New 2012 MotoGP Regulations - 4 Cylinders, 1000cc, Fixed Bore At 81mm

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, 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 website in PDF format here:

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Limiting the bore sets the minimum stroke which effectively limits RPM. Unless you spend a shed load of money on exotic materials. Did someone say 'unintended consequences'?

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Total votes: 148

The RC211V had two crank shafts right? What about the Suzuki and other v4 applications? Can you mix and match stroke lengths? Can fewer cubes and shorter strokes make more power than longer strokes and more cubes?

I find it hard to believe that this is going to be a magic solution to cost cutting.

Total votes: 130

Hmmm...can this really be considered a "silver bullet"?? Despite initial speculation that a limit on bore and/or stroke would be set with the new rules, I was expecting/hoping for something actual rev limit or fewer number of gears allowed ala Peter Clifford's original idea. Regardless, it will be interesting to see once the other details emerge what machines result from the new regulations, and if indeed they will help to bring in new participants to the series.

Interestingly...and very much on a side note, I notice that if by some absolute miracle of God MotoCzysz were to give entering MotoGP a second shot with their C1, unlike the "production " engines listed, they would actually have to decrease the bore of the C1's engine, as it comes in at 82mm according to the specs listed at MotoCzysz's website.

Total votes: 137

If revs are the problem, control revs. Stop eliminating engine diversity.

I understand the reasoning behind this change. Lightweight materials have triple or quadruples payoffs b/c the engineers can go oversquare which increases the rate at which number of ignition strokes increases while also maximizing peak engine performance by increasing peak revs.

If the manufacturers can't go oversquare, the incentives to use lightweight materials are reduced drastically; however, we know what happens when the governing body relies on diminishing marginal returns to do the work associated with controlling performance. Diminishing marginal returns are the MSMA's best friend b/c they have the deepest pockets. It's basically a technological caste system.

So close, yet so far away AGAIN.

More technical restrictions, still no effective performance controls that can be easily adjusted.

Total votes: 223

... but what did you expect, this is Dorna we're talking about. The only smart decision they ever made was going to 990cc... but that was before Ezpeleta, wasn't it?

Total votes: 119

and the move away from 500cc it's been all down hill. Just think if they would have stayed 500cc maybe we'd have competitive 4 strokes at the same displacement by now, or within a few years. Baby out with the bathwater in my opinion. If ya need a dollar to do what you could have done with fifty cents, you're not doing it right.

Total votes: 121

Something else I was curious about, as from what I read at various sites seems unclear. Is it actually "maximum number of cylinders: 4", which implies there could be future regulations for twins and triples also (even if no potential manufacturer ever produces either one), or is the series indeed going to be open to four-cylinder engines only?

Total votes: 130

...but I think that there has been enough talk about 'stability' of the formula contributing to holding costs down. I think it was the Ducati head engineer that stated that it was the rapid changing of formula that held costs high. If things stay stable, then the need to invent drastically new models every few years is gone and possibly purchased machines could continue to be competitive for satellite teams to use 2nd or even 3rd hand. Or at least as competitive as they are now. There may end up being 3 tiers of competitors, but hopefully they would still finish within a lap as they are now while the grid grows to make exciting racing for a 1.5 to 2 minute front to back range during the race.

Total votes: 131

The MSMA always talk about stability as a way to keep costs down, but stability is actually the antithesis of cost containment. If an investor is uncertain about the prospects of a certain business endeavor, the investor will avoid risking large amounts of money. If certain returns are guaranteed by commercial rights agreements, television deals, and rules stability contracts; an investor will be anxious to throw piles of money into the sport. The current economic recession is contributing to cost-containment, but when the economy recovers the 81mm bore rules will do nothing to control torrential development spending. If the marginal returns of spending are worse under the 81mm rule, history suggests spending will be more reckless.

The rules need to be more diverse and LESS STABLE while maintaining backwards compatibility. Moving from 990s to 800s to 1000s is ridiculously expensive and unnecessary, but using displacement to control performance doesn't allow for backwards compatibility. Bore rules don't allow for backwards compatibility either. If the bikes get too fast, they will have to redesign the entire engine to slow things down, or they will rev limit w/o allowing any technological diversity.

Engine and chassis are the last bastion of diversity b/c nearly everything else is bought from third party suppliers. Surely, the brightest motorcycle minds in the world can do better than cylinder mandates and bore-stroke rules? When times were good they changed the formula without considering the consequences, now that the sport is collapsing, they are clinging to convention?

I am so confused by these people.

Total votes: 127

What do you mean by backwards compatibility? The use of older machines racing against newer formula? I think their efforts to ensure that can only be realized by a commitment to not change things for a longer period of time. I doubt there is will to make the current machines part of the new era on some equal footing. So any new starting point is as good as it gets for backward and from there on out decisions could be made with that in mind.

I wouldn't disagree that it seems there could be a better solution. But if they aren't the brightest minds in the sport, they are the minds that count. I just don't think this cost containment panic is from only the current economic situation and doubt things will change when/if things get better. It's been coming for a lot longer and the increased rate of change in technology that came with 4 strokes has just reached a fever pitch where returns on investment, from a research to manufacturing perspective, don't add up. I don't think it was that Kawasaki didn't have the extra money for their MotoGP program. But it was that it just wasn't worth it.

Total votes: 182

I think the rules should be compatible with old equipment.

I know the MSMA are hesitant, but using engine dimensions to control performance has caused them to build 3 completely new 4-stroke prototype engines in only 10 years. Non-dimensional performance rules like rev-limits can be adjusted without requiring new engines. The teams would likely do some redesigning, but a change to the rulebook wouldn't preclude current teams from future participation even if they didn't have the budget to build and test an all new engine.

I shouldn't be surprised by bore-stroke b/c the Japanese already use it to regulate 600cc supersport bikes (formally or informally), but bore-stroke rules have not removed the possibility of yet another engine redesign in 5 years if performance is beyond what the MSMA anticipate.

Total votes: 182

There will be no separate regulation for twins and triples. Twins and triples are covered under the existing limitations of 1000cc and 81mm bore. A parity regulation as in World Superbikes is vanishingly unlikely. In practice, this means that all MotoGP bikes will be four cylinders, as a triple with an 81mm bore would have an incredibly long stroke.

Total votes: 128

That is disappointing...

I don't understand why these new regulations for MotoGP are designed so that all engines must essentially be 4's?? Surely similar but adjusted rules can be created for twins and for triples that would allow them to be competitive in this new formula. Allow twins a non-limited bore size, and triples somewhere in between that and the 81mm of the 4's. Give each a corresponding weight advantage over the 4's. At least ALLOW for the option of different engine configurations to be competitive. After all, aren't we trying to get more bikes on the grid, more competitors in the series?

Hhaha...are the Japanese afraid that if they give them the chance, that Ducati would embarrass them with a MotoGP super-twin??

Total votes: 127

You want some "Unintended Consequences". No mention of fuel. Somewhere in the rumours was no change. Engine designers are always going to go for as much power as possible, just as long as they can smooth out the driveability with electronics. So if you fix the max bore size,

- They'll push maximum piston speeds and hence revs as much as possible until rods, cranks and pistons start failing. Then they'll have to get exotic, risky and experimental or start replacing parts more often. And there's nothing yet about how many engines they'll be allowed (we still don't really know what the limit will be for 2010)
- They'll keep desmo, because they're Ducati, and air valves because they allow more aggressive cams and lower friction.
- They'll have to design, build and test new engines in the new size
- As Krop points out, any production engines will need to be bored and destroked.

And costs will go up.

As for "power is easier to come by in 1000s", Where's the evidence for this? There was a power race at the end of the 990 era. Do you really think there won't be again?

Total votes: 135

You want to know the real reason for this change?

To encourage Rossi to sign another 2 year contract this summer. So he can win a championship on another MotoGP formula. And keep the money hose going that he represents in MotoGP's global marketing.

Total votes: 148

Ian Drysdale:-
I make that a minimum of 48.5mm stroke. This gives a B/S ratio of
1.67, which is not radical by any means.

At a relatively safe race MPS of 25.0 m/s, that comes to 15,465 rpm.

Pushing the friendship at MPS of 29.0 m/s comes to 17,940 rpm.


That all looks high enough to me to make desmo and pneumatic valves an advantage.

Total votes: 141

Thanks for that, very interesting. Two things come to mind here: first, 15,500rpm is fine with steel valves, no problems. Second, 17.5K is not so hot on steel valve springs, the Honda RC212V was just managing it last year, but the engine maintenance interval was allegedly 300KM, which is not going to cope with the 6 engines for 18 races rule.

In fact, the limiting factor is going to be the engine limits, rather than the rev limits. If you have a fixed bore and unlimited engines, you push for the upper limit. If you have a fixed bore and the motor has to last for 3 races, you have to be considerably more conservative.

In effect, MotoGP now has three factors limiting it: A fixed bore limiting revs; a minimum engine life, also limiting revs; and a spec tire, limiting horsepower.

Total votes: 171

I wonder if any of the teams have published bore-stroke figures for their current engines. ISTR that MotoGP is pushing up into F1 territory on piston speed. And given they are currently running to about 18k I doubt they are using much more than an equivalent B/S ratio now.

It's going to be quite a balancing act. Pushing for revs to get the power but at the same time, doing a lot of work on rod and piston design to try and get it to hold together with the limited engines.

I think there's also the desmo factor in here. Ducati have a lot of experience now in trying to make very wide combustion chambers work. Key to this was some radical cam shapes with unfeasibly large valves. Limiting to 81mm pulls them back even though some of that experience will still apply to more normal shapes and B/S ratios. So can we detect some Honda-Yamaha influence here to try and keep Ducati in check?

Where's Neil Spalding when you need him? ;)

Total votes: 233

When Noyes was writing his article at speed TV he revealed that Ducati was the only team outside of the current bore limitation. He was convinced (as anyone would have been) that they were referring to Ducati's 990cc engine which was 86mm according to the D16RR replica. The D16RR has a bore-stroke ratio of 2:1.

It is possible the remarks about Ducati may actually apply to the current GP9 engine now that we know the bore limit is only 81mm. If the bike has a bore greater than 81mm it would have a bore stroke of 2.1:1 or 2.2:1. Such measurements could be possible given the reduction in piston size when the bikes were changed to 800cc capacity.

I dunno, maybe the entire rumor about Ducati is just a red herring, or maybe they are just going to stroke the 800s so major redesigns aren't required.

Stroking the 800s would make sense. The current engines can probably hit 20,000rpm. If they increase the stroke by 25% revs should go down pretty substantially.

Total votes: 131

I would think your 100% correct jbond as to the real reason for the 1000cc rule. Just wish Rossi would wake up one morning and say "Let's bring back 500cc two strokes, would much better for sure".

There are technologies already used that will raise the bar on existing performance levels don't forget. It took 6 months for F1 to recover the rpm/hp after their imposed engine life limit.
Which again will see cubic $$ burned to see who can run reliably for 2500km piston speeds of 30m/s. What's the bet Ducati will be first Honda last?

Total votes: 141

Interesting that they set a limit on bore rather than stroke. Setting a min stroke at 48.5mm would give you exactly the same dimensions in a 4 cylinder engine, yet allow triples and twins without crippling them with a huge stroke.

Better yet, why not just specify a max bore/stroke ratio?

Total votes: 135

limiting stroke would favour triples and twins. max bore/stroke ratio I personally feel would be the wisest option. But I pity the poor non-technical commentator that has to explain to the fans the ins and outs of piston speed and it's relation to stroke and rpm, and therefor displacement to the general public. Not to mention that would require flatly admitting that brake mean effective pressure ratios have improved less than 10% in the past 50 years. Something the manufacturers association (Honda) would be somewhat red in the face to have come into the public consciousness.

Total votes: 131