Lancia Beta Volumex supercharger

Pictures of a Volumex Supercharger
Volumex Supercharger: Front, no pulley, Side, no pulley, Side, Front (Mark Grant)
The Volumex supercharger was a roots-type two-lobe rotor design of 1130 cc capacity, running at 1.32 times engine speed, and was designed by Lampredi while working for Abarth. The unit consists of an aluminium casing in which the two figure-eight rotors counter-rotate, supported by bearings at each end and driven by gears at the pulley end. The gears and pulley-end bearings are lubricated from an oil reservoir, while the bearings at the far end are lubricated solely by grease.

The end result is to give 6.5 psi boost, increasing power by about 13% and torque by about 18% over the standard two liter engine. The actual power increase is however greater than this, since the compression ratio of the engine was lowered to allow it to take the additional pressure. With the supercharger disconnected performance drops dramatically, and I'd be surprised if the engine was developing more than 100 bhp.

Nominally, the supercharger is less efficient than a turbocharger, since the turbo uses the exhaust gas from the engine, whereas the supercharger takes power from the engine (about 3 bhp at full boost in this case) directly, via a toothed belt connected to the crankshaft. However, this ignores the changes to the engine required to accept the turbo, additional backpressure from the exhaust, etc, which will reduce the efficiency of the engine, and also the supercharger takes very little power when the engine is running at a constant speed. As a result of this, the fuel consumption of the Volumex cars is very good on long constant speed runs, but can be appalling when driven hard.

In addition to the Lancia cars, the Volumex engine was used in the Pininfarina Spidereuropa Volumex, based on the Fiat 124 Spider.

Maintainer: Andrew Cliffe
Last update: 1st April 2001