[BlakeBehrens]

Looking to get a DP for my 2019 440i, what are some of the pros and cons between the catless/catted downpipes? Or is there virtually no performance difference? New to all this and appreciate any input

[Wires]

Originally Posted by BlakeBehrens

Looking to get a DP for my 2019 440i, what are some of the pros and cons between the catless/catted downpipes? Or is there virtually no performance difference? New to all this and appreciate any input

Catless: makes your car stink like unburnt fuel and you will get a O2 CEL unless you run a tune to disable that check or put in a O2 simulator for the bottom O2 sensor. Exhaust note sounds tinny and harsh.

Catted (high flow): Good ones won't trigger the CEL, and have marginally less performance than catless. Stick to catted downpipes with the 4" catalyst vs those bragging 5" on a 4" downpipe. The 5" versions will give the CEL, and sound horrible (boomy raspy sound).

[sigterm2.0]

Also...

I would add that it depends on your location. If you have emissions testing, you probably would need to research the catted downpipe brand that're you're thinking of too...

Also, your future goals may impact this choice... I went catless for my pending turbo upgrade. I want the best possible flow for the increase cfm of the new turbo. My goal is pushing the stock long block to the max.

Our engines are nothing more than a high-powered air pumps. Anything impeding the flow of air through it from start to finish will cause a power loss. Significant loss? Depends on a few factors but for day-to-day driving, you'd probably be ok with catted.

[J3Vr6]

Another thing to consider is what you're doing with your car. I track my car at Homestead Motor Speedway and I went with a high performance downpipe. 3/4 into my run time at the track the internals of the cat dislodged and clogged due to conditions and the constant driving hard. Maybe I had a bad batch, but I decided to go catless from then on. The smell people complain about maybe only happens at start up and isn't really that noticeable. At least to me.

[mike@x-ph.com]

power gains is the same on stock turbo

Catless has a louder tone, but also raspier
Catted has a deeper sound
I personally prefer the catted sound

Catless has a fuel smell
Catted does not

[SpoolinAddict]

Before going catless I thought it was gonna be something I wouldn't really mind. But after actually going months catless, I can't stand the smell. Being in someone else's car temporarily wasn't that bad, but dealing with it daily is horrible (for me)

[mobbinthesteez]

Do all high flow cats not cause CEL or is it just the AA one?

[mbanks21]

I've been catless since 2016-17 and don't smell anything. My wife smells like a bloodhound and can tell if I lit a candle on the other side of the house and she's never complained about the smell either.

[alohasurftoad]

Originally Posted by mobbinthesteez

Do all high flow cats not cause CEL or is it just the AA one?

HJS, Fabspeed(with HJS) and CGPrecision DS-1 are others that won't cause CEL.

Although they may not propagate a CEL, it shouldn't be confused with passing emissions tests which vary from state to state

[sigterm2.0]

Originally Posted by mbanks21

I've been catless since 2016-17 and don't smell anything.

Same I can't smell a thing!

...I mean, I hate to ask... But did you guys tighten down the clamps tight enough?

As for the raspy tone... I only have that when the exhaust flaps are open and I don't a load on the engine (like revving in neutral or something), otherwise, driving, and under boost, it sounds great. This is with stock exhaust from the downpipe back...

[mike@x-ph.com]

Originally Posted by mobbinthesteez

Do all high flow cats not cause CEL or is it just the AA one?

the majority of the catted downpipes will trigger the check engine light.

Active Autowerke is the most proven and comes with a no CEL guarantee (it use GESI EPA approved cats)

Fabspeed use HJS cats which are excellent as well and wont trigger the check engine light

the CG has a good history with CEL but does not come with any guarantee and they do not disclose which cats they use

[Wires]

Originally Posted by sigterm2.0

Same I can't smell a thing!

...I mean, I hate to ask... But did you guys tighten down the clamps tight enough?

As for the raspy tone... I only have that when the exhaust flaps are open and I don't a load on the engine (like revving in neutral or something), otherwise, driving, and under boost, it sounds great. This is with stock exhaust from the downpipe back...

You just need to walk behind the car when idling, or leave the windows down with a slight tailwind at a stop light. Car smells, and you can smell cars that have cats pulled out driving by. It's impossible for the car not to stink with the catalytic converter removed. Just not possible.

As for the raspy note, just have someone take your car and do a part throttle drive by. It has a tinny / raspy note and it's noticeable.

[DieselDuck]

Originally Posted by Wires

You just need to walk behind the car when idling, or leave the windows down with a slight tailwind at a stop light. Car smells, and you can smell cars that have cats pulled out driving by. It's impossible for the car not to stink with the catalytic converter removed. Just not possible.

As for the raspy note, just have someone take your car and do a part throttle drive by. It has a tinny / raspy note and it's noticeable.

Something must be wrong with people's noses if they don't smell when a car is catless haha.

It doesn't really bother me though.

I'm on catless dp but stock midpipe and m performance muffler and imo it sounds perfect. Under load sounds kinda loud and bass-y (only so slightly raspy, but I guess it's subjective) and normal driving it's not over the top, and constant speed I'd say it doesn't draw any more attention than a completely stock exhaust would.

[mike@x-ph.com]

Originally Posted by DieselDuck

Something must be wrong with people's noses if they don't smell when a car is catless haha.

Yes its definitely there and noticeable. While some might not find it bothersome but to say they can even smell it is surprising

[sigterm2.0]

My bad... 🤷🏻

I'm not saying it's not there... I'm saying I don't smell it while I'm in the car, windows down. Even sitting at a stop light...

If I get out of the car, walk to the back, I can smell it... If I bend over a bit and put my face closer to the exhaust, I can smell it. I had a friend rev it in neutral, I could smell it...

But I can't when I'm in my car. It's been rather warm these last few weeks so I ride with the windows down (I like hearing my turbo.. sadly, I miss old school BOV noises... Sigh.. I digress), but I just can't smell it in my car.

Sorry... Not sure what to tell everyone. I guess I'm broken. Lucky me I guess...

[Wires]

Originally Posted by sigterm2.0

Sorry... Not sure what to tell everyone. I guess I'm broken. Lucky me I guess...

It's because you have your head out the window like a dog smelling the flowers driving at mach 200. What everyone is talking about is a loooonnnngg way behind you. Rest of us just needs to drive faster!

[sigterm2.0]

Hahahah!!!!

And is that not the secret of life... When all else fails, drive faster!! 😂🤣

[mike@x-ph.com]

Originally Posted by sigterm2.0

Hahahah!!!!

And is that not the secret of life... When all else fails, drive faster!! 😂🤣

[Mogli]

New guy here. I went with catless and I’d agree they do smell a bit but not enough to change my mind. However, the raspy tinny sound when you first start up bothers me, so…. Not sure if I’m going back to stock or try a high flow cat dp. Any recommendations for a good, but affordable high flow cat dp?

Cheers,

Bill

[mike@x-ph.com]

Originally Posted by Mogli

New guy here. I went with catless and I’d agree they do smell a bit but not enough to change my mind. However, the raspy tinny sound when you first start up bothers me, so…. Not sure if I’m going back to stock or try a high flow cat dp. Any recommendations for a good, but affordable high flow cat dp?

Cheers,

Bill

if CEL is not a concern, get the MAD catted

if CEL is an issue, get the active autowerke