Just the facts, ma’am
The mid-1970s decision by the McGees to pursue a radical new line in drag racing engines, speci cally one targeted at nitromethane-burning vehicles, such as Top Fuellers and Funny Cars, was a brave move. And not just commercially, either.
Top Fuel dragsters were then and remain the quickest accelerating racing vehicles in the world. Today the fastest competitors reach speeds up to 338mph [544kmh] and nish the 1000 foot [305m] run in 3.62 seconds. They accelerate from standstill to 100 mph [160kmh] in as little as 0.8 second in just 60 feet and can exceed 280mph [450kmh] in just 660 feet [200m], half the old quarter-mile race distance.
Such vehicles now almost universally race over the shortened 1000ft distance because of the difficulty in stopping them when racing over a full quarter mile (1320ft). The launch acceleration rate is over 8Gs, equaled only by carrier-launched jet aircraft and greater than the space shuttles ever reached.
Today it is estimated (nobody knows for certain, as there is no dynamometer that can measure the combination of power and revs up to 10,000rpm) these engines make around 11,000-horsepower, maybe more. In the mid‘70s the power outputs were probably around the still signi cant 4000-5000 horsepower. Torque today is estimated at about 7000 ft/lb (9,500Nm).
Under full throttle, a dragster engine consumes 1-1/2 gallons of nitromethane per second; a fully loaded 747 consumes jet fuel at the same rate with 25 percent less energy being produced.
A stock V8 engine cannot produce enough power to drive the dragster’s supercharger. With 3000cfm (cubic feet per minute) of air being rammed in by the supercharger, the fuel mixture is compressed into a near-solid form before ignition. Cylinders run on the verge of hydraulic lock at full throttle.
Nitromethane burns yellow. The spectacular white ame seen above the stacks at night is raw burning hydrogen, dissociated from atmospheric water vapour by the exhaust gases. The ame front temperature measures 7050 deg F (3899 deg C). Dual magnetos supply 44 amps to each spark plug (three per chamber), the output of an arc welder in each cylinder. The upward pointing exhaust headers provide about 2000 pounds [907kg] of downward and forward thrust on the rear of the vehicle, and if one cylinder stops burning fuel it can unload that side of the car enough to cause it to swerve violently towards that side. The large rear wing adds as much as 3000kg of downforce at 300mph, and the front canard wings another 550kg, causing the chassis between to visibly arch upwards.
Spark plug electrodes are totally consumed during a pass. After halfway the engine is essentially dieseling from compression, plus the glow of exhaust valves. Only cutting the fuel ow can shut down the engine.
If spark fails early in the run, unburned nitro builds up in the affected cylinders and can then explode with sufficient force to blow cylinder heads off the block in pieces or split the block in half. To avoid excessive carnage the external engine components are held by ballistic blankets, straps and plates.
The combustion of nitromethane produces, amongst other compounds, nitric acid vapour, which causes lungs to shut down and eyes to water. Photographers, officials and race crew around a drag strip start line can tell you all about it.
Amazingly, given the circumference of the rear slicks, which grow considerably under centrifugal force during a run, Top Fuel engines turn approximately just 540 revolutions from start to nish line! Including the burnout, the engine must only survive 900 revolutions under load.
All that burning fuel creates noise. Seismologists have measured two cars leaving the line at 2.3 on the Richter scale, and noise levels reach around 150 decibels, equivalent to a jumbo jet.
Get the application of this sort of power wrong and the vehicles can suffer serious rear tyre shake. This can be as much as 21G from side to side, breaking welds and/or rendering a driver unconscious if not brought under control instantly.
And when the parachutes deploy a Top Fuel dragster decelerates faster than it accelerated.