Catless downpipes for 335i

[str8_6 268]

Mine is completely stock without a tune and it pops and bangs. 
Do the e92’s have a different exhaust than the 90’s/91’s?

[jasera94 29]

On 10/19/2019 at 9:53 AM, AlexL said:

How do you not have no pops and bangs? My car is standard exaust and tune and it pops and bangs on decel and sometimes on upshift

It just gave a deeper sound without adjusting burple on the tune. It was a 135i so maybe different exhaust system. 

[KwS 2372]

23 hours ago, str8_6 said:

Mine is completely stock without a tune and it pops and bangs. 
Do the e92’s have a different exhaust than the 90’s/91’s?

I seem to recall something about the E90/91 having an extra muffler?

[Matth5 471]

On 10/20/2019 at 1:17 PM, str8_6 said:

Mine is completely stock without a tune and it pops and bangs. 
Do the e92’s have a different exhaust than the 90’s/91’s?

Yes, they don't have secondary cats so are a bit louder. 

[Seba 1]

Hi anyone get more vibration after fitting catless downpipes? Mine is vibrating more than before kind of loose confort. It’s normal???

[Ninjaspartan 23]

On 12/2/2020 at 11:35 PM, Seba said:

Hi anyone get more vibration after fitting catless downpipes? Mine is vibrating more than before kind of loose confort. It’s normal???

Not that I remember. However I put some bellows in.

 

[jon dee 500]

On 12/2/2020 at 11:35 PM, Seba said:

Hi anyone get more vibration after fitting catless downpipes? Mine is vibrating more than before kind of loose confort. It’s normal???

I'm going with an increase in vibration that makes the car less pleasant to drive ? If so, then there are a number of factors at play that could result in an increase in vibration compared to stock catted pipes. The catless pipes may be made from a lighter gauge of material than OEM pipes if they are of the lower cost Chinese variety. Lighter material is less able to attenuate/contain the pressure waves generated by combustion. The cats in the OEM pipes reduce turbulence in the exhaust flow and dampen pressure waves, which help keep the exhaust quiet. What you have installed are effectively two resonators without any internal baffling or sound absorbing material, and if you are unlucky you may get an annoying resonance at certain engine speeds.

In addition (as mentioned above) you have eliminated the flexible bellows section from the exhaust system. This will allow lower frequency vibration from the engine to transmit to the exhaust system that is rigidly bolted to the chassis under the drivers seat. So it is possible that this vibration may be felt inside the car. Generally speaking I would expect all of the above to produce "vibration" that more obvious at certain engine/road speeds rather than being constant at all speeds. Otherwise there are the usual suspects of the pipes rubbing against each other or the frame or loose fasteners.  Good luck

Cheers...

PS: For what it's worth, if I ever decided to go to the trouble of installing downpipes I would get the Wagner pipes. No sense in expanding to 3 inch and then squeezing back down to 2.5 inch. Gives a bit more clearance for installation as well.

[SmackJackTheCrackerMan 54]

For anyone thinking of installing catless Downpipes, here’s a fairly good guide. 
https://www.e90post.com/forums/showthread.php?t=104333&fbclid=IwAR0Ui5TMQqyQQ3t4mEjUFL3kJTCQS_2Bme1JFMHf2jH_XYCyPoTQb6IUv4M

Mine just arrived, so weather permitting I’ll be installing (or at least trying too) this weekend. 
Anybody in Wellington/Kapiti who would like to offer a hand would be much appreciated 👍🏼👌🏼🤔😂 there will be some nice craft ale in it for you 🍺 🍻 

[HalfJobHarry 106]

On 7/22/2021 at 8:49 AM, SmackJackTheCrackerMan said:

For anyone thinking of installing catless Downpipes, here’s a fairly good guide. 
https://www.e90post.com/forums/showthread.php?t=104333&fbclid=IwAR0Ui5TMQqyQQ3t4mEjUFL3kJTCQS_2Bme1JFMHf2jH_XYCyPoTQb6IUv4M

Mine just arrived, so weather permitting I’ll be installing (or at least trying too) this weekend. 
Anybody in Wellington/Kapiti who would like to offer a hand would be much appreciated 👍🏼👌🏼🤔😂 there will be some nice craft ale in it for you 🍺 🍻 

Do follow up on how it goes and if the fit is good, where you got your pipes. I've read stories of needing additional spacers and what not. I'm waiting until I need to drop the subframe (maybe sometime later or early next year) to hit the sump gasket (and probably do a water pump) 

[Chrisf 0]

Anyone had wof issues with catless downpipes? Since it's illegal to remove them for street use in NZ

[jon dee 500]

Good question Here is the official NZTA REASON for REJECTION at WOF time...

2. A vehicle (other than group L vehicle or a class MA or MC motorsport vehicle with a valid motorsport authority card) that was first registered in New Zealand on or after 1 May 2010 and manufactured from 1 January 1990 has a catalytic converter (or diesel particulate filter (DPF) in the case of diesel powered vehicles) removed where there is evidence that one was originally fitted, and there is no written evidence issued by an entry certifier that the vehicle passed a prescribed metered emissions test in this condition

As it is written in typical bureaucratic language the meaning is not immediately clear. So here is my positive interpretation...

2. If your car was built after 1 January 1990 and first registered in NZ before 1 May 2010, you can safely remove the catalytic converter (if the car was originally fitted with one). First registered in NZ after 1 May 2010, built after 1 January 1990 and factory fitted with cats, be prepared to explain why you don't have cats fitted if the inspector asks.

The hook here is that is your car is a used import (like mine) manufactured in 2008 but first registered in NZ after 1 May 2010, then according to the rules it should have a cat present and correct to obtain a WOF. As I still have the cats installed I would probably have an off the record chat with the garage that does my warrants before fitting downpipes. Just to see if they are likely to reject a respectable car with an otherwise clean exhaust (no smoke, unhealthy smell or CEL) just because the cats are missing. And if need be, use an emulator or otherwise make sure you are not showing an O2 sensor fault.

I'm not sure how many suburban garages actually have emissions testing equipment, so that is another factor that may act in your favour at WOF time. Having a good tune so your exhaust does not smell like a gas oven is also a wise move

Cheers...

[Ninjaspartan 23]

5 hours ago, Chrisf said:

Anyone had wof issues with catless downpipes? Since it's illegal to remove them for street use in NZ

Not sure how primary/secondary cats play into the legislaion, but these cars have secondary catalytic converters as well. So if you have thoses then should be good as a catalytic converter is still present?

From experence never had an issue getting a wof with catless downpipes. 

[jon dee 500]

Yusss.... there is what is theoretically legal / illegal to the bureaucrats and there is this ^^^^ which is what happens in the real world Primary cats do the real work and secondary cats are there to help out during cold starts before the primary cats have reached full operating temperature. But since not all cars have two sets of cats you are pretty safe to assume that the average suburban garage will see "cats present" and tick that checkbox.

Not sure that I would want to try getting that past a BMW Service Centre though !!

Cheers...

[KwS 2372]

I've had customers enquire on prices for new cats because they were failed a WOF, so it does happen. Usually makes them shite their pants too at the cost to genuine ones 😂

I do recall looking under the E91 when i had it and unless you knew what you were looking for, the under body trays make it hard to tell its had decat downpipes fitted. The only real giveaway was the shiny stainless pipes.

[Chrisf 0]

On 11/14/2021 at 8:18 PM, Ninjaspartan said:

Not sure how primary/secondary cats play into the legislaion, but these cars have secondary catalytic converters as well. So if you have thoses then should be good as a catalytic converter is still present?

From experence never had an issue getting a wof with catless downpipes. 

I believe technically removing any emissions equipment is illegal. You could probably replace the cats with high flow ones without issue.

[dragonz 16]

Catless Downpipes

I have catless downpipes, got cheap ones, work great. MHD 2+ tune

I had the opportunity to do some emmissions testing on a few vehicles as a part of a research project, so I slotted mine into the test group. Was done at a VTNZ station & they checked the cars over. Noone noticed the lack of cats in the downpipes (they are fairly buried and the secondary cats are visible, so it needs someone knowledgable on these cars to pick it up).

Long story short, mine was a little "dirty" on its emissions when cold, but once warmed up, it was as clean as any other car tested.

If challenged, take it for a strop round the block & tell them to stick the sniffer up a tailpipe. They will give up & pass you as your car won't fail unless it has other issues. I was worried that the MHD tune might over-richen it, but no issues at all.

Vibrations

My car has a very slight vibration noise just above idle, then sweet as. one of the pipes is just very slightly contacting an unidentified bracket & this makes some noise. Get the car up on stands, start the engine & go looking. Ideally get someone in the car to vary the revs up & down until you hear the vibration & follow the noise. Welding gloves highly recommended for this exercise btw

Pops and Bangs

Nope, have none, but have had experience in a variety of cars. The most likely cause is an air leak in your exhaust, most likely the joint where the downpipe comes off the turbo. The closer to the exhaust port of the cylinder, the more likely to pop and bang. As a younger hoon, I used to deliberately make my car exhausts bang, but as a more refined gentleman I do prefer to fly under the radar a bit more

 

[E63 55]

This is the most positive review of catless downpipes I've seen to date. I had sort of resolved not to remove my cats but I'm tempted again now.

[E63 55]

Has anyone removed cats on an N62N?

[KwS 2372]

On 4/19/2023 at 8:09 PM, dragonz said:

Pops and Bangs

Nope, have none, but have had experience in a variety of cars. The most likely cause is an air leak in your exhaust, most likely the joint where the downpipe comes off the turbo. The closer to the exhaust port of the cylinder, the more likely to pop and bang. As a younger hoon, I used to deliberately make my car exhausts bang, but as a more refined gentleman I do prefer to fly under the radar a bit more

 

Since you're already running MHD, turn on the exhaust burble option. On my E91, with stock exhaust other than decat, it could pop and bang with the best of them. Its horrible for the turbos though I believe. 

[SmackJackTheCrackerMan 54]

So here is the long awaited update/not update.

I ended up returning the china DP after hearing about so many fitment issues (probably should have kept them 🥺)

I then purchased the VRSF 3" catless downpipes with the high temp coating + VRSF 3.5" Street exhaust to pair them up to.

I'm currently installing them (have been for months now) and I can't get the DP's even close to where they should be. The rear turbo DP seems to be in the correct position, but the front turbo DP is miles off. I have loosened both v bands and tried rotating them but the front one is still way off.

Does anybody who has already installed them have any tips/tricks to make them work? 

I'm at the stage now where I'm going to have to take the car to someone and get them to cut and weld the exhaust to match up to the DP which isn't ideal.

Any help much appreciated