# Stock exhaust diameter?



## SquashAZ (Apr 21, 2008)

so... I have been looking at new exhaust systems for my 225 and i was wondering what the Stock exhaust diameter size is? please let me know, thanks.


----------



## cincyTT (May 11, 2006)

*Re: Stock exhaust diameter? (SquashAZ)*

180 has a 2.25
225 has a 2.5 through most of it.
A 2.75" is plenty big for stock to over 400whp


----------



## SquashAZ (Apr 21, 2008)

*Re: Stock exhaust diameter? (cincyTT)*

so..is the down pipe/cat the limiting factor on a 225 system?


----------



## Murderface (Nov 13, 2006)

*Re: Stock exhaust diameter? (SquashAZ)*

Yup. Read the "exhaust" post in my blog (check sig) for details on exhausts...


----------



## XXX 1.8T (Aug 10, 2002)

*Re: Stock exhaust diameter? (Murderface)*

This may be a silly question but if i go 3" 42DD down pipe and keep my cat back 2.5" am i restricting the engine? 
Ie is it worth while for me to make the catback pipe 2.75"?


----------



## Murderface (Nov 13, 2006)

*Re: Stock exhaust diameter? ( XXX 1.8T)*

I think for a stock K03/K04, a free-flowing 2.5" catback should do fine. A 3" would have slightly more top end but it would lose low end at the same time.


----------



## XXX 1.8T (Aug 10, 2002)

*Re: Stock exhaust diameter? (Murderface)*


_Quote, originally posted by *Murderface* »_I think for a stock K03/K04, a free-flowing 2.5" catback should do fine. A 3" would have slightly more top end but it would lose low end at the same time.

Thanks


----------



## cincyTT (May 11, 2006)

*Re: Stock exhaust diameter? ( XXX 1.8T)*


_Quote, originally posted by * XXX 1.8T* »_This may be a silly question but if i go 3" 42DD down pipe and keep my cat back 2.5" am i restricting the engine? 
Ie is it worth while for me to make the catback pipe 2.75"?

there will be more power if you go larger. The 225 catback has crushed pipe in some place restricting flow. Plus the muffler is a big chambered muffler also restricting flow


----------



## iminthegaragedear (Jul 18, 2007)

Yeah I noticed a nice bump in power/breathing with the DP through stock exhaust, and probably about the same amount of improvement when I went with the Blueflame exhaust. Stock exhaust is really heavy too, and is also flow restricted/pinched in the back, just before going into the big can. Upgrade both, if you can.


----------



## XXX 1.8T (Aug 10, 2002)

*Re: Stock exhaust diameter? (cincyTT)*


_Quote, originally posted by *cincyTT* »_
there will be more power if you go larger. The 225 catback has crushed pipe in some place restricting flow. Plus the muffler is a big chambered muffler also restricting flow

Thanks i should have been more clearer.
i have a 2.5" deresonated MTM cat back exhaust system.
Now is it worth my while to go up to 2.75" in the piping?


----------



## cincyTT (May 11, 2006)

*Re: Stock exhaust diameter? ( XXX 1.8T)*

Yes, the muffler is chambered instead of strait through and that alone can cost you a 5-10hp. Increasing the diam can also gain you another 5-10hp since it will give it more room to flow.


----------



## XXX 1.8T (Aug 10, 2002)

*Re: Stock exhaust diameter? (cincyTT)*


_Quote, originally posted by *cincyTT* »_Yes, the muffler is chambered instead of strait through and that alone can cost you a 5-10hp. Increasing the diam can also gain you another 5-10hp since it will give it more room to flow.

but apparently the MTM muffler is high flowed and they claim 5hp increase in power not sure if its true or not but i'd immagine it would be 10x better than the OEM muffler.


----------



## cincyTT (May 11, 2006)

*Re: Stock exhaust diameter? ( XXX 1.8T)*

sorry, i was talking about the stock muffler, didnt see you switched. The same still stands if it has baffles in it instead of strait through


----------



## SquashAZ (Apr 21, 2008)

*Re: Stock exhaust diameter? (Murderface)*

ok thanks


----------



## SquashAZ (Apr 21, 2008)

*Re: Stock exhaust diameter? (Murderface)*

So can you expect any gain from replacing the stock cat-back with a new 2.5" cat-back (say Borla)? I hear the 42 draft down pipe is on a serious back order so I will have to look for other mods until it is once again available.


----------



## DnA-TT (Oct 21, 2003)

*Re: Stock exhaust diameter? (SquashAZ)*

W/ the Borla, you'll be eliminating some of the crush bends. So, yes, you'll get some increased flow from that.
I think the Borlas have a chambered muffler...can't say for sure, though. If they do, you wont get much benefit over the stock muffler.
Just a word of warning - take a look at the tips on the Borla system for TTs. They stick out a good 2" or so. It looks really lame, IMO.


----------



## SquashAZ (Apr 21, 2008)

*Re: Stock exhaust diameter? (DnA-TT)*

who makes a cat back with a straight through muffler?


----------



## jwalker1.8 (Mar 4, 2008)

*Re: Stock exhaust diameter? (SquashAZ)*

thinking about exhaust options myself...anyone know of a reasonable priced 3" for a 225 or have diy for a nice 3" setup? maybe just pics links anything would be nice...I could make my own pipe bends just need nice muffler options.


----------



## Blue20thAE (Jul 8, 2006)

*Re: Stock exhaust diameter? (jwalker1.8)*

get a good downpipe - these are hard to fabricate and 42dds quality is awesome
but when it comes to catbacks save your $, dont buy into the hype, and piece together your own system. its not hard, plenty have done it, and there's countless options as far as configurations are concerned








edit: and you can also mix and match certain things...try a resonator, no resonator, same with mufflers. since you saved the money by not buying a pre-made product you can mess around until you get the perfect tone/experiment with what feels and sounds best


----------



## Blue20thAE (Jul 8, 2006)

*Re: Stock exhaust diameter? (cincyTT)*


_Quote, originally posted by *cincyTT* »_Yes, the muffler is chambered instead of strait through and that alone can cost you a 5-10hp

that and the stock muffler weighs ~35lbs







get rid of that fatness


----------



## cincyTT (May 11, 2006)

*Re: Stock exhaust diameter? (Blue20thAE)*


_Quote, originally posted by *Blue20thAE* »_
that and the stock muffler weighs ~35lbs







get rid of that fatness









The B5.5 passats have a mid-muffler that weighs 40lbs + another muffler at the back. Talk about heafty


----------



## TTracing (Mar 20, 2008)

*Re: Stock exhaust diameter? (cincyTT)*


42DD 3" turbo back + Supertrapp baffle!!! Check it out ,add plates for more noise and more hp, or remove plates for less noise and more torque...It holds on with a screw and I remove it at the track... Will get more pics.


----------



## exboy99 (May 14, 2002)

*Re: Stock exhaust diameter? (TTracing)*

you've gotta give us a better pic of the stack of plates.
I've seen supertrapps on muscle cars setup to drag
and just saw them on a Harley..... first time I've seen
these on a TT.


----------



## TTracing (Mar 20, 2008)

*Re: Stock exhaust diameter? (exboy99)*

 This one has 6 plates.Almost quiet but a lot of torque.Excellent at the autocross where we have a noise ordinance. This one is the second i build, 15 plates, more noise but more hp.
I use it for commuting ... What can you expect from Mr.Big Muffler for $120...
There is superb straight aluminium pipe from 1552 in the plans...


----------

