A Look Inside the New Engine Powering the Enduro Veloce

MV Agusta’s 931cc triple maxes out the displacement of the current engine architecture.

It all started from the need of MV Agusta to access the liter displacement class with a unit that would be more competitive and versatile than its 1,000 inline-four. Investing in a new engine was out of the question; thus the mission was to investigate a potential displacement growth using the structure of the 675/800 triple. This led to MV Agusta’s new 931cc triple.

Before diving into this technical analysis of the new MV Agusta 931, go back to the very competent story in which Editor-at-Large Blake Conner analyzes the complete technology of the MV Agusta Enduro Veloce. Of the highest interest is his analysis and comment about the new 931cc triple that powers the new Enduro Veloce—”The triple in the Enduro Veloce is, in one word, awesome”—after sampling the bike in Sardinia.

After you’ve perused Conner’s test, here we dive into the less colorful yet just as interesting technical analysis of the new MV Agusta 931 triple, trying to tease out how the MV Agusta engineering team succeeded to develop such an “awesome” engine.

An Engineering Challenge
The MV Agusta 675/800 triple is an excellent example of advanced motor engineering. It is solid, reliable, and features a high thermodynamic efficiency thanks to its state-of-the-art combustion chamber design and valve train. MV Agusta’s engineering department played with a great number of potential bore and stroke combinations that could be reasonably considered to get the largest possible increase in displacement while preserving reliability and the organic efficiency that made the 675/800 so largely appreciated.

Given the absolute obligation of keeping most of the tooling and manufacturing process, the parameters at the foundation of the project posed a real technical challenge to the MV Agusta engineering team since no alterations were allowed to the basic outer measurements. And we are not talking of deck height and crankcase width, but even down to preserving the geometrical coordination of the engine mounts and the axis of the front sprocket.

All of the outside measurements of the engine had to remain the same to save on tooling and manufacturing costs and complexity.

Mechanical Solutions
The accurate research led to a bore increase of 2mm, to 81mm, and a stroke increase of 5.9mm, to 60.2mm, producing a total displacement of 930.6cc. Not a classic number, but now the MV Agusta triple had almost reached the goal of 1-liter status.

Bore was increased from 79mm to 81mm.

The only axis that could be set at a different geometrical relationship to the others was the crankshaft, so the lower half of the crankcase was redesigned to locate the crankshaft in a lower position in relation to the deck height. This allowed increasing rod length from 105.1mm to 115mm which produced a 1.91 lambda in relation to the increased stroke, practically unchanged compared to the 1.94 lambda generated by the 800cc rods. The rod length-to-stroke ratio is fundamental to elevate the organic efficiency of a given engine by reducing the secondary imbalance and the pistons’ side thrust; it also improves the thermodynamic efficiency by extending combustion time of the charge happening at maximum pressure while the piston dwells fractionally longer at TDC.

The same attention was reserved to strengthening the crank assembly. Given the increased crank throws, the crankshaft received larger main end journals, from 33mm to 37mm, and crank journals, from 33mm to 35mm. This way the crankshaft was both beefier and, very importantly, the overlapping section between main end and crank journals grew to 5.9mm, in addition to the increased load capacity of each Daido plain bearing.

The crankshaft was beefed up to handle the increased horsepower.

These are the mechanical differences that separate the 931 triple from its 800 triple ancestor. In addition, it also received a new oil sump, wider and less deep. Cooling and oiling systems were duly adapted to the additional displacement.

From the first-generation MV Agusta triples, the 931 inherits the clockwise rotating crankshaft that contributes to reducing the rotational inertia that would otherwise combine with that of the front wheel to make the steering heavier. As all inline-triples, the new MV Agusta 931 is equipped with a counterrotating shaft that is duly counterweighted to cancel the primary order imbalance typical of an inline-triple.

Power Numbers
In its early edition, the 931 triple generated 112 hp at 10,000 rpm. Major power progresses came from the radical evolution of the Eldor Nemo ECU which manages the integrated injection-ignition system, while a big boost came with the evolution of the 3-into-1 exhaust system; that brought the power numbers up to a claimed 124 hp at 10,000 rpm with torque peaking 75.2 lb.-ft. at 7,000 rpm, with 85 percent of that available beginning at 3,000 rpm.

To get the most out of a Euro 5 homologated engine, the exhaust system is fitted with an electronically controlled butterfly valve that softens the exhaust note up to around 4,000 rpm, then the valve opens and lets the engine roar. Not only is the specific torque output very remarkable, most important is that the 3,000 rpm span between peak torque and peak power is a strong sign that the engine is extremely flexible.

Cylinder Head
This comes from a highly refined cylinder head that features a well-profiled combustion chamber, with valves set at an included angle of 23 degrees. Steel valves at both inlets are 31.8mm, and exhaust is 26.7mm. Cam lift is 7.6mm for both. Distribution is by Morse-type chain driving dual overhead camshafts with inverted cup cam followers treated with DLC to reduce friction. The cams followers are 28mm in diameter and valve return is ensured by twin coaxial springs. The distribution chain is driven off a sprocket at the left end of the balancing shaft. Intake cams reach maximum lift at 100 degrees ATDC; exhaust cams reach maximum lift 112 degrees  BTDC.

Pistons
Pistons are forged aluminum and look like racing units, thin, light at 190 grams, with two rings plus oil ring. The piston top features a clean profile with wide enough squish areas and a slight depression at the center that should grant additional control of the turbulence for a very positive thermodynamic efficiency at all rpm.

Mikuni Fuel Injection
The induction system utilizes 47mm throttle bodies by Mikuni with individual Mikuni injectors, which is a meaningful departure from the common practice with all other MV Agusta engines that use twin injectors per each throttle body, one shower style and one next to the valve head. This is a positive confirmation of the radical evolution of the Eldor integrated engine management unit—a meaningful evolution of MV Agusta’s global electronic system.

Crankcase
The crankcase is horizontally separated and has been beefed up in all critical areas to safely stand up to the additional loads coming from the larger displacement. After all, this is a 931cc triple that generates 124 hp at 10,000 rpm with a limit up to 12,250 rpm—rather impressive. Thanks to the short stroke, piston mean speed remains within safety margins at 80 feet per second even at that extreme rpm, while piston mean speed at peak power rpm is a totally safe 65.6 feet per second. The solid crankcase structure makes it very reliable and functional with the adoption of a cassette-type six-speed gearbox, another distinctive feature of the MV Agusta triple family, including the latest 931cc.

The 931 triple started life on the limited-edition LXP Orioli then transitioned to the regular production Enduro Veloce, but its potential is vast. At a wet weight of 125 pounds it generates around 1 hp per pound, and with that superbly flat torque curve it would make for a great engine in multiple models, especially a sport-tourer.

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