Mid Pipe and MOT

[Deano123]

Seeing conflicting comments online re the impact on the UK MOT and the installation of some Active Autowerke Equal Length Midpipies.

Does anyone UK based have any experience of these being installed and then the impact on the MOT?

Im just about to pull the trigger on the order but don’t want the hassle of having to find a “special” MOT centre.

[t5pilot]

The simple answer is, for emissions, if you have retained one set of cats, the car will pass.
I have decat downpipes but my secondary cats still in place.
Your problem comes with the newer visual inspection. Which is easy as the car is up on a ramp having other stuff scrutinised.
If it’s obvious to the tester that a set of cats shoud be there, in your case the secondary cats, then it’s a straight fail, regardless of passing emissions or not.
Easy with primary decats, as they can’t really be seen from underneath without taking the under tray off, which they won’t do.
So it’s always riskier with the secondaries missing.
So it really does depend on the actual tester, on the day.
Obviously this won’t apply if you already have a “friendly” tester, in which case stick with them.

[Deano123]

I think i need to find a friendly tester then.

[jaylazy2020]

Originally Posted by t5pilot

The simple answer is, for emissions, if you have retained one set of cats, the car will pass.
I have decat downpipes but my secondary cats still in place.
Your problem comes with the newer visual inspection. Which is easy as the car is up on a ramp having other stuff scrutinised.
If it’s obvious to the tester that a set of cats shoud be there, in your case the secondary cats, then it’s a straight fail, regardless of passing emissions or not.
Easy with primary decats, as they can’t really be seen from underneath without taking the under tray off, which they won’t do.
So it’s always riskier with the secondaries missing.
So it really does depend on the actual tester, on the day.
Obviously this won’t apply if you already have a “friendly” tester, in which case stick with them.

I’m really hoping that retaining the secondary cats will help me thru either a NCT test in Ireland or TUV in Germany.

I know visually you can’t really see the down pipes but the smell of fuel I get from exhausts doesn’t fill me with confidence that it’ll pass the emissions test!

[Rusticm3]

Hi mate,

I have catless down pipes and a resonated equal length mid pipe.

Unless you have some one that will over look it, it will fail.

What I done, which isn't a lot of drama was swap out the mid section for the standard with secondary primary's leaving the catless dp's for the test.

This way it will pass on emissions, the down pipes are pretty hidden and I've not had an issue getting it past the visual check. They will more then likely look at the secondary's and presume they are the only cats as it passes the emissions test.

[aaron84]

This discussion is exactly what I've been looking for. I do have a follow up question to the original if you guys will permit...I'm considering getting catless dp but I'm concerned about making the sound of the M4 even worse. In an ideal world I would run catless dp with an equal length midpipe fitted to my MPE, but I can't go through the bother of changing the midpipe for MOT every year. Have any members got real world experience of hearing an s55 with catless dp and MPE? What does it do for the rasp?

[t5pilot]

Originally Posted by aaron84

This discussion is exactly what I've been looking for. I do have a follow up question to the original if you guys will permit...I'm considering getting catless dp but I'm concerned about making the sound of the M4 even worse. In an ideal world I would run catless dp with an equal length midpipe fitted to my MPE, but I can't go through the bother of changing the midpipe for MOT every year. Have any members got real world experience of hearing an s55 with catless dp and MPE? What does it do for the rasp?

I run catless downpipes & MPE. Secondary cats still in place.
In efficient mode there’s next to no difference. It just sounds meatier when the valves do start opening.
In sport or sport + it’s loud but not particularly raspy. On a stock map (CP anyway), the burbles can be annoying.
Through BM3 I have all burbles set to off. With that setting you still get some, but they’re natural & not artificial, so sound much better. IMO of course.