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M2 Technical Topics > S55 Engine / Drivetrain / Exhaust / Bolt-ons / Tuning > Milltek exhaust - full system

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      04-27-2019, 12:20 PM   #45
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it looks good! is this the ece approved? what are those 2 cilindrical things, secondary cats?
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      04-27-2019, 01:30 PM   #46
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Yes, EC approved, not race.

Yes secondary CATs in place of OPF. This means 2 things for the UK:

1. I can remove primary CATs in future and still pass UK emissions test.

2. Secondary CATs will pass "visual check" that an OPF is still in place at annual test (MOT)

These CATs are 200 Cell hi flow cats with very little restriction compared to OPF.

They also will keep the noise down when I remove primary cats soon.

Remember before OPF the S55 had secondary CATs anyway..

Last edited by doughboy; 04-27-2019 at 04:55 PM..
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      04-28-2019, 02:27 AM   #47
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Originally Posted by doughboy View Post
Yes, EC approved, not race.

Yes secondary CATs in place of OPF. This means 2 things for the UK:

1. I can remove primary CATs in future and still pass UK emissions test.

2. Secondary CATs will pass "visual check" that an OPF is still in place at annual test (MOT)

These CATs are 200 Cell hi flow cats with very little restriction compared to OPF.

They also will keep the noise down when I remove primary cats soon.

Remember before OPF the S55 had secondary CATs anyway..
So am I right in saying you have the Milltek backbox, you have then replaced the OPFs with a set of secondary cats (which I assume the M2C does not have as standard due to OPF).

OPF have been replaced with 200cel sport cats?

I had the secondary cat bypass fitted to my M4 CP bit i assume doing this to the M2C will run a higher chance of the CEL throwing up and potentially limp mode.

Apologies for the questions as I'm just trying to ascertain which way I'll go with the Milltek.

Preferably I'd have the same set-up as my M4 with the Race system, OPF bypass and primary cats in place meantime. That will likely mean coding to disable the OPF sensors.
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      04-28-2019, 02:43 AM   #48
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Yes it's the milltek OPF bypass with sec Cats. They did the same product for pre OPF M3/4. You can buy it with or without 200 cell CATS. It's aimed at those wanting primary cat delete but keep MOT pass.

So now the car is the same as a NON EU car with milltek mid and back boxes. But better in that the new sec CATS are high flow versions.

My theory is the slight back pressure from the SEC cats might keep OPF sensors happy as that is all they monitor, which after 150+ miles it seems to be working, but time will tell.

If I went pure OPF bypass then it would be too noisy with prim CAT delete later on, and fail MOT emissions in future, which does concern me as I intend to keep this car a while.

From my N54 days it seem's even OE secondary CATS have very little effect on performance, it's the primary CATS that have the most effect.

Last edited by doughboy; 04-28-2019 at 02:48 AM..
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      04-28-2019, 04:52 AM   #49
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Quote:
Originally Posted by doughboy View Post
Yes it's the milltek OPF bypass with sec Cats. They did the same product for pre OPF M3/4. You can buy it with or without 200 cell CATS. It's aimed at those wanting primary cat delete but keep MOT pass.

So now the car is the same as a NON EU car with milltek mid and back boxes. But better in that the new sec CATS are high flow versions.

My theory is the slight back pressure from the SEC cats might keep OPF sensors happy as that is all they monitor, which after 150+ miles it seems to be working, but time will tell.

If I went pure OPF bypass then it would be too noisy with prim CAT delete later on, and fail MOT emissions in future, which does concern me as I intend to keep this car a while.

From my N54 days it seem's even OE secondary CATS have very little effect on performance, it's the primary CATS that have the most effect.
Thanks for confirming.

I'll be reading with interest how you get on.

Enjoy.
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      04-28-2019, 12:31 PM   #50
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Quote:
Originally Posted by DazC View Post
Quote:
Originally Posted by doughboy View Post
Yes it's the milltek OPF bypass with sec Cats. They did the same product for pre OPF M3/4. You can buy it with or without 200 cell CATS. It's aimed at those wanting primary cat delete but keep MOT pass.

So now the car is the same as a NON EU car with milltek mid and back boxes. But better in that the new sec CATS are high flow versions.

My theory is the slight back pressure from the SEC cats might keep OPF sensors happy as that is all they monitor, which after 150+ miles it seems to be working, but time will tell.

If I went pure OPF bypass then it would be too noisy with prim CAT delete later on, and fail MOT emissions in future, which does concern me as I intend to keep this car a while.

From my N54 days it seem's even OE secondary CATS have very little effect on performance, it's the primary CATS that have the most effect.
Thanks for confirming.

I'll be reading with interest how you get on.

Enjoy.
This makes me wonder if my car will pass it's first MOT in three years time with the AA mid pipe, I.e. no OPFs and not even and secondary cats? Probably won't pass. What would you recommend in this instance?
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      04-28-2019, 02:16 PM   #51
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It will pass the emissions test as that checks CAT efficiency and you still have primary main CATS (DPs).

There is no physical test for OPF efficiency (same as diesel DPF has no test).

The iffy bit will be the "visual check" that all emission control equipment is in place. Very much depends on how friendly / daft the MOT man is. Take it to little back street MOT shop, cash only well away from anywhere reputable!

They can't remove covers or trays to carry out the visual check, so DPS are pretty easy to get away with as they are hidden by undertrays.

But OPF are right there open and uncovered.
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      04-28-2019, 02:53 PM   #52
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Quote:
Originally Posted by doughboy View Post
It will pass the emissions test as that checks CAT efficiency and you still have primary main CATS (DPs).

There is no physical test for OPF efficiency (same as diesel DPF has no test).

The iffy bit will be the "visual check" that all emission control equipment is in place. Very much depends on how friendly / daft the MOT man is. Take it to little back street MOT shop, cash only well away from anywhere reputable!

They can't remove covers or trays to carry out the visual check, so DPS are pretty easy to get away with as they are hidden by undertrays.

But OPF are right there open and uncovered.
Thanks for the advice. Back street MOT centre it is then 👍🏻
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      04-28-2019, 03:44 PM   #53
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...in the meantime - nearly 3 years - enjoy the car and don't worry about it
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      04-29-2019, 01:29 AM   #54
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Quote:
Originally Posted by doughboy View Post
...in the meantime - nearly 3 years - enjoy the car and don't worry about it
that is what i have always done. enjoyed the car and if close to inspection i put the stock exhaust. i recently had an inspection with my camaro. i'ts heavily cammed and has a long tube headers with cats but... well i passed the inspection even thou the only stock parts was the steering wheel. i was a little bit out with the CO but the mot guy managed to make it pass . usually when they see a good car they try be no very picky so i wouldn't think to much

we want a video though
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      04-29-2019, 02:05 AM   #55
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I'll get a video up as soon as I can....
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      04-29-2019, 04:23 AM   #56
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      04-29-2019, 05:20 AM   #57
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Quote:
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...in the meantime - nearly 3 years - enjoy the car and don't worry about it
That's the plan. Another track day at the Bedford Autodrome on 6th May Bank Holiday
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      04-30-2019, 12:01 AM   #58
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I'll get a video up as soon as I can....
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      04-30-2019, 03:00 PM   #59
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Quote:
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I'll get a video up as soon as I can....
Hope it sounds damn awesome!

I have the same exhaust coming to me this week, but with opf bypass and downpipes with highflow cats.
Though i can't install it before 14.5, when i go to the first 2000km service.
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      04-30-2019, 03:43 PM   #60
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let us know how it sounds. my car is coming next week and i believe i will get it by the end of the month. the set up you get, in my opinion and hearing the sound thought videos, is the best available for the competition.
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      05-01-2019, 01:40 AM   #61
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Quote:
Originally Posted by ICantDrive4Sht View Post
Hope it sounds damn awesome!

I have the same exhaust coming to me this week, but with opf bypass and downpipes with highflow cats.
Though i can't install it before 14.5, when i go to the first 2000km service.
Here's how your exhaust setup sounds

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      05-01-2019, 06:52 AM   #62
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Be careful, there's two options there.

Either decat DPs with hiflow CATS in midpipe in place of OPF.

Or hiflow CATs in DPs with straight through OPF bypass.
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      05-01-2019, 07:04 AM   #63
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Quote:
Originally Posted by doughboy View Post
Be careful, there's two options there.

Either decat DPs with hiflow CATS in midpipe in place of OPF.

Or hiflow CATs in DPs with straight through OPF bypass.
Are the cats used in the dp the same used in the mid pipe?
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      05-01-2019, 07:34 AM   #64
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Originally Posted by doughboy View Post
Be careful, there's two options there.

Either decat DPs with hiflow CATS in midpipe in place of OPF.

Or hiflow CATs in DPs with straight through OPF bypass.
Which option do you think has less chance of causing OPF fault issues?
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      05-01-2019, 02:20 PM   #65
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Unfortunately the OPF pressure sensor pipes are attached to the DPs. So if you fit aftermarket DP's then you lose those connections and will have 100% OPF fault. (Super sprint DPs have sensor pipes but not seen any others, they cost a fortune though).

You need to remap for decat DP's anyway so just map for OPF removal too. If you fit hiflow CAT DP's without OPF pressure pipes then you won't have CAT fault but you will have OPF fault even if you have OPF still fitted.

I've got no faults with OPF replaced with hiflow secondary CATS as yet. But if I fit decat DPs in future I will have to remap anyway.

Last edited by doughboy; 05-02-2019 at 03:24 AM..
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      05-02-2019, 06:04 AM   #66
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Would the milltek exhaust fit the AA midpipe if one wanted to use that midpipe instead?
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