Rulebook / Fuel System

Fuel System

Fuel system requirements applicable to all Ultra4 competition vehicles.

Section 2.15 • Common Vehicle Requirements

2.15.1 FUEL: TYPES

  1. Any of the following commercially available fuels may be used:
    • Service station pump gasoline (the type normally used in passenger vehicles for highway use, this also includes E85.)
    • Racing gasoline, as originally manufactured
    • Commercial aviation gas
    • Diesel fuel: Alternative fuels, including biodiesel, WMO, WVO, etc., on approval of Ultra4.
    • Propane or natural gas
  2. Commercially produced, nationally advertised fuel additives may be used.
  3. Alcohol and nitromethane are not permitted.

2.15.2 FUEL: STORAGE

  1. Safety fuel cells are required for all vehicles. Auxiliary fuel tanks may be added. Auxiliary fuel tanks must also be safety fuel cells.
  2. There must be a substantial cross member and firewall between the fuel tank and the occupants.
  3. Fuel tanks shall be mounted in a fashion to protect the tank from damage due to a rear-end collision, impact from debris or rocks from below the vehicle, damage due to roll over, or the possibility of damage from chassis flex.
  4. Safety fuel cells shall consist of a bladder enclosed in a smooth-skinned container. The container shall be constructed of 20-gauge (1mm) steel, 0.060” (1.5mm) aluminum. Magnesium is strictly prohibited. Container must be securely attached to vehicle with bolts or steel straps. All fittings must be built into the container skin and bonded to the container skin as an integral part of the tank or mechanically sealed by a ring and counter-ring system by either flat joint or an O-ring. Internal baffling is mandatory in all fuel cells. Foam is an acceptable form of internal baffling. Bladder construction shall be of nylon or Dacron woven fabric impregnated and coated with a fuel resistant elastomer. Rotary molded polymer cells are acceptable when encapsulated in a container constructed of 20 ga. (1mm) Steel or 0.060” (1.5mm) aluminum.
  5. Fuel accumulator tanks (accumulators) are permitted under the following guidelines. Accumulator tanks shall be constructed of .125” (3.25mm) aluminum or steel and shall be mounted to the chassis using rubber isolation and shall have a capacity of no more than one quart. Accumulators shall be mounted in a manner that protects them from damage due to impact.
  6. No jerry cans or other portable fuel containers shall be permitted in or on any entrant vehicle during the event. Use of jerry cans or other portable fuel containers will subject entrant to a time penalty or disqualification.
  7. Alternative fuels (propane or natural gas) must use an approved fuel cell as determined by DOT standards and with the approval of Ultra4. Forklift propane fuel tanks are permitted. Alternative fueled vehicles shall not use auxiliary fuel cells.
  8. Substitute methods may be approved by Ultra4

2.15.3 FUEL: PLUMBING, FILLING & VENTILATION

  1. Design and installation of fuel tank and related components (plumbing) must prevent fuel escaping from fuel pickups, fuel lines, fuel fillers and fuel vents if the vehicle is partially or totally inverted. Fuel isolation valves that facilitate isolation of the fuel tank from the fuel supply line, fuel return line, and fuel vent line are required. Ball valves, or a combination of ball valve and one-way check valve, located at the supply, return, and vent line are acceptable. Fuel isolation valves shall be located such that, with the vehicle in any position, they may be rapidly closed to restrict the continuous flow of fuel onto the ground in the event of a fuel line failure. See Section 10.3.5 ENVIRONMENTAL SAFETY for more information and rules related to environmental concerns and considerations.
  2. Accumulators shall have supply inlet, supply outlet, return supply, and return outlet connections with isolation valves.
  3. Fuel tank must be filled from, and vented to, the outside of the occupants' compartment.
  4. Fuel filler lines and positive-locking, non-vented fuel filler caps must be located and secured in such a manner as to prevent them from being knocked off or open during vehicle movement, rollover, or accidental impact. Monza/flip-type caps are strictly prohibited.
  5. All fuel fillers attached to the frame, or a body panel must be connected to the tank using flexible couplers. All fuel fillers must be surrounded by a boot or splash guard (body panel is acceptable as a splashguard, if it is sealed). Boot or splash guard must direct fuel spillage to outside of vehicle and away from occupants’ compartment, engine, and exhaust. A fuel filler rollover-check-valve must be incorporated into all fuel cells. It is highly recommended that detachable fuel filler caps have a flexible strap or chain to secure them to the vehicle.
  6. Fuel vent lines must have a rollover check valve incorporated at the fuel cell, and must vent outside of occupants’ compartment, and be directed away from the engine and exhaust system.
  7. Fuel vent line must pass 4 inches above the highest point of the fuel cell or above the highest point of the fuel fill opening, whichever is higher. Additionally, the fuel vent line must pass beyond each of the 4 planes created by the furthest point of the cell forward, rearward and on both sides of the cell. The vent line must terminate at least 3 inches below the lowest part of the cell.
  8. Fuel vent line must use one of the following routings:
    • Fuel vent line must extend to the highest point of the roll cage nearest the fuel cell, above the fuel fill, across the width of the vehicle, and down to below the belly pan of the vehicle or 3” (75mm) below the fuel cell, whichever is lower.
    • Fuel vent line must loop above the fuel cell to a point that is 4” (100mm) above the top of the fuel cell and above the fuel fill. From there it shall be wrapped one full loop around the outside of the fuel cell near the top of the fuel cell and then be routed down to a point 3” (75mm) below the lowest point of the fuel cell.
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