Uncut: Cathcart
Uncut, unedited, uncompromising...
VEE TWO DUCATI MONSTER S2R TECHNICAL: SuperCharged
To deliver that muscular extra performance from the stock 992cc Ducati desmodue motor, Vee Two has mounted a twin helical-screw Sprintex compressor unit - same as the one on the Super Squalo - above the front cylinder, that’s compact enough to fit between the frame rails underneath the stock Monster fuel tank, sitting atop a billet aluminium plenum chamber (carbon fibre in production) replacing the stock Ducati airbox. The original pair of throttle bodies have also been junked in favour of just a single 48mm Vee Two-manufactured one with a single butterfly. The supercharger compresses mixture at 6.5 psi/0.46 bar, and is belt-driven off the front cylinder’s bottom camshaft pulley, which has a small clutch arrangement on it designed to operate as a cutout mechanism in the event of any problem with the compressor, to avoid risk of damage to the engine itself. A drive belt runs from that pulley to a larger intermediate pinion which gears up the drive speed for the compressor by about 1.24:1 to a relatively slow 11,500 rpm, via another belt leading directly to the supercharger.
This Monster desmodue system is more rational and less complicated than the Super Squalo installation, since firstly thanks to improved access through the frame rails, there’s no need to reverse the drive rotation as on the Testrastretta version, which permits Vee Two to route drive via the male supercharger rotor, rather than the female one (which of course rotates in the opposite direction), as on the Super Squalo. Furthermore, there’s no need for the latter’s system of vacuum-operated check valves in each cylinder’s inlet tract, with supplementary injectors staged to operate sequentially so as to enhance low-down rideability. On the reduced power Monster configuration, the desired linear throttle response is exclusively delivered via engine mapping and fuelling. Moreover, this is obtained not via a costly MoTeC engine management system as on the Super Squalo, but by retaining the Monster’s standard Magneti Marelli ECU, complete with all the software which Ducati spent millions of Euros on developing, and which also assures Euro 3 homologation, according to Vee Two CEO Tony Hamilton. Vee Two then adds an additional third injector into the airbox which provides the background fuelling, controlled by a secondary ‘blue box’ ECU made to their specification in South Africa.
This supplementary ECU ultimately controls all the key parameters such as ignition advance, temperature compensation, fuelling etc. by interfacing with the Marelli to receive a variety of the signals from this primary ECU, then re-interpreting them so that it effectively assumes control of those elements, without creating any problematic additional side issues. “Traditionally what’s happened is that when you instal a secondary aftermarket ECU on a Ducati motorcycle, the ‘check engine’ light comes on,” says Tony Hamilton. “Because the Marelli ECU is pretty sophisticated, it regularly sends intermittent messages to the system to check if this is being interfered with - as by installing an aftermarket component! If it doesn’t get the right response, the ‘check engine’ light comes on virtually straight away, and puts the motorcycle into limp-home mode. There are several manufactures of aftermarket ECUs that won’t currently supply their box for use on a Ducati because of that exact problem - fitting it effectively switches the ECU off. But we’ve circumvented this, and with our ECU we can do what we need to do in terms of engine management over and above what the Marelli offers, yet in doing so without creating an environment for it to go on strike and go into limp-home.” Vee Two also retain the stock Ducati exhaust system, complete with catalytic converter and lambda probe oxygen sensors, maintaining the bike’s likely Euro 3 compliance from both an emission and noise standpoint - the power-up Monster complies with the stationary 88dBa noise limit even now fitted with the supercharger, since the small amount of induction whine from this is irrelevant, claims Hamilton.
All other mechanical (and chassis) elements of the mega-Monster remain as standard, although it’s possible that further into the future the transmission may need to be uprated. The Vee Two VRod I first rode three years ago had to be fitted with a heavy duty Barnet Kevlar clutch to handle the extra torque produced by supercharging the eight-valve Harley engine, and although Hamilton says that in normal riding conditions the Monster’s standard Ducati dry clutch has so far proved adequate, he recognizes that enthusiastic use of the supercharged engine’s performance will probably make a carbon clutch more appropriate in the interests of longevity. The extra torque and horsepower do take their toll, and Vee Two are developing their own in house aftermarket carbon clutch option.
Interestingly, there’s quite a heavy load on the drive mechanism of a supercharger when you rev the engine up - but there’s even more of a load under deceleration. It’s significant because there’s pressure building up in the compressor when you back off the throttle, and on top of that you have the reverse inertia of the rotors and the gears which drive them, which you’re now trying to slow down, meaning the loads in the drive mechanism go the opposite way. Only drawback to the whole installation is that the 8 kg. additional weight of the supercharger and plenum is mounted rather high up in the frame, though its forward location does at least load up the front wheel a little more than stock, for extra grip in turns. I can’t say I noticed any adverse feedback from the Monster’s consequent higher cee of gee, though.
