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Aftermarket Exhaust options!

OMG70

Master Bruce!
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113
LA/OC, California
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Hey Rob, congrats on the purchase. However, being completely new to car modifications and not mechanically inclined at all, it seems the more I read, the more confused I am. Hoping you can help me out here.

So adding the downpipes removes the catalytic converter, yes? How are the cars street legal after that? Where I live we must obtain an emissions inspection to renew license plates and I don't see how one could pass without it.

Are there viable downpipe options that leave the CC intact or reinstall new ones?

Also, are the secondary cats also needed for emissions compliance? It seems most of the cat-back systems remove these, yes?

I just don't want to be in a position where 2 years from now when it's time to renew my plates, that I have to drop another $2k to bring the car back to stock to pass inspection.
I don't believe adding downpipes means that you lose your cats. The idea is to get pipes that breathe better (aka larger diameter). The cats could be a source of restriction so many would likely opt for a high flow variant to substitute for the OEM parts. In cars with 2 cats, some people/cars can still get by with only 1 cat installed

Unless I'm mistaken, what you're thinking of is "straight piping" a car. (which is also achievable by just disconnecting the exhaust system and letting all your gasses leak out from basically under the two front seats how Honda ricers do)
 

matpal

Registered Member
106
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28
Genesis Model Type
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I don't believe adding downpipes means that you lose your cats. The idea is to get pipes that breathe better (aka larger diameter). The cats could be a source of restriction so many would likely opt for a high flow variant to substitute for the OEM parts. In cars with 2 cats, some people/cars can still get by with only 1 cat installed

Unless I'm mistaken, what you're thinking of is "straight piping" a car. (which is also achievable by just disconnecting the exhaust system and letting all your gasses leak out from basically under the two front seats how Honda ricers do)
I've read that the primary catalytic converters are contained in the OEM downpipes. Whether that is accurate or not, I don't know....
 

Vortex951

Registered Member
157
107
43
Genesis Model Type
Genesis G70
I've read that the primary catalytic converters are contained in the OEM downpipes. Whether that is accurate or not, I don't know....
So it gets a little tricky if you aren’t looking into the stuff deep and really studying it. There are primary cats. And secondary cats. The primary cats are in the downpipe that is bolted up to the turbos. The secondary cats are located at the very end of the mid pipes. ( there are some companies that sell straight midpipes and still call them down pipes though). You can replace all the cats with straight pipes. There is also high flow cat replacement options as well. If you decide to replace the midpipes with plain 2.5 inch pipes like I did you can which will delete the secondary cats. It will not effect the primary cats at all if you do so. I would love to run a 200 cell cat primary (which is a high flow cat) and you can also open it up to a 2.5 inch pipe instead of the stock 1.25 inch. Might be 1.4 inch I can’t remember off the top of my head. Keeping a primary imo is a good choice for a daily vehicle.

Hope this helped a little bit lol
 

matpal

Registered Member
106
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Genesis Model Type
Genesis G70
So it gets a little tricky if you aren’t looking into the stuff deep and really studying it. There are primary cats. And secondary cats. The primary cats are in the downpipe that is bolted up to the turbos. The secondary cats are located at the very end of the mid pipes. ( there are some companies that sell straight midpipes and still call them down pipes though). You can replace all the cats with straight pipes. There is also high flow cat replacement options as well. If you decide to replace the midpipes with plain 2.5 inch pipes like I did you can which will delete the secondary cats. It will not effect the primary cats at all if you do so. I would love to run a 200 cell cat primary (which is a high flow cat) and you can also open it up to a 2.5 inch pipe instead of the stock 1.25 inch. Might be 1.4 inch I can’t remember off the top of my head. Keeping a primary imo is a good choice for a daily vehicle.

Hope this helped a little bit lol
That does help, thanks, so all of the downpipes I am seeing truly do delete the primary CC. Do you know if the emissions system functions properly (passes inspection) with the secondary cats only?

And the only downpipes I can find with the HFC included are from Lap3.if you know if any others, I'd be interested.

Lastly, I'm guessing that just straight downpipes are an improvement even over after-market, larger downpipes with the HFC?
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joschneider

G70 Member
776
941
93
Las Vegas, NV
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Make sure you read this before installing: I'm at a loss...

Inspections depend on whether they use a tailpipe sniffer or just plug into OBDII. If the latter, then all you need is to make sure your tune can turn off the check engine light. CEL will happen when you take out primaries

There are no real advantages if you can’t tune for your mod. Our turbos are also known to have some issues with both HFCs and just straight piped. Check out the stinger forums for their issues with overboost codes and leaking oil before making any decisions
 

Vortex951

Registered Member
157
107
43
Genesis Model Type
Genesis G70
That does help, thanks, so all of the downpipes I am seeing truly do delete the primary CC. Do you know if the emissions system functions properly (passes inspection) with the secondary cats only?

And the only downpipes I can find with the HFC included are from Lap3.if you know if any others, I'd be interested.
Lastly, I'm guessing that just straight downpipes are an improvement even over after-market, larger downpipes with the HFC?
My guess will if you do a primary car delete with any of the possible options we have the car will not pass emissions at all unless you get a tune that will keep If from showing( might have to be an ecu tune but don’t quote me on that I have not looked into that at all as I still believe they are extremely rare for our platform).

As far as down pipes I believe ultimate performance makes a primary and mid pipe combo with a HFC primary and secondary delete. But it is 1500$ and can not be paired with any other midpipes due to its design.

Anytime you create more flow the car will perform better. Obviously straight piped is best for a turbocharged engine since they do not need back pressure like a N/A engine or a supercharged engine But yes we do have an overboost issue for our cars which is one reason I’d do a high flow cat if I ever get that far unless someone figures out how to fix that issue
 

Toddasaurus

REEEEEEEEEEEEEEEE!!!!!
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Portland, OR
Genesis Model Type
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IMG_20190823_083004.jpg


Lap3 primary downpipes with HFC's. They are beautiful, and I wish I had a shop nearby that was experienced enough to install them. It's above my level of comfort.
 
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Vortex951

Registered Member
157
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43
Genesis Model Type
Genesis G70
View attachment 23203


Lap3 primary downpipes with HFC's installed. They are beautiful, and I wish I had a shop nearby that was experienced enough to install them. It's above my level of comfort.
If those weren’t 1000$ and what looks like a pain in the @$$ to install I’d def get me a set. But I don’t wanna be pulling them out every 2.5-3 months for my oil changes lol

Did they come with the antifoulers?
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Toddasaurus

REEEEEEEEEEEEEEEE!!!!!
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If those weren’t 1000$ and what looks like a pain in the @$$ to install I’d def get me a set. But I don’t wanna be pulling them out every 2.5-3 months for my oil changes lol

Did they come with the antifoulers?
I ordered antifoulers separate. These ones I got actually have a mini-catalytic converter inside them. Pretty sweet, take a look...

IMG_20190830_132608.jpg
IMG_20190830_132625.jpg
 

Toddasaurus

REEEEEEEEEEEEEEEE!!!!!
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Portland, OR
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If you can take your car apart to remove and re-install the turbo, I would think this would be easy! Is there something that makes this hard?
This is true. Removing the turbos are a lot harder than removing the downpipes. Just gotta spray down those studs and nuts with PB Blaster or something beforehand and you'll have much better chances of not snapping a stud.

AWD cars are more difficult to reach all the hardware than RWD cars.

Only tools you need are a couple extensions and at least 1 u-joint.
 

matpal

Registered Member
106
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Genesis Model Type
Genesis G70
If those weren’t 1000$ and what looks like a pain in the @$$ to install I’d def get me a set. But I don’t wanna be pulling them out every 2.5-3 months for my oil changes lol

Did they come with the antifoulers?
Please tell me you really don't have to pull these to change your oil....
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CoconutRob

Registered Member
476
340
63
Genesis Model Type
Genesis G70
View attachment 23203


Lap3 primary downpipes with HFC's installed. They are beautiful, and I wish I had a shop nearby that was experienced enough to install them. It's above my level of comfort.
Congratulations, great job! Man I dont know if I would have had the patience. So the big question was it worth it? Do you notice any difference? Power, sound, ect.
 

Toddasaurus

REEEEEEEEEEEEEEEE!!!!!
2,290
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Portland, OR
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Congratulations, great job! Man I dont know if I would have had the patience. So the big question was it worth it? Do you notice any difference? Power, sound, ect.

Oops, I meant that the HFC's are installed on the downpipes - not on my car. Sorry!! I'm gonna sell them, not install them.
 

BlackedOutG70

Registered Member
94
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18
Genesis Model Type
Genesis G70
Oops, I meant that the HFC's are installed on the downpipes - not on my car. Sorry!! I'm gonna sell them, not install them.
How much are you selling them for? I assume the price you paid?
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Toddasaurus

REEEEEEEEEEEEEEEE!!!!!
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Portland, OR
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What are antifoulers? Do I have to have them?
Antifoulers prevent the CEL o2 sensor code. It fools the secondary O2 sensors into thinking your catalytic converters are operating normally.

These are useful when using HFC's, or removing the cat altogether. Even though HFC's usually prevent an o2 code from happening, it is still not as efficient as the stock cats, and on certain occasions it could still throw an o2 sensor code. The antifoulers eliminate that completely.
 
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