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As the weather turns cooler I find myself looking for ways to combat the lower temps. One option mentioned is a radiator block, but does it have any merit? On the one hand it makes sense: The more heat you reject the less heat goes toward moving the car, so do whatever you can to contain the loss. But on the other hand I don't see why it would work. The thermostat shouldn't be opening at all until the engine is at its specified operating temperature, so it shouldn't really matter what you do with the radiator. Heat is only dissipated through the radiator when it should be. Unless the object is to block the entire grill to bring up the temp in the engine compartment?

Comments?

yes, it brings up the engine compartment temps. but is also lowers the amount of "cooling drag". if you can do it without damaging anything its a good trick. i do it on my insight. in fact, i will be putting it back in this week.

Yeah, I'm thinking of doing something on the top opening of the
Prius just for airflow's sake over the hood, since otherwise
that's a big gaping hole that traps the direct oncoming air.
All the relevant cooling flow really goes through the lower
hole anyways, especially the part of the radiator that deals
with the inverter. [That's probably more important than ICE
cooling in the winter..] And high on the priority list at this
point is a better warm-air collector for the back of the engine
than the hideous kludge I dropped in last year.
.
_H*

Story time:

Brick,, many years ago the wife and i bought a 91 Tracer brand new. The first winter we owned the car I had to put a rad. block in it. One morning we had a frezzing fog event with temps in the single degits with a north wind. Was wired! The short of the long of it was the car couldnt stay warm enough to heat the cabin and windshield. I had the wipers stick to the windsheild in mid-swipe and rip the blades off. If you pulled over and let the car warm back up the thermostat would open, the car would shudder as the cold water hit the hot block. Then the heater and defroster would have to start all over again. A peice of cardboard slid down between the rad and condensor fixed it untill the artic blast left us. It really took me by suprise in this part of the country.

As for the Civic. I have studied on areo mods for the front. Grill blocks and such. Just cant bring myself to ruining the looks of my new Civic with such a mod.

I have pulled the factory CAI off from the air box to the first joint then stuffed a rag in the remaining duct tube. This with the combination of the engine belly pan has kept my intake air temps higher. At 10 miles into my daily grind intake temps are 10f above ambient. 20 miles in 20f above ambient. 30+ miles in 30f above ambient, maybe even 40f above ambient. So by the time i park at work my SG is showing me 80f+ intake air temps when it 45 to 49f outside air temp.

When temps get down into the 30's for morning lows and lower. I will stick a small alum. flex hose in the air box and lay the other end near the CAT right off the head of the r-18. My test late last spring and early summer shoed me there was more than enough heat by the CAT for me to find hope of 70 to 90f intake temps when real chilly out.

We havent had a hard winter here in several years. If this is the year to have one. I will use the cardboard trick again. :)

Last year, I did
http://techno-fandom.org/~hobbit/cars/warmair/
which definitely made a difference in IAT but didn't seem
to actually make any steady-state improvement in some test
runs. But I still think it helped with warmup time, so
I'm going to try and do a better one this year that actually
hooks to the first cat shield and uses *it* sort of like
a big air scoop from the back of the engine.
.
_H*

In the 2001-2003 Prius there is room in front of the radiator to slide in about a 12 x 18 inch piece of cardboard. Above about 50 oF air temp, on ahigh-load uphill drive, this will get the ICE coolant temp up a bit high. Any cooler and it should be all good.

The newer Prius has more plastic bits that may make it hard to get cardboard in. People with those tend to put foam tubing on the outside air inlets.

DAS

So today I had some time, and got the new WAI in! This is a
somewhat more elegant pickup hose that ends just above the top
of the heat shield over the little exhaust header, with its own
little bracket held down by the heat shield bolts. A fairly
generous amount of warmed air comes leaking up through the narrow
slit at the top of the heat shield and hopefully I'm managing
to pick enough of it up when the throttle opens. A quick test
today had me running IAT about 30 degrees over ambient, which
I thought might do better given that it was about 60 degrees
outside, but we'll see as the weather gets colder.
.
_H*

Anyone in chicago want to help me set up my car with a radiator block and wai? I'm generaly too lazy to do it without someone holding my hand. :)

Anyone in chicago want to help me set up my car with a radiator block and wai? I'm generaly too lazy to do it without someone holding my hand. :)

haha tom i feel the exact same way :) I may just cardboard and use tape sooner or later, since i'm willing to cough 100 bucks to install my block heater. Just wondering which tape I can use that won't damage the car's paint.

I started out by progressively blocking off more and more of my radiator opening with clear packing tape until I found out what size radiator opening my car actually needed to keep from from overheating on the hottest summer day, then I made a permanent cover with Coroplast. When I get the time, I want to install a shutter with a control cable running into the cabin so I can adjust the opening on the fly. My car turned out only need a 4"x 4" opening in heat of the summer and no opening at temps below 80F.

If you want to invision how much drag your radiator is causing, imagine driving down the highway with 1/3 of your windshield missing and your side windows open so that the air blasting through the hole in your windshiled can exit through the side windows.

Benefits of a grill block:
Reduces drag by drastically cutting the amount of air whistling through your engine compartment and adding to the turbulent air flow under your car as it exits out the bottom of your engine compartment.

Allows your ICE to warm up quicker after starting.

Increases the temperature of the intake air feeding your ICE, decreasing the power output and fuel consumption of your ICE and allowing it to operate at wider throttle openings (less suction loss) for the same power output.

HMMMMMMMMmm can someone show me pics pics pics! I'm hoping a grille block can improve coasting ability as well! So wow never overheats as long outside temps is below 26 degrees C eh... holy crap man... I've been missing out!

basjoos do you use an engine block heater as well?

I'm going to get cardboard and clear tape right now! I'm guessing the cardboard has to fit perfectly in the holes of your front.

I don't use and engine block heater.

A pic of my grill block.

http://img.photobucket.com/albums/v417/MikeMariettaSC/80MPG%20Honda%20Civic/Civic7.jpg

ok some details about my grille block.

Ok on short trips (3 miles or less) its GREAT. I reach operating temp much faster (if I had to guesstimate by looking at the water temp, I'd say 20% decrease in warm up time since the savings is probably 50 militers of gas as opposed to full blown grille. So what does means is that by the time I get to my destination, my engine is all nice and toasty at its hottest temp.

But....

The first day of my commute work (8.5 miles) i pulled in with a 48 mpg segment, and I notice once the temps reach 90 degrees C, things will start going wacky. Sometimes when pulsing I'll see it rising towards 95C then as I FAS it spikes some more, yikes! At one point up to 96 and then as I bump start the temp drops down to 90 again... did the cooling system kick in? If so did the engine has to work harder to provide that extra cooling? Does gasoline cool down? SO if I idle in N would I cool my engine? Hmm.... these numbers were bouncing back and forth pretty rapidly via scangauge but the temp gauge needle remained the same throughout...

Now what bothers me is that is not the fact that the temp swings around... but when I FAS i can hear a fan going on! Must be the radiator fan, wow I never knew my car had one!?! I've heard it come on for the first time when FASING (since I think the fan only turns on if the A/C system is on). As I pulled in my driveway with the engine killed, I notice the fan turning and humming. Oh no if i'm going to save gas and have a fan running I might as well say good bye to my lead acid! Hm... I think its a little too hot for the grille block... so the engine has to work harder to shrug off the heat, so less FE benefits!!! WEll at least my engine is all nice and hot and the oil is probably cooking a bit... kill those deposits in my engine ;)


So I will cut a hole like basjoos did, wish me luck! When I see snow I'll full blown grille again.

no need for the hole! the magic is in the car's temperature control systems. ALl this time I've been putting the setting at COLD (lol avoid robbing heat from the engine, but now I have a grille block things are different) and since I'm warm when I'm in the car anyway, having a warm enviroment was a big bonus! Espically when the windows can remain crisp and clear while the thermostat is rising even more! So now putting the setting on HOT avoids me from turning on that pesky fan and now COLD TRIPS DON"T SCARE ME NO MORE!


cardboard for life i'll just get a raincoat for the board or something when the time comes.

Does the water (coolant) pump run all the time on all cars? Does it place more drag on the engine through the belts when the thermostat is open or closed?

I imagine that thoughtful blocking of the exterior grille could improve aerodynamics. Would simply blocking the radiator have any significant aerodynamic benefits or is it simply to raise engine compartment and air intake temperatures?

Is replacing the thermostat with a higher temperature alternative a safer way to decrease the radiator cooling, since radiator blocks will not deactivate if the engine coolant gets too hot? I doubt anyone would ever dream of replacing the thermostat with something to block the coolant flow =).

I imagine it varies between cars, but what is the coolant flow like between the engine block, thermostat, radiator, and heater? Does the thermostat limit coolant flow to the heater as well as the radiator?

I'm planning to try blocking the grilles of our 2006 Prius and 2002 Elantra for the first time this year, when the temps stay around freezing, December to March.

The water pump runs whenever the engine is running on most cars. Like most pumps, it works hardest and places the most load on the engine when it is actually pumping liquid when the thermostat is open. Under most operating conditions, the thermostat is open when the engine reaches its normal operating temperature. In most cars the thermostat limits flow to the heater core and well as the radiator.

A grill block improves mileage primarily through reducing aerodynamic drag by reducing the amount of air flowing through the radiator block, through the engine compartment, and reducing turbulence under the car when this air is exhausted out the bottom of the engine compartment. Secondarily it reduces the engine's fuel burn via its effects on increasing the intake air temp. Increasing the intake air temp reduces its density, reducing the amount of oxygen it is carrying into the engine. The engine controller reduces the amount of fuel that it adds to this reduced amount of oxygen, reducing the engine power, which means that you have to use more throttle (reduced suction losses) to get the same power output.

On most cars, the radiator's opening is sized for the most powerful engine option operating under the most difficult operating conditions (towing a trailer in summer in Death Valley), so most of the time only a fraction of the radiator's cooling capacity is needed (especially when hypermiling). On my car, I 've only needed a 4"x4" opening to keep is cool even at 100F or when climbing a steep hill at 90F. And when the temps are below 80F, I don't even need that opening. With aircraft, they have long known that cooling exacts a price in aerodynamic drag, and since reducing drag is paramount in increasing speed and reducing fuel burn rates with aircraft, they have devised cowl flaps and radiator doors to match the amount of cooling to the amount actually required by the engine.