"We have made a lot of computer simulations of a V4 and we have found good and bad points," Furusawa said in a media presentation. Yamaha preferred the in-line four because it permits a more compact engine and a shorter wheelbase.
Furusawa admitted that valve springs had a ceiling of 19,000-20,000rpm. But he said: "Increasing the rpm increases the power, but at the same time you have more friction between the piston and the cylinder. And I don't think that over 20,000rpm is the way to go. I would like to make an engine that has lower rpm but good torque, one that makes a good 'conversation' between the rider and the tyre."
Yamaha has tested a pneumatic-valve engine this year, but Kouichi Tsuji, leader of the M1 project, said: "From the point of view of fuel efficiency and power, we have had no gain from it. If we find a benefit we would be ready to use it."
Kawasaki is currently proving that an in-line engine can match the V4s used by Ducati, Honda and Suzuki: in qualifying at Valencia
Randy de Puniet was quickest through the speed trap at 300.8kph (186.796mph). But
Valentino Rossi, the quickest Yamaha rider, hit only 293.5kph (182.263mph - 4.533mph slower).
Why is the Yamaha still lagging? "We are struggling to maintain horsepower and fuel efficiency," Furusawa admitted. "We always try to make a good engine, but the result isn't always the same as our plans."
Rossi and
MotoGP newcomer
James Toseland will be hoping that Yamaha can recover power parity with other manufacturers during winter testing prior to the 2008 season.
Sunday am – Michelin Accuses Riders and Dorna of 'Panic'
Michelin chief Jean-Philippe Weber has lashed out at riders who have criticised his tyres this year for using the rubber controversy as an excuse for their failure to beat new world champion
Casey Stoner.
The French company has been the focus of criticism as Stoner and his Bridgestone-shod Marlboro Ducati have scored processional victories, and Dorna chief Carmelo Ezpeleta proposed at one stage that MotoGP might become a single-tyre series in 2008.
