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karizma
Dodge Dakota
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2/25/2003
02:27:00
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 Subject: Emissions
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Message:
I had my 3rd cat removed and when i took my truck in to be inspected, it didn't pass. I thought my truck would of passed with just 2 cats. Does the 3rd one make that big of a difference, and is it necessary for it to be on there in order to pass?
If i want high-flow cats, should i get all 3 of them as high-flows or should i just get 1 high-flow cat? I ask this because it would kind of be expensive to buy 3 high-flow cats. I could really use some feedback.
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Dan Gruber
GenIII
2/25/2003
05:30:02
|  RE: Emissions
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On the high flow vs. stock cats: Not sure on this one, but common sense would tell me that you wouldn't realize a significant flow gain if you only replaced 1 or 2 of your cats with the high flow cats. But that's just my opinion.
On your issue about not passing emissions: Short answer is that your truck obviously needed the 3rd cat to pass emissions otherwise it wouldn't have failed without it. Not intended as a slam or anything, but that's the obvious answer. That's why Dodge has had 3 cats on the 4.7 since day one in CA and switched to 3 cats on all state models for 2001 or 2002...3 cats means better emissions on the 4.7.
Longer answer: Cats are part of a three-way system. Part 1 is in the cat and consists of a honeycomb coated with palladium and platnium for oxidation of HC and CO, and functions best under slightly lean conditions. Par 2 is a honeycomb coated with rhodim for reducing the NOx emissions, and it works best under slightly rich conditions. Part 3 is your oxygen sensor, which tells your powertrain control module to rapidly alternate between slightly rich and slightly lean to give both parts of the converter a chance to work. So if you removed your oxygen sensor(s) when you pulled your 3rd cat, you removed the ability of the PCM to switch between rich and lean, meaning your converters aren't getting what they need to function correctly.
But even if your O2 sensors are still in place, why 3 cats? First two are help kill cold start emissions...they get up to operating temperature much faster than the 3rd cat. The third cat then plays clean-up and removes whatever the first two don't catch. Dodge wouldn't have gone to 3 cats unless it was required to pass emissions...the metals in the cats are expensive, so the engineers undoubtedly put just enough in each cat to do the job. Remove 1/3 of your cats, and you're likely to not pass emissions. I'm not saying that vehicles won't pass with the 3rd cat removed because I know that someone here will tell me that they passed emissions without it. But the 3rd cat is there for a reason...it operates as part of a system.
Dan
2000 CC SLT 4.7 4X4 Auto 3.92 LSD
3 inch Performance Accesories lift & 32 inch BFG MT KM's
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Texas Todd
Dodge Dakota
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2/25/2003
09:42:37
|  RE: Emissions
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Message:
The two 'pre cats', y into one main cat.
1 or 2 cats hi-flow?
The third cat has NO 02 sensors!
Do either of you REALLY know what your'e talking about?
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karizma
Dodge Dakota
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2/25/2003
13:23:51
| RE: Emissions
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So, what are you trying to say Texas Todd? You don't need your 3rd cat?
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Jake
Dodge Dakota
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2/25/2003
13:27:10
| RE: Emissions
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1 or 2 cats high flow? What do you mean by that?
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b1llyw
DakotaEnthusiast
2/25/2003
14:44:54
| RE: Emissions
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My '02 only has one cat, no pre-cats. Yes, I'm sure, I double-checked.
Bill White
2002 QC 4x4, SLT , 4.7, 5 spd, 3.92 LSD
1995 CC 4x2, SLT, 318, 5 spd, 3.55 LSD
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Demon Dakota
DakotaEnthusiast
2/25/2003
14:47:45
| RE: Emissions
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Only 1 cat on a 2002? They are all "supposed" to have 2 precats and 1 primary cat. O2 sensors are on the precats...
K&N Drop in AF (CAI during summer months)
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
14.52@94.2 MPH at Silver Dollar Raceway
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Demon Dakota
DakotaEnthusiast
2/25/2003
14:51:07
| RE: Emissions
IP: Logged
Message:
Also, for the trucks with 2 precats and 1 primary cat, the 2 precats are only for start up/cold engine emmisions. The third primary cat that you cut off (just like I did) is the one that cleans up the unburnt fuel and stuff AFTER the truck is already warmed up and running under normal circumstances.
K&N Drop in AF (CAI during summer months)
True Dual exhaust and removed third cat
HO Cams & HO Intake
FASTMAN 70mm TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
14.52@94.2 MPH at Silver Dollar Raceway
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b1llyw
DakotaEnthusiast
2/25/2003
15:12:57
| RE: Emissions
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Message:
Check your factory service manual. The emission codes are NAA, NAE, etc. California, is 3 cats. 50-state is 3 cats. Federal is only 1. My '02 FSM gives a pretty clear explanation.
Bill White
2002 QC 4x4, SLT , 4.7, 5 spd, 3.92 LSD
1995 CC 4x2, SLT, 318, 5 spd, 3.55 LSD
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Texas Todd
Dodge Dakota
JOIN HERE
2/25/2003
15:19:24
| RE: Emissions
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Message:
Jake,
I was just repeating what was said in an earlier post. I was pointing out how would you have 2 hi flow cats, when that wold make 1 side with a dif. flow cat than the other, on the 3 cat models.
karizma,
I still have my 3rd cat, I'm kind of lazy, but want to loose my third cat soon. As many have stated, they didn't fail emission without it. You didn't say if it was the exhaust gas that failed, or the fact they could tell you were missing a cat.
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SMO
Dodge Dakota
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2/25/2003
17:18:45
| RE: Emissions
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Hey, say I want to do true duals. I myself wouldn't want to leave 1 pre-cat on one side and 1 pre-cat as well as the primary cat on the other side. That leaves it unbalanced. So what would i have to do? Would i have to remove the primary cat on the other side and risk not passing emissions? Or would i have to add another primary cat to the other side that doesn't have it?
Could I try taking off all the cats, and just putting 1 primary cat on each side and forget about the pre-cats alltogether? Would that work?
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karizma
Dodge Dakota
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2/25/2003
17:21:47
| RE: Emissions
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Question: If you had to stick to the Y-pipe, would my dak still pass emissions if i changed the primary cat to a Car Sound high-flow cat and left the stock pre-cats? Would it make any difference?
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Jack
Dodge Dakota
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2/26/2003
18:59:06
| RE: Emissions
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I have the same question about the cat thing that SMO does. I could use some feedback as well.
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