I make the largest diameter Sports Cats on the market for these cars. My concern with placing the catalyser substrate in the gas-flow is to minimise the back-pressure, hence the use of the largest available. With a metallic substrate, they can withstand a lot of abuse but given their positioning on the car, that’s not too much of a worry.

Let me clarify one important point. The removal of anything causing exhaust back-pressure on a 4-stroke engine will improve performance provided the fuelling demand is matched to the increased gas-flow. The Lotus/Toyota ECU will adjust, eventually. IMO, you’re better getting one of the many re-flashes available. Throttle response is also improved – this is a small point but the difference is noticeable.

What I’m trying to do is keep the lower emissions but also present the least back-pressure to the exhaust gases. This means using an OBD2 compliant 200 Cell substrate. I use the metallic base for extra strength/reliability. Now, combine the open area of the 200 Cell substrate with the large diameter and you’re definitely on the right track. I make the largest Sports Cats on the market for these cars, and I’ve always seen a power/torque improvement.

Let’s take a look inside the std Lotus/Toyota offering for the 2zze motor (Type A). This is fitted to the Elise 111R/EliseSC/Exige S and er, the 1zze Elise S. With a cell density of 600 Cell psi on a ceramic base, it’s restrictive enough on the n/a motor, even more so on the Supercharged install. Why do Lotus fit the same Catalyser to a 134bhp motor (Elise S), a 190bhp motor (Elise R) and the 220bhp (Supercharged motors)? umm, answers on a postcard please.

Substrate Comparison
Type A	Type B	Type C

Compare that with the 200 Cell substrate I use (Type B). Type C, now this is the 100 Cell Race design – again, a larger open-area but these won’t work with the OBD2 – (well, work progresses ………..).

Some forums would have it there’s no point in fitting a Sports Cat. Take a look at this “rogues gallery”. Some of the designs/claims I’ve seen are laughable. I wonder if the disgruntled owners have one of these fitted! There’s “Sports Cats” then there’s 2bular Sports Cats.

I’ve seen these Catalysers offered for Lotus Elise exhausts – they’re rated to 120bhp

Fit this and it will probably perform worse than the std offering!

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