When Ducati first debuted their new engine braking reduction system in pre-season testing last month, the rumor mill went wild. As far as observers could tell, the Ducati Desmosedici MotoGP bikes were basically freewheeling into the corners, as if the rider had pulled in the clutch as he started braking.
Ducati soon made an official statement regarding the system, the goal of which was claimed to be improved fuel economy. Riders Carlos Checa and Loris Capirossi both had problems with the system, Capirossi crashing in testing and both riders crashing in pre-race practice, these crashes being attributed to the unfamiliar engine-braking system by many observers. Capirossi in particular was reported by the Italian press to be unhappy with the system, but the factory made the final decision and announced in press releases that they would run it during the Jerez race.
In the end, Ducati opted not to use the system during the race, claiming they had discovered unusual chain stretch as a result of its use. We suspect that the factory succumbed to pressure from the riders, who were obviously opposed to implementing a “gizmo” that would slow their race pace.
So why would Ducati want to make their MotoGP bikes freewheel into corners in the first place? It is well known that the new 990cc four-stroke MotoGP bikes have more engine braking than the old 500cc two-strokes, and all the teams on the grid have implemented systems to reduce the force of this engine braking since the switch to four-strokes was made. Most of the teams use a slipper clutch to moderate the effect of back-torque on the rear wheel, allowing the engine braking to slow the bike slightly without causing the rear tire to lock or chatter.
So too much engine braking is bad, but a mild amount can definitely be beneficial during corner entry. Even the 500cc two-strokes weren’t entirely devoid of engine braking, and by using a slipper clutch the effect can be modulated to an ideal point somewhere between that of a two-stroke and that of a standard (non-slipper clutch) four stroke. The rider can use this moderate engine braking to smoothly transfer the bike’s weight forward when he starts to slow for a corner, or even use it to tighten his line mid-corner by rolling off the throttle slightly.
Capirossi and Checa both started their careers on two-stroke machines, but they have had several years to acclimate themselves to the engine-braking characteristics of the four-stroke bikes. Why, then, would the factory try to force them to radically change their riding style within a matter of weeks before the start of the season, to accomodate a bike that acts as if it is in neutral when entering a corner? Although we initially doubted Ducati’s claims that the “freewheel” system was intended to improve fuel economy, we are now forced to conclude that this may indeed be its purpose.
With the bike basically pulling in the clutch whenever the throttle is shut, the engine would be able to drop RPM rapidly and settle into a low, fuel-conserving idle. With this year’s reduction on the maximum allowable fuel tank size, such economy measures may be necessary to ensure that the bike finishes the entire race.
The problem with this theory is that the Ducatis competed at Jerez without using the freewheel system, and were still able to finish the entire race without running out of fuel. Why is it, then, that fuel conservation was so critical that Ducati tried to force this unpopular system on its riders just a few weeks before the start of the season?
We suspect that Ducati may have developed a much higher specification for the Desmosedici engine, one that produces quite a bit more power than the current motor but also uses its fuel more rapidly. If this is the case, Ducati could have developed the freewheel system to allow them to use the more powerful engine and still have enough fuel to finish the race. This would mean that they switched back to their old motors before the Jerez race. Ducati has already announced that the new engine-braking system will not be used this weekend at Estoril, either, but that testing of the system will continue.
