My water cooling system. (Photo's!)

[Wulfthang]

A few weeks back, I posted about wanting to use a tube type oil cooler as a supplemental radiator on my rail. My engine never runs hot when I'm off road running in Arroyos or climbing old mining trails but the temperature does start to climb some when I'm running it down the interstate at 80 + mph. It has never overheated but it does get pretty warm.

The radiator is less than a year old and is full sized with four cores. It has a shroud (more on that later) with two twelve inch fans controlled by a thermostat. It also has a fourteen inch fan mounted under the radiator for extra cooling if needed. (110 degrees is standard for Tucson weather and it's hit 115 several times so far this year)

It has a huge 14 x 14 inch plate style oil cooler with it's own thermostat controlled fan.

The oil cooler also has a "ram air cooling system".

That started life as an experiment. I had full intentions to make it "official" and nice looking if it worked but it worked so well, I just left it as is. It catches air flowing across the roof and directs it down to blow thru the oil cooler. Yeah yeah, I'll make it pretty one day!

I got the "tube cooler" installed and tested and it works pretty good. You can feel the heat coming off of it. Truthfully, I have no idea how much extra cooling it does but it has to be some just because of the way it's designed with fins on the inside and the outside.

Besides, it looks cool. (No pun intended!) Other off roaders ask "WTF is that thing"? I tell them with a straight face "It's a Turbulator Thermogulation device of course. Duh"!

I spent a lot of time driving around with little ribbons tied all over the place to check the airflow in different places. My Wife drove alongside while I talked to her on the radio: What's the group on the roof doing? How about the ones behind the radiator? Etc. Etc. I discovered something interesting. The windshield was stealing my air!

Air flow comes at the car directly from the front. The radiator sits "on her back" as high as I could put it and still keep it out of the bushes and trees for as much as air flow thru as possible. The windshield was directing the air flow upwards and over the radiator. Yeah, a lot of it was gong thru the radiator but a lot of it was going over the top too. I wanted more!

So I built the air scoop. It catches a lot of the air that would normally be lowing upwards and redirects it backwards towards the radiator. More importantly, it stops a lot of the upwards force allowing more air to flow directly at the radiator.

Yeah, the hood scoop on the roof does actually work. It keeps a nice breeze blowing on my head and shoulders even at low speeds in the "Outback".

The flapping ribbons in front of the radiator flapped a lot more after I built it. Plus, it serves as a sun shade since it's made from molded tinted Acrylic.

All together, my engine runs as cool as the thermostat while off road and gets a little warm going fast on the interstate on hot Tucson days.

More about the radiator shroud:
I used to run without a shroud, just two big fans on the top and more on the back. It used to run cooler at high speed and get warm on the trails. Then I installed the shroud and now the exact opposite happens: It gets warm at high speed and cool at low speed. The reason is because of the Venturi Effect. At higher speeds, the air flow over the sharp edge of the top of the radiator was sucking air up thru it, not so much at lower speeds. Since it's primarily for off road, I'll leave the shroud on.

Overall, I'm happy with the results.

[L5wolvesf]

driving around with little ribbons tied all over the place to check the airflow a.k.a. "tuft testing". I believer Mark Donahue came up with that but could have been before him.

Profile / side video of the car while running would be very useful for this. Then you can study it better.

The getting hotter while at highway speeds suggests a change in the airflow at those speeds. Air does "funny" things that people don't always expect it to do.
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[Wulfthang]

The first time I saw the little ribbons to "see" the sir flow, was in Germany on gliders. They were tied on the nose and the leading edges of the wings so you could actually see when it was getting ready to stall. That would have been in the very early 70's but it was an old idea even then.

[oprn]

Thanks for the informative post!

As you just learned, sticking random cooling system bits up in the air doesn't necessarily get the job done. The aircraft people have known that for a hundred years now. Airflow is a science, and tuft testing goes a WAY back. There are other tools in that toolbox too. In an open car you can physically feel the shape of the wind with your hands at speed. A thermometer with quick response time will let you track where the heat is going too. Temperature also can be felt by hand to some extent.

A couple years back I was concerned about the cooling air flow for my Manx copy as I was contemplating an engine change from upright to radial off the crank fan. Tuft testing was not so informative because I needed to know what was happening further out from the body of the car. I learned a lot!

Another thing that is very informative is an oil leak. You will be amazed at where the oil droplets show up! I don't really recommend this test though, it's quite messy!
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[PhillipM]

A lot of people overlook how much the windscreen deflects air clear of the roof - roof scoops or cooling on a rail will barely ever work because of it, it's why our scoop cranks all the way forward to pickup the high pressure air from the windscreen, similar to your deflector:

With a scoop on the roof itself the car would start to overheat when running over about 70-80mph on trails - the airflow just cleared the scoop and it was sat in a low pressure zone.

[Wulfthang]

[PhillipM]

Yeah, bit of a rebuild, but used to run the car like that all the time on the old setup, works well.
Plus taking the boundary layer off there makes air reattach much closer to the bend on the actual roof above the scoop - in fact there's a secondary scoop in the middle up there that takes cooling air for the intercooler as well now, it basically has a roof scoop for it's roof scoop

But the upper scoop wouldn't work without the lower pulling the turbulent high pressure layer off the windscreen first.

You'll find the radiators work much better with an airbox in front to let the airflow slow down and spread across the whole face too, if you can't do that set the fans off a couple of inches with a shroud instead - should help too, tend to find a 10-15% bump in cooling power with the same setup just from those.
'Ram' air only works if you can draw enough air in and slow it down and spread it out to build pressure.

But yes, amazing how many cars I see with barely functioning roof scoops because they didn't do that bit of research like you did.