An animation of the operation of a scroll-type supercharger. Air is confined between the two spirals and is compressed as it is forced towards the centre. In automotive application, the spirals would have far fewer turns.
This type of air pump, notable for low noise and high efficiency, was patented on 3 October 1905 by Léon Creux of France (US Patent 801,182).[1] Due to the very imprecise production methods of the period, however, it was not manufacturable for a long time, since the displacer (described below) inside the compressor comes within tenths of a millimetre of the housing wall without making contact. Only with the more advanced engineering methods of the 1980s, did it become possible to produce the G-Lader.
Contrary to expectations, Volkswagen's designs turned out to need relatively frequent repair in normal operation, which was one of the reasons why that manufacturer eventually abandoned this technology at the time. The main cause of its relatively high failure rate was that Volkswagen misrepresented the G-Lader as maintenance-free. Depending on RPMs, load, and design details, various parts wear out, with results ranging from impaired performance, to destruction of the G-Lader. Yet it is frequently possible to extend the life of the G-Lader, sometimes to several hundred thousand kilometres, by periodically overhauling it with suitable replacement parts.
The supercharger housing holds what is called the displacer plate (or just displacer), on both sides of which are spirals, with seals between the latter and the housing. The housing itself also has spirals on both sides that mesh with those on the displacer. Driven by the crankshaft, which is connected to the displacer shaft by a small belt, the displacer moves eccentrically with respect to the supercharger housing (like the rotor in a Wankel engine) and, through this motion, forces the intake air into a smaller and smaller space, ultimately producing a maximum gauge pressure of 0.8 bars (11.6 psi) with standard delivered pulleys.
Sizes and car models
The German name G-Lader comes from the shape of the supercharger (German: Lader), which looks like the letter G. The displacer's spirals are either 40 millimetres (1.57 in) deep or, in the larger version, 59.5 millimetres (2.34 in) deep, i.e. close to 60 mm. This is the reason we see the engine designations G40 and G60 in the names of Volkswagen models in which it was used:
Volkswagen Polo Mk2GT G40 (Typ 86c - Limited to 500 vehicles first series (all black, fog head lamps) and a second of approx 1500, standards colors plus 500 all black for French market only)
