[Indo Rider]

Originally Posted by ZheroG80

I am going to say your cars fuel trims are most likely way off based on the catless DP's and no tune. These new DME's are no joke, every car is different as well. My car may run them fine while yours may not, but the readings from the o2 sensor may be triggering your DME to throw this code.

Possible fix/trick may be o2 spacers to trick them to think it has cats on it still.

Maybe. But he said he was running the catless downpipes for a while without issues. So

[andyho123]

I am waiting to hear back from the dealer. I have never run into problems running catless downpipes without a tune. I have owned several bmw's and M's car up to now and all of them was modified. Some was tuned and some was not.

From researching this code, some have had a bad batch of gas, cracked charge pipes, and if anything aftermarket tune was too aggressive, various of reasons. I haven't seen any catless dp's without a tune cause any issues unless it was not installed correctly. Another possible culprit is the O2 sensor are damaged but I think it would have thrown a whole set of different codes.

I will keep you guys updated once I hear back.

[andyho123]

Originally Posted by ZheroG80

I am going to say your cars fuel trims are most likely way off based on the catless DP's and no tune. These new DME's are no joke, every car is different as well. My car may run them fine while yours may not, but the readings from the o2 sensor may be triggering your DME to throw this code.

Possible fix/trick may be o2 spacers to trick them to think it has cats on it still.

That maybe the case but It has been running months without any problems. Only codes pop up before would be the catless codes. The 02 spacer is really just to trick it so it doesn't throw CEL for catless

[hellcat2m4]

Originally Posted by andyho123

That maybe the case but It has been running months without any problems. Only codes pop up before would be the catless codes. The 02 spacer is really just to trick it so it doesn't throw CEL for catless

What was the update?

[andyho123]

Cleared the code and it never pop up again lol

[tac3331]

Knock would be stored in permanent code even if only occurred momentarily. I've heard of code being thrown for hitting potholes.

[danniexi]

bad batch of gas?

had that happen to me once when driving on the highway and i was passing a vehicle. the car started stuttering and threw codes. i freaked out a bit since it was on a mini road trip. filled up at a gas station, cleared the code, hasnt appeared since.

S58 stock (no tune, no downpipes).

[andyho123]

Yeah I think so too. That happened when I pumped out of a nearby Exxon that I never been to. I went back to my usually Shell station and it has been fine

[hellcat2m4]

Good to know it was nothing serious

[DieselG80XC]

Originally Posted by Indo Rider

Ok, but won't the car adjust short term fuel trims to hit proper AFR and then eventualy learn to correct the long term trims based on always having to adjust the short term trims? How does a JB4 account for catless downpipes? Plenty people have catless downpipes with JB4 or race chip and no such issues.

I'm just genuinely interested to understand these things better for S58 since not many people here talk technical details, it all just exhaust and front lips.. lol.

Actually I’ve been talking to quite a few people running very lean because of catless DP running on JB4

[G MONEY]

Originally Posted by DieselG80XC

Actually I’ve been talking to quite a few people running very lean because of catless DP running on JB4

Tick tick tick

[Fugazii]

When asking you get more Bee's with honey that being said the Forums are not obligated to answer your problem's especially with (sarcasm)!!!

[Indo Rider]

Originally Posted by DieselG80XC

Actually I’ve been talking to quite a few people running very lean because of catless DP running on JB4

OK, "very lean" compared to or meaning what? Logs or it didn't happen. Lol, j/k, but really this is pretty vague so...?

[BG22M3]

Lean means to much air in the combustion chamber causing burnt valves, ringland failure. Numerous amounts of problems. The problem with running catless anything without a tune is you have a pre cat sensor and a post cat sensor. That pre cat sensor is your AFR sensor. It counts on the post cat sensor to send its signal to the DME. The DME than will adjust the air/fuel mixture. Because that cat has to burn off the hydrocarbons. So when you take a cat out of the equation. That post cat sensor is sending information to the DME and the car is trying to correct it. That code will be back unfortunately. I’ve seen way to many people run high flow cats and or catless WITHOUT A TUNE and destroy engines doing that. The off the shelf tunes are not it. You want to do it the proper way get on a dyno get tuned properly. And go back every once in awhile to get retuned. Properly tuned cars don’t have that issue. Because the AFR sensor has a value it’s looking for that’s programmed by the tuner. And doesn’t need the post cat sensor to tell it what to do since there is no cat there. PAY TO PLAY IS THE NAME OF THE GAME.

[DieselG80XC]

Originally Posted by Indo Rider

OK, "very lean" compared to or meaning what? Logs or it didn't happen. Lol, j/k, but really this is pretty vague so...?

Attached circled column shows gear and afr if you give me your email I can send to you

[G MONEY]

Bingo. I see no reason to run catless DP with no tune. 🤷🏿‍♂️

[tac3331]

Originally Posted by G MONEY

Bingo. I see no reason to run catless DP with no tune. 🤷🏿‍♂️

Cause loud and rowdy. Now I'm gonna have to email jb4 about solutions.

[DieselG80XC]

Originally Posted by tac3331

Cause loud and rowdy. Now I'm gonna have to email jb4 about solutions.

Jb4 has no control over fueling it relys on the ecu to trim fueling as necessary. I believe something with the catless DP throws the trims way off.

[BG22M3]

Originally Posted by DieselG80XC

Jb4 has no control over fueling it relys on the ecu to trim fueling as necessary. I believe something with the catless DP throws the trims way off.

The problem with running catless anything without a tune is you have a pre cat sensor and a post cat sensor. That pre cat sensor is your AFR sensor. It counts on the post cat sensor to send its signal to the DME. The DME than will adjust the air/fuel mixture. Because that cat has to burn off the hydrocarbons. So when you take a cat out of the equation. That post cat sensor is sending information to the DME and the car is trying to correct it. You want to do it the proper way get on a dyno get tuned properly. And go back every once in awhile to get retuned. Properly tuned cars don’t have that issue. Because the AFR sensor has a value it’s looking for that’s programmed by the tuner. And doesn’t need the post cat sensor to tell it what to do since there is no cat there.

[tac3331]

Originally Posted by BG22M3

The problem with running catless anything without a tune is you have a pre cat sensor and a post cat sensor. That pre cat sensor is your AFR sensor. It counts on the post cat sensor to send its signal to the DME. The DME than will adjust the air/fuel mixture. Because that cat has to burn off the hydrocarbons. So when you take a cat out of the equation. That post cat sensor is sending information to the DME and the car is trying to correct it. You want to do it the proper way get on a dyno get tuned properly. And go back every once in awhile to get retuned. Properly tuned cars don’t have that issue. Because the AFR sensor has a value it’s looking for that’s programmed by the tuner. And doesn’t need the post cat sensor to tell it what to do since there is no cat there.

I've had no cel issues using big daddy spacers. Afr is another story.

[Indo Rider]

Originally Posted by DieselG80XC

Attached circled column shows gear and afr if you give me your email I can send to you

Interesting, so looks like AFR spikes for 1 sample after shifts and maybe after letting off? Hard to tell from that small piece of the log what'd going on. I'll bite since I'm genuinely curious and I'll PM you my email and if you send me full log I'll look closer.

I've run catless DPs for years with JB4 on multiple platforms, never had any issues.

[Indo Rider]

Originally Posted by BG22M3

Lean means to much air in the combustion chamber causing burnt valves, ringland failure. Numerous amounts of problems. The problem with running catless anything without a tune is you have a pre cat sensor and a post cat sensor. That pre cat sensor is your AFR sensor. It counts on the post cat sensor to send its signal to the DME. The DME than will adjust the air/fuel mixture. Because that cat has to burn off the hydrocarbons. So when you take a cat out of the equation. That post cat sensor is sending information to the DME and the car is trying to correct it. That code will be back unfortunately. I’ve seen way to many people run high flow cats and or catless WITHOUT A TUNE and destroy engines doing that. The off the shelf tunes are not it. You want to do it the proper way get on a dyno get tuned properly. And go back every once in awhile to get retuned. Properly tuned cars don’t have that issue. Because the AFR sensor has a value it’s looking for that’s programmed by the tuner. And doesn’t need the post cat sensor to tell it what to do since there is no cat there. PAY TO PLAY IS THE NAME OF THE GAME.

Lol, thanks for attempting to teach a lesson, but I call BS. Take your "destroying engines" fear mongering elsewhere. I'm interested in a technical discussion with someone who actually knows what they are talking about, I'm confident it's not you.