High Efficiency Downpipe VS Catless?

[WhiteFuryDC5]

TSP said they don't offer their tunes with turning off the O2 sensors, but they said they have a high efficiency cat. In their downpipe. That has good gains. Is this going to be as good as catalyst? I really want to hear that turbo whistle like I had on my old BMW with the catless downpipe. Nothing sounds better in my opinion. However, performance wise and sound wise is a high efficient Downpipe going to be. Good enough?

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[WhiteFuryDC5]

Also what about 02 non foulers? There are adapters I have used that actually work well. I have stacked 2 spark flug non foulers on my old bmw m3 and elongated the center out. Never had a light.

 

[PointByPatrol]

Ultimately depends on where you live and if you can slide in under the regulations. Catless will offer better heat extraction, flow, and power gains, but is likely illegal in all 50 states. The high flow cat options actually work quite well, and provide plenty of turbo noise.

 

[ctechauto]

HE cats like GESi (what TSP and RV6 uses), HJS, etc now are so good now, power gains over catless are pretty negligible. A couple/few hp (unless you're at like 700hp+). My shop is in an emission-less county but wont install catless for a customer (liability) because the surrounding major counties have emission inspections, but again, I explain its neglible anyway in terms of power differences. The turbo sound whistle will be a little more pronounced on a catless though.

 

[WhiteFuryDC5]

HE cats like GESi (what TSP and RV6 uses), HJS, etc now are so good now, power gains over catless are pretty negligible. A couple/few hp (unless you're at like 700hp+). My shop is in an emission-less county but wont install catless for a customer (liability) because the surrounding major counties have emission inspections, but again, I explain its neglible anyway in terms of power differences. The turbo sound whistle will be a little more pronounced on a catless though.

Is it turbo whistle and sound going to be a lot louder with efficiency downpipe versus the stock one?

I've heard that with my PRL intake and turbo inlet pipe as well as a front exhaust pipe high efficiency down pipe and full exhaust it should make about 380 whp with a tsp stage 1 tune is that about accurate?

 

[ctechauto]

Is it turbo whistle and sound going to be a lot louder with efficiency downpipe versus the stock one?

I've heard that with my PRL intake and turbo inlet pipe as well as a front exhaust pipe high efficiency down pipe and full exhaust it should make about 380 whp with a tsp stage 1 tune is that about accurate?

Its going to be more noticeable, yes. By how much? Thats subjective to an extent. I cant comment on powe figures, too many variables involved and I am not a ECU tuner.

 

[WhiteFuryDC5]

I wonder if the rv6 counted down pipe would throw a code? I have rv6 front pipe so I really want to possibly grab this one anyone have experience with it?

https://www.twostepperformance.com/products/high-temp-catted-downpipe-for-18-accord-2-0t

 

[Two Step Performance]

I wonder if the rv6 counted down pipe would throw a code? I have rv6 front pipe so I really want to possibly grab this one anyone have experience with it?

https://www.twostepperformance.com/products/high-temp-catted-downpipe-for-18-accord-2-0t

Yes, it likely would throw a code. If you are up for the challenge you may can get the de-fouler dialed in to work around it but it's not really an easy thing to adjust once installed in the car.

Our shop car makes ~575whp with our catted downpipe. No CEL and no smell. Even with catless I'm not sure how much more turbo noise you are going to get out of these relatively small turbos.

 

[Superhatch]

Please run a cat.

Aside from being illegal to run without one on the street in the US, NOx emissions are basically the worst things that cars produce. Having a cat, even a high-flow one really helps to reduce these pollutants in the air. The CTR out of the box is a ULEV50 vehicle which means it's emissions system does an extremely good job of filtering out NMOG, CO2, and NOx emissions.

A lot of the issues we had previously (smog/acid rain/ozone depletion) were due in large part to NOx and CO2 emissions, and adding cats and other emissions systems basically made it so we generally don't have to deal with those things anymore.

The difference between a cat and no cat is going to be a negligible amount of hp.

Fwiw a PRL intake helps to make a lot of the turbo noises more pronounced, and will add way more HP than removing a cat from a DP.

 

[Six-n-twins]

How long have you been with the EPA?

 

[Superhatch]

How long have you been with the EPA?

0 years. I just really enjoy breathing clean air.

 

[Six-n-twins]

What ever you do, don't look up china

 

[AZCWTypeR]

The downside of catless is the strong exhaust smell.

My OEM Audi cats kept falling apart in the '80's and I wasn't paying the big $ after the warranty expired, so I ran catless. Performance difference with a "test pipe" was negligible, but exhaust smell was very noticeable.

My son had a high-flow cat downpipe on his Gen4 GTI and at least the exhaust smelled okay. Still needed an O2 spacer to avoid a check engine light.

 

[Superhatch]

What ever you do, don't look up china

Yeah, I don't live there, or Jakarta, or Bangladesh. I'm not on boards with FL5 owners in China, but if I was I'd say the same thing.

I'm a bit older so I remember when cars were getting ruined in transport due to acid rain, where you would have to cover or move your car inside if there was a potential rain shower that could damage your paint.

Or when there was a hole in the ozone layer which was a big fucking deal which we solved through regulation. Or how in the 80's we recognized that kids who lived near major roadways had more respiratory diseases later in life or when you couldn't see the skylines on summer days in major US cities because of smog.

I'm on board with pretty much every modification of street cars, and I'm even ok with a car you're driving to a show every few weeks not having a cat, but for a daily I think it's shitty when people remove cats and other emissions related stuff to make 4hp, and at the same time spew some of the worst chemicals into the air around them.

Is one car going to make a huge difference, no, but if we change the narrative in the tuning community that running without a cat on a daily is a shitty thing to do that would be a net positive and why I post this stuff in threads like these.

 

[Clark_Kent]

Yeah, I don't live there, or Jakarta, or Bangladesh. I'm not on boards with FL5 owners in China, but if I was I'd say the same thing.

I'm a bit older so I remember when cars were getting ruined in transport due to acid rain, where you would have to cover or move your car inside if there was a potential rain shower that could damage your paint.

Or when there was a hole in the ozone layer which was a big fucking deal which we solved through regulation. Or how in the 80's we recognized that kids who lived near major roadways had more respiratory diseases later in life or when you couldn't see the skylines on summer days in major US cities because of smog.

I'm on board with pretty much every modification of street cars, and I'm even ok with a car you're driving to a show every few weeks not having a cat, but for a daily I think it's shitty when people remove cats and other emissions related stuff to make 4hp, and at the same time spew some of the worst chemicals into the air around them.

Is one car going to make a huge difference, no, but if we change the narrative in the tuning community that running without a cat on a daily is a shitty thing to do that would be a net positive and why I post this stuff in threads like these.

Good points all around. You're likely dealing with a troll; don't feed them. I expect them to return with more drivel that will guide a legitimate inquiry down the soul sucking political path.

It's 2025, a wonderful year where a catted downpipe won't crush your 500+ whp dreams. Catted downpipes are just that good, and the value proposition for catless is no longer appealing. The next item on the docket is this obsession with having the ability to disable or defeat emissions controls. Slaying one dragon at a time I suppose.

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