Shoestring Budget Exhaust advice/ideas please

MikeT · Post by **MikeT** » 14 Sep 2007, 14:16

Re the non-cat pipe: That section is the only good part of my exhaust so I don't really want to replace it, cheap as it is.

I'd still like to know what the effects of running without a silencer are and if it's legal?

Damn, I forgot about the turbo, will this have to come off to replace the manifold to downpipe gasket?

KP · Post by KP » 14 Sep 2007, 14:27

there is no manifold to downpipe gasket per say

the manifold connects to the turbo which then connects to the downpipe/mid section

I can only see it being illegal if its over say 100db when your flooring it but that wouldnt be easy if all you did was remove the back box

MikeT · Post by **MikeT** » 14 Sep 2007, 15:18

KP wrote:there is no manifold to downpipe gasket per say

There is on mine. I just bought the gasket kit for it. I can quite clearly see it, the manifold branches four into one where there's a spring-tensioned, bracketed joint going to the downpipe (or in this case, the midsection with cat all the way to the silencer. The turbo is offset to the right (drivers side) so I presume there's some joinery that I may need to consider when fitting said gasket. Hmm, it would be an ideal opportunity to fit an EGR sensor and rework the turbo joints too if needed.

EDIT: Oh yeah, I just looked on PR net and it's to the side of the manifold, yet from under the car it looks lower than that.

KP wrote:the manifold connects to the turbo which then connects to the downpipe/mid section

I don't know about that, it's hidden from my view. Damn Haynes for not providing full exploded diagrams

KP wrote:I can only see it being illegal if its over say 100db when your flooring it but that wouldnt be easy if all you did was remove the back box

I don't know how loud 100db is but I suspect mine will be a little bit noisier than stock when I've finished with it so I would like a definitive answer. I'll go search for the MOT handbook online.

MikeT · Post by **MikeT** » 14 Sep 2007, 15:23

Taken from http://www.ukmot.com/6-3.asp#Text_top section 6.3...

"b. assess subjectively the effectiveness of the silencer in reducing exhaust noise to a level considered to be average for the vehicle"

Average? Not very helpful. There are a considerable number of vehicles on the road with louder than average exhausts.

OR from http://www.motuk.co.uk/manual_710.htm

"b. a silencer in such condition, or of such a type, that the noise emitted from the vehicle is clearly unreasonably above the level expected from a similar vehicle with a silencer in average condition."

So it seems silencers are mandatory? Probably tester's discretion as to noise levels. Hmmm

handyman · Post by **handyman** » 14 Sep 2007, 21:12

The other thing you have to consider with your exhaust modifications are how it affects your car insurance. On the proposal form it states whether the car is standard or has it been modified in ANY way.

As all pattern parts carry the type approval stamps, they get around that but your DIY modified exhaust would need an engineers report to pass an MOT, as it is non-standard.

Your insurers could deem the car as non-standard and modified. If you had not informed them, your insurance could be void, which would give you a little headache if you had an accident and they refused to pay.

I think the traffic cops would also have a field day under the Construction and Use Regs. I do not think they have changed much since I took my exams for the IMI back in the 70s.

My Activa with the water injection does not have increased premiums but I did need to submit a written document about it to my insurers.

Handyman

dnsey · Post by **dnsey** » 15 Sep 2007, 11:37

Some years ago, there was a hangover from the days of steam engines, which may well still be in force.
The Law required all exhaust systems to have at least one baffle, so that hot cinders are notd eposited on the road

MikeT · Post by **MikeT** » 15 Sep 2007, 13:22

I may be lacking in common sense but I'm not daft enough to risk driving uninsured and would happily declare all mods I'm aware of.

However, getting back to the exhaust, do I buy a new replacement silencer or is there a legal alternative offering improved gas flow?

citronut · Post by **citronut** » 15 Sep 2007, 14:51

there is a gasket sealing ring at your manifold to down pipe joint with spring loaded bolts to allow it to move, there is a good second hand exhaust system on ebay at the moment, item No. 120158900128 and its in NOTTINGHAM, but i think he is asking a lot for it, the two parts from GSF would come to £115.15 inc vat
regards malcolm

MikeT · Post by **MikeT** » 15 Sep 2007, 15:04

I've already got the genuine gasket kit you mentioned as mine is blowing badly. The rear box is also shot but the centre piece with cat is mint. I'll probably just buy the £27+VAT silencer from Euro Car Parts and try and remove the cat internals if no-one can come up with a similar costing alternative to give improved gas flow.

Isn't the estate version longer (not sure which part) than the hatchback? Mine's the latter but his is currently at under £60 - it's not too costly. If he paid what he claims he did, it may even be a genuine Citroen part but his feedback is a little tarnished and being a breaker, how does he know how long it was fitted for and what price was paid? I think he's telling porkies.

MikeT · Post by **MikeT** » 22 Sep 2007, 19:28

davek-uk wrote:Over the weekend I'm going to fit the decat pipe and see if I can still run without a silencer. I'd much rather have a free flowing exhaust made up of two pipes (£16 and £7 - ex VAT, ex delivery) than having to buy a £50-60 silencer!

Any progress?

davek-uk · Post by **davek-uk** » 24 Sep 2007, 11:52

My exhaust saga is over now - and I brought a rear silencer.

I ran for a couple of weeks with the cat inplace and no silencer. Absolutely no problems with noise - just a little 'sports car' burble. 8)

After fitting my decat front pipe and starting the car it was immediately obvious I needed a silencer. Which shows how much the cat destroys the exhaust flow. So I had to admit defeat and buy an estate rear silencer.

The estate silencer is absolutely huge - twice the size of the BX estate one. I'm sure this size is unnecessary, did they just try and fill in the space?

Hatchback silencers are apparently 10" shorter than the estate ones. The mid hangers are the same but the rear hanger is on the outside for the estate and on the inside for the hatchback.

I've no idea if the gas flow for the estate silencer is the same as the hatchback. If I could weld I'd have been tempted to fit a hatchback silencer, make a rear hanger and extend the endpipe, but I don't know if it would have made any difference.

As has been said (Malcolm - citronut) the car is more responsive without the cat. I would have liked to find out if a free flow silencer (or none) would have added to the improvement...

MikeT · Post by **MikeT** » 24 Sep 2007, 17:26

davek-uk wrote:As has been said (Malcolm - citronut) the car is more responsive without the cat. I would have liked to find out if a free flow silencer (or none) would have added to the improvement...

Sorry to read about the lengthy box required for an estate, I guess that adds to the price too?

Lack of silencer flow/restriction is my concern also [as I hope to be pumping far more gasses in than standard] but also the legality/MOT issue of it. Obviously gutting the cat will release a bit of power and so I'll be happy (for now) to buy and fit a standard replacement silencer.

Thanks for the feedback Dave.