The K&N 57i is an inexpensive way to upgrade the cold-air induction system on the Elise. The difference in power is negligible however - the biggest problem is that the cone filter used is an open system which is fitted in the engine bay, so large amounts of warm ambient air will be drawn through the throttle system, which is not the best situation for an induction system.

If performance is your primary concern, you may want to think about the highly recommended Hurricane system, which is a sealed system using only fresh air from the side pods.

Anyway, back to the K&N system. Fitting the kit really is simple - you will require a small selection of tools - a screwdriver and (ideally) a small socket to tighten the circle clips supplied with the kit. The hard part is taking out the old air-filter box - although when I installed it I simply left the base of the existing box in the car (it does not get in the way, so I saw not real point in removing it).

Fitting instructions

1. Unclip the lid of the existing air-filter housing.
2. Lift off the lid, and take out the air-filter panel.
3. Remove the rubber pipe which spans from the filter housing to the throttle body. This is held in place with a clip-type jubilee clip; you make need a pair of long-nosed pliers to unclip it.
4. Assemble the 57i as per the instructions supplied; you should end up with the cone and the rubber pipe attached to it.
5. Push the 57i's rubber pipe onto the throttle body (in the same place that you removed the existing pipe) and tighten the jubilee clip - not too tight - just enough to hold it in place. Make sure that you line up the notch with the throttle body as described in the induction kit instructions.
6. Pull the cold-air feed pipe out of the rear of the old air-filter housing.
7. Direct the cold-air feed pipe at the cone. This should be placed around 10cm away from the cone.

You can also upgrade the cold-air feed pipe to supply more cold air to the cone - see my guide here.

Why should I fit the the K&N 57i?

- The induction noise is fantastic. You can hear the unit sucking air when applying throttle, and the exhaust literally roars when full-throttle is applied.
- Engine appears to rev more freely, especially at high engine speed.
- Slight increase in torque/power if air supply is improved.