Exhaust questions

[novaguy08]

Hello guys,

Im planning on doing some exhaust work, removing the cat (probs getting another cat and gutting it) but what i would like to know is do you have to have both silencers legaly?? cos if not im going to remove the centre silencer.....

Last MOT the emissions were pretty much Euro 4 standards, so im going to check that it will still pass the emmissions without the CAT before i put it on the road as apparently the roadside emmissions test are getting more and more frequent and considering my luck 1st time i take it to m-way i will get pulled and tested!

i know i know that there is not much point in doing this to a lil 1.2 (as its tuned to run with a restrictive CAT) but i think it would be worth it for poops & giggles :D

Any info would be greatly appreciated!!

[Cle]

For mot you'll need a cat on it, A mate of mine had a corsa XE and his exhaust had no silencers in it, suprised he didnt get pulled as it set car alarms off lol

[George g]

if a car had a CAT from standard then it is needed for an MOT and will 99% of the time not pass the emissions test without one.

dont need the 2 silencers by law, but if your exhaust is loud, be prepaired to get pulled and questioned a couple of times. and if it looks standard, be prepaired to just agree with the coppers when they tell you its blowing...

[novaguy08]

alarm setting offie aint a bother to me as a good V8 can do that with 8 silencers lmao :D

Only need a cat on it if the emmissions aint up to the job tbh thats why im going to get it checked to see if i need to keep the old one hanging about

[novaguy08]

ooooo if its still legal then im getting rid of centre box soon as i can :D ill keep the old CAT hanging about for MOT's but ill still get it checked once i got all the work done to the engine

[deanwilko]

you can fail a car on excessive noise on a mot now

[AlexW]

You could get a 1.2 Carb front and middle section exhaust so it does away with the cat and gives you nice metal to weld to remove the middle box.

My old nova only had a backbox. Wasnt bad at all!

[novaguy08]

i dont wanna be changing the whole exhaust!! thats more expencive!!

Ill be heading to a breakers yard getting myself a cat & gutting it......... then cut 'n' shut the exhaust to remove the centre box!

Dean, ill check up with an MOT tester mate to see if thats right but i would be shocked tbh if it is..... otherwise they would be failing loadsa cars due to this as loadsa old ones are quite loud!

[AlexW]

I know id rather spend £30.

But just make sure you get it the right lengh.

[Benn]

Empty cat in my finding are loud and drownie and sound shi*te.

[deanwilko]

thats what vosa said there bringing in when our supervisor went on there new course what they are doing and that was a couple of weeks ago

[novaguy08]

hmmmmmmmmm if thats the case might make myself a de-cat pipe....

[novaguy08]

how many db is too loud??

[deanwilko]

thats the question aslong as its not very loud on a fast idle emissions test then it wont fail also depends on the tester aswell

[novaguy08]

cant see anything about it on VOSA website so ill check with my mate on that one

[novaguy08]

if it "depends on tester" then you can get round it EASY they will need to set db regulations before they can put it right into the swing of things!

[DW-Nova]

If you go to a scrap yard trying to buy a cat for less than £30 theyre going to tell you to off as cat's are worth good money scrap !

[gaznovalet]

ive had a nova fail test as tester said was too loud. car was F reg and c20xe so didnt require a cat, only cars after 1st jan 1992 require cat for test, wen i asked tester told me noise level on roads was max limit 74db wether true or not i dont know just wot i was told. i know from personal experience that the noise limit for the same car on track was 98db at idle and it passed this for croft circuit.

[Benn]

74db cant be right, my mates totaly standard Astra Gte 16v is 92db.

[novaguy08]

74db is utter bollox, its quiet! if thats the case my car gonna fail on next MOT as the engine side of the car seems to make loadsa noise! certainly more then 74db!
According to what i just read:
74 Db is a honestly loud but sort of comfortable listening stratum for music at about 8 foot from large speakers spaced around 6/8 feet apart 1 foot from the wall at the rear them in an average sized room next to carpet 100 Db is vastly loud and 50 db is fairly soft this is compared to the everyday ambient noise height of the area + X Db X=0 Db above ambient resonance . this can be sort of a personal opinion but I be trained a audio engineer for a crucial stereo company . this is a very dificult sound out If you have a 3 Db tone at 100 Hz to be twice as loud it would hold to be 6 Db at 100 Hz and so on so 75 Db is way more than 25 % more than 50 Db and so on

Not sure if this is going to make any sence what so ever but from what it reads like its about the avg volume of a half decent stereo!

[George g]

74db cant be right, my mates totaly standard Astra Gte 16v is 92db.

:eek:

where from? noise is measured 1 meter at 90 degrees to the end of the exhaust.

i believe road-rally cars are only allowed to be 90dB at 3/4 max revs on events.

[deanwilko]

there isnt actually a legal limit at the minute for exhaust noise thats why there trying to bring in new laws

[Benn]

:eek:

where from? noise is measured 1 meter at 90 degrees to the end of the exhaust.

i believe road-rally cars are only allowed to be 90dB at 3/4 max revs on events.

Was measured at combe for a track day. 4k for 10sec.

[George g]

without wishing to deviate too much, the ground and surrounding area can have a BIG difference, so if the exhaust is pointing down towards tarmac it could echo up and amplify the noise, giving a false reading. alternatively if the noise meter is directly behind the exhaust, it will read louder also.

i dont know how they measure noise on a track days, but 92dB seems excessive from a "standard" car...

[novaguy08]

hmmmmmmmm well i got no need to really worry about noise levels at the moment apart from some un-needed attention from the oinks......... think ill have a look at AW06's idea though as i know a guy breaking a carb'd 1.2 see how much he wants for the exhaust

[novaguy08]

Question........... whats the difference between ceramic Cats and steel??

Im looking into getting a new Cat as im pretty sure that mine is knacked, been looking at some half decent prices normaly about the 70 notes mark but i just found a site thats offering a ceramic (70 or so notes) and steel (125 notes) im guessing that steels is better being more expencive but whats better about it and is it worth the extra 60 notes??