blocked grill, better mpg?

cheesie · 03-04-2011, 02:40 AM

Moderators Note:"FYI, this shouldnt be attempted unless you have a way to monitor the vehicle temperature by the odb2 port and you should make it easily reversable incase the temp gets warmer faster than you expect."

ive seen this before here where people talk bout covering the grill of the i2 in winter time, and they actually get more mpg

i live in socal and its been pretty cold here lately, also my mpg is dropping, i was wondering if this really works, how cold would it have to be for the car to be safe and not have problems if i block the grill

mornings get as cold as 50 and during the day it stays 60 but never hotter than 70

is that not cold enough?
should i just forget it?

**Jayemtee** · 03-04-2011, 07:48 AM

The main reason I do it is to get the engine up to it's ideal operating temperature.

I suspect your engine is fine with an OAT of 50. Do you have a ScanGage or something to monitor water temperature? With Springtime around the corner, I don't think you should worry about it.

ghammerly · 03-04-2011, 06:37 PM

I have an Ultragauge on my current car with temperature alarm set at 210 F just in case.
The opening on the grill is about 1.5" X 12", the car a smart for two. Today with a ambient temperature of 50F the indicated engine temp got to 195F which is the high point normally. When it starts to get higher than that I will just open the hole a little.
Car warms up much faster.

**freezin4** · 03-04-2011, 10:35 PM

Quote:

Originally Posted by ghammerly

Car warms up much faster.

I wonder how this happens. If the thermostat is rated at 180 deg F, or 190 deg F, then the coolant in the engine will heat up to that temperature in X amount of minutes, at which time the thermostat opens. The water in the radiator is unaffected until the thermostat opens at the pre-determined temperature. So, the grill block should have no effect on how fast the coolant in the engine block reaches operating temperature.

**Jayemtee** · 03-04-2011, 10:51 PM

I'll give you two things to think about.

1. What do you think happens to cold air that passes through a cold radiator? Where does it go from there?

2. What do you think happens when that thermostat opens? What happens to the 180 degree water leaving the engine? What happens when it is replaced with 35 degree water?

**freezin4** · 03-04-2011, 11:54 PM

Quote:

Originally Posted by Jayemtee

I'll give you two things to think about.

1. What do you think happens to cold air that passes through a cold radiator? Where does it go from there?

2. What do you think happens when that thermostat opens? What happens to the 180 degree water leaving the engine? What happens when it is replaced with 35 degree water?

Yes, it may make a difference if you drive before warming up the car. And the engine temp may take somewhat of a dip (although I haven't noticed much if any, at 40 deg F temps on my G1 with Scangauge monitoring), when the thermostat opens.

But I think it takes the same amount of time for an engine to reach operating temperature with or without radiator block. (unless the car is driven while cold)

cheesie · 03-05-2011, 01:18 AM

i dnt have a scangage
i wish i knew what it was....
i got no idea of what anybodys talking bout
i rather not blok the grill haha

Cobb · 03-06-2011, 11:16 PM

Blocking anything completely is a bad idea. Your license plate mod should account for something as it partly blocks thelower grill. Last summer I ran half a block with no problems even with ac use. In winder I blocked all but an inch of the lower grill.

Even if the t stat opens at a certain temp to allow coolant to go through the radiator, the blockage reduces the air flow through the engine compartment that can cause some cooling and delay the engine warm up. Furthermore a t state does not completely block the flow of coolant, it leaks and some flows through the radiator anyways even if its closed.

From what I can see out engines like 177 degrees. I do not know when the t stat opens, but Id try a colder one next time its replaced or if I get around to it.

livfreely · 04-05-2011, 12:06 AM

If you get the engine block heater would it solve this problem? Just plug it in over the night. And then you could also say you have a plug in hybrid.

ackattacker · 04-05-2011, 09:38 AM

I believe there is also a significant savings in cooling drag with the radiator block.

In aircraft, you can get save a lot of drag and get extra speed by altering the size of the cooling exits using variable cowl flaps. I think any reduction in flow of air through the engine compartment / radiator saves drag.

I believe blocking the air conditioning portion alone (if you don't use the AC) would represent a savings.

Imagine how much drag a radiator would be if you mounted it on top of the car sticking straight up. Inside the engine compartment it's hidden but it's still a major source of drag.