E90 335i Downpipes in the UK

twintub · 07-06-2015, 09:34 AM

Hi all,

I'm a new 335i N54 owner and am possibly looking at some tuning options.

Some suppliers are telling me that I can use catless downpipes and still pass the MOT / VOSA inspections. Is there any truth in this?

Thanks,

TT.

Aragorn30d · 07-06-2015, 09:57 AM

The 335i has four cats. one in each downpipe, then two under the car (one for each pipe) in the exhaust.

If you remove either pair, and retain the other pair, your car should pass the MOT just fine.

If you remove both pairs, it wont.

RajB · 07-06-2015, 10:20 AM

Yes in essence that is correct. You can remove either pair and still be fine.

You can even bin the secondary cats and run the sports cats (like the AR ones - and have even more performance gain without issues) and still pass the MOT - I had it tested to ensure this was the case.

But removing all will fail.

conscript · 07-06-2015, 01:53 PM

Does the N55 (2011) have four cats as well? Thinking about getting some DPs myself.

Aragorn30d · 07-06-2015, 02:14 PM

N55 doesnt have any cats in the main exhaust, they're just in the downpipe.

conscript · 07-06-2015, 02:21 PM

Quote:

Originally Posted by Aragorn30d

N55 doesnt have any cats in the main exhaust, they're just in the downpipe.

Just my luck! Cheers, might grab some catted wagners then

Rory · 07-06-2015, 02:24 PM

Ahhh threads like this tempt me to modify! Must resist ! lol

conscript · 07-06-2015, 02:30 PM

Quote:

Originally Posted by Rory

Ahhh threads like this tempt me to modify! Must resist ! lol

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Dann · 07-06-2015, 02:37 PM

Instead of DPs has anyone used N55 mid section?

Rory · 07-06-2015, 03:02 PM

Quote:

Originally Posted by conscript

Attachment 1239402

The amount of threads about the common failures of these engines has made me keep my wallet shut on mods so I can pay for repairs! lol

Raymonndo · 07-07-2015, 05:27 AM

Quote:

Originally Posted by conscript

Just my luck! Cheers, might grab some catted wagners then

Sure you can get decat Downpipes for these too as well as the N54!

phil200tdi · 07-07-2015, 07:49 AM

Mine was decatted and passed the MOT emissions test but I was always worried about the visual inspection.

I.e. if the tester sees that the cats have been removed then its a fail - its pretty obvious with the shiny downpipes sticking out.

conscript · 07-07-2015, 09:48 AM

My only worry is passing the M.O.T, especially if the only Lambda's are in the DP's and none mid section like the N54.

07-06-2015, 09:34 AM	#1
twintub New Member 3 Rep 15 Posts Drives: E90 335i Join Date: Jul 2015 Location: London iTrader: (0)	E90 335i Downpipes in the UK Hi all, I'm a new 335i N54 owner and am possibly looking at some tuning options. Some suppliers are telling me that I can use catless downpipes and still pass the MOT / VOSA inspections. Is there any truth in this? Thanks, TT.
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07-06-2015, 09:57 AM	#2
Aragorn30d Lieutenant Colonel 175 Rep 1,596 Posts Drives: E90 330d Join Date: Mar 2015 Location: Fife iTrader: (0)	The 335i has four cats. one in each downpipe, then two under the car (one for each pipe) in the exhaust. If you remove either pair, and retain the other pair, your car should pass the MOT just fine. If you remove both pairs, it wont.
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07-06-2015, 10:20 AM	#3
RajB Brigadier General 448 Rep 3,312 Posts Drives: E92 335i Join Date: Nov 2014 Location: Midlands iTrader: (4)	Yes in essence that is correct. You can remove either pair and still be fine. You can even bin the secondary cats and run the sports cats (like the AR ones - and have even more performance gain without issues) and still pass the MOT - I had it tested to ensure this was the case. But removing all will fail. __________________ E92 335i / M3 Hybrid - The Build
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07-06-2015, 01:53 PM	#4
conscript Private 1 Rep 58 Posts Drives: 335i Coupe Join Date: Jun 2015 Location: Kent, United Kingdom iTrader: (0)	Does the N55 (2011) have four cats as well? Thinking about getting some DPs myself.
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07-06-2015, 02:14 PM	#5
Aragorn30d Lieutenant Colonel 175 Rep 1,596 Posts Drives: E90 330d Join Date: Mar 2015 Location: Fife iTrader: (0)	N55 doesnt have any cats in the main exhaust, they're just in the downpipe.
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07-06-2015, 02:24 PM	#7
Rory Lieutenant 95 Rep 299 Posts Drives: E92 335i SE 6MT Join Date: Aug 2013 Location: Lanarkshire, Scotland iTrader: (0) Garage List 2005 Z4 3.0 6MT [0.00] 2007 335i 6MT [0.00]	Ahhh threads like this tempt me to modify! Must resist ! lol
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07-06-2015, 02:37 PM	#9
Dann Major 133 Rep 1,381 Posts Drives: E90 LCi 335i Join Date: Feb 2015 Location: Portsmouth, United Kingdom iTrader: (0)	Instead of DPs has anyone used N55 mid section?
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07-07-2015, 07:49 AM	#12
phil200tdi Colonel 112 Rep 2,621 Posts Drives: 335i M Sport E90 LCI manual Join Date: Jan 2011 Location: Aylesbury iTrader: (1)	Mine was decatted and passed the MOT emissions test but I was always worried about the visual inspection. I.e. if the tester sees that the cats have been removed then its a fail - its pretty obvious with the shiny downpipes sticking out. __________________ Car: e91 330d with Viezu map Gone but not forgotten: 2010 Jaguar XFR (Cat-back exhaust, pulley, intake mods and map), Highly Modified E90 335i LCI M Sport Manual (circa 480BHP/500lb ft)
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07-07-2015, 09:48 AM	#13
conscript Private 1 Rep 58 Posts Drives: 335i Coupe Join Date: Jun 2015 Location: Kent, United Kingdom iTrader: (0)	My only worry is passing the M.O.T, especially if the only Lambda's are in the DP's and none mid section like the N54.
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