Grille Block Makes Car Run Cooler??
 

I had some lower grille blocks (military duct tape) on my Focus. I did this is in the winter to help it get up to (and stay up to) temperature in the Winter.

I figure I'd save a bit of gas and it's better for the engine to reach the proper operating temp.

Yesterday it was 90 degrees out ... I decided to put my car in "Engineering Mode" to see how much hotter the car ran with the grille blocks.

I ran the same test loop, once with grille blocks ... once without grille blocks. For what it's worth, it was 1 degree cooler outside the second time


WITH 2 outer grilles blocked, middle open:
Running down the highway with A/C - 85-87C
Idling in parkinglot with A/C - 90C
After 10 minute off - warm start: 92C

WITHOUT any grille blocking
Running down highway with A/C - 87-89C
Idling in parking lot with A/C - 91C
After 10 minutes off - warm start: 95C

This ... doesn't make any sense.

I can think of two things
- Going down the highway, the air that is able to go through the radiator is going much faster since it can only go through one opening on the grille ...
- The temperature is just enough that the fan kicks on more and keeps lowering the temperature.

Input?

Maybe the engine doesn't need to work as hard at highway speed thanks to reduced drag?

Perhaps this points to the importance of ABA testing?

Another possibility is that the overly large stock grill is letting air *back* out* because there is too much pressure and so the air exits through the less effect part of the grill? The earlier Taurus with the small oval upper grill and the large lower grill apparently had air flow out of the upper grill.

But it could also be different ambient air temperature, or the lower drag loaded the engine less, as suggested above.

+1 for drmiller because I suspect the same thing in my civic. Upper grille block is in a suspected area of low pressure from air coming off of the bumper. I think this is possible.

I noticed the same thing. My Ranger runs about 6 degrees F cooler with the upper grill blocked, which I did about 9 months ago. Seems to have picked up about 1 to 1.5 mpg with upper grill blocked.

Just thought I'd bump this topic up.

I took out the grille blocks to do the test (more like tape along the openings) and never put them back on.

This weekend it's supposed to be warm and I'm going to be putting about 400 miles on the car. Not all interstate, either - a lot of it is going to be some pretty hefty hills in the adirondacks.

I took this trip last year when I first got the car and I averaged exactly 40.0 mpg ... that was before I really knew how to drive the 2.0 Duratec and the car wasn't broken in yet.

I plan on putting the outside grille blocks back in (but leaving the center open for some cooling). No doubt my parents will need A/C so that will suck a bit of mileage.

I'm going to put the car in 'engineering mode' so I can get an actual readout on the temp. I'm not sure what the ideal temperature on this car is ... My Jeep is happy around 210.