Exhaust smell after header install

[weederr33]

Originally Posted by Irace86.2.0

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.

Are you referring to a stock Civic SI? My catted front pipe is an aftermarket with a "high flow" cat. It smells till it warms up. I feel we are comparing apples to oranges, bruh. I get your science-based logic. I'm working on my PhD to teach kids in college how to logically think, too. But it is what it is. It's not damage, broken, or of some arbitrary design. It's just how HKS made it. I guarantee 90% of others who have a high flow cat frontpipe and catless headers at some point noticed a smell difference than when it was stock. I think a different odor after installing it was evidence enough for me.

[Irace86.2.0]

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.

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?

Missed or forgot about that first post. Just read the second post and thought you meant you had a stock front pipe.

Originally Posted by weederr33

Are you referring to a stock Civic SI? My catted front pipe is an aftermarket with a "high flow" cat. It smells till it warms up. I feel we are comparing apples to oranges, bruh. I get your science-based logic. I'm working on my PhD to teach kids in college how to logically think, too. But it is what it is. It's not damage, broken, or of some arbitrary design. It's just how HKS made it. I guarantee 90% of others who have a high flow cat frontpipe and catless headers at some point noticed a smell difference than when it was stock. I think a different odor after installing it was evidence enough for me.

Yeah, a single aftermarket high flow cat is probably not enough to remove all smells and definitely takes more time to heat up. I've read where some people have passed emissions with them in some states, so they must be a three way cat and be doing a decent enough job, yet I am not sure if they are coated for sulfur reduction.

It is always hard to judge by our nose because it adapts so fast to consistent smells. It is why I can't smell my cologne thirty seconds after putting it on.

[weederr33]

Originally Posted by Irace86.2.0

Missed or forgot about that first post. Just read the second post and thought you meant you had a stock front pipe.



Yeah, a single aftermarket high flow cat is probably not enough to remove all smells and definitely takes more time to heat up. I've read where some people have passed emissions with them in some states, so they must be a three way cat and be doing a decent enough job, yet I am not sure if they are coated for sulfur reduction.

It is always hard to judge by our nose because it adapts so fast to consistent smells. It is why I can't smell my cologne thirty seconds after putting it on.

It removes a surprising amount, but yeah my nose probably gets used to it. HKS advertises it as having more filtering materials. I don't know enough to know what's included nor do I believe it till I see a comparison. GDI, now I sound like you. lulz.

[Yoshoobaroo]

Originally Posted by Irace86.2.0

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.

Damn that is pretty far downstream for a modern car! Probably why they need such a huge cat too, despite the small engine.

[Irace86.2.0]

Originally Posted by Yoshoobaroo

Damn that is pretty far downstream for a modern car! Probably why they need such a huge cat too, despite the small engine.

Well, it looks large, but it could be the same volume as our two cats, and it could actually be two cats with the o2 between, so it is all housed in one compact package. It is hard to tell by the pics. Our two cats seem like they would add up to more size that this single unit, but it is hard to tell without doing a cross-section of each.

[Irace86.2.0]

Originally Posted by weederr33

It removes a surprising amount, but yeah my nose probably gets used to it. HKS advertises it as having more filtering materials. I don't know enough to know what's included nor do I believe it till I see a comparison. GDI, now I sound like you. lulz.

The big thing is probably surface area. Most OEM cats have a denser core, but I'm sure some are better than others based on materials.

Stock:




Performance/High Flow:

[solidONE]

Originally Posted by Irace86.2.0

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.

That's fair. As far as I can tell the front has pre and post cat O2's to measure efficiency. the rear cat? No. Also they seem to be very similar in size so, calling it "primary" or "Secondary" might just be arbitrary assignment. Tho the position of the O2 sensors should clue you in on which cat the OE designer considers more crucial.

Doesnt matter to me, no need to waste time arguing over technicalities. I know people make entire careers out of doing that, but meh.

[HaXx]

Give it to me straight, just how bad does a properly installed, no exhaust leak, full catless header and front pipe system small inside the cabin?

[solidONE]

Originally Posted by HaXx

Give it to me straight, just how bad does a properly installed, no exhaust leak, full catless header and front pipe system small inside the cabin?

If it still smell weird after a day, and running it hot for a while... Just check for leaks, no guessing. Nobody online can tell you if your exhaust is leaking or not. You got to check it.

[HaXx]

Originally Posted by solidONE

If it still smell weird after a day, and running it hot for a while... Just check for leaks, no guessing. Nobody online can tell you if your exhaust is leaking or not. You got to check it.

Assuming you dont have any leaks, how bad does a catless system smell? I feel like it cant truly be all that awful because there are a tremendous number 9f people full catless

[solidONE]

Originally Posted by HaXx

Assuming you dont have any leaks, how bad does a catless system smell? I feel like it cant truly be all that awful because there are a tremendous number 9f people full catless

If you're always moving forward and not just parked and idling you shouldn't smell it at all. 1st time i ran e85 catless, the smell almost made me throw up in my mouth a little when I parked it after taking some WOT logs. The factory cat went back on soon after.

[Irace86.2.0]

Originally Posted by HaXx

Give it to me straight, just how bad does a properly installed, no exhaust leak, full catless header and front pipe system small inside the cabin?

Have you never been to a classic car show? Have you driven behind a classic car? That is how you will smell to others driving down the road. You will probably smell a little bit with the windows down at low speeds and probably minimal to nothing at high speeds and nothing with the windows up unless stopped in traffic.

I went to the Ukraine in 2007. We were behind all types of vehicles on the highway. I don't know their smog laws, buy I wanted to hurl.

[solidONE]

People have different tolerance for toxic fumes, maybe. on 91 pump gas its not as bad as E85, but i dont think it's worth breathing all that in, specially something you commute in, for a couple of horsepowers.

[HaXx]

While were all talking about catless headers, can I ask if anyone has used an o2 sensor spacer to not upset the downstream sensor on a catless header? The j shaped vibrant performance one seems to have raving reviews. I dont want to spend hundreds to re-protune. Dont shoot me