what happens if i do this?

899 Views 12 Replies 6 Participants Last post by G-wrench, Feb 13, 2002

mrdejected

Discussion Starter · Feb 12, 2002

i want to put in the 3" dp and race pipe... but im worried that if i do it... there will be a buildup of exhaust gasses within the exhaust piping.. since its going 3>2.5>stock....
is there anything that can go wrong if i put the atp dp and race pipe on the stock exhaust?

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tobyc

· #2 · Feb 12, 2002

Re: what happens if i do this? (mrdejected)

the only problems that you might have are CEL because you have removed the cat.

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mrdejected

Discussion Starter · #3 · Feb 12, 2002

Re: what happens if i do this? (tobyc)

isnt it bad to have 3" piping... then it gets smaller and smaller and then down to stock size?

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Gambit

· #4 · Feb 12, 2002

Re: what happens if i do this? (mrdejected)

As long as you get a high flow cat of some sort (preferably the same size as the DP) you should be fine. I'm running 3" FM DP, 3" Cat, 3>2 adapter, Tdi bypass pipe (2") and Remus muffler (~2")

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RVs021.8T

· #5 · Feb 12, 2002

Re: what happens if i do this? (Gambit)

I just installed this setup as well. I have the ATP 3" dp/hf cat back to stock exhaust and have had no problems except CEL

I dont know why when I have the cat, but anyway at least you were smart Mrdejected and bought the motor mounts first. Thats where I screwed up.

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RVs021.8T

· #6 · Feb 12, 2002

Re: what happens if i do this? (Gambit)

Hey Gambit, which way is you cat installed? Is the o2 sensor in front(closer to dp) or in rear (closer to exhaust)? I have had conflicting opinions on this setup.

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20VT*J4

· #7 · Feb 12, 2002

Re: what happens if i do this? (RVs021.8T)

the first o2 sensor obviously goes in the dp but the second o2 sensor should be after the cat. if the second o2 sensor is before the cat, your cat is installed backward. The second o2 sensor is there to read the exhaust once it has passed through the cat to determine if the cat is working or not.

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RVs021.8T

· #8 · Feb 12, 2002

Re: what happens if i do this? (20VT*J4)

That is exactly what I thought, but for some reason the mechanic I took it to, said the opposite, and persuaded me to do it the other way, o2 sensor before, but If you think about it look at you stock dp/cat , that is the way it is setup?? Its weird?
Anyway did you have any probs with the second o2 sensor not fitting underneath the car? I did, it was too long and we had to bang up the heat shield some to make room for it. It is on right now, I had them change it yesterday. But when he banged up the heat shield, he hit the shift linkage and jammed it with the dent he put in the heat shield.

Now 2nd gear is how to go into. Before my tranny wouldnt even move at all. I was freakin out

Well its better but 2nd is tough. What should I do about this? The o2 sensor will not give way for the dent to come down anymore and allow that "knot" to come out so 2nd will shift easy. Any suggestions?

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Gambit

· #9 · Feb 12, 2002

Re: what happens if i do this? (RVs021.8T)

Just to clarify - the stock setup has one O2 sensor BEFORE the Cat and one sort of IN the cat. The one that's "IN" the cat is takinga reading AFTER the exhaust has gone through the cat. There's no 2 ways about it - you have to have one 02 upstream from the cat and one downstream - otherwise what's the point of having 2? The whole purpose of 2 O2 sensors have to do with measuring efficiency of the cat so to say (other things too I'm sure but that's the primary)

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mrdejected

Discussion Starter · #10 · Feb 12, 2002

Re: what happens if i do this? (RVs021.8T)

quote:[HR][/HR]I just installed this setup as well. I have the ATP 3" dp/hf cat back to stock exhaust and have had no problems except CEL

I dont know why when I have the cat, but anyway at least you were smart Mrdejected and bought the motor mounts first. Thats where I screwed up.[HR][/HR]

yea everyone said i needed motor mounts so i got em... for 16 bucks...
ill try and put on the dp soon
thanks a lot guys

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RVs021.8T

· #11 · Feb 12, 2002

Re: what happens if i do this? (Gambit)

I know thats exactly what I thought, but seriously have you ever looked at the stock dp/cat it would match up perfectly if the o2 sensor was before the cat, and I think it is before on the stock setup??

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Gambit

· #12 · Feb 13, 2002

Re: what happens if i do this? (RVs021.8T)

Don't confuse what LOOKS like it should be considering you are no longer using stock components. Just for your benefit - I took a very close look at my stock DP/Cat - the 1st O2 sensor goes right after the flex section. The 2nd one is right where the Cat starts getting thicker (or thiner) - this is PAST the actual catalytic element - not sure what the 2nd part of the cat is for - most likely sound dampening of some sort

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G-wrench

· #13 · Feb 13, 2002

Re: what happens if i do this? (Gambit)

I believe that the O2 sensor is in between the oxidation section of cat and the reduction section.

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