€3 per 100 kilometers, this is promised by both the VW E-up! and the CNG-up! (Compressed Natural Gas). Indeed there is one small difference, the natural gas-version can be had for half the price. The E-up! is more advantageous for the VW-concern because it brings in the highest CO2-savings.
However, don't let yourself be fooled, taking the present state of technology, no vehicle can combine economy with ecology as well as a natural gas car. What is becoming more and more well known, is the fact that natural gas must not necessarily be classified as a fossil fuel. As you can see from this example, it can also be acquired in an environmentally friendly manner.
Then there's the CO2-emission. The manufacturer promises 25% less, even though natural gas can only be acquired from the still abundant fossil deposits. In the past, a natural gas engine was, as far as performance is concerned, at a disadvantage. Indeed, due to the multiple possibilities offered by today's engine-management systems, all this has changed.
It's no longer even necessary to use petrol to start the natural gas cars. The amount of petrol in the tank is distinctly smaller, in proportion to that of natural gas. In the case of the CNG-up!, the amount calculated in liters, is even lower than the amount of kilograms of natural gas. Together with the factor 1,5, the CNG-up! with a full tank, has more than 60% natural gas on board. Thereby, it's total range is rather irrelevant. The car is not being bought to be operated with petrol.
The pressure from the tank is reduced from 200, down to from 5 to 9 bar, to then reach the intake system from a rail (see picture) through injection valves. According to Bosch, their valves have a resistance of 8,5 Ohms and, by the way, a service life of 240.000 kms, which is comparable with petrol engines. Apart from having only little weight, the precaution against leakage is important. Using a great deal of stainless-steel in the whole system, the necessary durability is provided.
A big advantage is, when both mixture-preparation systems come from the same source and the CNG-component doesn't have to laboriously, extract the values from the petrol- component. Thus all the functions can be supervised and regulated. Therefore, it is customary, that particularly short-term changes are achieved through the ignition and longer-term changes, through the fuel/air system. The same thing happens in the CNG-component.
The Motronic-control device has access to all areas. In particular, the high-pressure sensor with it's metal membrane and thus, the resistance-bridges, which provide the pressure with a proportional tension. They can handle pressures of between 260 and 280 bar, they cannot (yet) however, convert themselves, but do provide a classical signal, which probably, because of the fault detection, extends from not quite 0 to 5 volts. Thus, the system is protected from excessive pressure from the tank-area.
There is also another sensor, this time for the low pressure. It should regulate this pressure precisely because, together with the temperature-sensor, it provides for stable conditions for the determining of the injection timing. It also gives off a tension,which is however, oppositely proportionate to the measured pressure. In addition, an NTC-resistance in it's steel casing is also active. 09/13