Filters investigated

Below are listed the filters employed in the filter investigations. All the filters were used in both the 1.8MPi and the VVC under the same conditions of temperature and humidity, and on the same day. Each power run was repeated three times to ensure reproducibility.

K&N rolling road staff and observers were asked to leave the room when the filters were changed. When in situ, the panel filters were invisible from view inside the standard air box. When the cone filters were fitted, the appearance was disguised as much as possible. The aim at all times was to ensure that the individual performing the test was unaware as to the identity of the filter being tested.

Other filters were considered for the tests. ITG were invited to participate, but refused. The construction of the filter is near identical to the Ramair filter, as was the method of attachment to the throttle body (via a spacer tube). The ITG has no cold air supply, so one would expect the rolling road tests to be similar to the Ramair filter, but on the road, to be inferior due to higher intake temperatures.

Filters considered, but rejected from the tests: Green filters have a similar construction method to K&N, as do BMC filters. The kits from these manufacturers are not as developed as the K&N product- insofar as not comming with a spacer tube or cold air ducting. Performance would be expected to be on a par with aPipercross filter. Other filters have similar construction to the Pipercross items, therefore the Pipercross filters were considered 'generic'. For all other foam filters, read the results from the Pipercross PX. The Pipercross Vector is a superior development to the PX filter- and this was reflected in small gains with this filter in the results displayed on this page.

For purchasing details for any of the filters listed above, click here