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The expansion of polytetrafluoroethylene (PTFE, a synthetic polymer, better known by its Chemours brand Teflon) hose products to larger sizes is still a trend. This opens the door for companies such as Fragola Performance Systems to provide reliable piping options for exposure to the extreme fluid and piping pressures used on traction belts today.
Compared with traditional rubber or synthetic rubber hoses, there are big differences between PTFE hoses, especially for fuels that are known to cause problems, such as E85 and other competition fuels.
"I have not found a suitable rubber for these fuel applications. I have tested several different brands and they are not durable at all," said Fragola's Blind McClellan.
We reprinted the fuel system layout in the FAST EFI installation manual. The length of each fitting and hose is recorded on the form to ensure that our order for Fragola's hose and fittings is correct. If you do not regularly deal with AN accessories, there is a convenient size chart in the Fragola catalog, which allows you to carefully check the size of your accessories easily and accurately.
"PTFE hose products will not be degraded by corrosive fuels such as methanol, ethanol, E85, and nitromethane. Many racing drivers also believe that PTFE hoses are used for oxygenated fuels and exotic racing diesel blends," McClellan continued. "Rubber/synthetic rubber products will harden, crack and leak in a short time. It will also degrade as rubber particles enter your fuel pump, carburetor, injector, etc."
We are using Fragola series 6000 PTFE products to connect to the FAST EZ EFI 2.0 system. The FAST EFI system contains an E85 fuel program, where the recirculation fuel system is an opportunity to try fuel with Project Rover, which is a 10-second Camaro application.
PTFE hoses are not as easy to bend as other hoses, mainly because of the lining of PTFE hoses. The bending radius of this -8AN PTFE hose is 5.25 inches, as described in its technical catalog. We firmly install the hose connector on the relevant installation point and bend it as gently as possible, marking the length of the hose for cutting.
"About five years ago, the PTFE hose product line began to expand," McClellan said. "Hose and related accessories began to grow with the choice of larger sizes. Now, it is far beyond the -2 and -3AN sizes that have proven to be used for flexible brakes in the past few decades. Today, we offer diameters from 1/8 Inch (-2AN) to 3/4 inch (-12AN) PTFE braided hose and related accessories. Fragola fittings are specially coated to be durable under harsh conditions, just like PTFE wire."
Teflon hoses are also suitable for racing oil, brake fluid and coolant applications. Its durability under extreme burst pressure makes it suitable for dry sump oiling systems for severe pressure applications such as Top Fuel and Pro Modifieds. For example, the -8AN series 6000 hose from Fragola can withstand a working pressure of 2,000 psi and a burst pressure rating of 8,000 psi. This pressure resistance also makes it a flexible pipeline choice for nitrous oxide systems.
If you do some research on PTFE hoses, in general, you will notice that the product is available in "conductive" and "non-conductive" versions.
"We only sell the conductive version of the hose," McClellan said. "This allows fuel, oil, brake fluid, etc. to pass through it without generating static electricity. This extends the life of the PTFE hose in the racing car by eliminating the possibility of leakage due to damage caused by electrical charges."
When drawing PTFE pipes, you need to realize that the bending radius of solid PTFE hoses is more restricted than other hose types. We carefully arranged our system and considered the angled hose end fittings to avoid any extreme bending.
Our two major applications for PTFE hoses are for use with rare fuels, and then on the other end of the spectrum are high-pressure external tubing because of their high burst strength capabilities-Blind McClellan
We deliberately planned and ordered our PTFE hoses and accessories from Fragola. We are using -10AN pipes and accessories, from the fuel tank to the in-line fuel pump, the -8AN system to the FAST fuel flow sensor and EFI throttle body, and back to the fuel pressure regulator. We used Fragola EZ Street hoses and hose ends to connect the regulator's low pressure circuit back to the tank.
Fragola PTFE hose consists of a braided stainless steel sleeve covered by a plastic sheath and an inner liner made of PTFE material. A small aluminum "olive" ferrule is sandwiched between the PTFE liner and the stainless steel braid. The hose end of the AN connector and the hose socket are connected together around an olive thread.
Fragola's EZ Street hose product is a low-permeability fuel hose that looks similar to standard rubber fuel hoses, but is not affected by gasoline, methanol, ethanol, and extreme diesel mixtures. EZ Street hose uses an aramid reinforced braid inside the hose to prevent collapse when handling pressures up to 175 psi.
We used a large hose cutter designed to cut stainless steel braids. This is by far the cleanest method compared to a hacksaw or grinder cutting wheel, which leaves debris that must be cleaned thoroughly. After cutting the hose to a certain length, the outer black sheath is cut off by 3/8 inch, exposing the stainless steel braid. Use a pick to carefully process the stainless steel braid from the lining to the tip of the plastic cap.
After the package arrived, the assembly of our fuel system was relatively simple. It only takes a few extra steps to install the AN hose end to your standard braided steel hose. Cutting the hose to a certain length is similar to a standard braided hose. Use electrical or duct tape at the cutting point to prevent the braided stainless steel from fraying.
There are many ways to cut the hose correctly to a certain length. A fine-tooth hacksaw or abrasive cutting wheel can be used. Care must be taken to ensure that the thread is very clean after each cut. We prefer to use a specific hose cutter for use with braided steel wire. Compared with the PTFE material dust and stainless steel fragments left by other methods, this tool can leave a clean incision.
Push the PTFE liner carefully into the olive until it reaches the shoulder stop. This results in a braided steel part around the outside of the olive. The two external fittings are pushed together and threaded. It is essential to use light oil lubrication in each step of the assembly process.
Compared with the typical two parts of the standard-AN hose end, the PTFE hose joint is divided into three parts. Before cutting the wire to a certain length, the "socket" slides over the wire. There is also an AN Fitting hose end that will be installed in the hose and threaded to the socket. The third component is called the ferrule or "olive", and in the case of the PTFE hose end, it is installed between two standard hose end assemblies.
One of the key additions in the assembly step is to remove some of the black coverings on the outer surface of the hose. Fragola recommends cutting off 1/4 to 3/8 inches from the end. We have found that it is best to cut the smaller diameter hose by 1/4 inch and the larger -10AN tubing by 3/8 inch. We use a heavy utility knife to cut the circumference of the sheath and expose the stainless steel braid.
It takes a little muscle to screw the olive/joint assembly together. We recommend using high-quality steel wrenches instead of aluminum AN wrenches to avoid rounding the accessories. The tape on the hose shows whether the hose was pushed out during the assembly process. To avoid leakage, the hose should not retract more than 1/16 inch. Throughout the assembly process, we gently inserted the round chisel into the hose to keep the PTFE liner round.
In our case, the black sheath was cut to reveal the braided stainless steel. Using a small screwdriver or pick, we carefully process the stainless steel braid outwards without damaging the PTFE lining. During cutting or processing stainless steel braids, the lining may become out of round. We carefully use a round chisel to gently push into the lining to keep it round.
The "olive" is now installed above the PTFE thread and below the expanded braid. Then push the end of the hose into the inside of the PTFE layer, and then screw the socket and fitting part together.
"Some customers tried to cut the braided steel part from the PTFE liner to make the olive easier to install," McClellan said. "They will go to screw the socket at the end of the hose, you can literally pull the hose out and leak there. So we make sure the stainless steel goes all the way to the top of the olive."
We use Fragola's EZ Street hose for the low pressure return line of the EFI fuel system. Although it may look like a typical fuel line from the outside, it is impermeable to extreme fuels such as ethanol and methanol.
Continuous lubrication during assembly makes the whole process easier. Fragola does not approve the use of "WD-40" penetrating oil as a lubricant. We use light-duty assembly oils found in local auto parts stores for lubrication in all assembly steps.
Adding the oil return hose and accessories is a simple step in the installation process. Fragola EZ Street hose is a nitrile tube that uses an internal reinforced braid to make it durable under pressures up to 175 psi.
The high-pressure side of the -8AN Fragola 6000 series pipeline passes through the fuel flow sensor, through the throttle body, and then returns to the pressure regulator. The Fragola -6AN EZ Street hose acts as a tank return exit regulator. We carefully clamp the PTFE hose in any loose place to prevent vibration that may cause liner leakage.
We have obtained some preventive advice on the nature of PTFE tubing.
"Don't let the line shake or vibrate," McClellan explained. "In a racing environment where a longer hose cannot be moved, please fasten it firmly. If the inner lining is allowed to move in the racing environment, the inner lining may leak over time. In your racing car It’s really fixed at many points."
Our new fuel system is a typical representative of durable racing pipelines. The PTFE option is a solution to the degradation problem caused by extreme fluids and keeps racing pipes trouble-free in a high-pressure environment.
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