By Peter McLaren

Masao Furusawa, Yamaha's general manager of Engineering Operations, likes listening to Kawasaki's new screamer engine - but says the even-firing design will never again power a Yamaha MotoGP bike.

"We will never use a screamer engine again. Never!" said Furusawa, during an exclusive interview with Crash.net. "We threw away the screamer engine in 2003."

Furusawa, who has worked with Yamaha since the early 1970s, was put in charge of the YZR-M1 project upon Valentino Rossi's arrival in 2004 - and one of the first major technical changes was the introduction of a 'big-bang' 990cc engine.

Following Yamaha's example, the technology - previously seen in 500cc - was soon once again present throughout the premier-class field. However, last year's change to 800cc engines saw Ducati and then Honda return to a screamer, as maximum horsepower - the main advantage of a screamer - became a priority.

Whereas a screamer engine - so called due to its high-pitched engine note - features an equal amount of time between the firing of each cylinder, 'big-bang' engines have an uneven firing order.

So - in the case of a four-cylinder engine - two cylinders fire closely together (producing what sounds like one 'big bang'), then there is a longer than usual time period before the other two cylinders are fired (also closely together).

Kawasaki's development team rolled out the factory's superb sounding new screamer during the January Sepang test, although it didn't make a return appearance at last week's outing, much to Furusawa's disappointment.

"I hope Kawasaki brings it back! I like to listen to it. Their screamer is not here this time and honestly I don't like it," he smiled. "Please use the screamer engine!"

Nevertheless, Furusawa - who gave a detailed presentation on 'big-bang' at the season-ending Valencian Grand Prix - was happy to explain why Yamaha will be sticking with 'big-bang' for its grand prix prototype.

He describes the 'big-bang' effect in terms of a communication process between the rider and rear tyre, made via the engine. A communication process which, in the case of a screamer design, becomes increasingly distorted at high rev/min. 'Big-bang' engines keep this distortion to a minimum.

"Internally the 'big-bang' engine is very smooth during its rotations. It sounds like it is fluctuating a lot, because of the uneven combustion timing, but the reality is that it is very smooth at high rpm," he began.

"The screamer engine sounds very smooth, but over 12,000 rpm the motion of the moving parts inside the engine becomes a big problem. You can think of it as creating a big 'noise' that stops the rider from hearing what the tyre is 'saying' to him.

"The rider needs to listen carefully to the tyre and talk to it directly with the throttle, but the screamer engine makes it really hard to 'hear'. So the connection between throttle and tyre is not good with the screamer - don't explain this to the Kawasaki people!" he quipped. "I'm only joking!

"So the screamer engine sounds nice, but if the engine goes over 12,000 rpm then there are problems and in MotoGP the useable rpm is 14,000 to 17,000 - sometimes up to 19,000 - so a big 'noise' is happening at high rpm with a screamer and the rider cannot 'talk' to the tyre," he concluded.

Yamaha and Kawasaki both use an inline four-cylinder layout for their MotoGP engines, while Ducati, Honda and Suzuki use a V4 configuration.

Comments

Join the conversation - Add your comment

Please login or register to add your comment