Pipercross, the Northampton company which produces air filters for competition cars, have launched a range of their polyurethane reticulated foam filters for road cars. They claim that the filters not only increase performance but also economy. We've been trying one on a Golf GTi and, certainly, the engine feels stronger but, ever sceptical, we double-checked with two firms which have also tried them.
GTi Engineering told us that, measured on a brake, the Pipercross filter gave 3 1/4 bhp more than standard on a Golf GTi Mk 2 (4.8 bhp is claimed for the Mk 1), and Geoff Thomas of Autocavan confirmed that a Pipercross filter allowed a turbocharged GTi engine to rev at more than 1,000 rpm over a standard filter. Both companies will fit Pipercross filters to their cars in future.
As though that were not enough,. Pipercross filters cost less than the standard units making them far and away the cheapest performance booster ever.