Take It To The Mat

Holley’s New HydraMat May Be The Solution

Words: Jeff Smith; Photos: Holley Performance & Jeff Smith

Every once in a great while, a product comes along that you instantly know is going to not only solve a lot of problems but also save money, time, and hassle. This latest contribution to the betterment of high performance mankind is Holley’s HydraMat. This simple device looks like a flat, oversized filter, but it really is an incredibly intelligent idea that solves an increasingly common fuel delivery problem. If you are considering installing EFI in an older car or experiencing fuel delivery issues with your EFI package, this story and Holley’s HydraMat will make your life easier.

The essential requirement for any kind of EFI fuel delivery system is a constant, high pressure fuel feed to the injectors. If the fuel pump pickup is uncovered even for an instant, the pressure will instantly drop. With a common, ‘60s style fuel pump inlet in the tank, fuel slosh from acceleration forces (fore-aft or lateral) will uncover the pickup. When this happens to an EFI system, the pressure instantly drops causing the engine to stumble or die.

With production EFI, the car companies solved this fuel slosh issue by designing complicated plastic reservoir buckets that encapsulate a high pressure pump, continuously submerged in fuel. This works very well, but these tall, OEM buckets are difficult to retro-fit to shallow muscle car fuel tanks. The aftermarket has come up with many excellent ways to equip muscle car fuel tanks with reservoirs and related solutions. Companies like Tanks, Inc. Rick’s Tanks, and others have created specialty tanks that locate an electric pump mounted in a low area of the tank. Aeromotive has come up with a universal conversion kit called the Phantom system that works extremely well. All of these solutions perform well. The only issue is that they can be somewhat expensive and in the Aeromotive case, requires some minor tank fabrication work.

Holley’s HydraMat has created an interesting alternative to these ideas with a simple product that you can think of like a bionic sponge. The patented HydraMat material is a woven nylon media that employs a combination of surface tension and fluid wicking techniques to create the unique ability to consistently pull fuel even when only a fraction of the mat is in contact with fuel. The rest of the cells exposed to air close off, allowing the pump to continue to draw fuel from that portion of the mat. If you want to experience this first-hand – try punching small holes into a straw above the liquid line and then attempt to drink through that straw. This doesn’t work very well as you get almost as much air as liquid. The Holley HydraMat works like a properly functioning straw by eliminating the air by closing off any cells not immersed in fuel. We’ve witnessed a demonstration where the mat was placed in a large plastic box. Even with only a small amount of liquid in the tank, as long as any portion of the mat was exposed to liquid, it continued to be pumped out of the tank.

Holley recommends using the largest HydraMat that will fit inside the fuel tank. Multiple HydraMats can be used in one tank by employing a Y connector between the two inlets. Also, HydraMats can be employed in two separate fuel tanks without difficulty. Some have expressed concerns over longevity, but Holley engineers predict that the mat will perform for six years or 60,000 miles depending upon application. Dirty environs like off-road racing will reduce the lifespan because the HydraMat also doubles as a pre-filter equivalent to a 15-micron element, which means no other inlet filter should be used with the HydraMat. As an added plus, the HydraMat is fully compatible with gasoline, E85, ethanol, and methanol but is not recommended for diesel fuel.

The mat is available in multiple configurations and sizes that are listed at the end of this story. Each HydraMat is fitted with either a 3/8- or ½-inch NPT female fitting to which can be adapted either an AN hose end or a hose barb to connect to the inlet side of the pump. The mat is also pliable enough that it can be easily rolled or folded to fit inside even a small ‘60s stock GM sending unit hole in a gas tank. Holley also considered that the HydraMat needs to adhere to the tank so it doesn’t move with the fuel so engineers came up with small magnets available in a separate kit that feature pins that connect to corner holes created in the HydraMat. For plastic or poly fuel cells, Holley also offers either a sandwich magnet kit that uses one magnet on the outside and another on the inside of the tank, or a Click-Bond kit that glues fasteners to the inside bottom of the tank.

One of the most popular applications for the HydraMat will probably be muscle car enthusiasts who plan to convert to EFI. Because most EFI systems require a separate return, we found a great option for many different muscle cars offered by McRobb Performance. This unit features ½-inch fuel pickup and return lines built into a robust aluminum flange. The pickup also mounts a stock style sending unit. This makes it easy to connect the inlet to the HydraMat. All you have to do is to remove your original sending unit, fold up the HydraMat and place it on the bottom of the fuel tank with the magnets. Then connect the sending unit to the HydraMat with a flexible hose and zip-tie the return line to point it at the HydraMat. Connect the inlet of the McRobb sending unit to the inlet of an external pump and the installation is complete. The HydraMat will turn that stock gas tank into the equivalent of a reservoir style tank.

This is a great place to point out a few details that will help any electric fuel delivery system work more efficiently. The ideal position for an electric EFI fuel pump is to mount it inside the tank where it can be fully submerged in fuel. This not only drastically improves pump cooling, but a standing column of fuel that is higher than the inlet side of the pump uses the weight of that column of fuel to create head pressure that more efficiently feeds the inlet side of the pump. All of these points combine to create the ideal in-tank pump location.

If an internal pump is not possible, the next best option is to locate the fuel pump as close to the inlet and as low as is safely possible. This position helps siphon feed the inlet side of the pump as long as the hose length between the HydraMat and the inlet side of the pump as short as possible. The worst place to mount a fuel pump would be somewhere in the trunk where the pump must pull fuel vertically. This creates a low pressure situation that is a perfect breeding ground for vapor lock.

To illustrate an installation, we’re using an early Chevelle fuel tank. You can fabricate your own inlet/return sending unit or purchase one of the McRobb sending units. We chose the narrowest 15 x 3-inch HydraMat (PN 16105) to ensure it would fit through the stock sending unit hole in the stock fuel tank. Next, we also mounted a Holley magnet set to opposite ends of the HydraMat to position the mat to the tank floor. Finally, this mat was equipped with a 3/8-inch hose barb which we wrangled over the larger ½-inch tube in the McRobb unit.

The key is to make all these connections before installing the HydraMat as there is no room to do this once the mat is inside the tank. We placed duct tape around the inside diameter of the sending unit hole to prevent damage to the HydraMat and then rolled the mat until it fit inside the sending unit hole. With some effort, we squeezed the HydraMat into the tank. We used a long, blunt screwdriver to position it and then replaced the sending unit in the tank.

Frankly, this is a lot more difficult than it sounds only because the sending unit access hole is really small on ‘60s Chevrolets. A much easier plan would be to invest in a more modern aftermarket fuel tank like those from Rick’s or Tanks, Inc., or any of the other tank companies. These tanks offer much larger fuel pump openings and could also accommodate an in-tank pump that would position it in its ideal location while still benefitting from the HydraMat’s advantages. The good news is that there are plenty of choices.

If the simplest of solutions are among the best, then the HydraMat will quickly become the go-to idea for retrofitting EFI fuel injection into literally any car.

Parts List

Description PN Source Price
HydraMat 15×15 cross, 2.5 leg width 16-100 Summit Racing $299.95
HydraMat 15×8 cross, 2.5-inch leg width 16-101 Summit Racing 199.95
HydraMat 15×8 cross, 2.5-inch leg width 16-102 Summit Racing 199.95
HydraMat, 8×8 cross 16-103 Summit Racing 189.95
HydraMat, 11×11 cross 16-104 Summit Racing 229.95
HydraMat, 15×3 rectangle 16-105 Summit Racing 149.95
HydraMat 11×11 square 16-106 Summit Racing 249.95
HydraMat 15×15 square 16-107 Summit Racing 319.95
HydraMat 8×3 rectangle 16-108 Summit Racing 139.95
Magnet kit, 4-40 connectors 16-203 Summit Racing 21.95
Magnet kit, 6-32 connectors 16-204 Summit Racing 23.95
Magnet kit, backing magnets for poly tank 16-205 Summit Racing 26.95
Mount kit, Click Bond for metal tanks 16-201 Summit Racing 26.95
Mount kit, Click Bond for poly tanks 16-202 Summit Racing 39.95
Holley 2-wire bulkhead kit 26-152 Summit Racing 89.95
McRobb Perf. ½” inlet sending unit 1076 McRobb Perf. 149.00

Sources

Holley Performance Products
holley.com

McRobb Performance Products
robbmcperformance.com

About Jeff Smith

A clue into how long Jeff Smith has been writing technical automotive stories might be his following of second generation readers. Writing continuously for nearly 40 years, his focus with Xceleration covers all things technical. His collection of cars includes a bevy of Chevelles and El Caminos. When not writing about cars, he likes to spend time with his wife Valerye, children Amber and Graham, and granddaughter Celeste.