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Exhuast: Sports Cat w/ sensible cat back

1K views 23 replies 8 participants last post by  Boz-chis-tech 
#1 ·
My main objectives are to improve exhaust flow for power, but retain the option of a pretty sensible noise option whilst in comfort. Appreciate there is a lot of topic's on exhaust topics on here but couldn't find a topic that covered something similar.

Options for downpipes w/ sport cats are BCS, Cobra or Wagner. My preference would be for the BCS downpipe with the 100 cell sport cat - any advice on this would be appreciated.

My thoughts on the cat back, would be to either source an MPerformance exhaust and retain the two factory resonators, or a silenced remus cat back system. Has anybody taken a similar approach? I am not keen on the full BCS system as would like to retain a valved exhaust system and all of the other systems seem to be much louder which is what I want to avoid!

Thanks,
 
#2 ·
Isn't the BCS valved? I thought their systems work on boost pressure, i.e. the valve opens only when you're booting it.

The Remus valve will behave as per stock. The MPE isn't valved but if retaining the stock midpipe that setup shouldn't be too rowdy anyway I suppose.

A third option used in the Quicksilver system, has the valve operated by a remote fob. So whether you're pootling or hooning you have the option of quiet or loud.
 
#4 ·
The standard system can be modified to be free flowing with the benefit of changing the sound of the car.

Unlike the MPE, you can still retain the valve function, however the increase in tone in comfort is more than standard, due to the way the system is modified.

I know of a few high powered B58 cars still running the standard system, with modifications though so flow isn't an issue unless you are going crazy power.

Quicksilver are good systems and well worth looking into.
I work along side them and can offer a good discount on a group buy.
 
#5 ·
Thanks guys. Yeh the BCS is valved but only opens on boost like you say, I'd like to retain the control of the system. Wasn't aware the MPE wasn't valved! That's not ideal for me.

Are there any sport cats that ensure a CEL doesn't show? A cat is always the most restrictive part of the exhaust so the main part I want to get resolved. I think BCS can do a 200 cell cat too, would this resolve it?

Haven't heard of Quicksilver exhausts before, will check them out. When you say changing the standard system, do you mean like a PCW mod?

Thanks,
Chris
 
#6 ·
Similar to what they do, however we do the Chis-tech mod :lol2:

Some of our customers are running around 600bhp on the standard modified system, so its more than capable.

200 CEL sports cat should not show an EML on the dash and should pass an MOT while being slightly less restrictive.

Once you start to tinker with the exhaust system, the cold start cycle becomes louder.
 
#8 ·
Boz-chis-tech said:
Similar to what they do, however we do the Chis-tech mod :lol2:

Some of our customers are running around 600bhp on the standard modified system, so its more than capable.

200 CEL sports cat should not show an EML on the dash and should pass an MOT while being slightly less restrictive.

Once you start to tinker with the exhaust system, the cold start cycle becomes louder.
I have BCS cell 200 and the engine light displayed on mine. It's now hidden through BM3 though.
 
#9 ·
ah didn't realise it would still display a CEL! Would the Litchfeild map be able to resolve this? What backbox do you run with your BCS 200 cell? Recommend it? Any issues with MOT?
 
#12 ·
Ralston88 said:
ah didn't realise it would still display a CEL! Would the Litchfeild map be able to resolve this? What backbox do you run with your BCS 200 cell? Recommend it? Any issues with MOT?
I believe they can configure the map so it's sets a rule not to show. In all honesty I got this cat for the same reasons you want it for (MOT and cel light)

I've only had my car for 4 months so no MOT is due. When I look everywhere they say it would pass though.

Stock back box, nothing else changed yet.
 
#13 ·
Although mine is a M135, i have a modified back box, and resonator delete, it gives a nice noise, but it still fairly quiet in comfort, it does drone a little in sport, and it loudish on cold start, but not asbo loud.
 
#15 ·
Willo46 said:
Although mine is a M135, i have a modified back box, and resonator delete, it gives a nice noise, but it still fairly quiet in comfort, it does drone a little in sport, and it loudish on cold start, but not asbo loud.
My m135i had 200CPI BCS DP, remus midpipe and MPE - always drone free, subtle when you wanted it to be and naughty wrt being unruly when mood and circumstances dictated... No issue at TD noise checks

sound clip of it on YT...

 
#16 ·
Blind Pugh said:
Willo46 said:
Although mine is a M135, i have a modified back box, and resonator delete, it gives a nice noise, but it still fairly quiet in comfort, it does drone a little in sport, and it loudish on cold start, but not asbo loud.
My m135i had 200CPI BCS DP, remus midpipe and MPE - always drone free, subtle when you wanted it to be and naughty wrt being unruly when mood and circumstances dictated... No issue at TD noise checks

sound clip of it on YT...

The M135 had a valved MPE while the M140 MPE doesn't have a valve anymore

Sent from my iPhone using Tapatalk
 
#18 ·
Blind Pugh said:
Willo46 said:
Although mine is a M135, i have a modified back box, and resonator delete, it gives a nice noise, but it still fairly quiet in comfort, it does drone a little in sport, and it loudish on cold start, but not asbo loud.
My m135i had 200CPI BCS DP, remus midpipe and MPE - always drone free, subtle when you wanted it to be and naughty wrt being unruly when mood and circumstances dictated... No issue at TD noise checks

sound clip of it on YT...

Sounds well, DP makes it deeper, i keep meaning to get some vid of mine, i never get to enjoy it from outside the car.
 
#20 ·
Hi, did also consider doing this, would like some slightly bigger tips than standard, but the standard remus ones are too big imo! The problem I've heard with the removing the middle resonator boxes is that they create drone (apparently) and this must be avoided otherwise the misses will kill me!

BCS apund like they know what there on about for DPs although I can't find any comparibles for the sports cat. Apparently their 100 cat comes with a 40g coat which is significantly more than others. This will likely throw a CEL but can be coded out later on. The HJS Euro6 compliant 300 cell cats available in the Miltek offering will apparently not throw a CEL, however it is double the price! As I was going to get it mapped anyway not to concerned on about the CEL as long as it passes an MOT. Is the Miltek really worth double? I am leaning towards the BCS!
 
#21 ·
Ralston88 said:
Hi, did also consider doing this, would like some slightly bigger tips than standard, but the standard remus ones are too big imo! The problem I've heard with the removing the middle resonator boxes is that they create drone (apparently) and this must be avoided otherwise the misses will kill me!

BCS apund like they know what there on about for DPs although I can't find any comparibles for the sports cat. Apparently their 100 cat comes with a 40g coat which is significantly more than others. This will likely throw a CEL but can be coded out later on. The HJS Euro6 compliant 300 cell cats available in the Miltek offering will apparently not throw a CEL, however it is double the price! As I was going to get it mapped anyway not to concerned on about the CEL as long as it passes an MOT. Is the Miltek really worth double? I am leaning towards the BCS!
Probably if remove both resonators but the 235 had one the 240 has two so removing one should get you more noise but not drone

Sent from my iPhone using Tapatalk
 
#22 ·
I have the stock midpipe (both resonators in place) with a modified back box and a 4.5" decat.

It's the perfect balance in my opinion.
No drone with light throttle in comfort mode (city driving or motorway)
Loud enough in sport+ with pops and bangs

There may be drone outside the car but you never really hear it in the car.

I have heard the same set up as mine ^^ but with the resonator removed (not the oval one) again it's not droney but does sound more raspy when cruising around (2-3k rpm)
 
#23 ·
We have a range of standard exhaust systems in stock that have been modified, or can modify them to suit.

The most popular mods at the moment are first box mod, back box mod, this is an amazing combo and suffers very little drone.

PPF mod with back box mod.

Drone is not normally an issue, however everyone has a different take on it, its all down to personal preference.
Autos don't tend to suffer from drone to bad, manuals do.
So bare that in mind if going for a first box mod, res delete and back box mod.

I've lost count of how many we have done now.

No different to the other companies doing them, apart from being based in the same workshop as one of the leading BMW specialists in the UK :cool2:
 
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