Keep your cool: Why Ducati’s latest V4s are able to morph into parallel twins

Imagine for a moment that you’ve splashed the cash on a cutting-edge 1158cc V4 only to find it’s actually a 579cc parallel twin. That’s precisely what the £23,590 Ducati Multistrada V4 Rally and new £23,595 Ducati Diavel V4 are for much of the time and the whole transition is totally seamless.

Far from being some kind of swindle it’s the result of the latest iteration of Ducati’s cylinder deactivation system, which cuts the spark and fuel to the rear cylinder bank under certain circumstances.

First introduced in 2018 on the Ducati Panigale V4 superbike as a software update, the system was initially used only when the company’s V4-powered bikes were at idle but now extends to low-speed, low throttle riding as well on the Diavel and Multi, and the same strategy is likely to extend to more models.

Ducati are far from the first manufacturer to dabble with the idea. Indian also introduced a system to cut the rear cylinder on some of their V-twins at idle in 2018, something which has since spread to most of the company’s bikes, and Harley-Davidson have been at it longer still, having introduced their Engine Idle Temperature Management System (EITMS) as far back as 2008.

It’s no coincidence that all the examples of production bikes with cylinder deactivation systems have ‘V’ engines, and that it’s the rear cylinder, or bank, which gets switched off. On each, the deactivation happens under limited circumstances, and until the introduction of the Multistrada V4 Rally and Diavel V4, when the bike is stationary.

The main driving force behind the systems’ development is heat. Hidden in the middle of the bike, away from direct airflow, rear cylinders of V engines get hotter than the ones in front, and by turning them off, even just for a few moments each time the bike comes to a halt, those temperatures are brought down. What’s more, the rear cylinders are directly between the rider’s legs and below the seat, and their heat build-up means an uncomfortable in-traffic experience.

But there are benefits beyond simple heat management, as illustrated by the latest Ducati developments. Turning off the rear cylinders also boosts economy and – with less fuel being burnt – improves emissions performance.

It’s not just a case of turning off the fuel and spark, though. With only half the cylinders running, the throttles need to be opened further to keep engine speed – something that can be done seamlessly with ride-by-wire. That’s beneficial, reducing the pumping losses associated with sucking air through a closed throttle and allowing the remaining, running cylinders to work more efficiently.

Since emissions tests cover a simulated ride, including periods at low speed and idle, the system gives an edge when it comes to meeting ever-stricter emissions limits.

Are there downsides of note? Not really. Some variable cylinder management systems used in cars have had reliability issues but they’re far more complex than those seen in bikes so far, and are still generally dependable, with Honda and VW championing the idea across a broad range of models.

Ducati cylinder deactivation in detail

• New possibilities: Modern engine management, fuel injection and particularly ride-by-wire throttles has opened the door to cylinder deactivation systems that work seamlessly at low engine speed.
• Cleaner and more efficient: By cutting the fuel and spark, the rear cylinders are switched off to reduce heat build-up, save fuel and cut emissions.
• Reducing losses: Because the remaining cylinders are working harder, the throttles are opened wider, bringing them into a more efficient operating zone and reducing pumping losses.
• Lowering the tone: You’ll notice a change in the exhaust note as the cylinders cut in and out but other than that the system works seamlessly.
• Cooler rear cylinders: V engines benefit most due to heat issue in the rear bank, but when emissions rules get tighter, we might see inline engines adopting cylinder deactivation as well.