Driving a race car usually means driving a car with no air conditioner, no heat insulation in the cockpit, and the windows removed. Obviously this can make for a very toasty operating environment. Radiant heat from the engine, exhaust, and even track surface can quickly add 20-30F to the ambient outside air temperature. Pair this with racing in the southern United States, and just sitting in the car can become a health risk. I’ve had a close call with serious heat exhaustion in the past, driving my M3 at Texas World Speedway when the on track temps were near 110F. I swore that when I had a purpose-built race car that it would have every driver cooling aid I could fit.
The most common and certainly the most effective of these is the cooling shirt. Most folks just refer to them as “cool shirts”, but that’s an actual brand, so I’ll try to avoid calling it that. These systems have been around for sometime and are fairly common to club-level racing in the hot regions. It’s a very simple system, essentially cold water is circulated around tubes sewn into the driver’s shirt. The cold water is held in a cooler mounted in the car and the water is circulated using a 12V pump.
The vast majority of the parts used in the commercially available systems are actually just off the shelf items that anyone can purchase on their own. For example, the pump is just a 12V boat bilge pump. The only piece I didn’t make myself was the shirt itself. Some folks have made their own by simply sewing a length of tube into a plain t-shirt, which certainly helps save even more money. I decided to pick up F.A.S.T. Alpha shirt, which also has moisture wicking properties.
Here’s the parts list of the items I purchased, their retail cost, and supplier.
| Qty | Item | Source | Total Cost |
| 1 | Weatherproof Low-Voltage DC Connector Kit, 2 Pole, 16-14 AWG 9171T32 |
McMaster-Carr | $7.71 |
| 2 |
Air and Water Quick-Disconnect Tube Coupling
Through-Wall Socket with Valve, 1/4 Coupling, for 3/8″ Tube ID 5012K79* |
McMaster-Carr | $39.66 |
| 2 | Air and Water Quick-Disconnect Tube Coupling Barbed Plug with Valve,1/4 Coupling, for 5/16″Tube ID 5012K712* |
McMaster-Carr | $14.68 |
| 2 |
Air and Water Quick-Disconnect Tube Coupling
Barbed Socket with Valve,1/4 Coupling, for 5/16″Tube ID 5012K672* |
McMaster-Carr | $18.60 |
| 1 | Masterkleer PVC Tubing 5/16″ Id 7/16″ Od, 1/16″ Wall Thickness, 25 Ft. Length 5233K59 |
McMaster-Carr | $7.25 |
| 1 | Single Pinch Stainless Steel Hose & Tube Clamp 13/32″ to 31/64″ Clamp Diameter Range, 9/32″Band Width 5435K28 – 25 pack |
McMaster-Carr | $4.97 |
| 1 | Durable Nylon Tight-Seal Barbed Tube Fitting Reducing Straight for 3/4″x 3/8″ Tube ID, White 5463K648 – 10 pack |
McMaster-Carr | $7.40 |
| 1 | Engel 13 Quart Dry Box Cooler UC 13 | Austin Kayak | $43.99 |
| 1 | 3/4″ Clear PVC Hose – 1ft | Lowes | $1.00 |
| 1 | 3/8″ Clear PVC Hose – 1ft | Lowes | $1.00 |
| 1 | 500-600 GPH 12v Bilge Pump | Wal-Mart | $19.99 |
| # | Tubing Neoprene Insulation and Cordura Cover | Hydation Tube Covers | TBD |
*Different cooling shirts use different style connectors. Continue reading for more info on which type you need.
You’ll also need a few supplies, such as JB Weld and silicone to seal the fittings, zip ties to secure the hoses, and a setup to mount the cooler in the car. But in total, the homemade cooling shirt cooler cost roughly $175 once shipping is figured in. A much better proposition than the off-the-shelf models go for, using the same (or better) components.
Pump Installation
To start with, let’s mount the pump in the cooler. This is pretty straightforward, as most of these 12V bilge pumps are meant to be mounted directly to the bottom of the hull. The cartridge type I purchased (from Wal-Mart’s boating section) comes apart for mounting. Three simple screws are all that holds it in place. I drilled pilot holes first, then squirted silicone sealant in and around the holes prior to securing the base-plate. Make sure you use a silicone that is rated for submersion (many aren’t.)
Also take care to orient your pump so that the outlet hose is pointed to where you want the fittings to be. If I did this again I would mount the pump slightly closer to center (left of where it is located in the picture above) so that the twist out pump could be more easily removed.
Plumbing the Cooler
Now you must drill holes for the fittings. Part 5012K79 listed above is essentially a bulkhead fitting and barb on one side and a quick disconnect fitting on the other. The wall of the cooler is slightly too thick to allow for installation of the retaining nut on this fitting, so I drilled the hole to be as tight fitting on the barb as possible. I then sealed around it with some JB Plastic Weld (the putty kind.)
One of these fittings is simply a return port, so it can be left as is. The other one (it doesn’t matter which one) will be connected to the pump. The outlet of the pump (fairly standard sizing) is 3/4″, so a reducer is needed to size the hose down. This is where part 5463K648 comes in. It reduces 3/4″ down to 3/8″. I went to Lowes for a foot of 3/4″ and 3/8″ clear PVC hose, which you can find in the plumbing aisle for pretty cheap.
The photos above show the nearly finished product, pretty simple isn’t it? The last remaining step of modifications needed to the cooler are running the power and ground to the pump. The pump I purchased came with a long lead (~3ft), so I didn’t need to extend it at all. Once again, drill as small of a hole as possible to feed the two wires through the cooler’s wall. I drilled my holes up high, as to avoid prolong submersion which may lead to leaks. The wires were sealed off with silicone. Note: I found that all the silicones had a difficult time adhering to the plastic of the cooler, I eventually coated all the holes with JB Weld Kwik Weld.
Update 20150722: I learned that the JB Kwik Weld does not like being submerged in water either. It stayed soft and easily peeled off with just a fingernail scrape. So I found some JB Marine Weld, designed to be used under water once cured. You can find this at Advanced Auto Parts stores. Again I’ve found that most adhesives and sealants have a tough time sticking to the plastic of the Engel cooler. I scuffed the area and cleaned it with alcohol. I’ll be sure to update if I find any issues with this product.
Once the wire was through the cooler wall, I secured it to the outside with a cable clamp riveted to the outer plastic skin (not all the way through.) To terminate the wires I used part 9171T32, which is a Weatherpack electrical connector. These connectors are fairly common, work well, and can be assembled with an inexpensive pair of crimpers. You certainly don’t want to permanently wire your cooler to the chassis, as it is much easier to simply take the cooler out for cleaning and filling.
Before I went much further I bench tested the cooler and my shirt by just hooking it up to a spare car battery and temporarily connecting the lines. It worked like a charm, even just pumping room temperature water (I had also let water sit in the cooler to insure there were no leaks.)
Water Tubing
With the cooler operating properly, it’s time to make the lines which will run to and from your cooling shirt. First let me note that different brand shirts use different quick disconnects. The F.A.S.T. brand shirts use the quick disconnects with the metal buttons, which is what I ordered and all the part numbers above are. The CoolShirt brand shirts use the disconnects with the plastic buttons. Make sure you know which type you have before ordering. McMaster-Carr offers both types of disconnects at roughly the same price. You can even make your own simple patch tube, should you have multiple driver’s with different shirt types.
Metal (F.A.S.T.) on left, Plastic (Coolshirt) on right
Decide where you want to place your cooler so that you can determine the length your hoses need to be. The most popular spots are the passenger seat area and the trunk. I placed mine in the spare tire well, as I like the option of being able to run a passenger seat. This should also balance out some of the weight loss effects of removing so many items from the rear of the car.
Once you have that figured out, you can run a tape measure or just temporarily run your uncut water hose to see just how much you need. Remember to leave a bit of slack at the driver’s end to allow for connecting/disconnecting the lines once buckled in. Satisfied with the length of hose and routing the hose would take, I then trimmed the 5/16″ ID PVC tube. Note: Coolshirt brand seems to use 1/4″ tube, while F.A.S.T. uses 5/16″ ID. Just make sure you match your connector barbs and hose size.
Tube Insulation
Before installing the quick disconnects on the tubing, you must install the insulation. At first I planned on using the generic dark gray foam rubber pipe insulation, which is available from McMaster-Carr for cheap. After trying it out, I decided I wanted a cleaner, more finished look, and something less bulky. Unfortunately it was impossible to find the supplier who provides the insulation for the store brand cooling shirt systems, seems you must purchase their $100+ hose to get it. That’s when I contacted Hydration Tube Covers to see what they could do. They were very helpful and had done drink system covers for race cars in the past.
Hydration Tube Covers was able to send me four sections of 4 foot neoprene covers, fitted perfectly to the 7/16″ OD of the tube. These were slid over the PVC tube by hand, working on in a slinky like fashion. Once both lines (supply & return) were covered, a protective Cordura wrap was placed over them using a Velcro seam. The end result is a well insulated and protected set of cold water tube that looks like a true race car part. These covers were custom sized, so price will vary according to your application, but I guarantee you will save a lot of money over the name brand cooling shirt offerings. Contact Brandon at HydrationTubeCovers.com for more details.
Update: HydrationTubeCovers.com has updated their website with a page dedicated to racing applications, check it out here: http://www.hydrationtubecovers.com/pages/race-car-air-and-hydration-insulation
Finally the tubes were terminated using the remaining quick disconnects with male ends on the cooler side and female ends on the shirt side. I used the crimp connectors (part #5435K28) to secure them in place. I wouldn’t recommend using screw clamps, as they can easily cut your hand when trying to connect or disconnect from the car.
So how well does it work? Extremely well, that’s how! I’ve used it at Barber Motorsports Park in May, Carolina Motorsports Park in June and July, and all I have to say is that sitting inside the race car on a blistering asphalt grid was just as comfortable as sitting inside an air conditioned car. The cooling effect is immediate, it almost feels as though cold water were pouring over you. Heck, after a session I didn’t want to get out of the car because I knew I would immediately be hot. The 13qt system was plenty for a sprint race format (~30 mins). I don’t know how much longer it would be good for, but you could always opt for the 19qt Engel dry box for enduros.
Mounting
What about mounting the cooler? Since this is going to be car specific, I left this until the end. As I mentioned previously, I mounted my cooler in the spare tire well. There are off-the-shelf mounting plates available from the well known companies that produce cooling shirt systems, but I wanted something tailored to my setup. I wanted the cooler mounted as close to the front of the spare tire well as possible, as I had to have space for my differential cooler and also reduce the polar moment of having extra weight out back.
I used some plain aluminum right angle stock, riveted to the floor on three sides of the cooler. I cut a slit on the left and right pieces to allow a ratchet strap to pass through, which was also riveted to the floor. To keep the cooler from tipping forward under hard braking I bent a piece of flat stock aluminum into a brace, which was also riveted to the spare tire well and a cushioning strip of silicone was added. A simple ratchet strap (the smallest I could find) is used to secure the entire cooler firmly to the floor.
Note: In the photo above and left, you’ll see that I originally used a cam-lock style strap to secure the cooler. While this strap was easy to tighten and release, it also wasn’t as secure as a ratchet style strap. I found that after a session on track, the cam strap would slightly loosen and the cooler could rock fore and aft. I changed to a ratchet strap, which has been problem free since.
Electrical Control
So what about electrically controlling the pump? The simplest solution is a plain single pole switch to turn it on or off. Some folks have asked about a speed control. First of all, these pumps are not designed for variable speed. Reducing the power will slow the pump, but it wouldn’t take much reduction before it simply stops spinning. You risk damaging the pump and you won’t really achieve the results you are after anyways. If you want to control the amount of cooling, the best method is a timer. A few of the cooling system manufacturers offer these under their own brand, when all they really are is live well aeration timers.
You can find these fairly easily from any fishing or boating supply store, online or brick and mortar. These are simple to wire into your system, with just a 12v supply, output, and ground. When set to minimum time, the pump will run near continuously for maximum cooling. There are several different types, some have set delays, some are infinitely variable. The type I purchased allows you to vary the delay (or off time) from 2 second to 5 minutes and anywhere in between.
I mounted the timer on my switch panel, inline with a standard on/off switch. This way I can find a setting that works well for the day, set it and forget it while using the on/off switch to simply cut it off when not needed.
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