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Yamaha's M1 MotoGP Bike: The All-Rounder
by julian ryder, back home in the uk now, thanks
Wednesday, December 03, 2008

Twelve months ago, the Yamaha MotoGP team gave a short lecture at the Valencia GP. Maseo Furusawa explained the thinking behind the 90-degree crank concept developed for the M1 and now used in the R1. Last year I took two months worth of this column to go over the revelations. Furusawa's work identified for the first time why a big-bang crank works. In a nutshell, it gives linear torque output - if the rider dials in 20% more throttle he gets 2% more torque at the back wheel. Critically, this holds at the small throttle openings and high revs at which standard cranks generate anomalous torque spikes.

This was ground-breaking stuff, so I went to this year's lecture with high hopes. There wasn't the detailed analysis of last season but instead there was a fascinating insight into what it took to turn the M1 from an also ran into a bike that four riders could put on the front row and three of them could put on the rostrum this season. Some of the numbers involved were quite startling. Let's not forget that the difference in race and lap times between first and last in a MotoGP race is usually a few per cent. For instance, Ant West's race time on the Kawasaki was 2.5% slower than winner Stoner's at Valencia - and he finished seventeenth.

Cast your minds back to the '07 season, the Yamaha was a recalcitrant beast, prone to overheating, hard on its tyres and much, much slower than the Ducati. It was, we were told, also heavy on fuel. The inroads Furusawa and MotoGP Group Leader Masahiko Nakajima made into these problems while keeping the bike rideable by four racers with widely differing styles is more than impressive. The Yamaha men claim engine performance was increased by 12% and simultaneously fuel consumption was increased by 6%. That is a clever trick. Top speed went up by an average of just over 4mph (7kph) as well. At Qatar, where the Desmosedici so unforgettably blasted past Rossi in '07, the improvement was an astonishingly just under 10mph (16kph). At Laguna there was hardly an improvement at all. The other notably above-average top speed improvements were, not surprisingly, also at tracks with long straights. By far the best improvement in fuel consumption came at Estoril, a slow track that happens to have a long straight. Jerez, which has a bit of everything, also showed a seriously above-average improvement in consumption whereas Laguna, Shanghai and Donington guzzled gas at almost the same rate they did twelve months previously.

Obviously the adoption of pneumatic valves helped. Yamaha cite a 40% reduction in the weight of the valve system and higher valve lift. Getting rid of valve springs obviously liberates a good chunk of power and there was port and combustion chamber work as well to match the valve system but there were significant gains in areas you might not have thought of. Reduction of internal friction, and cooling. Would you believe water temperature was reduced by 10 degrees and oil temperature by 15? Managing airflow inside the fairing with particular attention to how air exits the bodywork was the key.

The emphasis on friction reduction brought to mind those photos of early Honda teams when the mechanics wore t-shirts with a large footprint on the front and the words 'Help stamp out friction.' The rules haven't changed, reduced friction equals free horsepower. Yamaha say they have reduced internal friction by 14%. Obviously the switch to pneumatic valves has helped, in fact it's reduced valve train friction by 20%. However, valve-train friction only accounts for a fraction of the overall losses.

Proportionally much larger gains were made with the pistons and crankshaft - which account for well over half the total losses. Rather imprecise phrases like 'surface treatments' and 'design optimization' were used about the pistons' 8% improvement but the major change to the crank is a single central oil feed, which is claimed to have lowered that component's contribution to friction by over 15%. Both of those are significantly greater contributors to the overall improvement than the valve train changes.

Anyone who's been paying attention to chassis design over the past few years will know that the black art of stiffness ratios has been top of the agenda. It still is. Compared to the '07 bike, Yamaha have increased chassis torsional (twisting) and vertical (bending in the plane of the wheels) stiffness by between 10 and 20% while decreasing lateral stiffness by around 10%. This is the mode of flexing when the bike is at maximum lean and the suspension therefore cannot work. It appears to be the key to making the bike behave both going into and coming out of corners. Note that this as not something that was done as a consequence of Rossi's change to Bridgestone tyres, all four riders got this modification. The Bridgestone's required some significant set-up changes, primarily in front-to-rear weight distribution, but the chassis modifications benefited the Michelin users as well.

The scale of the improvements being made show there is still much more to come from these engines. The lifetime of a racing engine design is usually five years, after which it has reached its limits. This is the second year of the 800cc MotoGP formula, so you would be expecting some serious improvements. However, the numbers involved while impressive also tell us very clearly that the original 2007 M1 was, frankly, a bit of a lemon. You can be sure that Ducati also made improvements in '08 but not at the rate Yamaha did simply because the original Desmosedici 800 was such a brilliant piece of work.

The people who should really worry are Suzuki and Kawasaki. Their '07 bikes were not far off the Yamaha so should have had just as much room for improvement in 2008. Unfortunately, there was precious little evidence of it.

ENDS

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