Fuel Tanks

A fuel tank stores the car’s fuel and must keep the pump supplied while the car brakes, corners and accelerates. This category holds petrol tanks of 20, 40 and 60 litres in black or silver, with filling connections in the same two finishes.

The tanks share a 260 mm width, while length and height grow with capacity. The 20-litre tank measures 300 × 260 × 260 mm, the 40-litre 410 × 260 × 380 mm and the 60-litre 510 × 260 × 460 mm. Those outer dimensions give the nominal volume, so usable fuel is a little less once wall thickness, any baffles and fuel left below the pickup are allowed for.

Fuel moves under load, and a tank running low can uncover its pickup in long corners and under hard braking. Baffles, a sump around the pickup or a separate surge pot keep the pump fed. The tank must also breathe as it empties and as fuel expands with heat, so its vent should run through a rollover valve, often to a catch tank.

Three points settle the choice:

• Capacity: the longest stint plus a reserve the pump can actually reach, remembering that a bigger tank also carries more weight when full.
• Space: measure the mounting area and allow room for the pump, lines, filler and vent before choosing a size.
• Rules: competition rules may require a homologated safety cell rather than a plain tank, so check the regulations for your class first.

Mount the tank inside the wheelbase where possible, away from the exhaust and crush zones, on rigid supports with straps and rubber isolation. Separate it from the cabin with a fireproof, liquid-tight bulkhead, as competition rules commonly require. Bond a metal tank to the chassis with an earth strap, because rubber mounts isolate it and static can build up during refuelling.

Before the first fill, test the tank with very low air pressure and soapy water, since a flat-sided tank bulges under modest pressure. Check the fittings and filler seal for weeping after the first runs, and drain and inspect the tank if the fuel filter starts collecting debris.