CT4-V CT4 BW ARH Downpipes

[Kawman]

Just because it's on the internet doesn't mean it's true, but.....

Where are the 4 catalytic converters on a Cadillac CT4-V Blackwing?

AI Overview

The 4 catalytic converters on a Cadillac CT4-V Blackwing (3.6L Twin Turbo V6) are located
in the exhaust system directly off the engine. There are two "primary" cats bolted directly to the outlet of each turbocharger (driver/passenger), followed by two "secondary" cats located further down the exhaust pipes,.

• Primary Cats (Pre-cats): Mounted directly to the turbocharger outlets on both the driver and passenger sides.
• Secondary Cats: Positioned further down the downpipes in the exhaust stream.

 

[Todd]

Just because it's on the internet doesn't mean it's true, but.....

Where are the 4 catalytic converters on a Cadillac CT4-V Blackwing?

AI Overview

The 4 catalytic converters on a Cadillac CT4-V Blackwing (3.6L Twin Turbo V6) are located
in the exhaust system directly off the engine. There are two "primary" cats bolted directly to the outlet of each turbocharger (driver/passenger), followed by two "secondary" cats located further down the exhaust pipes,.

• Primary Cats (Pre-cats): Mounted directly to the turbocharger outlets on both the driver and passenger sides.
• Secondary Cats: Positioned further down the downpipes in the exhaust stream.

Technically that description is correct. The secondary cats are positioned further down the exhaust stream (by 2”).

Typical cat assembly design.

 

[Kawman]

The OEM downpipes can be purchased today for $475 and $450. Hard to believe that after profit to the selling dealer, the material and labor cost to shape and weld the piping, there would be enough left for a more technical 2 stage cat assembly that contains palladium, platinum and rhodium.

 

[Todd]

The OEM downpipes can be purchased today for $475 and $450. Hard to believe that after profit to the selling dealer, the material and labor cost to shape and weld the piping, there would be enough left for a more technical 2 stage cat assembly that contains palladium, platinum and rhodium.

Secondary cats have less precious metal loading, they’re used mainly in conjunction with the primary cats during the warm up phase. Once the primary cats are up to temp, there is little demand on the secondary cats, that’s why they are unmonitored.

Further, because the primary cats take the brunt of the heat punishing from the engine combustion process, secondary cats can typically use a ceramic, vs metal, substrate, making them substantially cheaper to manufacture.

Secondary cats do very little of the overall catalytic work. But they are a federally recognized part of the OE emissions system.

 

[Todd]

Here’s the break down:

Purple arrow is the inlet, coming from the turbo outlet.

Green dot is the primary O2 sensor.

Light blue is the primary cat.

Yellow is air gap between the cats.

Red dot is secondary O2 sensor.

Dark blue is the secondary cat.

 

[TERRAVAST4]

Here’s the break down:

Purple arrow is the inlet, coming from the turbo outlet.

Green dot is the primary O2 sensor.

Light blue is the primary cat.

Yellow is air gap between the cats.

Red dot is secondary O2 sensor.

Dark blue is the secondary cat.

View attachment 33347

Yeah…. The CT4 Blackwing has two converters. Mine didn’t have rainbows on them but they are gone now

 

[ngoni]

Yeah…. The CT4 Blackwing has two converters. Mine didn’t have rainbows on them but they are gone now

I think only the special edition cars come equipped with the rainbow cats and polka-dot gas tanks.

 

[Kawman]

Upon more research and conversations, it seems Todd's explanation is 100% correct. The stock housing with the OEM downpipes has 2 cats in it. G-Sport does make a 2 stage option that has a 400cell primary and a 200cell secondary. The problem is it's 3" longer and ARH has said there is not enough room to use the longer 2 stage option. I was also able to verify which G-Sport cat part number ARH uses. It is part #85500, is rated for up to 1,000hp and cost $880ea.

 

[Todd]

Here’s the truth: 4BW downpipes have four O2 sensor bungs total—two per side, with one upstream and one downstream, on each of the TWO catalytic converters. Aftermarket downpipes from Tapout, etc. all replace a single cat per side, and the P0420/P0430 codes thrown with high-flow or non-cat downpipes confirm the downstream sensors are monitoring that cat directly. If there were unmonitored secondary cats being deleted, we wouldn’t see those codes from the downstream O2 sensors after swapping downpipes. It’s one cat per side; 2 total. Done.

None of this “air gap” or dual-stage cat nonsense matters when purchasing aftermarket downpipes for LF4-powered cars anyway, which is the topic of this thread that has really been derailed.

OP, I’m sorry your thread seeking aftermarket downpipes advice got way off topic.

PS: I do appreciate the part# confirmation used in the ARH kit if that is true. It looked like the most appropriate option in the g sport catalog.

Hey, you’re not doing your fellow enthusiasts a favor here. This a learning opportunity.

There are four cats, total.

Two per side.

One on each side is a primary cat, usually 800 cell.

There is an O2 sensor before and after this cat to monitor its function.

The second O2 sensor sits between the first cat and second cat, in an air gap.

The second cat is there to help with cold start emissions, until the primary cat is up to temp.

There is no O2 sensor after the second cat, so it can be removed with an aftermarket design and not set a check engine light.

Removing the second cat and making the primary cat a “high flow” design can unlock power.

But please understand that regardless of aftermarket “EPA compliant” claims, this second cat removal is not federal emissions legal.

That is all.

 

[Todd]

Not sure what’s up with your extreme hostility here.

My credentials? I’ve been in the performance exhaust design and manufacturing industry for 35 years.

Not a joke.

 

[Todd]

And CARB and EPA are two different things.

CARB is state level.

EPA is federal level, which supersedes state level.

EPA governs 50 states.

CARB extends to 14 states based on California emissions standards.

The more you know…

 

[Todd]

Oh, I’m not being hostile at all. You’re just wrong while being condescending when challenged with facts, plus derailing a thread with made up info. Still no proof! Sure, I’ll believe you are something you claim to be, but you’re still wrong and posting fake info anyway. Send it to my DM and leave the thread alone. Thanks!

Bizarre response.

 

[Melon]

That's interesting. I was curious so I dove into this myself.
GM refers to the assembly as a "Three way catalytic converter"

Site Maintenance

And sure enough, it's two sets of catalyst with an air gap.

Pretty interesting, learned something today.

 

[Todd]

That's interesting. I was curious so I dove into this myself.
GM refers to the assembly as a "Three way catalytic converter"

Site Maintenance

And sure enough, it's two sets of catalyst with an air gap.

Pretty interesting, learned something today.

Right? Not sure why someone would be so angry about learning something, strange.

Anyway, the more we understand how mods work, the more we’re educated consumers.

Considering how many people get CELs and flagged for emissions violations when modding, I didn’t see how I was “crapping on a thread” here.

Either way, I’m out…

 

[Melon]

Apologize to adding to the derailing of this thread. I just like learning new things.

 

[Kawman]

Staying away from the semantics, here is an after market part that contains 2 catalysts. The first catalyst contains 400 cells psi and the second catalyst contains 200 cells psi. Between the 2 catalysts is an air gap. It is within this airgap that an oxygen sensor takes a reading. A similar looking device without a bung hole for an O2 sensor would be a part with only 1 catalyst.

Phuck the cost, I'd order my downpipes with these cats if I could, but they are too long to fit on one side.