A radiator door for the grill block
 

As ambient temperatures rise as we move closer to summer, I've had to open up more area on my grill block to increase the air flow to keep the engine temps from rising above normal. At 85F while travelling at 65MPH on rolling terrain, I need a total grill opening of 4" X 3" to keep my engine at a normal temp. I figure that by late June I should have a good idea exactly how much grill area I need to operate normally under the hottest conditions I can get around here. But the main problem from the standpoint of drag reduction is that for most of the time I am driving, I don't need that maximal grill area and that extra grill area is just unnecessary MPG-wasting drag. I could go and tape over this unneeded grill area in the winter or when night driving, but this is a fairly cumbersome and crude method for adjusting the radiator's intake/drag to the current engine cooling requirements.

But we can steal another idea from the aircraft industry to solve this problem. Designers of piston powered aircraft have long known that increased cooling equals increased drag and install cowl flaps (for air cooled engines) or radiator doors (for liquid cooled engines), so the pilot can reduce cooling-related drag to the minimum level needed to maintain proper engine temperature. So once I know how large a grill opening that I need, I plan to design a replacement grill block for my car with a cable-actuated radiator door built into it so I can adjust the grill air intake from my seat while driving. Of course, the ultimate version of this would be an electronic controller that monitors the engine temps and automatically adjusts the grill air intake to keep it from rising above normal.

How about another hood
 

How about another hood release cable or something like that, pulls it back but it's on a spring so it can snap back shut!

I plan on completely
 

I plan on completely blocking off the front and mounting some aftermarket radiator somewhere else. I've considered a water/water heat exchanger and a water/oil heat exchanger, both plummed to a smaller radiator mounted in the rear somewhere.

Ohh I should mention, the
 

Ohh I should mention, the reasons I plan to do this are:

1. Aerodynamics

2. Thermal Efficiency - No reason to have a cooling system that could handle 300hp when I'm only making 92. Less water to haul around and to heat up means less time spent warming up and a lower curb weight.

Re: Ohh I should mention, the
 

Just curious Bunger. What are the stock 88-91 Civic radiators rated for? They're pretty freaking big, and I'm wondering if I just should find a smaller one to clear up some space.

Makes me wish I would have gotten that radiator out of the 93 civic I saw months ago in the junkyard.

Re: Ohh I should mention, the
 

I'm not sure what they are rated for, but I had a HUGE FMIC infront of my stock Si radiator on my turbo setup, and it was able to cool about 400HP without issue. I was running water wetter, stock cap and stock thermostat. I didn't run it hard in the summer though, so I'm not 100% sure if it would have held up under 105 degree ambeint temps.

Those 1/2 size radiators out of the EG civics are a good deal lighter, but also taller, so don't plan on just tossing it in there. Considering a single core one of those is able to cool 250HP (in my experience)... imagine how small of a dual core unit you could run only cooling 100HP!!!

Another thing we should consider is really how often are we asking 100% out of our motors??? When you aren't burning much fuel, you're not producing too much heat. You really put your cooling system to the test at road race events, which is where I can back up my claims as to what radiators are good for what HP.

Re: Ohh I should mention, the
 

Maybe I should look for a radiator out of a Metro or something like that. These huge radiators not only take up a lot of space, but they are a LOT heavier (as you mentioned).

Radiators are only $10 at my junkyard, so hopefully I'll get lucky soon.

Re: Ohh I should mention, the
 

I've been looking for 500cc (or around there) motorcycle radiators. I just can't decide if I'm going to do my accusump/remote oil filer/oil-water heat exchanger/water-coolant heat exchanger idea or not. It would be nice to pre-oil the engine. I've even considered cooling the engine through the heater lines, just need to figure out if that will have a negative effect on coolant flow overall and how to engineer a thermostat of sorts.

I just like to complicate things =)

maybe you already have a
 

maybe you already have a thread about this...
but size and shape of the radiator hole i would think would make a difference...
as in tall & skinny only cooling a few runners
and wide/narrow cooling a little of them all

Re: maybe you already have a
 

My grille block opening is at least 6" from the radiator surface. The opening is meant to allow air flow. The air can flow to a much larger area of the radiator compared to the area of the opening. If the grille block was laid against the radiator, then your statement would be more accurate.