas mileage improvement when they add a snorkel, even with the extra drag of the pipe going along the A pillar. I dismissed it, but it seems reasonable now.

My Cherokee's air intake temp gets up to 130F so there would be a big difference with a snorkel or better engine bay venting

[kopid03]

Well I finally blocked the upper grill. I didn't have any plastic to use, so I just made it out of cardboard, spraypainted it black, and put a layer of packaging tape over it. I hope it stays put at highway speeds.
I'm driving 1600 miles over the next 3 days, so I hope I get good mileage. Its gonna be hard to compare though because since my last tank I have changed to synthetic oil, put the grill block on, and changed my tire pressure from 30 to 44. Might also fold the passenger mirror in, and maybe go 48 on the tires.