Project Unfair Custom Fuel Tank - Super Chevy Magazine

Project Unfair Custom Fuel Tank Pressure Test

Editor’s note: This month’s article showcases the unique fuel system our Project Unfair Camaro will need to power a 1,400hp monster while still being street-friendly, serviceable, and reliable. The tank fabrication takes place in John Parsons’ small shop near Orlando, Florida. —Jim Campisano

With Project Unfair, the drivetrain system is being asked to perform in many different ways: street driving, road racing, autocross, standing-mile, and drag racing. Each type has a unique set of requirements for maximum performance and reliability. This month’s article will focus on how to supply the engine with fuel using the latest in fuel delivery components and electronic control systems.

Project Unfair Custom Fuel Tank Main Pieces

1. The tank consists of three main pieces. These were cut, broken, and punched by a local sheetmetal fabrication house. It was well worth the money to have these bent on a hydraulic brake.

1. The tank consists of three main pieces. These were cut, broken, and punched by a local

Project Unfair will cover the vast differences in operating environments that are needed in today’s high-horsepower, multi-use, pro-touring type cars—and then some. It will use very little fuel while cruising down the highway and idling but will need a very large amount of fuel when it comes time to make an 8-second quarter-mile pass or 200-plus-mph top-end run. It also needs to be able to perform well at lower fuel levels on a road or autocross course when the fuel sloshes from side to side.

On EFI cars, if the pump ever runs dry, the fuel pressure will fall and the engine will stop running. Under boost, the effects are much worse: Catastrophic engine damage can occur due to a lean condition. Keeping the engine supplied with enough fuel at all times is a must. Standard pump-on-a-stick or other aftermarket designs just won’t do for Unfair, nor will having it break down on the side of the road due to an overheated or vapor-locked fuel pump.

2. The pump insert, VaporWorx and GM retaining rings.
3. Notice how thick the VaporWorx rings are. That’s needed to keep welding distortion to a minimum.
3. Notice how thick the VaporWorx rings are. That’s needed to keep welding distortion to
4. Check out the perfect bend on the fuel pump insert. Most enthusiasts and even fabrication shops lack the specialized equipment to bend 0.125-inch aluminum that precisely.
4. Check out the perfect bend on the fuel pump insert. Most enthusiasts and even fabricat

After battling various fuel-related problems over the years, car owners John Parsons and Frank Serafine (owner of Prodigy Customs) turned to VaporWorx, a new company dedicated to solving difficult fuel delivery problems.

Project Unfair Custom Fuel Tank Walbro Venturi Pickups

5. The Walbro venturi pickups have a built-in filter, one-way check valve, and a locating boss. They are designed to be locked in place in tank corners and can provide fuel up to nearly the last drop.

5. The Walbro venturi pickups have a built-in filter, one-way check valve, and a locating

Borrowing the technology of today’s supercars, Unfair will be using dual Cadillac CTS-V fuel modules to do the pumping. The fuel module is an integrated fuel pump and surge reservoir. When fuel runs away from the module during hard cornering, the reservoir keeps the pumps submerged in fuel. A series of venturi pumps draw in fuel from the main tank to keep the reservoir full and overflowing with cool fuel. The modules are spring pre-loaded to the bottom of the tank so the venturi pumps can capture all of the available fuel in the main tank.

The supercharged engine in Unfair will also require a method to increase fuel pressure as boost rises. As manifold pressure increases, it pushes against the fuel injector outlet, reducing the amount of fuel coming out of the injector. The more boost from the supercharger, the harder the fuel system has to work to overcome manifold pressure to inject fuel into the intake port. The pressure range from idle to full boost could be more than 30 psi: from negative 14 psi at full engine vacuum to more than positive 16 psi at full boost. It’s a significant problem because the more boost there is, the more fuel the engine needs.

Project Unfair Custom Fuel Tank CTS V Fuel Module

6. This is the CTS-V fuel module with the optional fuel-level sender attached.

In order to keep the pressure across the injector constant, a rising-rate fuel pressure system is used. This is usually done with a mechanical fuel pressure regulator, but for Unfair a VaporWorx system will be used to control the speed of the fuel pumps and maintain proper fuel pressure.

Using a combination of MAP and fuel pressure data, the electronic systems will change the speed of the fuel pumps to maintain the necessary fuel pressure. This reduces the amount of heat added to the fuel load, increases the fuel pump life, and reduces electrical power demands. During cruise conditions the pumps will need 2-3 amps with an average output voltage of 6V (see sidebar), and they will consume 15-20 amps at an output voltage of 13V at full boogie.

Project Unfair Custom Fuel Tank Fill Port Radiator Hose O Ring

7. Clockwise from left: fill port (part of an old fabricated radiator hose we had lying around), sending unit bung, and two O-ring 8AN bungs (one for venting the tank, and one for draining the tank). Draining the tank is a requirement since the max effort engine tune requires race gas.

7. Clockwise from left: fill port (part of an old fabricated radiator hose we had lying a

Since the electronic control system does not need a bypass return like mechanical regulators, only a single pressure line from the fuel tank to the engine fuel rail is needed. The two 3/8-inch outputs of the modules will be tied into an AN10 “Y,” and a 5/8-inch fuel line will be routed to the fuel rails. No external filters are needed since the fuel modules have them built in, so the plumbing from the tank to the engine will be a snap.

The tank construction consists of 0.125-inch 5052 aluminum sheet with custom VaporWorx mounting rings to hold the fuel modules. The rings allow the use of the OEM sealing O-rings and cam locks so that repairs and replacement parts are easy to find.

The fuel level sensor wiring will pass through a bung made to house a hermetically sealed bulkhead that encases an 80-psi-rated PTFE covered wire. Standard wire cannot be used since it can wick up the wire and create a leak. John’s own II Much Fabrication tank vent system will provide fuel slosh control, filtered air, and eliminate fuel smell.

Follow along now as John shows how he integrates a custom aluminum fuel tank with VaporWorx parts and GM CTS-V fuel modules.

8. There are lots of wires required to enable PWM control of the fuel pumps from the MAP sensor (top) and to monitor fuel pressure (the brass transducer center bottom).
8. There are lots of wires required to enable PWM control of the fuel pumps from the MAP
9. The top box is the Delta Current Control (DCC) Pulse Width Modulation (PWM) controller. This is the muscle part of the fuel control system. The battery and fuel pump power connections are made here. The lower box is the VaporWorx Signal Conditioning Module (SCM). This is the brains of the fuel control system. It interprets the data from various sensors in order to control the speed of the PWM power output of the DCC controller.
9. The top box is the Delta Current Control (DCC) Pulse Width Modulation (PWM) controller
10. With all the components in the tank accounted for, John sets up to weld the pump insert to the tank top (the top is upside down). The steel bar is aligning the insert face with the top.
10. With all the components in the tank accounted for, John sets up to weld the pump inse

11. After welding the insert to the tank top, it’s time to work out where the pickups will go. It’s a little tricky getting two pumps, two pickups, a fuel-level sender, and the connecting host to all fit properly.
11. After welding the insert to the tank top, it’s time to work out where the pickups wil
12. John uses Oetiker clamps to secure the nylon pickup hose to the Walbro clamps. The stainless steel clamps won’t rust or dig into the soft nylon like a screw-type clamp would.
12. John uses Oetiker clamps to secure the nylon pickup hose to the Walbro clamps. The st
13. The fuel module is connected to the pickup and is ready for duty.

14. Here’s a shot of the top viewed from the “inside.” The fuel module rings, sending-unit wire bung, and pickup locators are all visible. If you look carefully at the pickup locators, you’ll see a hole drilled for the pickup locating boss, which will keep it precisely located.
14. Here’s a shot of the top viewed from the “inside.” The fuel module rings, sending-uni
15. These are the components for the fuel-level pass-through. The dual O-rings and sealed wire insert are rated up to 80 psi. It’s a quality solution for the old problem of passing wires inside a tank filled with fluid.
15. These are the components for the fuel-level pass-through. The dual O-rings and sealed
16. It’s time to weld the tank halves together. Check out the quality fit of the sheetmetal: It will make welding it together much easier.
16. It’s time to weld the tank halves together. Check out the quality fit of the sheetmet

17. The welding process starts by tacking the corners. John is using a plastic Quick-Grip clamp to hold while tack-welding.
17. The welding process starts by tacking the corners. John is using a plastic Quick-Grip
18. With the corners tacked together, John places tack-welds every 4 inches along all the seams then welds each seam in a single continues bead, stopping only when more rod is needed. Welding a tank is different than welding sheetmetal, where warping is a constant battle. Most leaks in a welded joint occur when one weld bead joins another, so the fewer stops and starts the better. The thick material will resist warping.
18. With the corners tacked together, John places tack-welds every 4 inches along all the
19. Next up is installing the fuel modules. The first step is to raise the pickup locater and slide the holes over the pickup boss.
19. Next up is installing the fuel modules. The first step is to raise the pickup locater

20. With the pickup placed into position, the fuel pump module is carefully lowered into the tank (don’t forget the O-ring) and locked into place with the retaining ring.
20. With the pickup placed into position, the fuel pump module is carefully lowered into
21. No fuel tank can be said to be leak-free until it’s pressure-tested, and 10 psi is a good test. Spraying soapy water on all the weld seams will quickly expose any leaks. The tank passed and is ready for installation.
21. No fuel tank can be said to be leak-free until it’s pressure-tested, and 10 psi is a
22. A common oversight with using a non-factory fuel tank is proper venting. This is a II Much Fabrication fuel tank vent/baffle and K&N filter. The vent/baffle is plumbed to the vent port on the top of the tank and from there to the filter. When used with an unvented gas cap, this system eliminates fuel slosh during high-g maneuvers along with fuel smell emanating from the car.
22. A common oversight with using a non-factory fuel tank is proper venting. This is a II