In the search for even a few more miles per tank, I blocked up the stock grille area before hitting the road tomorrow to commute to work, picture below.
So, how much can be blocked before it overheats?
I plan on carrying my #10 blade retractable scalpel, JIC. Oh, the cooling system on these trucks are overkill on the V6 model, as it is designed with the V8 in mind.
That may fly in Alaska, but don't try it in Vegas this week.
Ranger50 wrote: So, how much can be blocked before it overheats?
How long is a piece of string?
914Driver wrote: That may fly in Alaska, but don't try it in Vegas this week.
Good thing I don't have to venture to either of those places this week. 
Knurled wrote: How long is a piece of string?
As long as it needs to be.
Exactly.
So, what is "overheating"? Maybe you get best fuel efficiency at 250 degrees...
my Camaro is cooled by a strip of the bottom of the grille that is about 2" tall and 2 feet wide... that's all that isn't covered with black duct tape. the carb is also fed cool air from that same source, and the carb is almost ice cold after a few miles on the interstate in 90+ degree temps.. it gave me zero problems in 100+ degree heat last summer, and i predict that it will be the same way this summer...
I would start with blocking one part of the grill at a time until you notice it starting to overheat.
Even blocked, you might get adequet cooling at 50+ mph.. but below that it might get too hot
mad_machine wrote: Even blocked, you might get adequte cooling at 50+ mph.. but below that it might get too hot
That is my drive. It is drive 30 miles, traffic light. Drive another 20, hit another light or two and so on until I finally hit the "big town". By then, I just have to make 10 miles of hit and miss lights to be at work.
So, I guess I shall see.
Get a scan gauge or similar. Keep taping until you stay at about 200 F. really surprising how much you can block.
Ranger, did you make it to work today?
iceracer wrote: Get a scan gauge or similar. Keep taping until you stay at about 200 F. really surprising how much you can block.
Why stop at 200? It might be more efficient the hotter it gets.
Cup cars are running in the 240-250 degree range, I know WRC cars are too, and they're more concerned about power than efficiency.
When my RX-7's cooling system was marginal due to poor airflow (and it gets hotter with higher speed, not lower speed... more power vs. limited airflow) and I was running 200+ on the highway, my fuel economy was over 10% better than it is now that it's fixed and it runs 170-180. Less heat gets lost to the cooling system when the engine is running hotter.
That's a rotary and I feel iffy allowing them to get hotter than that, but Chrysler doesn't even kick the fans on until 245 sometimes.
It depends (as everyone has said), but I've seen a lot of factory vehicles get away with pitiful little slits in the bumper.
How about coming up with a way to let the air back out of the engine compartment...?
noddaz wrote: How about coming up with a way to let the air back out of the engine compartment...?
It won't help nearly as much as blocking it off in the first place, in terms of aerodynamics. It's important for cooling though.
A lot of new cars have louvered shutters over the radiator stack for just this reason.
as far as hotter being more efficent. years and years ago (20ish) I borrowed my father's 88 Grand Marquis to get paint so I could shoot my Fiat the next day. What nobody knew was the little elbow at the distributer was leaking and spraying coolant all over the engine compartment. Being 18, As I left the tollbooth on the Garden State Parkway, I floored the 5.0 and actually broke traction, something that sled had never done before.
5 miles later the hose blew in a spectacular fashion.
The engine was probably running hotter than usual from a lack of coolant.. and there for was making more power. Never again did that car break traction on a dry road, so it seems a safe observation
I have this much blocked off on my ranger:
The hole in the plastic valence at the bottom is more significant than the two on the sides of the grille. During the summer (in AZ) I run right in the middle of the engine temp range, though I need to get my Ultra gauge again to check it. During the winter, I need to block off more because it will rarely get above 1/4 of the way up the gauge.
Its kinda hard for me to fully trust what the ultragauge reads out though, since the sensor it uses is right next to the cylinder head and not later on down the coolant pipeline. So, anything with high RPMs will spike the temp quick (like up to 250ish) even though I doubt everything else is that high.
I'd say keep taping it off until you get scared or it overheats 
Also, I tested with cardboard and then ended up using some of this, painted black:
http://www.homedepot.com/p/4-ft-x-8-ft-White-090-FRP-Wall-Board-MFTF12IXA480009600/100389836
kind of a pain to cut, but we had extra lying around and I did the grille block as well as a small belly pan with it.
I just suggested 200 degrees as a safety cushion. For the heavy traffic or those extra hot days.
Well, made it to work. It did heat up sitting at he one light for 1 min or so, no cooling fan. It did cool back down but it took longer. I figure putting in 2 3" holes on the grille will keep it cooler at the lights just enough.
no cooling fan?
Without cooling fans, the size of your grill opening will have minimal effect on cooling. No airflow is no airflow and it will get hotter.
You are trying to create adequate airflow through the radiator. You can block off everything on the front and have the airflow pulled up from under the car in front of the radiator by installing a small deflector under the radiator at a lower height that the front deflector under the bumper. Many newer cars and possibly even your truck will have one of these installed from the factory!!
Just remember that there must be a pressure differential between the two sides of the radiator. Too little differential and you get hot...too much differential and you get additional drag.
I worked with a bunch of bright college kids that exposed me to many aspects of aerodynamics that are kinda neat!
I would suggest a cooling fan for times when you have no airflow due to movement of the truck. But knowing the areas that will have a positive and negative pressure is kinda important too.
Bruce
to save gas.. I recommend an electric fan
It's only a 4 cylinder, but I haven't seen any difference in engine temps between the stock nose and the new nose. You really need a fan of some kind. Overheating is not a worry when you're moving, it will happen sitting still.
mad_machine wrote: no cooling fan?
Fan clutch broke, replaced it, lost 2-3 mpgs, removed it, and haven't put anything back on.
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