The Filter Test Conclusions

1. The Panel Filters

The replacement panel filters represent a cheap way of replacing the standard paper element that Rover sells the car with. They can all be washed and reused, and thus represents a very good investment in the long term. But these filters do not liberate a huge amount of power. Whether they are worth while depends on a number of considerations. First, is whether you want to remove the standard air box to fit a cone filter or not. If not, then the panel filter is the way to go, as it simply replaces the paper filter. For 1.8MPi owners, a useful improvement in driveability results. The torque and power dip @ 3,500 rpm is removed. The throttle response is snappier resulting in a worth while improvement. I concluded that the K&N panel filter 'should be fitted as standard' when I had one fitted originally before converting to a K&N 57i kit. The benefits for VVC owners are less pronounced. I would therefore recommend that you fit a performance cone filter, as these engines really benefit from the improved breathing that these filters offer.

2. The Cone Filters

The cone filter conclusions are complicated by the issue of cold air feed to the air filters. The Pipercross filters are really handicapped by the lack of cold air supply, a fact that is reflected in these filters low cost. There is no reason why the able handed DIY-er couldn't fashion cheap cold air ducts to feed the filter- but this has not been assessed in these tests. Even if cold air supply were to be fashioned, the power gains are half that seen with the Ramair and K&N products.

Only the Ramair and the K&N 57i kits come complete with cold air supplies to the filters. These are also the only filters fitted with spacer tubes to move the filter away from the throttle body. Both of these features improve the maximum outputs recorded by these filters, and it is the VVC benefits the most from them. The 1.8MPi on the other hand, suffers from a power dip @ 3,250-3,500 rpm with these installations. The Pipercross filters that are clamped directly to the throttle body are not so affected. For 1.8MPi owners who live in the city, they should seriously consider fitting the Ramair and the K&N filters directly to the throttle body, as the improvement to the throttle response is marked. Whilst maximum power gain is halved by doing this, the difference is not evident until after 4,500 rpm, and then only minimally so subjectively (it is almost impossible to notice the difference between 4 and 8 bhp!).

Unfortunately, the Ramair filters are crippled by high pricing- 140 UKP versus 80-100 UKP for the K&N. For these reasons, the K&N 57i kit (part number 57-0238), emerges as the winner for K-series applications.