exhausts laws

[treeseries]

hello every1 can anybody tell me the laws on straight through exhaust, i want to fit a straight through (obviously) on a 318is on a h plate, i wanna know how many boxs i need? if i can fit it from manifold to back box or if i need a cat? any info would be great. thank u.

[Turbo-Brown]

Won't need a CAT on an H plate which is nice.

I believe the acceptable volume of sound is down to the MOT man so you could potentially find a deaf one and pass no probs.

The Ol' Bill or VOSA might have something to say though.

I've got a straight through twin 2" system on mine (although the turbos damp out a lot of noise) but I can't imagine your car being much louder than the average mentalled up Corsa if you have a back box fitted

[Simon13]

removing just the centre box on a 318iS does nothing. I did it and it made it no louder

i only did this because my 318iS was a 91 H and it had a cat fitted on it! as i was poor the easiest was weld some pipe in it's place!

just made it more raspy top end when flooring it

[harry_p]

as said, there's no legal noise limit, but if a coppa, or vosa inspector decides it's 'excessive' then you could be in trouble.

usually it would have to be stupidly loud to be considered excessive though.

[Brianmoooore]

MOT says on the subject- "clearly unreasonably above the level expected from a similar vehicle...in average condition", so clearly open to quite a bit of interpretation!

[jon_pure_british]

if police came up to you about it, expect a 7 day fit it thingy

[Turbo-Brown]

Does the IS have a 4-2 manifold?

If so it's possibly worth checking that the centre box isn't just a crossover rather than just a silencer. It is on the 6cyl cars and removing it can apparently lose you some low end torque