When the ASA decided to use GMs Vortec 5700 as a spec engine, it also had to complet
Except for the removable plate in the lower right with two electrical pigtails, this 15-ga
Removing the pump plate reveals the pressure regulator (right), bellows tubing for fuel an
The twin fuel pumps are buried deep within the cell and are actually lubricated by the gas
The interior surge tank keeps gas near the fuel pumps to prevent fuel starvation at low le
Two years ago when the American Speed Association announced that, beginning with the 2000 season, all competitors would be required to race a spec engine, the grumbling from fans and competitors alike was enough to make you think it was tax season. The sanctioning body had committed the sin of breaking away from the racing norm to spec in GMs Vortec 5700 powerplantan engine that is fuel-injected, nearly bone-stock and (gasp!) computer-controlled.
We didnt even think about trying to stick with a conventional fuel cell, says Joe Balash, the ASAs technical director. In the old engine the fuel pump is mounted on the engine, but, because the new engine has an electronic fuel delivery system that requires fuel to be delivered around 60psi, we knew we had to go with an electronic fuel pump and mount it somewhere in the fuel cell.
But 18 months into the era of the Vortec, much of the scorn has turned to admiration for the ASAs willingness to embrace technology. Competitors have found the engines to be more affordable and nearly bulletproof, while fans are enjoying close, competitive racing. But the change was more than just a little more wiring for competitors. Because the engine is injected instead of carbureted, the entire fuel delivery system had to be reworkedespecially the fuel cell. Because fuel-injected engines are going to be the standard in racings future, Circle Track decided to take a look at the entirely new fuel cell Aero Tec Laboratories (ATL), one of the most respected names in the fuel containment business, developed for the ASA.
When the engineers at ATL went to the drawing board for the new fuel cell, they had to meet three directives from ASA: the new cell had to be just as effective as the older versions at protecting drivers from crash fires and accommodating fast pit stops; it had to deliver fuel at high pressure to the electronic fuel injection (EFI) system and it had to be totally reliable in providing clean, uninterrupted fuel flow.
The first requirement, safety, was rather easy. Fuel cells are nothing new, and ATL has been building super-safe cells for Winston Cup and Busch Grand National Cars for more than 25 years. A NASCAR 2000 spec bladder was selected as the baseline model. Incidentally, the standard 22-gallon ASA cell was reduced to 15 gallons to fit the improved gas mileage of the Vortec engine. ASA officials were afraid of boring races as competitors tried to go the distance without pitting.
Explosion-suppressant foam baffling was installed in the bladder, and a new end-load 18-gauge steel container was fabricated. An aluminum check valve plate featuring a rollover vent ball and ATLs patented quick-fill Paddle Valve topped off the design.
Next came the second and tougher assignment: high-pressure fuel delivery. After extensive evaluation, the design team decided on a unique in-tank (submersible) electric fuel pump that can provide up to 100psi fuel pressure to the engine. Mounting this powerful 12-volt pump to a flexible fuel bladder required special bracketing together with a 30-micron, sock-type filter, a one-way check valve and a fuel-resistant 12-gauge wire harness.
The fuel pumps electrical supply is routed through a fuel rail sensor at the engine. In a serious accident, that sensor quickly shuts off the pump to help contain all gasoline within the fuel cell.
It was the third assignment, absolute reliability, that required a little creativity. It was decided to mount the all-important fuel pressure regulator directly into the fuel cell. The regulator device precisely maintains the 58psi fuel-injection pressure required by the LS-1 EFI engine.
This wasnt a problem with the old engine, says Balash. On the older fuel pump we were running somewhere between five to seven (psi). It was really suction that was pulling fuel into the system instead of now where we are spraying fuel into the combustion chamber.
But what if the fuel pump failed? ATL and the ASA decided on the redundant approach of installing two electric pumps in the cell. A driver-operated toggle switch selects one pump or the other, but not both, which would over-pressurize the injectors. Two completely separate electrical circuits with quick-connectors were also added so no single wiring fault would affect both pumps.
The final challenge was making every drop of fuel useable. An injected engine needs constant fuel pressure to atomize the inlet charge, but no one likes to carry around 30 pounds of extra gas just to prevent intermittent fuel starvation. Even a brief loss of fuel pressure could shut down the engine and a teams aspirations!
ATLs engineering group drew on its experience in Formula One Grand Prix fuel cells to design an integral Surge Tank or bladder-within-a-bladder. Built into the right-rear corner, the surge tank is outfitted with two trap doors that let fuel in and then hold it directly around the pumps inlet filter. A guide vein directs any fuel in the main cell toward these trap doors, relying only on the forward and lateral acceleration of the race car. By constantly ramming gasoline into the surge tank, there is little chance of the engine suffering from fuel starvation or even hesitation. Plus, the electric pumps, which depend on fuel as their lubricant, remain immersed right down to the last gulp of gas!