DITECH TECHNOLOGY  
  March 2002  
               

Innovation is a choice and a challenge. It is the area in which Aprilia tests itself against the current competition. To predict trends. To satisfy both reason and emotion. To interpret the needs of man in the era of technology.

In 1992, Aprilia was the first company to launch onto the market a two-stroke scooter with a catalytic converter. In 1993, the company began developing the first scooter with a “four stroke – four valve” engine: ecology and performance were finally combined into the one vehicle.
Now, in the year 2000, Aprilia presents DITECH (Direct Injection Technology) – the new frontier in the company’s ongoing search for the perfect balance between man and the environment.
Revolutionary technology that unites the following in a single engine: performance, record-breaking
low levels of fuel consumption and reduced emissions. In brief: fun, economy and environmental
compatibility.

The DITECH is an innovative engine using electronic direct injection, employing of the ultimate in
avant-garde technology. It represents a generation-spanning leap in terms of such engines and
demonstrates that Aprilia is the first company to arrive to such a position, thereby opening up a new technological frontier.

A huge leap forward in terms of performance, reduction in fuel consumption and pollution; without losing sight of the main aims: simplicity, reliability, safety, character, power and – above all – the thrill of riding.

This is technology at its most flexible, applicable to almost the entire range of Aprilia scooters, offering great scope for development. Which means that it is capable of responding with flexibility to possible future limitations in terms of approval, without having recourse to a catalyzer or other additional elements.

THE ADVANTAGES OF APRILIA DITECH

• Reduction in the consumption of fuel and oil:
2 litres per 100 km. In comparison with a two-stroke engine with a catalyzer, the Aprilia DITECH engine is capable of reducing fuel consumption by 40% in the ECE47 cycle and by up to 50% with constant speeds. In terms of reduced consumption, it is important to note that these excellent results were obtained while constantly achieving performances that were equal or superior to those of a powerful liquidcooled two-stroke engine. To these surprisingly positive results may be added a reduction in oil consumption of 60% (from 85 cc per 100 km, in the case of the catalysed two-stroke, to 35 cc per 100 km with a DITECH engine).

• Improvements in performance and reliability of functioning
In comparison with a catalysed two-stroke engine, the Aprilia DITECH offers a clearly superior acceleration: over a 100 m course, the improvement was 15% - corresponding to a second and a half. In comparison with four-stroke engines, the improvement was two/three seconds. Aprilia DITECH is not only distinguished by its remarkable acceleration. It is a much more highly advanced engine than its predecessors and ensures a perfect ignition every time at all temperatures.

• Polluting emissions reduced
In comparison with a traditional two-stroke engine, Aprilia DITECH reduces polluting emissions by 80%. Not only is it Euro 1 approved without the use of catalyzers, but it actually improves upon the limits by 50%. The arrival of DITECH heralds a new era in the world of motorcycling, guaranteeing further margins for development. In contrast with two-stroke or four-stroke engines equipped with catalytic converters, DITECH maintains the efficiency of its systems unaltered over time, without the need for maintenance or replacement of parts.

• Longer working life and greater reliability – with electronic control.
The APRILIA DITECH engine ensures a working life that is considerably longer and superior to that of the traditional two-stroke. This is thanks, firstly, to the injection of oil into the crankcase without its being diluted by petrol; the oil can thus act more effectively on the mechanical parts. Secondly, electronic control over the oil pump allows for optimum lubrication.

The DITECH engine is completely under the control of an electronic control unit. This unit enables a continuous self-diagnosis to be carried out on all the components of the system and signals in real time to the rider any possible malfunctionings that may occur.

• Comfort
Thanks to DITECH, exhaust smoke (even when the engine is cold) is completely eliminated, as is the emission of unburned oil particles. Normally, such particles would deposit themselves on the driver’s clothes, causing a highly unpleasant odour. In brief, a DITECH engine allows for a completely new use of the scooter: no longer is there any need for bothersome topping up on oil, no more flooded engines or problematic ignition when the engine is cool.

FUNCTIONING

 
 


DITECH represents the perfect solution for low capacity scooter engines.
The fundamental innovation of the DITECH engine lies in the fact that the petrol no longer enters
into the crankcase mixed with the lubricant, as occurs in two-stroke engines. Instead, it is directly injected into the combustion chamber by an injector. The entire process is under electronic control by means of sensors that are connected to an electronic control unit.

In a traditional two-stroke engine, the chamber is scavenged with the mixture. A considerable quantity of unburned fuel and oil therefore enters the exhaust directly and is discharged into the environment (greater pollution and higher consumption). In the DITECH system, the chamber is scavenged only with air. The mixture therefore enters only when the exhaust ports are closed.

 
 


• With DITECH, the ignition of the mixture is assured with each piston stroke. The misfire effect
is thus eliminated, which normally involves unburned petrol and oil being injected directly into the exhaust. Combustion is perfect thanks to an injector that is normally used in automobiles and which allows the use of a stratified charge. Normally, the mixture is composed of 1 part petrol to 14 parts air. In contrast, with DITECH we can use a mixture that is only rich in the part of the combustion chamber near the spark plug, controlling the propagation even in areas in which the mixture is so poor as to be barely capable of ignition. With DITECH, ranging from a homogeneously thin mixture to full throttle, we can reach, through the use of a choked throttle, a ratio of one part petrol to 30 parts air, and even arrive at up to 50 parts air with the engine at tick-over. Such values are similar to those achieved with a diesel engine.

• DITECH uses sophisticated electronic pumps to meter the petrol and oil. All the functional phases of the engine are controlled by sensors, which constantly send information back to the electronic control unit. Thanks to a continuous self-diagnosis of the system, the electronic control unit regulates the functioning of the engine and optimises it.

ELEMENTS OF THE APRILIA DITECH SYSTEM

ELECTRONIC PETROL PUMP – Takes the petrol from the tank to the air-fuel rail. This is not a traditional pump, however, but rather an innovative pump that functions under high pressure (approximately 6 Bar). Despite the high level of performance, the pump uses a very low amount of electrical energy, particularly when compared to a traditional pump.

AIR-FUEL RAIL – This element is made up of three distinct components:
• Fuel Injector: a charge metering unit, which injects a precise quantity of petrol into the Direct Injector. A fundamental characteristic of this element is its reliability; that is why the component chosen is normally used in the automobile field (EFI). It is a part that has already been produced in its millions and tested under every possible condition, thereby guaranteeing the utmost reliability and functional precision.

• Direct Injector: This is perhaps the fundamental element in the system. The role of the Direct Injector, which is electronically controlled by the electronic control unit, is to mix the petrol coming from the Fuel Injector with the compressed air, employing of the pressure of the latter (5 Bar) to inject it directly into the combustion chamber. The more the petrol/air mixture is finely nebulised and the charge well stratified, the more the yield from the system improves. In order to get an idea of the precision required of this component, one should bear in mind that an automobile injection system nebulises with particles that are 50 microns in size (SMD measurement, Sauter average diameter) and a direct-injection diesel engine reaches dimensions of 25-30 microns. The Aprilia DITECH system allows for a nebulisation with drops of 8 microns, which have an evaporation time that is less than one millisecond.

• Pressure regulator: The Fuel Injector functions thanks to a pressure differential between the petrol and the circuit of compressed air. The regulator guarantees that the pressure remains stable, ensuring precise opening times for the Fuel Injector valve that injects the required amounts.

COMPRESSOR – The 5-Bar compressor sends the compressed air to the Direct Injector. The intervention of the compressor serves to atomise the charge; in contrast, in an automobile engine, the compressor serves to supercharge the engine itself. The compressor is controlled by an eccentric on the crank of the drive shaft. This technical solution has allowed the designers to avoid using an external compressor, which would have involved the use of additional tubes, autonomous lubrication circuits and suction of filtered air. These latter elements would have represented a complicated and considerably more expensive alternative.

ELECTRONIC OIL PUMP – The oil pump is a solenoid pump, which is electronically activated in order to ensure maximum precision in its functioning. The DITECH system guarantees that only the right quantity of oil is supplied in order to lubricate the engine. This quantity is calculated on the basis of information received/processed by the electronic control unit.

IGNITION/COIL – The DITECH engine requires a powerful, precise and reliable ignition. Only by means of such an ignition can it ensure complete combustion, engine efficiency and the elimination of unburned hydrocarbons in the exhaust gas.

ELECTRONIC CONTROL UNIT (ECU) - The heart of the system, this is an extremely compact
electronic control unit which monitors and controls the in a complete manner.
The electronic control unit:
• Governs metering and injection times
• Governs ignition times
• Commands the petrol pump
• Commands the oil pump
• It also carries out a continuous self-diagnosis over all the electrical components of the system
with: signalling of any possible malfunctionings.
The electronic control unit governs all the functions of the engine and processes information – in real time – concerning the engine revs and throttle opening.

BUTTERFLY VALVE – In the DITECH engine, the traditional throttle body, which regulates the suction of the air (controlled by the throttle cable), has an added feature. The valve is fitted with an electronic sensor entitled TPS (Throttle Position Sensor), which reads the throttle opening and transmits the information to the electronic control unit.

 
                     
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