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S1 Exhaust System

The standard exhaust maintains back pressure to get the catalyst to optimum working temperature quickly. Changing the exhaust will reduce the back pressure and mean better air flow through the engine (but the catalyst will take longer to reach working temperature). The main reason for fitting an uprated or new exhaust is to improve engine noise, simply upgrading the exhaust on it's own little give a very small power improvement. Most sports exhausts are light weight (the standard exhaust weighs about 16kg) and have a less restrictive air flow. They ususally create a fair bit more noise and for some people will be too loud. A stainless steel exhaust will usually have a lifetime or >10 year guarantee, but they tend to be heavier.

The first 50 SVA Elise Sports 160's had the motorsport catalyst fitted. The external appearance of this catalyst is very different. The standard catalyst housing is made from two clams welded together to form a flattened oval casing. The motorsport catalyst is in a short cylindrical casing. The difference between them is the density of catalytic materials and the surface area of catalyst exposed to gas flow. The motorsport catalyst has a lower density, less surface area, and is hence less restriction to air flow. The difference in power between a motorsport catalyst and a bypass pipe is only about 2-3 PS. The former costs about Ł900 and the latter about Ł50.

Some insurance companies will consider it a performance modification and make you pay a higher premium. You must inform them if fitted.

Some cars exhibit an exhaust vibration at about 2000-2500rpm and this is also common to MGF's and Rover 200's. Lotus have produced an 'anti-tizz' bracket, part no. A111E6234S to solve this problem. There is a service manual update (code 1999/03) that details installation. Similar symptoms occur if the heat shield is too close to the exhaust or if the rear under-tray is not mounted correctly so check these things first.

Catalyst Bypass Pipe

Use of a catlyst bypass pipe in the UK is illegal on public roads. Combined with a sports exhaust, they can sometimes be too noisy for some tracks. All UK tracks have strict noise guidelines which must be adhered to and all cars are tested before entry ontoi the track is permitted. Suppliers of catalyst bypass pipes include:

Lotus Cars	Lotus now only offer a stainless-steel system for the S1 priced at £417.02 + VAT. There are still some Janspeed mild steel sports exhausts in the dealer network though.
Christoper Neil	Sells a stainless-steel bypass pipe for £39 + VAT. These are loud.

Exhaust Upgrades

Suppliers of exhausts include:

Lotus Cars	Lotus now only offer a stainless-steel system for the S1 priced at £417.02 + VAT. There are still some Janspeed mild steel sports exhausts in the dealer network though.
Brooke Kensington	Sell a stainless-steel sports exhaust for £295 plus VAT.
Christoper Neil	Sells a stainless-steel sports exhaust for £245 + VAT. These are loud.
Power Train Projects	Sell a stainless-steel (304 grade) sports exhaust for £276 plus VAT. It has a lifetime warranty and is made by Janspeed Performance Exhausts who used to supply Lotus Cars.