I had an extra stock exhaust laying around and decided to play a little. I gutted the 400 cell secondary cats and drilled a 2" hole in the back of the curved tube(per modified stock exhaust thread). I did this so that the car would sound a little better and hopefully had a little better turbo spool from the gutted secondary cats. I know that gutting both would have probably been better, but I still have to consider emissions here. The secondaries are supposedly the most restrictive being a denser cat.

The car sounds amazing IMHO. It really surpasses my expectations in the sound department. The car also feels like it spools a little better, but that could be placibo effect too. Overall not a bad mod and I think it will hold me off from spending any money on a real exhaust setup for a little while

 

My understanding is you have 2 300 cell cats on each side.
I don't have to worry about emissions and right now I can't afford to pay the $ it takes for a Markski or Switzer exhaust.

I used a 74mm hole saw and actually took out a little more then that out of the 1st cat from the turbo. I wanted to leave some for kind of a baffle effect.
I had already used a 1 7/8" hole saw like you did right after I got the car through the tail pipe.

Here is a sound clip from a cold start. I agree w/ you, I am happy till I can get a real exhaust. Drone is gone by maybe 85+%. and only between 1700 & 2300 rpms.

I took this clip on my Iphone, what do you guys think?

http://www.youtube.com/watch?v=mazzq...e_gdata_player

 

this mod is perfect at the end if you now change your first cats to 200cell or good 100cell...

 

I read somewhere that all four cats were 300 cells. I also read somewhere that the primaries were 100 cell and the secondaries are 400 cells. What I found when I opened up the exhaust was that the secondaries are definately denser than the primaries. But I have no idea by how much. I would be pleased to discover a HP gain from this, but not really counting on it. One things for sure, this car really sound like a beast now.

 

sounds good. I just gave a spare exhaust to a buddy that lives nearby so he can do that with his car. he hasn't done it yet.

 

That might be, I'm no expert. I was told this by an after market exhaust maker.
I did find the cats closest to the turbo to be twice as long as the other. Also, they look to be about the same in density.

I am not sure how much HP gain there is but you would think allowing the car to breath better would help some. The dyno from just opening up the tail pipe was 12HP. It is in the 25+ page tread on the mod.

I hope to get a real after market at some point but I have a lot of other things going on and can't spend that kind of $. Plus now that I have something that sounds better I am thinking I need to work on the suspension.

 

about time u modded that car man...

mines in pieces when i get the low down ill give ya a call

 

That sucks. At least it is the part of the season you won't need it a whole lot. Let me know what you come across.

Hogapalooza,
Initially the cats looked the same to me too, but if you look at the holes in the cat material you can see the secondaries have substantially smaller holes than the primaries. But like I said, I have no clue what the actually cell count is for sure.

 

VAGscum, you are probably right. In the end it really doesn't matter to me because the exhaust sounds way better then stock.

I'm not sure if I still want an aftermarket exhaust now because it will be
" so " much better or if it is to say I have " X " exhaust.
For me at lease, it's hard to read this place and not want to spend $$ on mods to keep up w/ the pack.

 

I'm right there with you. I would rather keep my car funds to keep the car running and maintenance. I am not sure that another 20hp on a chipped car for $3500 is a good deal. If a nice used exhaust surfaces than I will buy one, but I am not desperate yet.

 

Well a good tuner can get you about 80HP for about $1800. ( + or - on each $ & HP )
But this mod if very similar to Ruf & PBK and for about 5 1/2 hrs work ( for me at lease ) it was worth saving the 3K for the a real aftermarket exhaust.
Even a good used 1 will cost $1,200+ and that is a new rear GT3 adj. sway and Tarret drops w/ $600+ left over for something else.

Like I said, I am not sure if I won't just spend the mad car $ I save on other mods for now and worry about an exhaust later or not?

 

Another 80hp with an aftermarket exhaust? Wow! I would be interested in knowing if those gains are in turbo spool or what. 80hp seems to be alot for just an exhaust. Well, I guess I will keep looking for a deal on a used exhaust.

 

No 80hp from just a tune. Hey you live in denver. There is a stock k16 car with just a tune and exhaust and you can compare to see how much more power that gives you.

 

the tune upps the boost level and optimizes the timing and fuel maps so that is why you get such a large gain.

 

I knew about the 80hp from a tune. I thought he was saying another 80hp from just an exhaust. : /