Inside the Ducati Superquadro Mono Engine

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The compact house of power that is the 659cc single-cylinder desmodromic-head Superquadro Mono engine now introduced in the Hypermotard 698 Mono and Mono RVE. (Ducati/)

New-model press releases almost always leave out some of the most interesting details about the development process, so we wanted to fill in those blanks on Ducati’s Superquadro Mono single-cylinder engine that powers the 2024 Ducati Hypermotard 698 Mono and 698 Mono RVE.

More basic than that, we wanted information seldom discussed in a press release: How did Ducati choose to design and build this unusual engine? What challenges did engineers encounter?

To answer these questions and more, Technical Editor Kevin Cameron and I arranged an hour of digital face-to-face time with Ducati Engine Development Manager Stefano Fantoni, and Product Communication Specialist Edoardo Licciardello.

It was said at the recent press introduction for the Hypermotard 698 Mono that the bike was a “passion project.” But we would ask what recent Ducati model wouldn’t be considered such?

So, aside from passion, how did this project come into being?

The $14,495 2024 Ducati Hypermotard 689 Mono RVE and standard $12,995 Mono mark Ducati’s return to a single-cylinder engine and entry into a new class and market. (Ducati/)

“It was a marketing target to create a completely new engine,” Fantoni says. “Because Ducati would like to create a new vehicle that is light, slim, and has high agility, to deliver riding fun in twisty roads and city streets. We also had in mind that this vehicle can be appreciated in Supermotard use. It is directed toward new Ducatisti—young people who come to the Ducati world for the first time.” Ducati says its target customer for the Hypermotard 698 Mono is around 25 years old.

Creating paths into the brand is a never-ending conversation at motorcycle companies, particularly as it relates to young people, because loyalty is often fostered over generations. As an example, after 15 years Victory managed to grow annual sales volume to something on the order of 10,000 motorcycles. When Polaris launched Indian, total motorcycle sales for the company more than doubled in the first year. After that, Indian kept growing and Victory sales declined. Polaris ultimately closed Victory to concentrate on the historic brand whose name and style resonated in the larger culture across generations. There was simply a higher return on every dollar invested in Indian.

This also underlines that even with passion projects, motorcycle making remains a business. How do we sell more?

Related: 2025 KTM 690 SMC R and Enduro R Spied

Ducati openly states both in this interview and in the press information from the Hypermotard 698 Mono product launch that it is targeting the KTM 690 SMC R and its Pierer Mobility stablemates, the GasGas SM 700 and Husqvarna 701 Supermoto. Fun motorcycles make an excellent target. (KTM/)

“This segment is roughly 7,000–8,000 units yearly, worldwide, with what is substantially the same bike from KTM/GasGas/Husqvarna,” Licciardello says. “Even if we manage to sell one-quarter to one-third of this total yearly, for a small house like Ducati, with 60,000 worldwide sales, they are significant numbers.”

<i>Cycle World</i> road test of the 1965 Ducati 160 Monza Jr. Ducati was first a singles company, and then essentially combined a pair of single top ends on a common crankcase to deliver its first 90-degree V-twin. (Cycle World Archive/)

In motorcycles, Ducati began as a singles company. In the 1970s as the superbike was born and Honda CB750 Fours and others filled great demand, Ducati became a twins company by taking its bevel-driven overhead-cam singles (both desmo and spring head), and combining them into the 90-degree V-twin that defined the brand for decades.

Can’t mention classic Ducatis without mentioning Dr. Fabio Taglioni, the man responsible for bringing Ducati’s first V-twin to life. (Cycle World Archive/)

When in 1993 the Ducati Supermono 549cc single was introduced, it was a 90-degree V-twin with the vertical cylinder removed, but it kept the connecting rod and a piston-weight mass at the end of that rod working on an internal pivot, and in this way was perfectly balanced.

This is a direct scan of the fax Ducati sent to <i>Cycle World</i> for the 1993 Kevin Cameron tech story on the Supermono single—right out of the archive. The horizontal cylinder remains but the vertical cylinder was removed. The vertical cylinder connecting rod operated a reciprocating weight that made this single as smooth and balanced as a twin. (Cycle World Archive/)

It makes sense as Ducati returns to single-cylinder engines that it would take a slice of its recent superbike to build this new 659cc single.

“Our first idea was to take from our history: the big-bore 1299 Panigale engine that was the most advanced V-twin engine Ducati ever produced,” Fantoni says. “From this basis we started to develop this engine.”

Related: What Is The Nature Of The Combustion Chamber Shape?

If we just cut this right about here… Ducati 1299 Panigale engine that served as the basis for the 659cc Superquadro Mono. It is not uncommon for motorcycle companies to start with a combustion chamber as the basis for a new engine. With the Superquadro Mono, Ducati had much more than just a good combustion chamber shape to work with. (Ducati/)

Just as Ducati needed to maintain engine balance with the Supermono and introduced the clever connecting-rod method, so did this very large bore engine need balance. In addition to the primary balancing effect, the second piston in the 1299 exchanges energy with the other during rotation.

Another angle and different look at the 1993 Ducati Supermono engine internals. Two connecting rods, only one piston. Small print on the left edge of the image is the fax information: “Ducati Motorcycles SPA Bologna” from when it was sent to the Cycle World fax machine in May 1993. (Cycle World Archive/)

When one piston hardly moving near TDC or BDC, the other is near its maximum speed. But in a single with this same large (116mm) piston, it exchanges energy instead with the crankshaft. This causes crank speed to vary quite a bit during each engine revolution. Did that variation in crank speed create a problem on the Superquadro Mono?

“We were a little bit scared of this oscillation [cyclic variation of crank speed] but honestly speaking we do not have much issue about that,” Fantoni says.

Fantoni also made it clear that dyno running answered many questions. Will X be a problem? They run a test and find it’s not so bad. As much as can be done with CFD and stress models, motorcycle development remains a physical process aimed at problem solving.

“We had some issues however with the starting system,” he says. “We gave the driveline of the starting system a little torque-limiting clutch that has the opportunity to slip if this big piston kicks back during cranking. This preserves the mechanical safety of the starter driveline.”

The 116mm piston atop its fracture-split connecting rod. The rod is slightly shorter than that used in the 1299 Panigale, despite the Superquadro Mono’s slightly longer stroke—62.4mm versus 60.8mm. The hidden bottom of the piston is “box-in-box” reinforced—think of a multiroom apartment below the piston crown whose walls give great strength and pick up the short wrist pin. An oil jet is aimed at piston bottom for cooling. (Ducati/)

Photos of the short, stout connecting rod attached to the very large piston raised the question of rod length.

“Connecting rod length is 109.3mm, a little bit shorter than in 1299,” Fantoni says. “There is some cylinder offset to reduce piston side-thrust friction.”

Cylinder offset has been used on engines for more than 100 years but it’s come into more frequent use again recently. The “offset” is moving the cylinder centerline from directly above the crankshaft main bearings so that on the power stroke the rod has less angle and therefore piston thrusts against the bore wall with less force.

So many beautiful parts. The Superquadro Mono’s desmodromic valve gear is laid out next to the cylinder head, featured top dead center (see what we did there?). Deep ribs in the castings give strength; magnesium covers reduce weight. (Ducati/)

A goal with internal combustion engines is reducing what engineers often refer to as “cycle to cycle variation.” This means they work very hard to have every combustion event from idle to redline to be perfectly repeatable. This is particularly difficult in big-bore singles, especially at idle. Cameron offers that the problem can be dilution by exhaust product remaining in the cylinder: if the spark occurs as a whiff of exhaust gas swirls past the plug, there will be a misfire.

“During the design what we did to improve idle stability, compared to the 1299 Panigale engine, was to reduce valve overlap,” Fantoni says.

Related: 2022 GasGas SM 700 and ES 700 First Ride

The Superquadro Mono crankshaft uses plain main bearings, not rollers as Ducati did for so long. Fun fact: The 1993 Ducati Supermono single also used plain crank bearings, a feature engineering Massimo Bordi intended to introduce on the twins much sooner than actually happened. (Ducati/)

“Valve overlap is the period centered on TDC at the end of the exhaust stroke, when the exhaust valves have not completely closed, yet the intakes have begun to open,” Cameron explains. “If you imagine the engine idling, but with some wave action still taking place in the exhaust pipe, you can see that the longer this overlap is made, the greater the chance that the exhaust fraction in the gas above the piston may be high enough to cause some misfiring.”

“Alpha [valve overlap in degrees] of 1299 Panigale was 45 degrees, but in this, only 20 degrees,” Fantoni adds. “Duration and lift are also reduced. These changes have two main advantages: We get a smoother torque curve in wide-open-throttle condition and also improve combustion stability at low rpm close to idle.”

Throttle-body dimension is also reduced. “The round equivalent of the 1299′s oval throttle is 67.5mm. This one is only very huge at 62mm,” Fantoni adds with a smile.

This is a 15 percent reduction in intake area.

Cylinder liner is like that used in the 1299 Superleggera. Why? Weight! The standard 1299 Panigale liner was steel. The Superleggera and now Superquadro Mono is aluminum. (Ducati/)

In a further aid to stability, idle speed is raised to 1,700 rpm, a few hundred rpm higher than that of the 1299.

“The kinetic energy of a very light crankshaft is small at rpm close to idle—too close to the energy required to push the piston through compression,” Cameron says. “If the piston bounces back against compression, the engine stalls. Because kinetic energy rises as the square of speed, a modest increase in idle speed can help a lot. Fantoni noted that in this engine, the mass rotating at crank speed consists of the crank itself, a large-diameter alternator, and the two balance shafts.”

Cameron had speculated that some reduction of compression ratio might have been needed to stabilize idle, but not so. Compression is actually increased in proportion to the increase in stroke from the 1299 (from 1299′s 60.8mm stroke to 62.4mm in the SQ Mono), so it is 13.1:1.

“If high compression could be an issue, we immediately began to assess if it would work,” Fantoni says. “The knock tendency of this engine is not very high so changes to the intake and exhaust system and cam profile were able to provide combustion fast enough to prevent knocking events. We also added a knock sensor and ECU control to reduce spark advance in case of knock events—a safety device to protect the engine from strange atmospheric conditions or lower-octane fuel. There is one central spark plug, with two electrodes, as is typical for racing applications.”

He noted that the “intake duct is quite different from other manufacturers.”

We think it’s likely that Ducati has some form of “Combustion Department” that has made extensive work of all the technical influences on the combustion process, including intake angle as it relates to the cylinder centerline. It takes work to make a 116mm cylinder bore fire cleanly with a single spark plug. (Ducati/)

I asked Cameron about this. “Engines of many other makers have quite steep intake downdraft angles, close to 45 degrees,” he says. “Ducati engineers understand that intake angle and runner diameter influence the level of turbulence during combustion. The function of charge turbulence is to make combustion fast enough that chemical changes necessary for detonation have too little time to occur; it is as though detonation has ‘a fuse.’ This may be why the Superquadro 659cc engine has less intake downdraft—near 25 degrees, directing more energy into the in-cylinder ‘tumble’ motion that compression can turn into turbulence near TDC.”

Fantoni shared his screen to show us the engine’s torque curve, which though it has a shape similar to that of the 1299 Panigale, midrange has been fattened and the steepness of the rise to peak torque is reduced.

“We decided to reduce overlap and total duration, also to reduce a little bit the intake duct diameter,” Fantoni offers “We look for torque good for twisty roads and streets, not only at the track. You have to find the balance.”

A small reduction in intake runner diameter has long been used as a means of boosting midrange torque. This works in two ways: First, the resulting higher intake velocity can continue flowing into the cylinder past BDC (bottom center) longer, even against the rising piston, and second, higher intake velocity also boosts turbulence to achieve quicker combustion.

Intake valve lift, he said, is 14.4mm, which is 31 percent of valve head diameter and a 1.0mm reduction from 1299, or about 7 percent.

We asked about piston oil-cooling jets.

“We have only one piston oil-cooling jet, same diameter as the two in 1299,” Fantoni replies. “We were able to put it on the exhaust side.” The exhaust side of the piston is hotter, and shooting cooling oil there increases heat transfer.

He explained that to simplify plumbing, in 1299 the jets were in the Vee, hitting the intake sides of the pistons first. There are windows in the struts that stiffen the piston crown, allowing the oil jet to flow in contact with the hot aluminum clear across the underside of the piston to the intake side, where it is deflected down into the crankcase by the intake skirt.

A scavenge oil pump pulls a partial crankcase vacuum: “That is 40 millibars with respect to ambient,” Fantoni says. “There are a lot of rotating parts—crank, two balance shafts, and also the gears that drive them. If you have oil that interacts with these rotating parts, you lose performance, you increase friction. This dry sump system collects from the clutch and alternator area, not only from the crankcase, so the scavenge pump has to collect oil and gas, and transfer oil to the pan.”

Cameron asked the final question: “What aspects of this new engine especially please you?”

“It was a long design, begun four years ago,” Fantoni says. “At the end we are proud that this engine is compact and light: It is a real Ducati engine. When you hear it on the test bench you recognize it is very sporty and can run at very high engine speed. It is more similar to a V-twin engine than to a single. It’s a very sporty bike, very close to our DNA.”

How does a claimed 77.5 hp and 333 pounds wet, no fuel look on a track? Like this—a lot! <i>CW</i> staffer Bradley Adams tests the production Hypermotard 698 Mono RVE at a kart track in Spain. Read his <a href="https://www.cycleworld.com/motorcycle-reviews/ducati-hypermotard-698-mono-first-ride-review/" target="_blank">full review here</a>. (Ducati/)

Licciardello adds, “The present is a very positive time for Ducati. We are increasing our market, winning in competition and we are designing new products. The whole industry now is under attack from good Chinese products that are becoming competitive in price-to-performance ratio. The Japanese have capacity to produce many not-so-sophisticated models for Southeast Asian markets.”

This leaves to the European producers the up-market segment for sophisticated motorcycles of highest quality and performance—the market that Ducati serves so well.

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