The fuel pumps produce 100 psi and flow at a prodigal 85 gallons a minute. At idle, the engine guzzles 13 gallons per minute, but at the peak of the race, when the engine is roaring at 8,000 rpm, this leaps to upward of 70 gpm. Nitro gushes in so violently that, if engine load is momentarily lost due to wheel spin, the engine will "drop a hole"-the twin spark plugs in a cylinder are extinguished by the fuel.
"If the humidity is high," says Scott Okuhara, one of McCulloch's numerous crewmen, "we'll increase the blower speed to push more oxygen into the engine." When the engine is running at 8,000 rpm, the spin speed of the belt-driven supercharger is about 25 percent higher. "If the fuel-air mixture is a bit wrong and we burn a piston," adds Okuhara, "that means, besides the new piston, we also have to put in a new bore."
If all goes well during a run, the engine will be at full power for less than 5 seconds. With the additional burnout before each run-full pedal for a couple of seconds to heat and clean the tires on a watered-down surface-the total full-throttle life span of a nitro engine is less than 8 seconds.
While an onboard computer is used to analyze performance data after a run, tweaking for the next run is analog-strictly mechanical. What's more, computers are prohibited from controlling engine activities during a race, even though the technology is available now. But the officials and competitors in the sport were afraid that the costs of installing these systems in cars would spiral out of control (look at F1 costs).
Besides achieving a good reaction time, the driver has two additional duties. First, he must stay in the "groove" (the twin black stripes where tire rubber and traction are). Second, he must keep the throttle nailed open-most of the time, anyway. If the timing is bad, a good driver will instinctively let off the gas or hit the brake to prevent the tires from smoking and slowing down the car. At the end of the run, he manually releases the drogue chutes crossing the finish line, sustaining a 4.5-G deceleration load to match the 4.5-G load experienced at launch.