In 1921, Mercedes was the first to push a supercharged car into production, and certain racing classes haven’t looked back since. Yet up until Abarth began experimenting in 1975, nobody wished to apply the technology to small-displacement road cars. What’s more, following GM’s trials in the sixties with the Corvair’s turbocharged flat-six, BMW debuted its 2002 Turbo in 1973, and despite the first oil crisis hitting moments later, the world suddenly seemed ready for the turbo era. It began in Formula One with Renault’s Gordini V6 Turbo in 1977, and continued with Saab’s production 99 Turbo in 1978.
Not many remember the 1981 Fiat 131 Supermirafiori Sport Volumetrico Abarth. Mostly because the know-how soon landed on Lancia’s table, which used Abarth’s supercharged 2.0 Lampredi Twin Cam in their 037 rally car, as well as a few of the road-going Betas, HPEs and Montecarlos. But then came Volkswagen, and its revolutionary G-Lader engines.
114 horsepower from 1.3-liters:
The Polo’s experimental G40 engine used a twin V-belt driven blower-type supercharger mounted on the exhaust side, operating at a maximum of 10.4 psi “at all speeds.” Inside, the air got trapped between a stationery and a rotating spiral, and as the one in motion rolled down the solid one, the air got compressed before leaving the charger towards the intercooler. The pre-compressed air was chilled back to 55 degrees F before entering the combustion chamber, while the air/fuel ratio and ignition timing was managed by a computer VW called Digifant.
VW wanted to combine the robustness of a Roots unit with the feed characteristics of a vane changer, with an unchanged exhaust side for easy adaptation to emission control systems. Development began in 1978, and the blower was called G40 because it contained G-shaped spirals that were 40mm wide. They advertised it as not only more efficient and quieter than a Roots-style supercharger, but also great at eliminating (turbo) lag and producing “uniformly high torque.”
To make sure the 1.3-liter engine could handle the extra forty horses and peak torque of 109 foot pounds, Volkswagen applied a few upgrades. The G40’s valve gear used hydraulic self-adjusting bucket tappets instead of valve levers, as well as bigger valves and ports. The cross-flow cylinder head has been modified accordingly. The increased oil requirements called for a 50 percent higher capacity, roller chain-driven oil pump, as well as a beefier cooling system.
The Polo G40 also got a stronger, close-ratio five-speed gearbox, lower, stiffer springs, firmer shocks, and a set of alloys that helped to keep the weight increase down to 44 lbs. overall.
To make sure all of that worked, Volkswagen sent three Polo G40s to its high-speed oval at Ehra-Lessien, for an intense shakedown.
Instead of the stock 114 horsepower, the record runner trio had 127-hp engines, as well as optimized (duct taped) bodies and a single bucket seat, along with usual safety equipment.
These Polos could reach 136mph, but after having covered 3100 miles during their 24-hour endurance record run, their average speed was confirmed at 129.2 mph. Blame those fuel stops.
The Polo G40 entered limited production in 1987, hitting the circuits as a one-make DTM support series as well. Volkswagen claimed a zero-to-sixty in nine seconds, and a top speed of 121mph. Known as the Mk2F G40, the square-lamped full production version followed in 1989, along with the 5071-unit homologation special Rallye Golf G60, the equally Volkswagen Motorsport-built Golf G60 Limited, the Corrado G60, and the Passat G60 Syncro. This bigger cars used the 1.8-liter G60 engines, all based on the Polo’s G40 tech.
Today, if your plan is to supply your old VW four-banger with 34.5 cubic inches of compressed air per revolution, Volkswagen Classic Parts will be happy to sell you a brand new G40 supercharger for the equivalent of $2454.
That may seem expensive, but remember, according to the Volkswagen of the late eighties: “The G-supercharger operates with no appreciable wear and tear!”