Exhaust smell after header install

[mrg666]

Originally Posted by weederr33

Everywhere I've ever heard has stated the primary cat is in the header.

The oxygen sensors are on the header. Engine does not even care if the second cat is there unless it is clogged. I have replaced my front pipe with HKS dual resonated without cat. I have not even changed the tune; no CELs, no problems, actually engine runs better, revs up easier, higher mpg with normal driving. I agree that the primary cat is on the header. I think the second cat is only there to reduce emission while both cats are warming up. My exhaust smells a little bit more (no different then our Honda Odyssey) in the first two minutes during warm up and there is no different smell after the only cat on header warms up.

[Irace86.2.0]

I suppose the question is whether the primary and secondary cats are doing independent jobs and work as a system, or is it the case that one is doing more than the other. It sounds like you guys are saying the cat in the header is doing all the work, in which case, the secondary cat is either redundant, but capable of the same job, or redundant, but incapable of the same job.

It would be cool to do an emissions test:

-Stock
-header only
-front pipe only
-neither

Provided a situation where both cats are warm, if emissions equally dropped then both cats are identical in function and the second is redundant. If emissions dropped more with one than the other then it would be clear which one is primary. If NOx dropped more in one and less with the other, and reciprocally, if CO and HC dropped more in one and less with the other then that would suggest the two have unique rolls.

[weederr33]

Originally Posted by mrg666

The oxygen sensors are on the header. Engine does not even care if the second cat is there unless it is clogged. I have replaced my front pipe with HKS dual resonated without cat. I have not even changed the tune; no CELs, no problems, actually engine runs better, revs up easier, higher mpg with normal driving. I agree that the primary cat is on the header. I think the second cat is only there to reduce emission while both cats are warming up. My exhaust smells a little bit more in the first two minutes during warm up and there is no different smell after the only cat on header warms up.

Ah yeah. I have the HKS R-Spec front pipe which has their "super catalyzer" and it does a damn good job. Of course there's still smell when it's warming up. But after it's warm there is little to no smell! It also has bung behind the cat if you wanna route the second sensor behind it.

[weederr33]

Originally Posted by Irace86.2.0

I suppose the question is whether the primary and secondary cats are doing independent jobs and work as a system, or is it the case that one is doing more than the other. It sounds like you guys are saying the cat in the header is doing all the work, in which case, the secondary cat is either redundant, but capable of the same job, or redundant, but incapable of the same job.

It would be cool to do an emissions test:

-Stock
-header only
-front pipe only
-neither

Provided a situation where both cats are warm, if emissions equally dropped then both cats are identical in function and the second is redundant. If emissions dropped more with one than the other then it would be clear which one is primary. If NOx dropped more in one and less with the other, and reciprocally, if CO and HC dropped more in one and less with the other then that would suggest the two have unique rolls.

I would like to see a study like that. It would be nice information.

[Irace86.2.0]

Originally Posted by weederr33

Lol ok this is becoming comical. You don't want to be wrong, and that's fine. But you keep talking about how you won't believe what others have said. So I think I'll follow suit and accept what I've read countless times unless someone from CARB, Toyota, Subaru, or Tcoat says otherwise.

Actually, I really don't mind being wrong if someone can demonstrate it. I think it is entirely plausible that I am wrong. I would readily prefer to toss any erroneous beliefs/information I have, but it is harder to do that if what knowledge I do have is conflicting with new information that is not substantiated.

[mrg666]

Originally Posted by weederr33

Ah yeah. I have the HKS R-Spec front pipe which has their "super catalyzer" and it does a damn good job. Of course there's still smell when it's warming up. But after it's warm there is little to no smell! It also has bung behind the cat if you wanna route the second sensor behind it.

You have a catless header, right? I kept the stock header but just replaced with 2017+ improved one since I wanted to keep the JR factory tune. So you have eliminated the first cat, I eliminated the second one.

[mrg666]

Originally Posted by Irace86.2.0

I suppose the question is whether the primary and secondary cats are doing independent jobs and work as a system, or is it the case that one is doing more than the other. It sounds like you guys are saying the cat in the header is doing all the work, in which case, the secondary cat is either redundant, but capable of the same job, or redundant, but incapable of the same job.

It would be cool to do an emissions test:

-Stock
-header only
-front pipe only
-neither

Provided a situation where both cats are warm, if emissions equally dropped then both cats are identical in function and the second is redundant. If emissions dropped more with one than the other then it would be clear which one is primary. If NOx dropped more in one and less with the other, and reciprocally, if CO and HC dropped more in one and less with the other then that would suggest the two have unique rolls.

Nope I didn't say that. Second cat helps with emissions especially when the cats are cold. But the first cat is effective enough alone after warm up.

[weederr33]

Originally Posted by mrg666

You have a catless header, right? I kept the stock header but just replaced with 2017+ improved one since I wanted to keep the JR factory tune. So you have eliminated the first cat, I eliminated the second one.

Yeah I have the ACE CS400, but the catted front pipe. It seems to make more sense doing the headers first. Had I not already bought a front pipe a while back, I'd probably just run the oem.

Using the 2017+ header, did you have to change the JR tune any? are you running the CARB or a custom tune?

[mrg666]

Originally Posted by weederr33

Yeah I have the ACE CS400, but the catted front pipe. It seems to make more sense doing the headers first. Had I not already bought a front pipe a while back, I'd probably just run the oem.

Using the 2017+ header, did you have to change the JR tune any? are you running the CARB or a custom tune?

That is a very nice combination, I hope you are enjoying it.

I am still running the original JR CARB tune. It works just fine with 2019 header since about one year now.

[solidONE]

Originally Posted by Contender

Lol that is funny shit...

People have such trouble admitting to being wrong. It's okay to be wrong man.. it happens all the time lmao

[Irace86.2.0]

Originally Posted by mrg666

The oxygen sensors are on the header. Engine does not even care if the second cat is there unless it is clogged. I have replaced my front pipe with HKS dual resonated without cat. I have not even changed the tune; no CELs, no problems, actually engine runs better, revs up easier, higher mpg with normal driving. I agree that the primary cat is on the header. I think the second cat is only there to reduce emission while both cats are warming up. My exhaust smells a little bit more (no different then our Honda Odyssey) in the first two minutes during warm up and there is no different smell after the only cat on header warms up.

Originally Posted by weederr33

Ah yeah. I have the HKS R-Spec front pipe which has their "super catalyzer" and it does a damn good job. Of course there's still smell when it's warming up. But after it's warm there is little to no smell! It also has bung behind the cat if you wanna route the second sensor behind it.

What smells are you smelling?

Carbon monoxide has no smell, so if the catalytic converter wasn't turning CO to CO2, you wouldn't know by the smell.

I suppose if the hydrocarbons (gas) was not converted to CO2 then that would smell like gas, and if one thing is working then it is likely the other is working, but this would be an assumption.

NOx should smell like a diesel truck.

Rich mixtures have more fuel and more fuel means more sulfur and sulfur, from what I understand, can be just a natural part of the 3 way catalytic converter. It may be that all or some converters have coatings to reduce this odor.

Ammonia (NH3) and hydrogen sulfide (H2S) are both gases of obnoxious, characteristic odours. Ammonia, especially at higher concentrations, is a stifling gas causing irritation of eyes and the respiratory system. Hydrogen sulfide is the main compound of the “rotten egg” smell. Both gases are sensed by the human nose at very low concentrations. Therefore, their presence in the exhaust gases from vehicles operated in enclosed spaces is usually a matter of discomfort and appearance rather than a health hazard.

Ammonia and hydrogen sulfide can be generated in small quantities as undesired by-products from emission control catalysts, especially from three-way catalysts. Ammonia is generated by reduction of nitric oxide. Under regular circumstances, NO is reduced to nitrogen in the three-way catalyst. Under favorable conditions the reduction of NO does not stop at N2 but continues to NH3.

Hydrogen sulfide is generated in a similar manner from sulfur compounds that are present in the fuel. Therefore, the H2S formation is also dependent upon the sulfur content of the fuel. Most of the fuel sulfur is present in the exhaust gases as sulfur dioxide, SO2. In the three-way catalyst, under favorable conditions, SO2 may be reduced to H2S.

All conditions that favor or enhance the chemical reduction activity of the three-way catalyst are likely to increase the formation of NH3 and H2S. These conditions include:

high catalyst temperatures
low exhaust gas space velocities
rich fuel mixtures.
H2S is typically smelled on a busy highway whenever cars slow down or stop after a period of high speed cruising. At such moments the catalyst is very hot and the exhaust gas flow rate is very low which are precisely the conditions favoring H2S formation.

H2S formation can be prevented or limited by incorporating H2S suppressants into the catalyst washcoat. This is commonly done in today’s automotive catalyst technologies in North America. The three-way catalysts offered by Nett Technologies for the LPG forklift market, do include H2S suppressants.

H2S and NH3 formation from a given catalyst can be minimized or eliminated by tuning the engine to a leaner mixture. Whenever three-way catalysts are used in an uncontrolled system (“open loop control”), care should be taken than the engine is running at a slightly lean a/f mixture. This becomes especially important if H2S odor becomes a concern.

https://www.nettinc.com/information/...e-way-catalyst

[weederr33]

Originally Posted by Irace86.2.0

What smells are you smelling?

Carbon monoxide has no smell, so if the catalytic converter wasn't turning CO to CO2, you wouldn't know by the smell.

I suppose if the hydrocarbons (gas) was not converted to CO2 then that would smell like gas, and if one thing is working then it is likely the other is working, but this would be an assumption.

NOx should smell like a diesel truck.

Rich mixtures have more fuel and more fuel means more sulfur and sulfur, from what I understand, can be just a natural part of the 3 way catalytic converter. It may be that all or some converters have coatings to reduce this odor.



https://www.nettinc.com/information/...e-way-catalyst

You know, typical exhaust smells when you have a catless header lol

[Irace86.2.0]

Originally Posted by Irace86.2.0

Actually, I really don't mind being wrong if someone can demonstrate it. I think it is entirely plausible that I am wrong. I would readily prefer to toss any erroneous beliefs/information I have, but it is harder to do that if what knowledge I do have is conflicting with new information that is not substantiated.

Originally Posted by solidONE

People have such trouble admitting to being wrong. It's okay to be wrong man.. it happens all the time lmao

See above. I'm was a science major. Not a flat-earther, young earth creationist. I will happily shed any false beliefs/ideas I have in the face of solid evidence. I have done it many times before, but I will argue a point, especially if I am just to take someone's word. Appeal to popularity, authority, etc are all logic fallacies. It is always best to hold onto your current understanding/belief until presented with evidence to the contrary.

[Irace86.2.0]

Originally Posted by weederr33

You know, typical exhaust smells when you have a catless header lol

Well, we have another cat, so I was curious why the other cat isn't removing all the smells. For instance, the 2010 Civic SI has a 2.0 engine without a cat in the header and with one cat downstream--no smell.