Exhaust smell after header install

[Yoshoobaroo]

Originally Posted by Irace86.2.0

The main cat does most of the work. The precat is not necessary once the main cat heats up, but you are right about the smell. It should smell for 10 minutes (depending on temp/driving conditions) until the main cat fully heats up.

The cat in the header IS the primary cat and does most of the work. The one in the front pipe is secondary.

The smell does not go away after 10 minutes with a catless header. I personally hated the smell and ended up going back to the stock unit cause it wasn’t worth the 10hp bump over catback and 93 tune.

[Irace86.2.0]

Originally Posted by Yoshoobaroo

The cat in the header IS the primary cat and does most of the work. The one in the front pipe is secondary.

The smell does not go away after 10 minutes with a catless header. I personally hated the smell and ended up going back to the stock unit cause it wasn’t worth the 10hp bump over catback and 93 tune.

I believe you are mistaken. The main cat is the one in the front pipe. The precat is in the header. Koenigsegg actually has a bypass valve that divert air around the precat once the main cat heats up.

[Yoshoobaroo]

Originally Posted by Irace86.2.0

I believe you are mistaken. The main cat is the one in the front pipe. The precat is in the header. Koenigsegg actually has a bypass valve that divert air around the precat once the main cat heats up.

That’s really cool, didn’t know that, but alas this isn’t a Koenigsegg. CvK does a lot of things differently because he can afford to, and the cars aren’t held to the same regulations because of the extremely low production numbers.

Our primary cat is in the header. That’s why there’s an O2 sensor right before and right after it, and the front pipe does not have an O2 sensor.
https://www.ft86club.com/forums/showthread.php?t=71412

[Irace86.2.0]

Originally Posted by Yoshoobaroo

That’s really cool, didn’t know that, but alas this isn’t a Koenigsegg. CvK does a lot of things differently because he can afford to, and the cars aren’t held to the same regulations because of the extremely low production numbers.

Our primary cat is in the header. That’s why there’s an O2 sensor right before and right after it, and the front pipe does not have an O2 sensor.
https://www.ft86club.com/forums/showthread.php?t=71412

Maybe I missed it, but I didn't see anything in the link that shows something credible about which is the main cat.

https://en.wikipedia.org/wiki/Catalytic_converter

Vehicles fitted with catalytic converters emit most of their total pollution during the first five minutes of engine operation; for example, before the catalytic converter has warmed up sufficiently to be fully effective.

Some vehicles contain a pre-cat, a small catalytic converter upstream of the main catalytic converter which heats up faster on vehicle start up, reducing the emissions associated with cold starts.

It is best to put the catalytic converter away from the headers because it will have a reduced negative effect, but by putting the main cat downstream there is a problem with heating it up quickly because exhaust temperatures drop quickly as they leave the combustion chamber. Manufactures will use a precat on the header to solve this problem. By putting a catalytic converter close to the headers, it heats up faster, so it is able to reduce emissions, but then why not just have a single converter? If you look at the pre-catalytic converter on the headers and compare it to main catalytic converter, typically the main cat will be denser, and the precat will be less dense, so it isn't too restrictive.

The O2 sensor locations are typically coming right off the exhaust manifold (so they can read oxygen for fuel mapping) and between the precat and main cat. Some cars have them after the main cat as well, but the precat is much more likely to fail because of the heat/proximity to the combustion chamber in terms of melting (so it is the best one to monitor), and the whole point of the o2 sensor is to detect oxygen for fuel mapping. The downstream sensors can detect catalytic health, but it is not their primary function.

If you could show me a picture of the cat on the headers and the cat on the front pipe then I would accept what you say.

This explanation was a nice read:

https://mechanics.stackexchange.com/...ixture-control

[Yoshoobaroo]

Originally Posted by Irace86.2.0

Maybe I missed it, but I didn't see anything in the link that shows something credible about which is the main cat.

https://en.wikipedia.org/wiki/Catalytic_converter



It is best to put the catalytic converter away from the headers because it will have a reduced negative effect, but by putting the main cat downstream there is a problem with heating it up quickly because exhaust temperatures drop quickly as they leave the combustion chamber. Manufactures will use a precat on the header to solve this problem. By putting a catalytic converter close to the headers, it heats up faster, so it is able to reduce emissions, but then why not just have a single converter? If you look at the pre-catalytic converter on the headers and compare it to main catalytic converter, typically the main cat will be denser, and the precat will be less dense, so it isn't too restrictive.

The O2 sensor locations are typically coming right off the exhaust manifold (so they can read oxygen for fuel mapping) and between the precat and main cat. Some cars have them after the main cat as well, but the precat is much more likely to fail because of the heat/proximity to the combustion chamber in terms of melting (so it is the best one to monitor), and the whole point of the o2 sensor is to detect oxygen for fuel mapping. The downstream sensors can detect catalytic health, but it is not their primary function.

If you could show me a picture of the cat on the headers and the cat on the front pipe then I would accept what you say.

This explanation was a nice read:

https://mechanics.stackexchange.com/...ixture-control

Go unbolt the exhaust on your car if you don’t believe what has been discussed hundreds of times on this forum. You can search and find dozens of threads where the primary/secondary cats are discussed.

[weederr33]

Originally Posted by Irace86.2.0

Maybe I missed it, but I didn't see anything in the link that shows something credible about which is the main cat.

https://en.wikipedia.org/wiki/Catalytic_converter



It is best to put the catalytic converter away from the headers because it will have a reduced negative effect, but by putting the main cat downstream there is a problem with heating it up quickly because exhaust temperatures drop quickly as they leave the combustion chamber. Manufactures will use a precat on the header to solve this problem. By putting a catalytic converter close to the headers, it heats up faster, so it is able to reduce emissions, but then why not just have a single converter? If you look at the pre-catalytic converter on the headers and compare it to main catalytic converter, typically the main cat will be denser, and the precat will be less dense, so it isn't too restrictive.

The O2 sensor locations are typically coming right off the exhaust manifold (so they can read oxygen for fuel mapping) and between the precat and main cat. Some cars have them after the main cat as well, but the precat is much more likely to fail because of the heat/proximity to the combustion chamber in terms of melting (so it is the best one to monitor), and the whole point of the o2 sensor is to detect oxygen for fuel mapping. The downstream sensors can detect catalytic health, but it is not their primary function.

If you could show me a picture of the cat on the headers and the cat on the front pipe then I would accept what you say.

This explanation was a nice read:

https://mechanics.stackexchange.com/...ixture-control

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

[Irace86.2.0]

Originally Posted by Yoshoobaroo

Go unbolt the exhaust on your car if you don’t believe what has been discussed hundreds of times on this forum. You can search and find dozens of threads where the primary/secondary cats are discussed.

Too much work. I’ll probably find a picture eventually of the cats.

Originally Posted by weederr33

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

As in primary and secondary or 1st and 2nd? Because then the precat is the first one.

[weederr33]

Originally Posted by Irace86.2.0

Too much work. I’ll probably find a picture eventually of the cats.



As in primary and secondary or 1st and 2nd? Because then the precat is the first one.

As in primary is in the header. I think @CSGmike could answer that better. But I've always read the primary is in the headers.

[solidONE]

Originally Posted by goliath

When I installed my JDL headers earlier this year they smelled really bad for about the first week of driving. The smell is completely gone now.

From what I've read it takes the ceramic coating several heat cycles to fully cure.

That's right. Or it just might be the oils and chemicals from your hands and manufacturing process. A brand new car from the dealership does the same, bu more burnt plastic smells than oils.

I'd still check for leaks anyway and retorque after a couple heat cycles.

[Irace86.2.0]

Originally Posted by weederr33

As in primary is in the header. I think @CSGmike could answer that better. But I've always read the primary is in the headers.

Like I stated, if the pack density is different then we would know. If it was identical then it would depend on the materials inside. Assuming both were identical in volume or close enough in volume then the first one would naturally do the brunt of the work, but to truly know, we would have to remove one and do an emissions test then swap and run that test. If both showed an equal drop once up to operating temp then they are the same, but the first one does the brunt because it is first. If one did more by design then that one is the main one.

[Yoshoobaroo]

Originally Posted by Irace86.2.0

Like I stated, if the pack density is different then we would know. If it was identical then it would depend on the materials inside. Assuming both were identical in volume or close enough in volume then the first one would naturally do the brunt of the work, but to truly know, we would have to remove one and do an emissions test then swap and run that test. If both showed an equal drop once up to operating temp then they are the same, but the first one does the brunt because it is first. If one did more by design then that one is the main one.

Emissions standards require the Primary cat to have an upstream and downstream O2 sensor. Ergo.....

Not trying to get smoke to come out of your ears, but holy crap how many people need to tell you the same thing. These cars aren't Koenigseggs, they're not 90s MR2s either. They're not EJ25 Subarus. It's been long established that on these cars, and the vast majority of NA cars made in the last decade, the main (primary/supreme/heavyweight/wearing the pants in the relationship) cat is the one in the exhaust manifold.

[Contender]

Lol that is funny shit...

[Irace86.2.0]

Originally Posted by Yoshoobaroo

Emissions standards require the Primary cat to have an upstream and downstream O2 sensor. Ergo.....

Not trying to get smoke to come out of your ears, but holy crap how many people need to tell you the same thing. These cars aren't Koenigseggs, they're not 90s MR2s either. They're not EJ25 Subarus. It's been long established that on these cars, and the vast majority of NA cars made in the last decade, the main (primary/supreme/heavyweight/wearing the pants in the relationship) cat is the one in the exhaust manifold.

It depends on who is telling me more than how many. There is a big difference too between making statement and providing evidence or explanations. EPA official? Work at CARB? Design cars for a manufacture or emissions equipment? I would love to see the law or a link. I wasn't aware there was a mandate.

The 3rd gen MR2 quoted was like 1999-2007. Just saying. Kinda after OBD2 adoption and not that long ago.

I mean it makes sense what you are saying, that they would just use two high density units because why not remove as much pollutants as possible, regardless of detriments to performance.

Most newer vehicles have electronic fuel injection systems, and do not require air injection systems in their exhausts. Instead, they provide a precisely controlled air-fuel mixture that quickly and continually cycles between lean and rich combustion. Oxygen sensors monitor the exhaust oxygen content before and after the catalytic converter, and the engine control unit uses this information to adjust the fuel injection so as to prevent the first (NOx reduction) catalyst from becoming oxygen-loaded, while simultaneously ensuring the second (HC and CO oxidation) catalyst is sufficiently oxygen-saturated.

https://en.wikipedia.org/wiki/Cataly...r#Installation

I am curious if tuners use both o2 sensors for tuning like the OEMs, and I also wonder if the secondary cat is negatively effected in its ability to work by installing headers. I wonder if installing headers leads to premature failure of the other cat, and/or if the secondary cat can't do its job without the primary cat or without the ability of the oxygen sensors to properly manage the fuel delivery. I understand people often use o2 foolers, but it seems like those would provide some fixed value and not a dynamic value, which means the engine isn't getting the best feedback, which could make the engine run rich/lean.

I have a Harrop kit with E85 on a Delicious Tuning tune, so I'm curious if their tune supplements the stock tune, or if it entirely replaces it, and if so, is it not using the second sensor or is it not considering emissions at all. I feel like it much be not altering things too much because when my engine is started while cold the rpms raise and bla bla bla just like normal. Still.

[weederr33]

Originally Posted by Irace86.2.0

It depends on who is telling me more than how many. There is a big difference too between making statement and providing evidence or explanations. EPA official? Work at CARB? Design cars for a manufacture or emissions equipment? I would love to see the law or a link. I wasn't aware there was a mandate.

The 3rd gen MR2 quoted was like 1999-2007. Just saying. Kinda after OBD2 adoption and not that long ago.

I mean it makes sense what you are saying, that they would just use two high density units because why not remove as much pollutants as possible, regardless of detriments to performance.



https://en.wikipedia.org/wiki/Cataly...r#Installation

I am curious if tuners use both o2 sensors for tuning like the OEMs, and I also wonder if the secondary cat is negatively effected in its ability to work by installing headers. I wonder if installing headers leads to premature failure of the other cat, and/or if the secondary cat can't do its job without the primary cat or without the ability of the oxygen sensors to properly manage the fuel delivery. I understand people often use o2 foolers, but it seems like those would provide some fixed value and not a dynamic value, which means the engine isn't getting the best feedback, which could make the engine run rich/lean.

I have a Harrop kit with E85 on a Delicious Tuning tune, so I'm curious if their tune supplements the stock tune, or if it entirely replaces it, and if so, is it not using the second sensor or is it not considering emissions at all. I feel like it much be not altering things too much because when my engine is started while cold the rpms raise and bla bla bla just like normal. Still.

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.