[Fez_7]

As per title, under the new MOT rules is a backbox delete an MOT fail? I've been told it's been changed to you must have the required number of silencers for your car.

For those who have had it done have you now run into any issues come MOT time?

I've only got the single exhaust on my 320D and wanting to convert it to a twin tip. Custom exhaust shop recommends a backbox delete but if it's illegal then I will go for the BMW retrofit instead where you just cut the single tailpipe off and clamp on the twin tips.

[kitster]

Originally Posted by Fez_7

As per title, under the new MOT rules is a backbox delete an MOT fail? I've been told it's been changed to you must have the required number of silencers for your car.

For those who have had it done have you now run into any issues come MOT time?

I've only got the single exhaust on my 320D and wanting to convert it to a twin tip. Custom exhaust shop recommends a backbox delete but if it's illegal then I will go for the BMW retrofit instead where you just cut the single tailpipe off and clamp on the twin tips.

I had the BMW twin pipe retrofit on my F31. Never had any issues at the MOT.

[Watsey]

No, it's not parts of the emissions controls so it won't have any effect on the MOT as long as the car is within noise limits.

[Fez_7]

Yeah I know the retrofit won't be a problem as the back box will remain however I would prefer to go custom so I can choose my own tips to be welded on as I want black instead of stainless steel. The only issue is though if I go custom then the shop want to delete the backbox altogether.

I know it shouldn't be a problem for noise or emissions but apparently you must now have the required number of silencers for your car so without the backbox I guess it would technically fail?

[Pobsey]

Originally Posted by Watsey

No, it's not parts of the emissions controls so it won't have any effect on the MOT as long as the car is within noise limits.

And that’s where the fun starts as it’s upto the not tester to decide if the car is noticeably louder than a stock exhaust.

[Lorcan]

Alpina D4 has no back box, not sure an MOT station can look up "how many" silencers should be fitted.

[john lummis]

I had my rear silencer deleted in May, I asked my MOT guy before I had it done and he said NO problem as the cat and resonator were still in place and it didn't affect emissions and didn't do much for noise anyway so back box delete is fine

The Alpina above has a lot of pipework on show, if I was sat in a car behind it, that's all I would see, which is why I had the pipework on mine redirected up into the cavity where the rear silencer was so anyone sat behind me only sees the tips, plus the pipework is sprayed in heat resistant black paint

[JD6]

Originally Posted by Lorcan

Alpina D4 has no back box, not sure an MOT station can look up "how many" silencers should be fitted.

I take your point, but doesn't every ordinary car, such as the OP's 320d, have a back box from the factory?

[robbiep]

Originally Posted by Fez_7

The only issue is though if I go custom then the shop want to delete the backbox altogether.

Remind the place that 'The customer is always right'. Doesn't matter what they want to do, it's entirely possible to do it the other way

[john lummis]

The MOT deals with emissions and whether there are holes or corrosion on the exhaust and excessive smoke, not noise, otherwise all the McClaren's, Lambo's and Ferrari's etc would never pass a MOT due to excessive noise.

I've never known the silencers be counted on any of my cars and I watch the MOT being done, to the extent that I'm under the car with the guy when he's checking it on the lift

But I'm not an expert

[AlwynMike]

If going custom, then an extra small box at the back, or at the pipe split will count as a silencer won't it?

[Fez_7]

Thanks for all the responses, seems like its up to the testers discretion then so don't know whether it's worth the risk.

Safest bet will be the BMW retrofit. Has anyone with standard twin tips (I think 70mm / 2.75") found any black or carbon sleeves to fit over the stainless steel tips, or is this not possible?

Alternative option will be to go custom but ask them to keep the backbox or make a new one?

[john lummis]

You can buy an exhaust system , dual tips with a back box like the Cobra system, but be prepared to pay £500-600 plus fitting, mine is legal and meets all MOT criteria for less than a third ( £180 ) of that, mine isn't noisy, just a slightly deeper tone.

It's horses for courses, do whatever you feel is right, I did