The Grand Prix Commission, MotoGP's rulemaking body, met today in Geneva to discuss a number of issues, clarifying a number of open points in the rule book concerning Moto2, as well as a few other minor points. But the point that MotoGP fans around the world had been waiting for most fervently was the new rules for MotoGP to take effect from 2012.
In the huge press release with regulation changes just issued by the FIM, the part covering MotoGP's new rule changes were incredibly brief- just four lines:
Basic concept for MotoGP
- Maximum displacement: 1000cc
- Maximum number of cylinders: 4
- Maximum bore: 81 mm
And so as predicted (most prophetically by Dennis Noyes on Speed TV), the "silver bullet" Carmelo Ezpeleta described is limiting the bore. Speaking to MotoGP.com, the Dorna CEO described the decision to limit the bore to 81mm as follows: "It's a very important measurement because with this we can have all the characteristics of the engine."
The theory is simple: engine costs - especially the amount of maintenance an engine requires - is determined chiefly by the maximum engine speed; the higher the revs, the more fragile the engines and the more often the engines need to be rebuilt, which is a very large part of the cost of running the current MotoGP prototypes. Higher revs also makes the use of desmodromic and pneumatic valves necessary, as ordinary steel springs are incapable of closing the valves in time and prone to facture. They also demand more aggressive valve action, as there is less time to fill the cylinders with fuel/air mixture before the valves shut. Valves have to be forced open and closed much more quickly, which in turn makes the engine more peaky, requiring more electronics to control.
The limiting factor for engine speed is a parameter called piston velocity. This is basically the maximum speed at which a piston can travel through the cylinder bore, but a more accurate way to describe the limitation is how fast the piston can accelerate from top dead center to the middle of its stroke, then decelerate again as it approaches bottom dead center (see the graph on this page). The way that engine designers usually limit piston velocity is by making the bore bigger and the stroke shorter, meaning that the piston has less distance to travel in a shorter time. By mandating a maximum bore, the Grand Prix Commission is cutting off this avenue for chasing power and chasing engine speed.
Of course, this does not mean that the chase for higher revs is over. The main avenue for finding those extra revs may have been closed, but rest assured, motorcycle engine designers will right now be rushing down the following avenue, which is that of mass. After all, the problem is not so much piston velocity, as piston momentum, which is mass*velocity. With a fixed bore, if you want velocity to increase, you have to decrease mass. What that means - and this could be a blow to the search for cost-cutting - is that the pursuit of "unobtainium" materials (very light metals, ceramics, alloys) for use in pistons and connecting rods will be the next avenue to explore. The question is, will the expense of extremely unusual materials be worth the power gains from a couple of hundred extra revs?
The answer to that is probably no. The lesson learned from the 800cc bikes is that the key to making a motorcycle go fast is drivability, or a smooth, predictable power delivery. With 1000cc engines, producing horsepower should be less of a concern, or at least less difficult to come by. There is more potential to affect lap times by concentrating on power delivery, getting out of the corners fast and with plenty of control. Long-stroke engines help here, which is one reason why large cruisers have long-stroke motors, to provide smooth, torquey power.
The decision to limit bore size to 81mm is an interesting one, as that is larger than all of the current crop of 1000cc production superbikes currently use. Any team wanting to use an engine from, say, a Suzuki GSX-R1000, a Yamaha R1, or even a BMW S1000RR will find themselves with bore to play with. All of those production bikes use a bore less than 81mm, most a couple of millimeters or more less. And so to take advantage of the extra engine speed a larger bore would provide, engine builders would have to shorten the stroke, modifying crankshafts, crankcases and connecting rods to a significant extent. So much, probably, that they will not resemble the production engines they were once based on at all, and evading the wrath of Infront Motor Sports, the holders of the commercial rights to the World Superbike series.
More details on the final set of rules is due to emerge before the start of next season, but from here, it's all detail. Limiting the bore to a maximum of 81mm, and limiting the number of cylinders to 4, sets some clearly defined parameters in place for engine designers to start thinking about.
As well as the announcement on MotoGP, there was a major clarification of the rules for the Moto2 class. We'll examine that in more detail at a later date, but the most important points were the following:
- Engines will be handed out at random, and will be sealed
- Teams can design their own exhaust systems, but the inlet system, including airbox, filter, throttle bodies and injectors, must remain untouched
- Teams can design their own radiators and external cooling systems, but they cannot interfere with coolant pumps and oil pumps
- The teams must use the stock ECU and electrical systems. ECU software can only be modified using the standard software provided
- The teams must use the standard Datalogger and sensors. Extra channels are available, which may not be used at official events.
If you'd like to read the full FIM press release for yourself, it's up on the official MotoGP.com website in PDF format here: http://motogpinfo.motogp.com/2009/fim/gpcomission_dec09.pdf