Idea: spray bar instead of rad fan?

[pgfpro]

Originally Posted by meanjoe75fan

Well, sorry to say that the experiment was a failure... The spray bar only provided modest cooling, and--for practical use--would require a resevoir the size of the gas tank! This really surprised me, considering how much better water is than air at quenching metal, for instance.

Oh, well...can always find a use for the pump, and it won't be too much work putting the shroud back on. I think my next move is to close off from the front bumper to the rad bottom, to get the air to go through, rather than around.

Just wanted to report the bad news, in case anyone else was considering travelling the same road...don't bother.

Very much appreciated on all your work. Tested ideas, success or fail, are all good data.

Without data you have no direction. Thanks again for all your efforts!!!

[RH77]

I just thought of something that might help...

Back in my crazy horsepower days, I drove a Mitsubishi Evo-8, Turbo-Intercooled (The Subaru STI may have the same contraption I'm describing...)

It had a reservoir, pump, lines, and spray nozzles activated by a rocker switch on the console, to spray water on the intercooler. The idea was to get a volume of cooler air so the ECU would allow more power through the A/F ratio when at full-throttle.

Instead of using water, someone on a related forum had the idea that Isopropyl Alcohol is readily available from pharmacies in quantity, did not damage the lines, pump, or intercooler, and provided much better evaporative cooling. I would buy the highest % Isopropanol in for about 99-cents per quart and kept that in the reservoir tank.

The cooling effect was significant and resulted in the goal of better A/F ratios with more power at full boost. It also did not freeze in the Winter, so it cleaned the fins if they became clogged with road grime or snow. Since the pump whole setup was essentially a big windshield-washer spray system, it would tolerate the washer fluid and ultimately the alcohol.

You may give it a "shot" to see if it helps.

Use caution as it may be flammable if highly concentrated and/or used near open flame

RH77

[Christ]

CO2 in a cloud bar would probably work better than water. Added benefit is that you can use the CO2 for more than one thing in a circuit, so you can put a bulb in the intake tract that it will run through, do something else with it, and eventually exhaust it to atmosphere through the radiator, which will cool it more effectively than water alone.

Just an idea in case anyone wanted to pursue this further. Also, one might try replacing the thermo-switch for the fans with a lower-temp one, so that the spray happens sooner... it might help to keep temps down before they really come up.

[aspera]

Snow Performance: Home

Subaru guy here. Subarus have had a few different intercooler spray systems from the factory. The one that I thought was the best was the one with a big HDPE plastic tank bolted behind the rear seats in the trunk. It took up very little usable space, held lots of fluid, and kept the weight off of the nose of the car.

I think what the original poster should try is painting the radiator black (if it isn't already black from the factory.)

If he's still got lots of energy and money...then he should step up to Lexus LF-A dual rear radiators. THAT is how it should be done on a car. The 'ghetto' way to do it would be to mount your radiator in the trunk and seal off the whole nose.

Then the problem becomes "How do I get air through the radiator?" You need a way IN and a way OUT. A way OUT is easy; just cut a hole in the rear. The bumper cover is plastic. The trunk is already on hinges. There are a million ways to do that part. The tricky part is how to get the air IN. You could build a huge NACA inlet in the roof ($$$) or make use of the trunk lid or rear wheel wells. My favorite idea would be to build ducts to both rear windows. That way you could open or close the rear windows with your fingertips, thereby feeding or blocking the rear mounted radiator intakes.

Do you think that two NACA ducts behind rear side window glass (in 'standby' mode) would look a bit odd to other cars on the road?

[Frank Lee]

Excess heat and trapped underhood ozone kills plastic and rubber parts prematurely. So the engine compartment needs ventilation no matter where the radiator sits. Since the compartment needs ventilation anyway, why make a remote radiator set-up?

[aspera]

I just meant sealing off the nose, not sealing the engine bay airtight. That would be nearly impossible anyway. Even with all the gaps sealed and a full belly pan, there would still be plenty of airflow. There'd be less heat to deal with as well, since the radiator(s) wouldn't be there anymore.

In most cases a person converting to rear-mounted radiators would still have a giant hole underneath the engine. Plenty of ventilation. Check out European Rallycross cars to see how it would be done.

In a car designed from the ground up to use rear-mounted radiators, like the Lexus LF-A, there are additional aerodynamic benefits. Not only did they get rid of the big parachute-like hole in the nose and clean up the air going under the car, but they got rid of the big rectangular radiator (and radiator support) in the nose. That allows the nose to be shaped for low drag and high downforce without concern for radiator packaging.

[Christ]

Now you want me to redesign my entire car... Sheesh.

[aspera]

Well, you ARE Christ.

[Christ]

Ok, well, I was half serious in that post... and half mocking.

The serious part doesn't see much of a net gain by moving the cooling system to the rear of the vehicle, because there will still be a good bit of turbulence, and you'll be adding weight for the lines, extra fluid, more drag on the engine because the water pump is now moving a larger volume of fluid, etc.

Weighing the good against the bad, I can't see a reason not to try it, though, especially if you can vent your cooling airflow into the wake area, where it might act like a virtual boat tail, filling the area of negative pressure behind the car.

You could also take your cooling flow from the wheel wells, as you suggested, which means that undercar flow could be directed toward the wheel wells while still maintaining a fairly clean profile along the sides and top of the vehicle.

I'd like to see what Aerohead has to say to this effect, though. He's got a few more miles of experience with aero and fluid dynamics than myself, and I'm going on intuition alone with a lot of unanswered variables.

[Frank Lee]

Not saying rear cooling is without merit- look at GM Precept and the low Cd. Gotta weigh pros-n-cons though.