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jason gaines
Dodge Dakota
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10/28/2003
16:39:25
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 Subject: i know its illegal...but
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has anyone taken a catalytic converter off of their dakota. i have a 95 model that is rattling like hell. any probs with me cutting it out and putting a straight pipe there?
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Cata
Dodge Dakota
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10/28/2003
16:57:49
|  RE: i know its illegal...but
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Why not just take it off and use a rod to knock the broken elements out and then put it back on. Be sure and wear a dust mask.
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jason gaines
Dodge Dakota
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10/28/2003
17:05:16
| RE: i know its illegal...but
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i thought about doing that also.
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draugluin
Dodge Dakota
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10/28/2003
17:12:47
| RE: i know its illegal...but
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you might be able to cut it off, but in some vehicles removing the cat converter causes a miss in the truck cause the oxygen sensor picks it up, and the miss will cause the truck to keep missing even after fixed, which will make you need a tune up. Had it happen on a van.
I would just take it to a muffler shop, but if you don't fairly soon it will stop up and all your power will be gone, and you will be getting towed unless you do cut it off, in that cause you'll have a miss probably cause of the oxygen sensor near the cat converter, which DOESN't let you drive without it. :( kinda a lose lose situation really.
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jason gaines
Dodge Dakota
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10/28/2003
17:20:33
| RE: i know its illegal...but
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thanks, that helps. i could continue to drive it, its been doing it now for over a year. its annoying however. maybe i will just cut it out and weld in a new one.
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jstdume
Dodge Dakota
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10/28/2003
19:32:41
| RE: i know its illegal...but
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Unless the oxygen sensor is in the front part of the catalytic converter there should be no way that by removing the cat a miss will occur. An oxygen sensor that is located before the cat is used to calculate the air fuel mixture, however an oxygen sensor that is after the cat is used as a catalytic converter efficency monitor only and has absolutely no effect on engine performance. Unless the cat is becoming plugged up or there have been no other engine modifications made there are really no appreciable power gains to be made by removing the cat, the only thing that is being affected are the emissions readings coming out of the tailpipe. I myself have an 89 dak with a 3.9, I have redone the complete exhaust with 2.75 inch pipe to include a new y-pipe,edelbrock headers, and a bullet muffler. I tried running with and without a cat...appropriately sized of course..and found no difference in either power or mileage...the exhaust in itself however gave me noticeably more mid range power and about 1.5 mpg more
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Greg555
Dodge Dakota
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10/28/2003
21:04:41
| RE: i know its illegal...but
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casperelectronics.com they sell plug-ins that tell the computer everything is fine. i have no cat in mine and it works fine. cost about $65 but its worth it. so now i have headers to a y pipe to 4ft of 3" pipe a muffler and a turndown.
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grumpy
Dodge Dakota
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10/28/2003
22:51:44
| RE: i know its illegal...but
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I took mine off gutted it welded a straight pipe through it and welded it back on. nobodies the wiser.
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JIMMBO
Dodge Dakota
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10/28/2003
23:03:15
| RE: i know its illegal...but
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CATA YOUR RIGHT JUST TAKE THE BEADS OUT OF THAT THING IT WILL RUN A LITTLE BETTER TOO.
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NOSDART68
Dodge Dakota
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10/29/2003
20:09:32
| RE: i know its illegal...but
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I replaced my cat on my 92 with a piece of straight pipe and it DID make a noticeable hp gain. It had been replaced before, and someone put a 2 inch converter on the 2.5 inch pipe, really really restricting the power. Since mine was screwed up, it was just about the biggest bang for the buck mod I have done. Just my .02
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IntenseDak39
*GenIII*
10/29/2003
20:34:44
| RE: i know its illegal...but
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the problem that some have encountered is the effect of the second O2 (after cat) reading the same air quality as the first O2. The second sensor is to detect changes in the air and the effiecency of the catalytic converter. If you gut the cat or remove it.. the second sensor is gonna read the same air and it messes with the computer a bit and can make your vehicle run a little different... sometimes not good. The aftermarket plug-in's change what the computer is reading and allows for better running. Another, cheaper, thing to do is just remove the rear sensor and mount it on the frame with a zip-tie or two... but leave it plugged in. This will cause the second O2 to read cleaner air and keep everything a little more zing. Be sure to cap the hole where the O2 sensor mounts, though.
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jstdume
Dodge Dakota
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10/29/2003
21:14:04
| RE: i know its illegal...but
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I am curious but what kind of changes in the air does the after cat o2 read.
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cata
Dodge Dakota
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10/29/2003
21:34:05
| RE: i know its illegal...but
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the second o2 sensor is susposed to read an increase in temp as the catalyst reacts with the poluntants in the exaust.
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jstdume
Dodge Dakota
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10/29/2003
22:19:27
| RE: i know its illegal...but
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An oxygen sensor senses the level of oxygen left in the exhaust. If there is alot of oxygen the sensor produces a very low voltage which in turn will richen the fuel mixture, if there is very little oxygen the sensor produces a higher voltage and terefore will lean the mixture out, this strategy applies to pre cat o2 sensors only. Now the post cat 02 sensor works exactly the same way, high oxygen=low voltage and vice versa, however the post cat 02 sensor has no effect on fuel mixture. It's sole purpose is to monitor the amount of oxygen left over after the cat haas done it's job. If you have ever viewed the post cat o2 waveform on a dso on a properly running vehicle that has a cat in good working conditon there is not a wide range of switching(voltage going from high to low and low to high). The reason for this is that the cat needs and stores oxygen for use, as the cat breaks down it can no longer store and use the oxygen that is required for proper operation, when this happens the post 02 sensor reads a greater fluctuation in voltage transitions and thus will turn on the check engine light and store a code for low cat efficency, it will in no way alter the air fuel mixture. A high cat temp just means that the cat is working excessively and not an indication of how well it is doing it's job
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IntenseDak39
*GenIII*
10/29/2003
22:54:49
| RE: i know its illegal...but
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i dont think that they actually since oxygen content... i think they sense heat and use that to figure out oxygen content.
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jstdume
Dodge Dakota
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10/29/2003
23:23:06
| RE: i know its illegal...but
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For an 02 sensor to operate it has to reach a certain temperature..somewhere around 450 degrees minimum I believe..at this temperature the chemical reaction begins to take place that makes it possible for the o2 sensor to measure the amount of oxygen present in the exhaust system. Exhaust temperatures vary to much depending on engine load and speed, to try to determine the amount of oxygen based solely on temperature would be impossible.
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IntenseDak39
*GenIII*
10/30/2003
05:08:12
| RE: i know its illegal...but
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http://www.autotap.com/oxygensensors/ppc_oxygen_sensors.html
dang... pretty good jstdune, but you had the voltage fluctuation wrong and the temp just a couple hundred degrees off. Thats a pretty good article on O2 sensors.
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Dangerous
Dodge Dakota
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10/30/2003
07:45:15
| RE: i know its illegal...but
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This is completely off topic but Intense, do you have a drop kit on your truck. It has a nice stance. Also what kind of rims are those.
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IntenseDak39
*GenIII*
10/30/2003
08:13:52
| RE: i know its illegal...but
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lol... drop kit
here's some pix and i'll let you decide
and the wheels are American Racing Outlaw II
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jstdume
Dodge Dakota
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10/30/2003
09:57:03
| RE: i know its illegal...but
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how is the voltage fluctuation wrong lean=low voltage and rich=high voltage
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jstdume
Dodge Dakota
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10/30/2003
09:59:12
| RE: i know its illegal...but
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BTW INTENSE that is one sick ride!!!
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