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drake
Dodge Dakota
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2/03/2010
16:29:12
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 Subject: cat converter
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alright not saying im going to do this haha but lets say i wanted to hollow out my cat converter for better performance and sound..but i have an O2 sensor right behind it..is this even possible to do? since it would mess up the readings?
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daddio
Dodge Dakota
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2/03/2010
16:34:18
|  RE: cat converter
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Even though it will "mess up the readings" you can do it. And the MIL will stay lit up. Why would you want to "gut" it? You probably won't gain enough in performance to notice the difference.
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Chris G
Dodge Dakota
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2/03/2010
17:52:38
| RE: cat converter
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You could always get a "o2 simulator" I think it's called. It'll be lying to your computer, though, so that's a good and bad thing.
And you need some back-pressure.
If you're that hell-bent about "beefing up" your cat, you can always get a high performance one that flows better.
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drake
Dodge Dakota
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2/04/2010
14:11:28
| RE: cat converter
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i am actually wanting to take a smaller cat off of another vehicle with the same size pipe and gut it and put it on mine. and i have had several mechanics tell me that it will have a noticable increase in power and gas milage. alls im wanting to know is if its even possible with that O2 sensor because when one goes out you get awful performance so im wanting to know what one does when you have no cat converter on
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daddio
Dodge Dakota
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2/04/2010
14:52:27
| RE: cat converter
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The pre-cat O2 sensor is the one that helps the PCM determine fuel mixture. The post-cat O2 justs tells the PCM if the cat is doing it's job or not.
Those mechanics that told you you would get gains are the ones working on the truck?
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Chris G
Dodge Dakota
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2/04/2010
14:56:54
| RE: cat converter
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If I remember right,
the front/upstream o2 sensor does the signal for the fuel/air mixture, and the back/downstream o2 sensor just tells the computer if the Cat is working or not; so, the downstream isn't really necessary for performance. But, if that sensor gets a bad signal, it'll flip the MIL light and probably put the engine in Limp, which will hurt performance.
Get an "o2 Sensor Simulator", or something of the sorts. It'll give the computer a false signal and keep the MIL light off, which is what you're going for.
Or, build one:
http://forums.clubrsx.com/showthread.php?t=296791
Looks easy enough- keeps the sensor away from the pollutant exhaust gases.
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drake
Dodge Dakota
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2/05/2010
20:18:54
| RE: cat converter
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hey chris G i appreciate that man.
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DakotaGuy22
Dodge Dakota
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2/06/2010
01:08:16
|  RE: cat converter
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If you remove the rear o2 sensor from the exhaust stream and mount it safely on the frame rail, clear of wires and what not, this will fix your problem believe it or not. I know it sounds crazy but I read it on here years ago and it does work, no codes! The sensor reads clean air! The main thing is to remember that the sensor gets hot so you need to be mindful of this. You will just need a plug that will thread in place of the sensor. The other option is to get with someone like me and pick up a custom tuned SCT tuner. I have successfully turned off the rear O2's with SCT. And at the same time you are getting a performance flash. Send me the info on your truck and I will be glad to offer more assistance and answer questions.
Jason
Never Enough Performance
neverenoughperformance@msn.com
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dakownr
Dodge Dakota
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2/08/2010
20:13:16
| RE: cat converter
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In my experience, daddio is steering you right. The guts of my stock cat broke and was rattling horribly while the truck would run, so I just gutted it and put it back on. The MIL was constantly on (even with the "wiring to the frame" mod that was suggested).
I noticed NO improvement in mpgs or power- in fact, I saw a slight drop in mpgs. The only thing that happened was that the exhaust sounded waaaaay louder than before (even with a knock-off flowmaster still on). Granted, it sounded sweet, but in the end, I put on an entirely new exhaust system with magnaflow high-flow cat and flowmaster 40-series. The truck still sounds sweeeet, there's no MIL, and I don't have to reset the computer whenever I get it inspected (to get rid of MIL). I am happier now than I was then. Just my $.02. Good luck and have fun, whatever you decide!
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drake
Dodge Dakota
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2/11/2010
12:25:29
| RE: cat converter
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yeah i was just going to gut it because it would be a free way of getting better sound and performance but its getting to complicated since i have an O2 sensor behind it so im thinking about going with a high flow magnaflow now. you said it sounded better but did it bring up your performance at all? and how much did that run you? i mean my truck sounds decent already for a v6 i have a magnaflow muffler on it already but i wouldnt mind it getting louder
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DakotaGuy22
Dodge Dakota
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2/11/2010
16:22:49
| RE: cat converter
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Fellas,
You are not "wiring to the frame"... Maybe if by that you mean using zip ties? You simply remove the sensor from the bung behind the cat and safely secure it away from anything that would be affected by the heat. Pick up a plug to fill the open hole, and thats it. It sounds crazy but it worked on my 4.7 truck until I discovered SCT. My truck sounded AMAZING with headers dumping into a true 2.5" Y pipe to a 3" 40 series flowmaster!!! I never got a check engine light and passed emmisions. I had a 3" pipe running through the case of the stock cat to make it look stock. There are pics and a video on my website of a setup I did on a customers truck.
Of course now my truck sounds like a powerstroke on crack with the turbo and no muffler or cat at all... (Still no lights using SCT and not a single factory O2 sensor, only an Innovate wide band.) I still need to update the website once I get it back out this spring.
www.neverenoughperformance.com
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Bucket
GenII
2/12/2010
19:54:18
| RE: cat converter
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If you live in Cali nothings free, there will be hell to pay when you have to get it smogged, and end up having to buy a new cat. Dont do it. my 94 has the sensor in front of the cat so i run a straight pipe to the muffler till smog time then i put my cat back on, i dont do it for sound i just do it to prolong the use i will get out of this cat, and the sound by the way, is very noticeable....much louder than with the cat on.
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dakownr
Dodge Dakota
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2/14/2010
20:04:09
| RE: cat converter
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Drake, sorry for the long wait for a reply, but my computer decided it no longer wanted to live, so I couldn't get online for a few days.
Dakotaguy22- "wiring to the frame,"- hahaha! Give me a little more credit than that! I suppose I should have said securing it to the frame. I did do the exact same thing that you described, but did not have any luck at all.
Anyway, Drake- I am unsure as to your question about the sound (pre- or post- magnaflow cat), so I'll answer both ways. With the hollowed out cat, the sound was VERY VERY loud and a bit tinny/hollow, with no noticeable gain in mpgs or power at any point in the rpm band. WITH the aftermarket cat, The sound is still loud (but quiet enough so that passengers don't get too annoyed:), and no big difference in mpgs and power between it, the stock cat, and the hollowed out cat.
I got mine off of ebay, and the current prices are ~$167 with free shipping for the magnaflows, and a little cheaper for no-names. Walker brand cats are a little over $200 from advance.
IMO, I don't think that this mod is worth the effort for a couple of reasons. First, you will likely not see any gains in performance or mpgs. Second, you will have a tough time passing inspection with an illuminated MIL or an absent cat. Third, due to their design, modern-day cats don't really restrict air enough to harm the performance your street-driven truck enough to make it worth replacing or gutting them. The only really good reason to replace your stock cat would be either because you want alot more volume, or your stock one is clogged or broken.
P.S. The walkers and magnaflows are direct-fit cats with the appropriate-length of exhaust included. Mine bolted right in with NO problems. Very quick and easy.
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drake
Dodge Dakota
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2/15/2010
12:45:58
| RE: cat converter
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hey man thanks for all that info. i wasnt worried about passing inspection because we dont have them here in arkansas. i was going to keep my old one and re-weld it on if i ever sold it. but i cant seem to get away with this O2 sensor behind the cat so i was thinking about a magnaflow. i honestly dont know how to tell if my stock one is clogged up or not? i mean i do have 125,000 on it. so i was wondering was the sound alot better going from stock to a magnflow cat?
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Hey
Dodge Dakota
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2/15/2010
13:36:08
| RE: cat converter
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Drake do you use ebay?
if so check out Item number: 200437515089
I put one in my truck and was pretty impressed.
(picked up a bit more low end)
or the link
http://cgi.ebay.com/ebaymotors/2-5-Catalytic-
Converter-High-Flow-Thunderbolt-
OBDII_W0QQcmdZViewItemQQhashZitem2eab01c351QQitemZ
200437515089QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAc
cessories#ht_1920wt_948
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DakotaGuy22
Dodge Dakota
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2/15/2010
19:48:40
| RE: cat converter
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Have you even tried what I said yet? I understand it is possible that it wont work but why not try and see? You can just pull the sensor and try it before you actually remove the cat. The upstream sensor is the one responsible for keeping the engine in check, then the rear one just looks for a difference between it and the front one, so in theory it should work. It worked for me and I have heard others have had luck, so why are you listening to just one person who said no?
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dakownr
Dodge Dakota
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2/15/2010
21:47:42
| RE: cat converter
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Drake- I can't say how much of a difference in performance or sound going from the stock cat to the aftermarket one made because there was such a long lapse of time when I just had a hollowed out cat (being a poor college student and all). Unless you are noticing a difference in your engine performance, I wouldn't even bother with it. There are plenty of other ways to spend your money and get better results.
I am not telling you that you shouldn't hollow out your cat, or even try what Dakotaguy22 said (I am just one example, after all). I am just giving you my personal experience with what you are asking about.
Want louder sound? Try a glass-pack, or go to a local shop and see if they have a decent and cheap performance muffler. Even if you'd buy a flowmaster, you would spend less than half of what you would pay for an aftermarket cat. Like I said before, just my $.02!
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drake
Dodge Dakota
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2/15/2010
22:28:54
| RE: cat converter
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oh hey man sorry i wasnt listening to just one guy that saud it wasnt working i have just heard it from a few people around town too..but i think i still might try it..but what do i do about the plug it goes in? and man already have a magnaflow muffler on it and it sounds pretty good..pretty much the best you can get for a v6, sounds like a small v8. but i wouldnt mind ut getting a little louder and deeper rumble if anyone has any ideas. always looking for better horse power and gas milage since i have it lifted 3 inches and have 32x11.5 mudd tires on it
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DakotaGuy22
Dodge Dakota
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2/15/2010
22:37:37
| RE: cat converter
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You should be able to pick up a threaded plug to go in there. Or ask around, maybe someone has a bad one you could just cut the wires off of and put in place... And you know, I was just thinking... I know someone out there sells a cheaper version of the O2 simms you hear about which is just a simple resitor or something. I'll have to ask my buddy about that when I get back home from this deployment. On, another note... If you are going to delete the cat, just cut behind where the sensor goes and get a long enough piece of pipe to weld in.
Good Luck!
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drake
Dodge Dakota
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2/15/2010
23:19:19
| RE: cat converter
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i dunno where i would get a threaded plug for it though cause if you went to autozone or a mechanic and asked for that they would imidiately turn you away. i still want to try doing this though. and about that thunderbolt..did it make your truck any noticeably louder? i looked at it and its really cheap i was just wondering how the sound was with it? my truck sounds pretty nice like i said just alway am trying to get it a little deeper and louder
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DakotaGuy22
Dodge Dakota
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2/16/2010
14:54:48
| RE: cat converter
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Just toss a flowmaster on it! You could use a single chamber race model. Or my usual choice with a cat is a 40 series. Without a cat the 50's sound nice if you dont want it to be annoying. My advice when trying to figure out exhaust is to listen to it without a muffler first and go from there. See what it sounds like with the cat and no muffler. While your at it, take a look up the pipe and see if the cats core looks like its all in tact. If it sounds good, just a bit raspy, the single chamber flow will be pretty cool with minimal sound control. I was pretty impressed with my girls 4.0 jeep. It has the pre-cats, a turbo and a single chamber flow. Sounds really nice!!! But it was really raspy down low and at idle without the muffler.
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