Cat Converter on Duramax -- Thoughts?

[mcmonroe]

From what I understand the CA LB7 versions of the Duramax had cat converters and now all of the LLY's have cat converters.

I wonder how well cat converters will hold up on engines burning diesel fuel before clog up or whatnot.

Does anyone have any thoughts on this? Any ideas how long the cat converters are designed to last on these engines? Are they much of a restriction on power in lower or higher mile engines?

Thoughts in general?

Thanks in advance,

Mark Monroe
Harrisburg NC

[mark45678]

they had them on 6.5td back in 98 and newer I dont think theres any reason to remove it! lly will set a EGR code if it is removed....

[DmaxMaverick]

lly will set a EGR code if it is removed.... Impossible. There are no sensors before, at, or after the cat. If you get an EGR code after removing it, something else is wrong.

There should be no adverse effects from removing it. However....Unless it becomes plugged it should be no hinderance to a stock engine. There may also be an issue with you local smog requirements.

[FlyRod]

Good Question Mark. The one on my LLY seems very large. Maybe they built in some extra capacity fo later on. If anyone does know the specific science behind the converter (compounds used, build up, burn off), please teach the rest of us.

[oyazi]

Mine is a CA LB7. IIRC there is federal law re alteration of emission systems ~ which the CAT is a component ~ not to mention local laws. Seems I recall that Fed law requires of manufacturers, a certain std of longevity of emission systems/components on new vehicles also. It used to be 5yrs it might be longer ~ I know because of it, our state doesn't require smog testing during the first 5yrs.
The CAT is huge ~ thinking it is indeed designed for diesel applications. Re your questions ~ not a clue ~ have asked the same questions for a couple of yrs now w/o any satisfaction primarily, because it was seen to be a CA issue and for most of them would simply eleminate the CAT and be done w/it. I'm not personally afraid of removing it but I do respect the law (major go around w/a county bldg inspector 30yrs ago). Now, that more people are faced w/the issue, perhaps we can gather some knowlege/experience on just how much impact of performance the CAT really has ~ would not be surprised if it had minimal effect.

[ 07-02-2004, 01:51 PM: Message edited by: oyazi ]

[MIKE WIENER]

Have a 2001 3500 DA orderd it new. I am in the LA CA area. my truck never had a cat it is speced as a calif fedral truck. so go figer that one out. maybe on the good side of a factory BOBO. I have put a banks 4" on now. I just hope I do not get greaf when it comes time for smog.

MIKE

[OC_DMAX]

The CAT/EGR system did not arrive on the Calif DMAX's until 2002. Model year 2001 has just a muffler in the exhaust system and no EGR. I actually could care less about the CAT on the exhaust system. It is the EGR that I would avoid at all cost.

[w1ngsmk]

I've got new LLY, 2500 miles on it, 20 MPG highway unloaded doing about 75 cruise. Live in Vegas, and county has new ordinance for any truck 10,000 lb or less has to be smogged...I've bought the MBRP turbo back exhaust, mainly because this set up comes with sections Flanged just like the stock exhaust...I can remove or replace the exhaust Cat pipe whenever I need it to pass emissions testing...As to the SES throwing codes, all indications are that the P0401 and P0404 codes (most noted thus far) are related to the EGR pressure to the induction side of recirculation...If the cat pipe is removed, it appears that less back pressure can cause less EGR function...This can cause SES light to go on...Mine already goes on steady every time I fill up....My owners manuel says Steady SES light is emissions related, and may happen anytime...GM is so greedy to become 50 state emisions compliant, and thus able to sell more vehicles, they have made all new LLY models with emissions...I agree with how worthless Cat pipes are...If you can get rid of Cat without introducing to much cab noise, then I'm down with that!

MK

[OC_DMAX]

w1ngsmk wrote: GM is so greedy to become 50 state emisions compliant, and thus able to sell more vehicles, they have made all new LLY models with emissions...I agree with how worthless Cat pipes are...If you can get rid of Cat without introducing to much cab noise, then I'm down with that!

A little history, the EPA writes emission standards that ALL states must meet. Additionally, states are allowed to up the requirements. Certain states, most notably California (where I live), are aggressive in writing their own standards. This is mainly to combat the smog problem we have in the LA basin. So what the auto manufactures face every year are standards written by the EPA and MORE STRINGENT standards written by CARB (Calif Air Resourece Board). Starting in 2004 and for the years ahead, the diesel emission standards are the same for all 50 states. The fact that the standards are the same has nothing to do with GM being "greedy". GM is spending a lot of R&D funds to meet these new standards (which I am certain the "bean counters" would rather not spend).

Additional info, there has been a big push by the EPA to get diesel emissions under control. The EPA is targeting the NOX and particulate emissions. The big crunch will come in 2007, when some form of TBD exhaust after-treatment and ULSD (ultra low sulphur diesel) will be required. On the LLY engine as well as my LB7 (EGR/CAT equipped engine), the EGR is used to lower peak combustion temps to reduce the formation of NOX. By lowering the combustion temps, additional soot is generated. The CAT is used to reduce this and to make the particulate size smaller. Things will only become more complicated in the years ahead for diesel powered vehicles. Lets hope technology wins out and the performance keeps increasing (as has happened with gasoline powered vehicles).

[oyazi]

Guess I was mistakeningly thinking CARB (Clean Air Resources Board?) was focusing on the diesels to distract/redirect attn from their failed attempts at air quality improvements of their enhanced smogging program.

[OC_DMAX]

Actually, the LA basin air quality has improved substantially over the last 25 years. I remember in the 1960's one could not see the local hills 5 miles away, let alone the mountains 30 miles away (Angeles National Forest). Today, the local hills are always visible and the mountain 30 miles away are visible at least 75% of the time. In the mean time, the population has tripled.

The California Air Resources Board is located at:

http://www.arb.ca.gov/homepage.htm


Alan