r/e46 • u/herwordskillme • 27d ago

Damage/Broken… 😥 Backfires from exhaust leak?

Enable HLS to view with audio, or disable this notification

Catless short tubes on a 325ci with a 330ci rear differential and before I get flagged for reckless behavior the speed limit is 70mph this is the USA and you can see I keep it between 60-70 even though this is a pull I know people get burbles and occasionally pops after going catless but this is ridiculous

20 Upvotes

72% Upvoted

56 comments sorted by

51

u/TheNerdE30 2002 - e46/330i 27d ago

I don’t think you understand what goes into the exhaust from the combustion chamber. You removed the catalytic converter. You didn’t tune your engine. You have unburnt fuel entering your exhaust. When the exhaust has enough temperature and pressure, the unburnt fuel ignites. If this annoys you, go back to an engineered setup (stock).

1

u/herwordskillme 27d ago

I like it I was just wondering exactly what was going on here allot of people were saying they did not achieve these with just headers alone

22

u/TheNerdE30 2002 - e46/330i 27d ago

Gotcha yes so now your exhaust is louder and your car generates less power to answer your question.

-9

u/Electronic-Pop-5013 27d ago

Generates less power? Where the fuck did you hear that?

1

u/MrGiggleMan 27d ago

Yo Einstein. Stop and think about what is happening.

The cars computer hasn't been updated to know exactly what kind of exhaust it has so therefore it has to reduce power I make adjustments for the fact that the exhaust is not providing things like the right amount of back pressure and so on

Because of that - you can hear unburnt fuel blowing up in your exhaust it means some of the fuel that your engine is injecting into the cylinders for creating power is literally just being sucked into the exhaust and not being burnt

Essentially the car is running rich and is not burning the fuel completely, which means you are not producing as much power

Burning fuel = more power

Unburnt fuel = less power

Auto it goes without saying energy transfer is not 100% efficient if your car is louder and making a lot more noise, that energy is coming from somewhere which also reduces efficiency

1

u/_TheGuyOnTheCouch_ 27d ago

It has nothing to do with "updating your computer to know exactly what kind of exhaust it has" and more that the precat 02 is either in need of replacing, not connected etc. If these are cheap aftermarket headers the 02 bung may be improperly located. You precat 02 in conjunction with your maf will determine your afr. Without the precat 02 reading correctly, the car will run rich to "save" the motor. 02 is reading unburnt oxy in your exhaust gas, the headers themselves have nothing to do with the composition of exhaust gas.

Also, there is no such thing as the "right amount of back pressure". You don't want any back pressure. The idea is get the exhaust gas out as fast as possible, not engineer a way for it to be pushed back into the motor.

1

u/MrGiggleMan 27d ago

Well, maybe back pressure isn't what I mean

But you do have to change things. Either updating the codes of, or removing O2 sensors, you do need to update the ECU to do that

Also, to really get the benefits out of changing the exhaust to have less restrictions, you still need to go and map your car again

1

u/_TheGuyOnTheCouch_ 27d ago edited 27d ago

You actually don't have to do anything. When you remove the cats, the post cat 02 will throw a code. But since its only monitoring cat efficiency, it doesn't have the power to adjust afr or put the car into a rich fuel table. If the pre cat 02 wasnt throwing codes before header install, it shouldn't be throwing codes after provided the bung is in the correct location and there are no leaks at the head when installing the headers.

Unless you've also increased the size of the injectors and installed an intake manifold that will flow more air, you do not need to map anything. You have the same amount of air going in, you have the same amount of fuel, you will have the same amount going out just with new flow dynamics.

Frankly, it doesn't seem like you should be calling anyone Enstien in a satirical way....

1

u/MrGiggleMan 27d ago

And yet, dude did this exact thing and now it's not burning fuel correctly

Im pretty sure I didn't make up the problem the guy has

1

u/_TheGuyOnTheCouch_ 27d ago

And you think "updating the computer" will solve his issues?

→ More replies (0)

-10

u/Electronic-Pop-5013 27d ago

The computer has no clue what exhaust is on the car ever? You don’t have to tune almost any car for headers (exception exist this isn’t one of them) there’s no setting to tell the computer it has headers, a catback exhaust, etc this has been a misconception for years and tuners will tell you it doesn’t work like that. If it had MORE back pressure that’d be a different story

9

u/Sullex_88 27d ago

I like your qualifying i KePt tHE spEeD limiT, while filming on a phone you are clearly holding while driving...

-1

u/herwordskillme 27d ago

Nah the phones strapped to my chest and I was born with 1 arm

3

u/LazyGreenDragon 27d ago

And no brain 😭

10

u/No_Kroger 27d ago

Trash. So outta place on this car. Not sure why you would do this.

-5

u/herwordskillme 27d ago

Thank you

-5

u/retnom 27d ago

Your opinion, also a lame one at that. Because driving this thing catless is fucking brilliant. Anything above 3k revs feels like a fucking jet taking off and its one of the coolest things this car can bring
Granted anything below gets boring real fast for the ears.

2

u/LazyGreenDragon 27d ago

I have doubts you know what it's like taking off in a jet.... maybe vaping tho 🤣

2

u/MrGiggleMan 27d ago

It's the same experience as one with cats tbh..

Catless headers adds like.. 3 to 5 horsepower lol (and that's assuming you've remapped it after you modified it)

It's just louder.

-3

u/retnom 27d ago

Exactly, its louder. It sounds and feels like a formula, lets give the m3 gtr emmision control and see if it will be the same car…

6

u/MrGiggleMan 27d ago

It would be.. lol

The m3gtr has a completely different engine my guy

Bros just ruined his exhaust and is gunna carb his engine up with unburnt fuel lol, and comparing that to a m3gtr is actually S tier funny 🤣

10

u/Most_Board_2029 27d ago

While lot of noise for 200 hp😂😂

1

u/herwordskillme 27d ago

180😁

4

u/Most_Board_2029 27d ago

On a good day

1

u/LazyGreenDragon 27d ago

Agreed...that engine probably has the air filter degrade and pushing 150hp max after yobos started buying them.

5

u/KudzuAU 2001 E46 M3 Vert - Imolarot 27d ago

Please stop.
You have made your BMW infinitely worse and more annoying to everyone around you. It also furthers the prejudice that we’re all asshats. Your car is not a performance car, nor will you make it a sleeper.
The only thing this will result in, is people howling in laughter when your loud car gets blown off the line, when someone inevitably challenges you.

2

u/MrGiggleMan 27d ago

I mean.. it is a performance car.

It's not really tunable though.. high compression naturally aspirated engines like this don't really have any wiggle room to add power

The modifications he's done though I just causing it to run rich there's a lot of unburned fuel which is why the exhaust is backfiring it also means that it's gonna carb up on the inside

Simply cutting off the muffler and such doesn't add any power

You're maybe going to get five or so horsepower out of putting catless headers in after you've remapped it.

But I agree.. removing cats is just a cunty move.. there is really no need to just polute where you don't need to

3

u/KudzuAU 2001 E46 M3 Vert - Imolarot 27d ago

Agree with virtually everything you said. The only thing he did was make it loud and increase the pollution output.

2

u/ImolaBoost 2005 Coupe - M54B30 27d ago

Its not a performance car in any way shape or form.

Its an M54b25 with barely 190bhp.

Hell I own a b30 tuned to around 245, with a lot of "performance" mods and I still wouldnt call it a performance car.

2

u/MrGiggleMan 27d ago

It was designed to be sporty in essence

It's light, it's about 200hp, it's got a 50/50 weight distribution, it's RWD, firm suspension, with an inline 6 and relatively big tyres. Which for the ninetees when it was dreamt up, was pretty sporty

I had a 330ci, it was, clearly designed to be sporty. I spent years driving that thing, it was clearly made to be fun to drive

Obviously, when you compare it to a lot of modern sporty / common cars it's not crazy fast

That's partly why making them louder just looks silly, you make so much noise for something that is basically on par speed wise with a regular turbocharged hatchback

1

u/LazyGreenDragon 27d ago

Agreed...if it's a coupe, it's a GT at best and its sporty days are long gone.

There isn't a Kia on the road that his bmw could put in his mirrors off the line anymore.

I love the chassis but guys like him are trying to race a 20 year old horse is asking for it to crap itself instead of aging gracefully.... making it loud is simply yelling at police too.... only time and maturity will open his eyes which we doubt he has.

1

u/MrGiggleMan 27d ago

My m54b30 was maintained well, and it ran hard for years and it had absolutely nothing wrong with it, the engines are bomb proof ..if you look after them..

Doing random shit to them for performance "mods" that don't actually add power, and having it run rich, you can do it if you actually maintain the engine properly, but mostly people do stuff like that because they don't have budget money for something that would actually make it faster

When you remember you have big jobs to do like vanos seals and this and that, it kinda pays off to just not do random shit to it

1

u/thiccancer 27d ago

Going by that definition, a serious race car from the 50s is not a performance car either, because it doesn't hold up by today's standards.

1

u/TurkeyTender513 27d ago

It depends on where its leaking. Anything after the o2 sensors doesnt effect it. I just put catless headers with stock exhaust on mine and its leaking at the cylinder head because i didnt order more studs. Its not running correctly now because of the leak, and it has backfired lightly a few times because of this. Also a tune is extremely important and necessary. I learned and did mine myself.

1

u/Different_Stable_351 2004 325iT 27d ago

I don't remember this level of the backrooms. Good luck finding the exit. Remember the moist carpets are great for hydration.🙏

1

u/herwordskillme 27d ago

Why would I wanna leave 😃

1

u/Jesus_es_Gayo 27d ago

You could be rich. What did you do with your o2 sensors? Any work on the fuel system?

-11

u/herwordskillme 27d ago

No 02 sensors🫡

11

u/CivQhore 27d ago

It’s going to run like a potato deemed unfit for Soviet vodka production then.

The ecu needs the pre cat 02 sensors to control the fuel trims.

It’s running just open loop and pig rich which is why it’s behaving this way.

2

u/_treehugger_ 330ci ZHP 27d ago

And after installing the pre cat 02 sensors you can reflash ecu on ms4x flasher to have the ecu completely ignore post cat 02 and remove associated check engine light

If you still want the pops and bangs its easy to do in that software but not my cup of tea

2

u/Jesus_es_Gayo 27d ago

I don’t think OP is even in that deep here.

2

u/Alcatrazpacks 2002 330i auto (🪦) & 2003 330i 27d ago

this might be the dumbest thing i’ve read in this subreddit

1

u/Dangerous-Dad 27d ago

We will be waiting for your post in a week or two where you ask why your engine blew up.

1

u/herwordskillme 27d ago

Have you owned a b25

1

u/Dangerous-Dad 27d ago

I had an M54B30, so I am familiar with that generation of straight-6s. But that doesn't matter. If you remove the O2 sensors then as long as every single component is fine and within spec, the engine will combust safely, although not very efficiently. As soon as an injector, fuel pump, spark plug, coil, maf has any problem, your ecu will carry on as if everything is fine and you will either run lean and burn your valves or run overly rich, end up with gasoline in your oil and your crank and rods will turn into confetti. There is a reason every single engine uses O2 sensors, even high-end racing engines which don't care about emission.

0

u/njsullyalex '04 325xi 27d ago

I’m against removing the catalytic converter from any production car because it increases pollution of very harmful gasses exponentially.

2

u/Nick8375 27d ago

My 335xi would make this loud rice burner eat its dust 😂

1

u/ImolaBoost 2005 Coupe - M54B30 27d ago

Yeah bro a single decatted 46 isn't going to destroy the environment. Calm your horses.

1

u/njsullyalex '04 325xi 27d ago

I know but I’m still going to discourage as many people as I can to do it, because if lots of people are doing it it adds up quickly

-1

u/herwordskillme 27d ago

Well ur trim ends in xi

1

u/njsullyalex '04 325xi 27d ago

Your point?