Readers' choice: Top technology stories of 2009

The editors look back at the past year's most significant articles according to readers of Automotive Engineering International AEI Online, and Truck & Bus Engineering Online

“Uneven- or irregular-interval firing has been employed in racing engines-the so-called ‘Big Bang,’ with more than one cylinder firing simultaneously,” said Masao Furusawa, Executive Officer of Yamaha Motor Co. and Senior General Manager of Engineering Operations, Motorcycle Headquarters, when telling the secret of Yamaha's winning formula in the MotoGP racing series. “Then there is the ‘Long Bang,’ with crank phases out of sync. Uneven-interval firing race engines have been known to improve lap times versus even-interval firing ones. How and why they work has not been clearly defined,” he said. Furusawa observed that, by simultaneous two-cylinder combustions, peak torque would double, producing a momentary burst of power, but conversely the total number of combustions decreases, thus obtaining the same total. “What the rider wants is combustion torque proportionate to the throttle work, not inertia torque,” said Furusawa, who drew an analogy to signal-to-noise ratio (SNR), an electrical engineering term. “Combustion torque is a signal, and inertia torque is noise. Unfortunately, noise increases proportionately to the square of revolutions, greatly deteriorating the SNR.” Verification of the Yamaha SNR theory was performed by directly measuring fluctuations in rear tire revolutions during cornering using frequency analysis. Furusawa concluded that the 90° crank engine transmitted the signal/combustion torque singularly and effectively to the driving wheel; this was proven when Racer Valentino Rossi won the MotoGP World Championship astride the Yamaha YZR-M1 in 2004 and 2005. The 2008 season was still young when Furusawa revealed his unique SNR theory and the smallest hint of the YZR-M1 technology.

Full story at sae.org/mags/aei/5586