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Old 01-30-2009, 10:37 PM   #1 (permalink)
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What do you guys think about a grill block behind the grill?

Just like the Title says.

I'm considering doing a motorized grill block on the TDI; but I'd rather it look stock (I get enough questions already). I'm aware it wouldn't be quite as effective as on front, but how much difference do you guys think it would make?

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Old 01-31-2009, 04:51 AM   #2 (permalink)
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If the radiator creates so much drag that you need to block air with a flat piece of material from it, then you already have an inside grill block don't you? .....
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Old 01-31-2009, 07:02 AM   #3 (permalink)
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A block behind the grille, as in right behind the grille so it's pretty much sealed, should be almost as effective as a block in front of the grille at speed.

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Old 01-31-2009, 08:18 AM   #4 (permalink)
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Originally Posted by tasdrouille View Post
A block behind the grille, as in right behind the grille so it's pretty much sealed, should be almost as effective as a block in front of the grille at speed.
Agreed. Now if your grille block was stuck to the radiator, you'd have good heat but your aero properties would be slightly at a loss. Then again, if you dont often travel at speed it won't matter much.
I blocked the rad on my kia cee'd on the outside but found it also blocked my intercooler and blocked the air inlet too so fuel consumption was way worse. Now i have cardboard shoved up between the rad and the aircon rad. This still affects the aircon when my wife drives so she leaves it on longer (all the time)
and the fuel consumption is like everybody elses. Sometimes i wonder why i bother!!

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Old 01-31-2009, 08:54 AM   #5 (permalink)
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I'm gonna agree that there probably isn't a real large difference. However, you'd have to look at specific applications and make the best educated guess you can. Its all going to depend on the grill and shape of the front end. If you have a hugely recessed grill, then its probably much better to make a block that completely eliminates the recessed cavity vs just a block that goes over the front of the grill. In the case of my Matrix and its lower grill, I'm still debating if its worth the hassle of doing a flush mount, or just put it behind. I'll post that info in my arduino grill block thread most likely.
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Old 01-31-2009, 09:30 AM   #6 (permalink)
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I know you want motorized to account for the times you need more air.
I live in Virginia, near the ocean, the low temps here don't get much below freezing in winter but the highs in summer get to 99*F @ 99% humidity. Heat index around 120*F.
My daughters grill is 100% closed. I used foam pipe insulation and crammed it between the horizontals. White car + blue foam = odd look. You might want to color match.
My point, (ah good you think, finally a caboose to his train of thought)
She never had an overheating problem last summer and she drives like a maniac.
Two speeds;
Haul@$$ &
Maybe you don't need the motor?
Just my .02,

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Old 01-31-2009, 04:07 PM   #7 (permalink)
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I'm driving a 2000 TDI, and here's been my situation with static grill blocks, to compare with the need for an active one:

I'm up in Alberta, dealing with a temperature range between -40C to +38C (-40F to 100F).

Since November 2006, I've had two pieces of coroplast stuffed against the radiator, behind the upper and lower grill, and behind the bumper, and the radiator support in front. About 2/3 of the radiator has been blocked internally.

In the summer of 2008, I blocked off the lower grill entirely, and then covered the lower half of the upper grill (avoiding the upper driver's side quadrant, where the stock engine air intake is).

The only time I had an issue with being too blocked off, was with the lower grill entirely blocked in the summer during a long highway drive (4-1/2h each way, 35C, very humid, and driving 90-100kph). After that drive, I made a gunslit in the centre of the lower block, about the size of the hole on the plastic grill piece -- so, about 1/9th the original open area. And as an extra precaution, I removed one of those two interior coroplast rad blocks.

At colder temperatures, in the winter, I had to tape up that 1/9th hole when temperatures approached freezing.

Summer peak temperatures:
Air temperature at 30C-38C
Highway cruise: 70-85C
After highway city stop-and-go: 75-90C

Winter temperatures IF I could warm up:
Air temperature -40C to 0C
Highway cruise:
65C-72C when lower grill was 8/9ths blocked.
58-64C when the lower grill was full open.
City stop and go: 55-70C.
When temperatures approach 0C (freezing point), the engine would be 65-75C.

An active block would probably be more ideal for the TDI. There are times you need the grill more open
  • mainly city driving after a long highway cruise
  • in a near standstill city stop and go where you're inching ahead

Again, all of this was done with 2/3 of the radiator blocked off, topped off with exterior blocks.

Being dremd's stomping grounds are MUCH warmer than mine in Alberta, he'd have more need for an active grill, than I would.

Myself, I really don't see there being much room to work with behind the grills. That's why I originally went with radiator blocks (to let the engine warm up faster in winter). I'd concentrate on an active slot or flap off a blocked lower grill, and there'd be a few inches of working room. I'd suggest dealing with the lower grill or space behind for any sort of active/motorized block.

I do think there's merit in pursuing a grill block with your TDI, dremd. The TDIs benefit more from faster warmup, summer, OR winter. So, a near 100% block benefits the car in almost all seasons and temperatures. The active block ends up being a "safety" for ensuring you get enough airflow to avoid having the fans running and/or overheating.

P.S. My 2 cents are TDI-centric. YMMV for other vehicles, of course.

Last edited by ChrstphrR; 01-31-2009 at 04:08 PM.. Reason: Post Script!
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Old 02-02-2009, 02:03 PM   #8 (permalink)
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Originally Posted by metroschultz View Post
She never had an overheating problem last summer and she drives like a maniac.
I have a coroplast panel completely blocking the front side of my CRX's radiator, behind the grille. The temps got too high for me on two occasions:

1- When driving 70 MPH on a long freeway trip on a relatively cool night. Backing off to 50 MPH brought the temps back down to the normal operating range.

2- When driving 55 MPH on that same longish freeway trip on a very warm (~70F) afternoon. Slowing down to 50 MPD did not bring the temps back down, so I had to remove the block. It has since been re-installed for my short daily commutes.


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