Motorcycle Grand Prix racing is always an exciting spectacle, and the multi-class race weekend provides race-goers with multiple world championship events to watch. Although the old 50, 80, 125, 250, 350, 500 cc and sidecar classes have regrettably gone now, the top MotoGP class is supported by Moto2 and Moto3 on race weekends.
Moto2 nowadays uses a spec Triumph engine (Courtesy of Triumph)
Initially powered by a race version of the Honda four-cylinder CBR600 engine, the current Moto2 engine is now based on the 765 cc three-cylinder Triumph that powers some of its popular road bikes (see RET 115, December/January 2019). All the Moto2 engines are identical, and are built, serviced and maintained by Spanish company Externpro, which had previously looked after the Hondas.
Owing to its larger capacity, the engine has more torque than the Honda, and it is thought to be better rider preparation for the move to the 1000 cc MotoGP bikes with their huge power and torque.
By the end of this season, Externpro’s technical director Trevor Morris estimates that in the four seasons of competition, the Triumph engines will have completed a total of about 1.2 million racing kilometres. The total mileage to date (ahead of the Thailand MotoGP on October 2) was almost 950,000 km on 258 engines, and more than 1200 engine rebuilds. That represents 74 race meetings so far, each with a starting grid of 30 riders.
While there are a lot of club racers who have raced the older 675 cc three-cylinder Triumph machines, the reliability demands of Moto2 in a much more public arena bring certain pressures. Morris is quick to acknowledge the good work done by Triumph who, he says “did a lot of endurance testing before we received any material [the engines].
“That enabled us to concentrate on making the transition [from the 600 cc Honda engines to the 765 cc Triumphs]. For example, Triumph ran two bikes with three test riders under race conditions for 3000 km – double the mileage we do before a rebuild – and as far as I know only the standard cam chain tensioner guide was upgraded to a billet one in the process.”
Triumph’s sophisticated I3 is the basis of the current Moto2 engine (Courtesy of Triumph)
Even with this base level of reliability established, it is important not to rush to introduce a very significant upgrade immediately, and Morris notes, “We introduced the engine and ECU in stages, starting with a standard engine and ECU, and progressively moved up to the spec we have now. That meant we could highlight any issues as we went along and not be influenced by too many changes.”
In such a popular class, there have been many riders who raced Moto2 initially with the Honda and then the Triumph. I asked what the riders felt about the change and how it affected their approach to racing. On the subject of the increased torque, Morris notes that this requires the riders to be “precise on the throttle” and that riders really like the fact that the Triumph engine has a real “race engine characteristic”.
Choosing the engine
Choosing the engine The 600 cc engine, with its lower torque, allowed riders to take more corners at full throttle, which led to a feeling that many corners therefore had “one line, one gear, one throttle opening”, according to Morris.
A number of riders from the Triumph Moto2 era have graduated to the top MotoGP class with varying degrees of success. Morris says, “I have spoken with numerous riders who have moved up to MotoGP, such as Remy Gardner, Marco Bezzecchi and Brad Binder, and they all say that in the first three gears the current Moto2 is more difficult than the 600 cc variant, that you have to really control the early throttle openings.
“Bezzecchi adds that the character of the bike is very similar to MotoGP, just less performance. That is exactly what we were looking for.”
Morris was given a relatively free hand to propose a new engine specification for Moto2, and I asked if he had been pointed in a specific direction.
He says, “It was left to me; we knew the championship more than anyone. There were a few proposals on the table, and I just used a process of elimination to make the final decision. “I ran a costing for building our own race engine with various partners, but that proved to be way too expensive; we could not go back to the last of the 250 cc two-stroke days when it cost $1 million to lease a bike. Even a return to two-stroke was considered but we felt the world was not ready for that. With costs dictating the path, it was clear that we had to continue with a production-based engine but we had to make sure it was suitable for Moto2.”
Morris won’t elaborate on the other engines under consideration but is happy to discuss his method for choosing between them. “I made a ladder system that worked on an elimination process to narrow down the options. For example, it had to weigh around the 50 kg mark, use fly-by-wire throttles, have more than 130 bhp, be as small as possible, and preferably not already in MotoGP. The Triumph engine just scored more points than any other.”
The Moto2 engine is more powerful than the standard road version it is developed from, but it is certainly not tuned to the limit of what is possible. The aim is to produce a good race engine that combines performance with reliability and very low performance degradation over a sensible rebuild interval.
Based on the reaction to Moto2, Triumph released a more powerful variant of the 765 cc engine in a sportier version of its Daytona road bike. The Moto2 engine shares the 78 x 53.38 mm bore and stroke of the road bike.
Externpro’s dyno cell showing an engine on test. A drive coupling rather than a chain drive is used (Courtesy of Externpro)
Given a free hand, one option was clearly to carry on with the engine Externpro had experience with, but Morris was keen to change and make an improvement. He says, “As we had the opportunity to change, I wanted to move away from the typical Japanese inline four-cylinder engine. The Japanese manufacturers were not investing in these models; Japan had changed its licence regulations, the licence before unlimited being reduced to 400 cc from 600, so the market for 600 cc almost disappeared.
“Also, the exhaust emissions regulations are forcing them to produce models that are not suited to Moto2. The Triumph gave us more of what we were looking for, and for me it really stood out as the best candidate for the future of Moto2. That was confirmed by listening to people that ‘track ride’ them: it has that balance between performance and being able to enjoy racing that we were looking for.
“Another big incentive was to introduce another manufacturer into MotoGP, especially one with such an iconic name as Triumph.” Although Triumph had not been seen as a particularly sporty brand before its entry into Moto2, the name does have a strong history in racing.
The fact that the basic road engine is suited to hard racing with very few component changes is testament to the fundamental strength of the design and the components. Despite the mechanical parts being largely standard, the engine’s performance has been improved relative to the road bike.
Morris says, “The main area for performance that was worked on was the breathing. The inlet porting has such an influence on the performance and the consistency between individual engines, and having so many engines that is quite critical. With batches of 30 engines, our target was to keep the power range to just 1-1.5% difference.
“We have increased the size of the injectors [still a production item] and mapped the ignition and fuelling for the Marelli system. The riders have 20 engine brake/ torque maps to choose from.” The use of the single-spec Marelli ECU and associated software places another limit on development, and puts the focus on the rider while giving them enough ‘tools’ to tune the engine’s output to their style.
Road bike engines need to be very flexible, and engines that are too ‘racy’ can be painful as a road bike as they only really work nicely at high engine speeds. Conversely, road bike engines that are not properly modified for racing can feel ‘strangled’ at the higher parts of the engine speed range in which they typically operate, as gas speeds in the ports and through the valve seat area are too high. The porting of the Triumph engine increases the port sizes so that the engine is optimised for the narrower, higher-speed use seen on the track, bringing port and seat speeds back to more effective values.
One obvious aspect of racing compared with road motorcycling is the use of racing tyres, and these present new challenges for the engine. The improved tyre performance allows increased levels of acceleration and braking, plus much higher cornering lean angles.
Sump modifications
Sump modifications Sump (oil pan) modifications are quite normal in race series where wet-sump production engines are used. The use case for passenger car engines used in downforce cars is actually worse, owing to the oil being forced to the sides of the oil pan, sometimes leaving the oil pick-up without oil. In a motorcycle, the free surface of the oil – that is, the top surface of the oil – should remain flat relative to the bike, because the bike and the oil-free surface should always assume the same angle relative to the ground in cornering.
In acceleration and braking, however, that is not the case. Ignoring pitch effects owing to the suspension, the bike should remain level, while the free surface of the oil will assume an angle that depends on the level of acceleration or braking. Without being specific about the modification, Morris says the sump is modified to prevent oil starvation.
However, even though the ‘cornering effect’ on oil pick-up should be minimal on a motorcycle, the tyres do have an effect on the sump, specifically because of cornering. On a road bike, especially ones where the tyres are used for racing with little modification, high cornering angles often lead to contact between the racetrack and fairing/exhaust. On a Grand Prix motorbike though, it is simply not realistic for the performance of the motorbike to be limited by the exhaust scraping on the ground on one side of the bike.
The sump is therefore also modified to allow the exhaust system to be tucked in closer to the centreline of the bike and therefore no longer limiting ground clearance during cornering. While Moto2 uses a single specification of engine, it is used in race bikes from various makers, so the modification to increase cornering ground clearance has to work with all of them.
Morris explains, “We use a race generator to reduce the weight and width of the engine.” Without the additional electrical loads imposed by lights and so on, or a requirement to keep a large battery charged, a race alternator can be of smaller output and therefore be smaller and lighter.
An additional change is a new clutch cover that repositions the clutch actuation arm to the top of the cover. It is one of only a small number of parts that had to be redesigned by Externpro for using the Triumph engine in Moto2.
Although the Triumph engine is clearly suited to the rigours of racing, the much higher duty cycle and accumulation of fatigue cycles through constant high engine speeds is bound to shorten component life considerably compared with the relatively sedate use of a road motorcycle. For example, Morris uses cylinder heads and crankcases for “around 3000 km” before replacing them with new components. Other parts that are replaced more often are the cranktrain (crankshaft, pistons and rods) along with bearings and valve springs.
Each engine will do a total of 12 race meetings before being retired. During that time, it has two minor rebuilds where the cranktrain, bearings and valve springs are replaced, and one major rebuild where those components, plus the cylinder head and crankcases, are replaced.
With full grids and a long season, this necessitates a lot of rebuild activity for Externpro, with Morris saying, “Normally, we will service around 220 engines in the year.” That is spread out over the season of course, and logistics plays a part in how it is done.
Morris says, “We supply a complete batch of 30 engines to the teams at the circuit, which are chosen from a random selection by each team.” This process is widely used in motorsport, and is seen as a guarantee of fairness. Morris says each team will “use the engine for three races, return them and we start the process again”. After each race meeting, every engine in use by the teams is sealed by Externpro’s trackside staff to prevent them being used for private testing outside the Grand Prix meetings.
Trevor Morris: “Moto2 has a clear objective to highlight a rider’s potential for their possible move into MotoGP”
There is no routine mechanical work or parts replacement between an engine leaving Externpro’s possession and it returning to them three Grands Prix later. Morris explains that the data review is possible for two staff because “we have developed programs that enable us to process all the data from all 30 riders in around an hour. It means we can very quickly see if someone is over-revving, has too high a water temperature, is mis-shifting and so on.”
The riders and team engineers have a degree of control over how the engine is used. With a fly-by-wire throttle on the Triumph engine, there is scope for control of throttle maps, engine braking and so on. Torque mapping so that the throttle position correlates to a certain torque in each gear is now widely used, and riders have 20 variations of torque maps to help them tailor the bike to their particular riding style. Engine braking is also now more controllable thanks to the use of a slipper clutch.
Steering clear of electronic control
Steering clear of electronic control Although there is scope in the capability of the ECU for the use of electronically controlled systems such as traction control, wheelie control and so on, there are no plans to introduce them. Morris says, “Moto2 has a very clear objective to highlight a rider’s potential for their possible move into MotoGP, and we do not want the electronics to influence that.”
The thinking is that if the riders start to lean heavily on such systems to control the performance of a 765 cc engine, they will find the leap to the much greater torque of the 1000 cc MotoGP machines too difficult. The greater adjustability of electronics in Moto2 also plays a role in ensuring a sensible graduation step for race engineers from Moto2 to MotoGP. If the technological gulf from one race class to another is too large, it becomes difficult to cross over.
Looking beyond club-level motorcycle racing, where production road bikes are used for motorsport, a common modification is to replace some or all of the gear ratios. The Moto2 version of the Triumph 765 follows the tried and tested formula of using a longer first gear and more closely spaced ratios thereafter.
As Morris notes, “It will always be a challenge to get a road-designed gearbox to perform in the conditions we put it through, but with a great deal of help from the Marelli ECU we manage it.” The role of the ECU is to control the quality of the gearshift and to prevent mis-shifts and over-revs at gear changes.
The latest incarnation of Moto2 has been a real success. It prepares riders and engineers better for the challengers of the top MotoGP class, and the increased performance makes for compelling racing. The riders enjoy the extra performance, and the bikes produce a great sound that the fans enjoy. Triumph, which was effectively a relatively new company using the sporting heritage of the old company of the same name, now has a genuine top-level racing presence based on a production engine of its own.