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muffler bypass vs MOT

cvega

Well-known member
Joined
25 Feb 2013
Messages
437
Hi folks,

as i have to change my mufflers anyway (mine are rotting and making all kinds of rattly sounds) i'm considering either a Topgear exhaust OR just a porscheshop and/or fabspeed straight pipes out of cats. Anyone running a straight piped 996 in the UK? I've seen videos on youtube of folks from US and australia, but want to hear from someone here.

- noise - how's that gonna go down at MOT? i don't see a dB limit anywhere just "excessive noise" - sounds like the tester will have free hand there
- emissions - are they affected bymufflers? I'd guess no, but I don't really know?
 
I think back boxes may affect emissions. (Although I can't understand how)

A couple of years ago my 997 failed emissions on one side, the tester stuck the probe in the other side and passed it, told me he thought it was due to gases escaping either through the seam in the back box, or the join with the centre section.

I had the back boxes off for gundo, and couldn't see anything on inspection.

Passed the next MoT so I'm not sure if it was the join or his probe was playing up.

Straight through pipes would fail on noise I imagine, so you'll have to accept the chore of an annual pre-MoT swap.

Personally I would go with top gear. Straight through is obnoxiously loud in my opinion.

James
 
I've run bypass pipes before and the first 996 wasn't an issue on the MOT emissions whereas the current one took a while to claw its way through on the CO readings - I suspect the engine temperature on my car for the latest test wasn't quite as hot as it could have been which wouldn't have helped. I've just fitted Topgear boxes and 200 cell cats (the bypass pipes will be sold). My bypass pipes werent that popular in the village I live in for non petrolhead neighbours as they make a considerable noise on cold start-up BTW, though mine is used as an occasional 2nd car.
 
I had a painfully loud exhaust on a Nissan 350z I had once. I measured it at 106db inside the cabin. On its MOT the tester just made an advisory that the exhaust was loud and passed it.

My Ducati 996 has a similar advisory sometimes with its open race pipes.

So based on that I dont think noise is something they can fail on, and it will be fine as long as the car passes the emissions test.
 
ive run straight out from Cat in mine before (had a loop to mimic the route through the back boxes though).

Measured 105dB outside at track testing distance/conditions.

On the road it sounds awesome with pops/bangs/crackles etc, but it was robbed of some low down torque which was noticeable. Ended up asking Top Gear or one of them to make me an After Hours style exhaust which gave me back the torque and some pops.
 
kingston said:
ive run straight out from Cat in mine before (had a loop to mimic the route through the back boxes though).

Measured 105dB outside at track testing distance/conditions.

On the road it sounds awesome with pops/bangs/crackles etc, but it was robbed of some low down torque which was noticeable. Ended up asking Top Gear or one of them to make me an After Hours style exhaust which gave me back the torque and some pops.

Any pictures of that ?
 
Hi,

I have £20 mod done at local exhaust repair shop, it is not as loud on start up and if driving slow you can live with it but under load noise is insane in good and bad way depends on your day I guess :lol:

BAD:
M62 J21 to J22 (uphill) 6th 70-80 MPH on top of the motorway your ears screaming why are you doing this to us :floor: you can do it on 4th bit better but economy :eh!:

GOOD
Manchester night out all people screaming for rev, also on A roads experience is x2 with high revving as noise is so close to F1 mixed with V8 :thumbs: and on motorways I use rev as a honk so far works 100% every time :mrgreen:


So my kit is 2x 90 degrees pipes, unfortunately back tips will be with different angle but still looking nice forgot to take picture but:


You will lose power as I can feel it so if you would like to do it more correct you should make it longer I think every repair shop should do it for you as it will be very easy job.

Some pictures:
 

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I just did small drawing like I was planning to do so :D
 

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Nothing has made me smile on our meets as much as following you home Szymon!! :thumb: :grin:
 
Jesus!

If nothing else, this thread proves how different we all are. :grin:
 
Marky911 said:
Jesus!

If nothing else, this thread proves how different we all are. :grin:

What do you mean ? :)
 
OMG £ 148......... I will take your boxes out and install mine pipes in this price this Friday...... :D

I can give away my pipes as I'm back in muffler sound :puh:


PM if interested.
 

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