Petrol Direct Injection 2008
The petrol direct injection is that important for the future reduction of the CO2 values, that it's worthwhile to give an interim report for 2008. Recently the injection pressure has reached the 200-bar mark.
Nearly all manufacturers have directly injecting petrol engines in their programme, some even in all model ranges (Audi). There are manufacturers who have adapted all their engines, e.g. Porsche (figure) this year.
VW combines the four cylinder direct fuel injections with single- or two-step turbo-charging.
Most systems still work with a homogeneous mixture. This causes economic- and regulation problems, because stratified charge operation is
expensive, due to the costly,
further treatment of the exhaust gasses the control management is substantial. Often however, with a dubious success rate, and as VW, the first user of this technology, (2000) discovered, expensive. The main-
disadvantage here were probably the wall guiding through the piston and the limited savings possible only in a relatively small RPM range. Even speeds of 130 km/h were under no circumstances possible.
Mercedes Benz - still rather hesitantly, and BMW are attempting once more, the process that perhaps together with stroke-controlled and time-controlled valves, promises another up to 20 percent savings. By the way,
these engines are by no means becoming any quieter, they appear to strive for a reduction of the CO2 emission values and also for the noise caused by the diesel engine, which in some cases they even
exceed. One may expect vibration free engines, at least in the case of BMW. Thus upper-class saloon cars, with a fuel consumption which was common in previous mid-range cars can be operated. Naturally it is still
far from the ambitious EU target.
From the standpoint of fuel, it is, first of all more expensive, because these super-cars need the sulphur-free variety which can only be had as 'super-plus' with, of course, the accompanying additional costs. The
injection spray is led more directly to the spark plug and can through a wide range of activities, reach the intake valves doing what the Thumble flaps earlier would have done and more, i.e. generate a well ignitable
mixture around the spark plug, and still
function economically. Unfortunately thereby, the engine becomes even hotter than it already is now which attacks the components and does not make the turbo charging and the mass reduction that comes with it,
possible at the moment. 07/08