996 sports exhaust
Discussion
You will just need to make sure the existing boxes are ok & aren't corroded too much. A friend ending up buying some boxes modded by Carnewal. If you take it to a specialist they can also grapple with the rusted bolts & clamps which can be an utter bu**er to get off & sometimes even need cutting off. The bypass mod is well worth it & will make you smile....a good specialist will also talk about how much noise you need as they can vary the size of the bypass to make more/less 
Hey 911god, I've just done this mod last week to my 997 - its often called a 'Gundo Hack' amongst other names and in my opinion is well worth doing. The same mod can be used on both the 996 and 997 Carrera, and simply involves a bypass pipe welded in between the inlet and outlet pipes on the two silencers.
I took mine off myself, turned out to be quite difficult, as the previous poster mentioned the nuts holding the mounting brackets and the clamps can get very corroded. I then got a local welding shop to add the bypass pipes, I used 1 3/4" stainless tube. Refitting is very easy - as would removal be if it wasn't for the rusty nuts!!
I would deffo recommend it, has transformed the sound of mine, it now snarls on acceleration and pops on overrun - sounds great whilst not being to over bearing either, no drone at motorway speeds etc.
I posted a bit more in depth info on another forum if you look for that or just do a general search for gundo hack and you will come up with lots of info and pics
Go for it, you won't regret it!
I took mine off myself, turned out to be quite difficult, as the previous poster mentioned the nuts holding the mounting brackets and the clamps can get very corroded. I then got a local welding shop to add the bypass pipes, I used 1 3/4" stainless tube. Refitting is very easy - as would removal be if it wasn't for the rusty nuts!!
I would deffo recommend it, has transformed the sound of mine, it now snarls on acceleration and pops on overrun - sounds great whilst not being to over bearing either, no drone at motorway speeds etc.
I posted a bit more in depth info on another forum if you look for that or just do a general search for gundo hack and you will come up with lots of info and pics
Go for it, you won't regret it!
If you're near Autostrasse in Leeds then Zorstec are close by and are well regarded. I haven't used them myself but they gave me the best price and knew their stuff when I was looking to get my 996 done - but they were just too far from me.
Your more difficult decision is not where to go but what diameter bypass pipe to go for. 1" is the size closest to a standard factory PSE but some report it's not quite loud enough. I went for 1.5" and am very happy with it, a nice 'bark' on start up, not much louder than stock up to 3000rpm (doesn't annoy the neighbours in the morning), but above that it's the lovely flat 6 sound that you become addicted to hearing. Your fuel bill WILL go up
Your more difficult decision is not where to go but what diameter bypass pipe to go for. 1" is the size closest to a standard factory PSE but some report it's not quite loud enough. I went for 1.5" and am very happy with it, a nice 'bark' on start up, not much louder than stock up to 3000rpm (doesn't annoy the neighbours in the morning), but above that it's the lovely flat 6 sound that you become addicted to hearing. Your fuel bill WILL go up
stuckmojo said:
I want to get the mod done on mine but I am not sure what happens with regards to emissions. Will that affect them badly?
AFAIK it makes no difference to emissions. The bypass is fitted to the rear silencer box which is after the cat, which replicates the factory PSE option but without the switchable valve. Mine's been MOT'd with no problems
I had cat by-pass pipes put on my 993 which has a similar effect - the last 2 tanks of Vpower have returned 14mpg and 15.9mpg. Souded rather good though 
interesting read! im looking into this as mine has a pair of newish boxes on it(replaced 2 years ago) and they are standard,but i want a bit more noise from it.
how loud does the 1.5 pipe get then?i dont want it too loud and droney as ive come from cosworths and like the fact the car has loads less road noise and is easy to live with on a journey at 3k revs but when im giving it some throttle i like to hear a bit of what its doing
when people say the fuel bill goes up im assuming thats down to my throttle use because you are pushing it harder not because its affected the engine in anyway?
how loud does the 1.5 pipe get then?i dont want it too loud and droney as ive come from cosworths and like the fact the car has loads less road noise and is easy to live with on a journey at 3k revs but when im giving it some throttle i like to hear a bit of what its doing
when people say the fuel bill goes up im assuming thats down to my throttle use because you are pushing it harder not because its affected the engine in anyway?
monstro said:
Hey 911god, I've just done this mod last week to my 997 - its often called a 'Gundo Hack' amongst other names and in my opinion is well worth doing. The same mod can be used on both the 996 and 997 Carrera, and simply involves a bypass pipe welded in between the inlet and outlet pipes on the two silencers.
I took mine off myself, turned out to be quite difficult, as the previous poster mentioned the nuts holding the mounting brackets and the clamps can get very corroded. I then got a local welding shop to add the bypass pipes, I used 1 3/4" stainless tube. Refitting is very easy - as would removal be if it wasn't for the rusty nuts!!
I would deffo recommend it, has transformed the sound of mine, it now snarls on acceleration and pops on overrun - sounds great whilst not being to over bearing either, no drone at motorway speeds etc.
I posted a bit more in depth info on another forum if you look for that or just do a general search for gundo hack and you will come up with lots of info and pics
Go for it, you won't regret it!
I think I will do this, but know that my exhaust bolts are pretty rusty and will probably need drilling - one of the bolts rusted through and I had to get a weld to do fix it last week. Did you have to drill out the bolts? How was the condition of the rest of your exhaust? I am hoping on mine (a 1999 with low miles that appears to have had a fairly dry life when you see the body/soft-top)that the rust is just surface and when I get it off it'll just brush away....I took mine off myself, turned out to be quite difficult, as the previous poster mentioned the nuts holding the mounting brackets and the clamps can get very corroded. I then got a local welding shop to add the bypass pipes, I used 1 3/4" stainless tube. Refitting is very easy - as would removal be if it wasn't for the rusty nuts!!
I would deffo recommend it, has transformed the sound of mine, it now snarls on acceleration and pops on overrun - sounds great whilst not being to over bearing either, no drone at motorway speeds etc.
I posted a bit more in depth info on another forum if you look for that or just do a general search for gundo hack and you will come up with lots of info and pics
Go for it, you won't regret it!
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