instead of gutting pre cats...
#1
instead of gutting pre cats...
what if we cut off the pre cat and weld in a straight pipe? just read some horror stories on the forum about the pre cat failings and the damage it can cause to the engine.
#2
problem number one... that area is not straight lol...
someone.. stillen maybe? used to make a pipe that deleted that front pre cat.. kinda like the one that you car still buy for the cat right before the b-pipe....if you find it let me know.. lol
someone.. stillen maybe? used to make a pipe that deleted that front pre cat.. kinda like the one that you car still buy for the cat right before the b-pipe....if you find it let me know.. lol
#5
Straight piece of pipe if anything.
With the VQs they aren't tuned as richly as the QR is, those engines tend to have the issues you talked about with the precats failing and destroying the engine, the VQs don't have this problem, if there is even one
#6
now im kinda scared. my pre-cat has been making a rattling sound when you rev the engine for at least 15,000 miles. I never knew there was potential engine damage from this. can anyone verify that a bad precat will destroy a VQ35? if this is the case I guess its time for me to change/gut it.
#7
now im kinda scared. my pre-cat has been making a rattling sound when you rev the engine for at least 15,000 miles. I never knew there was potential engine damage from this. can anyone verify that a bad precat will destroy a VQ35? if this is the case I guess its time for me to change/gut it.
Like I said above, I never heard it happening on a VQ but on a QR engine I hear its a severe problem.
#8
P420
I am getting the dreaded code after replacing my o2 sensor-white wire. I am wondering if there is a how-to or diagram on how to replace the precat. I am worried about possible engine failure down the road. I thought about the antifouler repair but I have a stock exhaust and read the antifouler bandaids the problem only if you have aftermarket exhaust system.
#9
the precats on the 02/03 are known to break down causing the particles to get sucked back in to the cylinder and then causing oil usage. I have this, and its relatively common, if i had known before hand i would have removed the precats since they are pretty much pointless in the first place.
I plan on gutting mine anyway and putting in an o2sim to run my sensors.
I plan on gutting mine anyway and putting in an o2sim to run my sensors.
#11
i think the cheapest route would be to gut the cats and get the o2 sim. Headers would be nice though. i think i may try the gut / o2sim route and see how i like it. i am not looking for any HP gains i am just looking for that damn noise to go away
#13
the precats on the 02/03 are known to break down causing the particles to get sucked back in to the cylinder and then causing oil usage. I have this, and its relatively common, if i had known before hand i would have removed the precats since they are pretty much pointless in the first place.
I plan on gutting mine anyway and putting in an o2sim to run my sensors.
I plan on gutting mine anyway and putting in an o2sim to run my sensors.
#14
#15
#16
the precats break down over time yes. but there is something else that causes the oil consumption. Although everyone makes a big deal about it, on average 1-2 qt per 3000-5000 miles is what i've heard. Ls1's and LS2's burn just the same and so does the Honda s2000. Just some people make a big deal out of it then others
#21
im thinking ill have the straight pipe welded in, this way even if i needa put the cats back onfor any reason, i can have it welded back in. any idea how much this should roughly cost?
#22
#23
Well first. Its not worth welding a pipe. The first attempt didn't go to well. I tried gutting the rear one while it was still on. But it was a brand new solid precat, so i gave up the first day. Next morning i took them both of and it was pretty easy after that. If your precats are old they'll after a few wacks with a hammer. After you finish and everything is back together. You are going to have a CEL. You'll need a o2 sim or spark plug anti-foulers (worked for me) heres a link that'll help http://forums.maxima.org/5th-generat...or-spacer.html
#24
Well first. Its not worth welding a pipe. The first attempt didn't go to well. I tried gutting the rear one while it was still on. But it was a brand new solid precat, so i gave up the first day. Next morning i took them both of and it was pretty easy after that. If your precats are old they'll after a few wacks with a hammer. After you finish and everything is back together. You are going to have a CEL. You'll need a o2 sim or spark plug anti-foulers (worked for me) heres a link that'll help http://forums.maxima.org/5th-generat...or-spacer.html
#25
Pretty much. I found the front much easier. My rear cat was new but it was rattling. I actually had to drill it till it broke into pieces. But usually they get old and brittle and break up quick.
#27
I just did this pretty easy if your mechanically inclined some of the nuts are tricky to get to but not bad with the right tools. I would like to note that this will make your exhaust louder. I have a megan catback and it made it way more throaty. I was not expecting it to make the exhaust louder it does drone slightly with my catback which I didnt care for but its not that bad. Other than the drone at highway speeds I think it sounds real good.
#28
i would love to see a dyno of someone with gutted cats or at least someone who've ran a 1/4 mile time with gutted cats, im really thinking about doing this... any idea on a ball park price for what a mechanic would charge???
#29
I just did this pretty easy if your mechanically inclined some of the nuts are tricky to get to but not bad with the right tools. I would like to note that this will make your exhaust louder. I have a megan catback and it made it way more throaty. I was not expecting it to make the exhaust louder it does drone slightly with my catback which I didnt care for but its not that bad. Other than the drone at highway speeds I think it sounds real good.
#32
i see, didnt think they looked like that, thanks for the pic! how many hours did it take you to get thisdone? reason i ask is ill probably have a shop do it.did you have to get the cat out with the header? or can you unbolt it seperately
#34
ahmad im gonna get the o2 sensor extender, looks really simpleto work with, do we just simple install this with the o2 sensor so that it "reads" less emmisions? and i need just 1 right? and what size do i get, there isnt much space in case i get one thats too long. thanks man!
Last edited by hotstartup; 06-18-2009 at 08:06 AM.
#36
#37
ahmad im gonna get the o2 sensor extender, looks really simpleto work with, do we just simple install this with the o2 sensor so that it "reads" less emmisions? and i need just 1 right? and what size do i get, there isnt much space in case i get one thats too long. thanks man!