Moto Guzzi’s Liquid-Cooled V100 Mandello

[Hugh Janus]

CAD images of Moto Guzzi’s new V100 Mandello engine show how compact this new liquid-cooled design is. (Moto Guzzi/)

Cycle World’s test riders are praising Moto Guzzi’s new “Mandello” for somehow combining agile responsiveness with tour-capable comfort. Its all-new liquid-cooled compact-block engine preserves the classic Guzzi appearance, meets Euro 5, and makes 115 hp at 8,700 rpm. It delivers a broad “haystack” torque curve peaking at 77.5 lb.-ft. at 6,750 and having 82 percent of that maximum available from 3,500. Guzzi tells us Mandello is sporty but comfortable, of bold character, and rich in torque. Curb weight is given as 514 pounds.

In our two-wheeled world there are a few classic designs that remain so popular with riders that they cannot be abandoned. Among these are BMW’s flat twins, Harley’s air-cooled V-twins, and Guzzi’s longitudinal-crank 90-degree V-twin.

Moto Guzzi has been forced to step into the modern world with a brand-new liquid-cooled engine, primarily to be able to more easily meet strict new emissions rules like Euro 5. (Milagro/)

We’ve come to expect these manufacturers to apply cooling and emissions Band-Aids to such designs to enable their sales to continue. Harley and BMW have notably added “strategic cooling” to them in the form of liquid coolant circulated around or near critical hot components such as exhaust valves.

Meanwhile there remains the question of when to take action on the supposedly inevitable combustion-to-electric transition. On the one hand, first movers potentially gain an advantage—as has been attributed to Tesla in the auto world. On the other, as we’ve seen with Harley-Davidson’s LiveWire electric, being “early” may just frighten your loyal customer base so badly that your stock nosedives and your top management has to be replaced.

Yet another question—regarding which no one dares present any forecast—is this: Will the motorcycle market one day just start buying electrics as they are presented in showrooms, as if the question—combustion or electric—were just a detail? Or will the electrics act on the market as a whole as LiveWire acted on Harley’s stock price?

Moto Guzzi obviously is confident enough in the future of IC engines to dive in and build a brand-new platform to carry the company for at least the near term. (Milagro/)

I am therefore fascinated to see that Guzzi has taken the step of cleverly and fundamentally upgrading its signature engine architecture with the all-new liquid-cooled V100 Mandello. Given Harley’s experience with LiveWire, could Guzzi responsibly have acted otherwise?

By taking this step, Guzzi expresses confidence that sales of this comprehensively modernized engine and the ingenious motorcycle into which it is integrated will not only cover its R&D and tooling cost, but will continue as a market earner into the foreseeable future. This is confidence that motorcycles will remain good business.

In the design of this bike Guzzi has addressed long-standing problems as well as providing a fresh technical basis for meeting standards beyond Euro 5. Engines with cylinders disposed to the side potentially clash with rider foot and lower-leg placement. The new engine (itself just over 4 inches shorter than the V85 TT small block) is moved ahead plus tilted forward by 5 degrees. This extends Its swingarm length to a modern 22-3/4 inches, pivoting on the gearbox just as did that of Guzzi’s fabled 500 V-8 roadracer. Nothing projects from the front of the engine—if it were set on its nose, nothing would project beyond the front faces of the cylinders. The 550W permanent magnet alternator is now behind the cylinders.

Moto Guzzi’s 500cc V-8 racer. (Moto Guzzi/)

Guzzi is very clear that this engine is a 100 percent departure: It “…does not share even one component with previous engines built in Mandello.”

Providing more room, not only for the rider but for a modern, high-performance intake system, the cylinders have been rotated 90 degrees, placing the intake system and its 52mm throttle bodies in the cylinder Vee with the exhaust ports facing down.

Top view of the V100 engine and its 52mm throttle bodies. (Moto Guzzi/)

Looking at a section drawing of the head, we see that this is a DOHC four-valve with the entirely modern valve included angle of 25 degrees and bore and stroke of 96 by 72mm equaling 1,042cc (63.6ci). Pistons are essentially flat-topped. In the classic 1980s era of US Battle of the Twins racing, John Wittner brought an early 4V Guzzi V-twin into being, but four valves make poor partners with air-cooling. Why? The cylinder head metal between the two exhaust-valve seats and ports, being heated from both sides, is so hard to cool with air that such designs must take measures to avoid head cracking. One is to locate two undersized exhaust valves as far apart as possible (providing more metal between to act as a heat conduit) or to make a bimetallic head with all valves seated in a tough bronze or austenitic iron “skull” onto which the rest of the head is cast.

Dr. John Wittner and the Moto Guzzi his team fielded in the mid-’80s Battle of the Twins series. (Cycle World Archives/)

Why is liquid-cooling necessary now? Not only can liquid-cooling make four valves routinely reliable (as in our world’s millions of 4V auto and truck engines) but by enabling quick, controlled warmup and constant-temperature operation in all conditions, liquid-cooling ensures maximal fuel evaporation all the time. The temperature of air-cooled engines goes up and down with the weather, so when the air is cool or cold, less than 100 percent fuel evaporation takes place. Unevaporated fuel becomes unburned hydrocarbons (UHC) in the exhaust.

Also, liquid-cooling puts an end to oil-polymerizing high cylinder wall and piston-ring groove temperatures. Classic air-cooled engines locate their top piston ring farther down the piston, in hope that being farther from the heat will lower ring groove temperature enough to fend off ring sticking. But placing the rings lower increases the ring crevice volume into which the compression stroke pushes unburned fuel-air mixture. That mixture is held there by combustion pressure until the exhaust valve(s) open, and only then can it begin to emerge—still unburned—to become UHC in the exhaust pipe. With liquid-cooling, piston temperature is reduced, so piston rings can be located higher, reducing crevice volume and UHC emissions from it.

A look inside Kawasaki’s ZX-10R engine illustrates the use of finger followers, which reduce weight allowing higher revs.

While Guzzi was giving this engine DOHC via three hydraulically tensioned chains, it also gave it finger followers in pure racing style. Why? In a racing application, engineers know that a finger follower can save 75 to 85 percent of the weight of a classic cylindrical inverted-bucket tappet. That lighter weight translates to reliable valve train operation at higher revs so as to make more power.

Advanced features such as these can have purposes other than success as a World Superbike homologation special. Guzzi adopted finger followers because they can also enable use of fast-lifting but shorter-duration cam profiles that can make power without the usual valve overlap that leads to loss of fresh charge out the exhaust pipe. The lighter the valve train, the easier it is to make reliable at short duration and high lift. Guzzi hints at this in its press release, saying finger followers allow “….more aggressive valve lift” that “makes for ideal combustion by eliminating any fuel waste.”

Valve overlap is that period, centered on TDC at the end of the exhaust stroke, during which the intake valve(s) have begun to lift but the exhaust(s) have not yet closed. More overlap can boost power by starting the intake process early, but there is the danger that entering fresh charge may in part flow out the exhaust, thereby becoming UHC.

Two characteristics long inherent in Guzzi’s V-twins are 1) rapid engine acceleration causes some roll reaction by the bike, and 2) the old problem of the rear of the bike rising and falling as the throttle is opened and closed. (Some call this “pinion climb.”) Both have been alleviated by design changes. In the new design, a smaller, lighter crankshaft drives a counter-rotating shaft carrying some mass that in turn drives the alternator. The fact that engine acceleration torque is now exerted in these opposite directions causes the roll reaction to decrease as much as 50 percent as compared with the 1,200cc 8V.

The V100’s alternator is driven by a counter-rotating shaft that cancels some of the roll reaction that is inherent in a longitudinal-crank V-twin. (Moto Guzzi/)

Engine torque reaction was very familiar to Navy carrier pilots in the piston engine era. If the tailhook failed to pick up a wire during an attempted arrested landing, the pilot had to firewall the throttle to make a go-round. Props on American aircraft rotated to the right (as seen by the pilot) so the roll reaction turned the aircraft to the left, away from the island. But British engines turned the opposite way, possibly causing the accelerating aircraft to veer toward the island. Pilots have a lot to think about. At the end of that era, experiments were just beginning with contrarotating props that reduced torque reaction to zero.

Rear suspension rise and fall is reduced in Mandello by the increased swingarm length, which puts the lift force at the end of a longer lever.

The shorter engine has enabled a longer swingarm, which helps reduce pinion climb. (Milagro/)

The Mandello’s intake, exhaust, and combustion processes have been designed by 3D computer fluid dynamics (CFD). This can allow the designer to set goals for the process being studied, and then let the computer simulation cycle hundreds of times, making small design changes each time, to converge on a best solution. As once observed by the late Keith Duckworth (whose flat-chambered 4V “Cosworth DFV” F1 engine is the grandfather of modern practice), maximizing airflow via flow bench studies is only a beginning. The real problem is then to burn the charge in the cylinder rapidly (to minimize heat loss) and completely (to realize full energy from the fuel).

Duckworth reached a new level of understanding in 1967 through experience and experimentation, but that knowledge has now been “canned” in the form of computer recursive simulation software.

Testifying to Guzzi’s success in achieving rapid combustion is this engine’s high 12.6-to-1 compression ratio in a large 96mm bore. Such a large bore requires excellent combustion if it is to avoid the abnormal form of combustion known as detonation or “knock.” Raising compression ratio increases engine torque at all rpm.

Another view of the 52mm throttle bodies nestled into the V100’s Vee. (Moto Guzzi/)

As often happens when an old design is reimagined, components find new and more appropriate places for themselves. The flat-fronted engine can be both farther forward than before and provide room for the coolant radiator. The placement of the intake system in the cylinder Vee allows the intake airbox to be placed directly above it. As you might expect, fuel displaced by this airbox has been pushed back under the rider’s seat. Tank capacity is 4.9 gallons. The adoption of liquid-cooling means that the exhaust ports need no longer face the wind.

The V100’s flat-fronted engine can be positioned farther forward, while making room for the coolant radiator. (Moto Guzzi/)

With the cast aluminum single-sided swingarm pivoting on the gearbox and the engine becoming a structural element, the tubular steel chassis devolves into a simple “bracket” attaching at six points to the engine and carrying the steering head at the front and the rider/passenger to the rear. Steering geometry is not touring-slow at 24.7 degrees rake and 104mm (4.1 inches) trail.

This engine’s six-speed gearbox is for the first time able to employ an up/down quickshifter. This is a ride-by-wire engine and clutch diameter (and therefore its rotational inertia) has been reduced by switching to a wet, multiplate clutch.

Moto Guzzi angled the drive shaft inward by 6 degrees to create clearance for a wider 190/55-17 rear tire. (Moto Guzzi/)

By angling the Mandello’s drive shaft inward at 6 degrees from rear wheel to gearbox, there is both width at the rear for the wide 190/55-17 rear tire (on a 6-inch rim) and rider-accommodating, reduced width in the middle of the bike. There are mechanical torsional dampers in the driveline and a rubber damper on the drive shaft itself. Their job is to convert the strong torque pulses from large cylinders into a smooth delivery of power to the rear wheel.

The engine has wet-sump lubrication by the usual trochoid pump, and the only communication between the flat sump and crankcase is via a reed valve. This positively prevents oil slosh in the shallow sump from hitting the spinning crank during vigorous maneuvering.

I have not discussed suspension (Öhlins semi-active on Mandello S) or Guzzi’s adoption of a six-axis inertial platform, cornering ABS, the heated grips, or the adaptive aero said to reduce rider wind pressure by 22 percent. Why not? I suspect folks would like a breather after penetrating the engine-centered text above.

Mandello is a new beginning for Guzzi in an engine and chassis system that can serve many models and riding disciplines. Mandello is an integrated design, a fresh start in the modern manner.

Source

[Catteeclan]

That alternators gonna be nice and toast between them cylinders

[Buckster]

1 hour ago, Catteeclan said:

That alternators gonna be nice and toast between them cylinders

And behind the radiator. The older ones are below the cylinders on the front of the engine, crank driven and behind a cover that is directly in airflow. It will be interesting to see if this turns out to be this engine designs weakness.