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performance cats


ididntodit73
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Hi all.

I'm after some cats for my new build.

The engine is a ls1/6 5.7.

help needed please!

Why???? Hot cat's don't like being submerged in cold water and you'll get better figures without them fitted. You won't pass an MOT without them fitted but there are ways around this.

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SVA / IVA you will need them.

MOT you will need them.

Depending on where you buy your engine it could well come with some OEM cats.

'A friend' uses a cat replacement pipe in his Lotus Elise and keeps the factory cat safe on the shelf for the once a year it's needed for the MOT. Saves having to replace it every few years and is good for performance. Yes, you could use expensive (you won't see change for £500) low density sports cats but they really aren't well suited to off road vehicles and will not be as effective as factory cats meaning a greater chance of emissions failure.

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I'd pester the local exhaust supplier, most cats are one of a few basic designs with a specific bendy bit of pipe welded on to suit the car, ISTR a chappy with a J**p who got quoted a ludicrous amount of cash for a new cat, ended up buying a job lot of standard cats (minus the J**p specific pipe) for about 1/10th the price and punting them out to grateful owners for a small margin. As long as the tube size is right, I'd got with it - the LS isn't exactly going to notice being a HP or two down because of added restriction :lol:

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I'd pester the local exhaust supplier, most cats are one of a few basic designs with a specific bendy bit of pipe welded on to suit the car, ISTR a chappy with a J**p who got quoted a ludicrous amount of cash for a new cat, ended up buying a job lot of standard cats (minus the J**p specific pipe) for about 1/10th the price and punting them out to grateful owners for a small margin. As long as the tube size is right, I'd got with it - the LS isn't exactly going to notice being a HP or two down because of added restriction :lol:

Especially if the vehicle only makes one short journey a year with them fitted. ;)

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SVA / IVA you will need them.

MOT you will need them.

Depending on where you buy your engine it could well come with some OEM cats.

'A friend' uses a cat replacement pipe in his Lotus Elise and keeps the factory cat safe on the shelf for the once a year it's needed for the MOT. Saves having to replace it every few years and is good for performance. Yes, you could use expensive (you won't see change for £500) low density sports cats but they really aren't well suited to off road vehicles and will not be as effective as factory cats meaning a greater chance of emissions failure.

Based on what? An SVA build is a lowvolume type approval, emisions are not part of this, or at least not when I did it.

Daan

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Lambda is a measure of air:fuel ratio so I would hope all engines would be capable of meeting Lambda = 1 as that's the optimum point for combustion. The emissions that cats reduce so greatly are the other bits (CO2 / HC) which you simply will not pass without a cat if the test was designed for cat equipped vehicles - the cat on my Freebie disintegrated and the emissions were about 10x the limit :blink: so that tells you the difference the cat makes.

However, as Daan said it really depends what the SVA test is going to require.

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well sean from north off road said i would need a cat for my sva/iva.

but going down the local exhaust place sounds like a plan.

Thanks

Only VOSA can tell you if you'll need one really, it very much depends on what they make of your vehicle and what flavour of test it'll be in for.

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