The 2019 Ducati Diavel 1260, which we showcased last week will boast the DVT variable valve timing system first pioneered by Ducati in 2015.
Already present on the Ducati Multistrada 1260 and Ducati XDiavel, the system is designed to allow a motor to work at its optimum at both high and low engine speeds. With variable timing of both the exhaust and intake valves, Ducati’s system is one of the most advanced around.
Why you need it
The dream of every manufacturer is to produce a motor that’ll respond well from tickover, drive strongly though the middle of its rev range and then perform properly with a searing top end. However, the laws of physics mean that normally only two out of the three are possible.
One of the most important things that determine a bike’s character is the amount of intake and exhaust valve overlap. The overlap angle is defined as the interval of crankshaft rotation, expressed in degrees, during which both the intake and exhaust valves are open at the same time.
This overlap occurs between the end of the exhaust stroke and the start of the intake stroke and is normally a single value. Having some valve overlap has advantages, as the delayed closing of the exhaust valve encourages the final remnants of gas to head towards the exhaust port.
There’s also the advantage of the opening of the intake valve before top dead centre which lets a fresh charge to enter, which can help force the exhaust gas to flow out of the exhaust port and replacing it with an additional charge to be burned during the following cycle.
The more overlap a machine has the more efficient it is a higher rpm. However, the longer the overlap, the worse it is at low rpm and the poorer the emissions because the combustion process is less efficient. But a variable valve timing system has the potential to stop this and also improves smoothness at low rpm – very important on big Ducatis.
How it works
A valve timing adjuster is fitted to the end of each of the two camshafts per cylinder head. The DVT system consists of an external housing, rigidly connected to the cambelt pulley and an internal mechanism which is connected to the camshaft and can independently rotate inside the housing.
The rotation of the internal mechanism is controlled by varying the oil pressure in special chambers. The oil pressure is adjusted by dedicated valves and the timing of each cam is controlled by a sensor located in the cam covers.
This sensor is fed information from the ECU related to gear position, engine speed, load and rpm do give the optimum valve overlap in every riding position. It means the engine’s overlap can constantly vary according to demands.
It’s the best of both worlds
It gives a huge range of adjustment. For example, in the highest-performing Testastretta V-twin we’ve ever seen was the 1198 superbike this gave 41 degrees of valve overlap while the detuned version of the Testastretta motor, which is still used in this year’s Diavel, gives 11 degrees, to help with flexibility and midrange power.
However, the Testastretta DVT is not limited by a fixed valve overlap angle. It allows bigger angles of overlap than the 1198 at high rpm for optimum power while at the same time smaller angles than the current Diavel for emissions and low-speed performance. It’s the best of both worlds.
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