Replacing primary cats with secondaries to avoid CEL?

Len_Beach · 08-06-2011, 01:35 PM

I'mlooking to mod an OEM X-Pipe and have read that removing the primaries gives the biggest gain.

I still need cats to pass a UK MOT emissions test.

Would it be possible to cut the secondary cats out and replace with straight pipe then reinstall the secondaries in place of the primaries?

Would this still pass an emissions test and not throw a CEL?

1MOREMOD · 08-06-2011, 02:05 PM

Interesting. Not sure of the answer would think this may work but wanna hear from others.

ScorpionT · 08-06-2011, 04:59 PM

You could just replace the primaries with straight pipes and re-install for emissions. The way you are talking about sounds like more work than necessary.

Simrokkzz · 08-06-2011, 06:03 PM

what real sense?

1MOREMOD · 08-06-2011, 06:18 PM

Ehh what?

saeedg48 · 08-06-2011, 06:19 PM

just spend the money on a tune after you delete your primary cats.

1MOREMOD · 08-06-2011, 06:58 PM

Yep that's my plan as well challenge and evolve. Cel on now and waiting on tune to arrive.

Len_Beach · 08-07-2011, 06:25 AM

I'll be using the Evolve-R so I'm sure Sal and the boys can accommodate the cat mods.

I want to use the secondaries in
place if the primaries as I don't want to be in a position where I have to swap pipes each year.

My understanding us that the secondaries are 200 cell? Will these provide enough filtration?

MilehighM3 · 08-07-2011, 08:54 AM

Quote:

Originally Posted by Len_Beach

Would it be possible to cut the secondary cats out and replace with straight pipe then reinstall the secondaries in place of the primaries?

No. The secondaries are larger than the primaries in diameter. The stock primaries are semi flat for clearance reasons. If you were to fit the secondaries there, they would hang down considerably. Which is why all aftermarket X-pipes do not have resonators or cats in that location.

Jon@Bimmersport Automotive · 08-08-2011, 08:43 AM

Quote:

Originally Posted by saeedg48

just spend the money on a tune after you delete your primary cats.

That will only get rid of 1 of his problems. Depending on how stringent the emission testing is over there will determine if using secondary cats is enough.

The easiest way is to use a bolt on X pipe to switch quickly (it can be used WITH a O2 delete tune as the primary cats and oxygen sensors will be functioning) or extend the rear O2 sensors but like said the secondary cats may not be enough.

persian54 · 08-08-2011, 03:44 PM

Quote:

Originally Posted by Len_Beach

I'mlooking to mod an OEM X-Pipe and have read that removing the primaries gives the biggest gain.

I still need cats to pass a UK MOT emissions test.

Would it be possible to cut the secondary cats out and replace with straight pipe then reinstall the secondaries in place of the primaries?

Would this still pass an emissions test and not throw a CEL?

What you will be doing is essentially having a HFC Xpipe (like one from Gintani or AA)

It'll be easier for you to buy one of those than to modify you stock one the way you want to do it
you'll have clearance issues putting the stock 200 CELL cats in the front

08-06-2011, 01:35 PM	#1
Len_Beach Major 186 Rep 1,247 Posts Drives: 435d Join Date: Jun 2011 Location: UK iTrader: (1)	Replacing primary cats with secondaries to avoid CEL? I'mlooking to mod an OEM X-Pipe and have read that removing the primaries gives the biggest gain. I still need cats to pass a UK MOT emissions test. Would it be possible to cut the secondary cats out and replace with straight pipe then reinstall the secondaries in place of the primaries? Would this still pass an emissions test and not throw a CEL?
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08-06-2011, 02:05 PM	#2
1MOREMOD - 11817 Rep 23,187 Posts Drives: Race car-> Join Date: Mar 2009 Location: check your mirrors iTrader: (5)	Interesting. Not sure of the answer would think this may work but wanna hear from others. __________________ 02 Tiag e46 M3\|6MT\|GC plates\|MCS c.o.\|GC bars\|GC race control arms\|GC bushings\|BW eng. & tran. mounts\|subframe kit\|BW race shifter\|BW Jaffster\|Euro header\|BW exhaust\|K&N c.a.i.\|Epic race tune\|Rouge pulleys\|Seibon CF hood\|CSL bumper\|apr gt 250 & splitter\|ST-40\|XR-2\|SS lines\|half cage\|Recaro profi\|Profi 2 harness\|BMWpedals\|BW studs\|
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08-06-2011, 04:59 PM	#3
ScorpionT Private First Class 6 Rep 101 Posts Drives: 335i, SL65 Join Date: Apr 2011 Location: Arctic Circle iTrader: (0)	You could just replace the primaries with straight pipes and re-install for emissions. The way you are talking about sounds like more work than necessary.
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08-06-2011, 06:03 PM	#4
Simrokkzz Private 1 Rep 92 Posts Drives: E92 M3 Join Date: Aug 2010 Location: Germany iTrader: (0)	what real sense?
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08-06-2011, 06:18 PM	#5
1MOREMOD - 11817 Rep 23,187 Posts Drives: Race car-> Join Date: Mar 2009 Location: check your mirrors iTrader: (5)	Ehh what? __________________ 02 Tiag e46 M3\|6MT\|GC plates\|MCS c.o.\|GC bars\|GC race control arms\|GC bushings\|BW eng. & tran. mounts\|subframe kit\|BW race shifter\|BW Jaffster\|Euro header\|BW exhaust\|K&N c.a.i.\|Epic race tune\|Rouge pulleys\|Seibon CF hood\|CSL bumper\|apr gt 250 & splitter\|ST-40\|XR-2\|SS lines\|half cage\|Recaro profi\|Profi 2 harness\|BMWpedals\|BW studs\|
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08-06-2011, 06:19 PM	#6
saeedg48 Brigadier General 342 Rep 3,574 Posts Drives: Porsche 991.1 GT3 Join Date: Nov 2008 Location: Newport Beach, CA iTrader: (1)	just spend the money on a tune after you delete your primary cats. __________________ 2015 Porsche 991.1 GT3 2015 F80 M3 -- Individual; Space Grey
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08-06-2011, 06:58 PM	#7
1MOREMOD - 11817 Rep 23,187 Posts Drives: Race car-> Join Date: Mar 2009 Location: check your mirrors iTrader: (5)	Yep that's my plan as well challenge and evolve. Cel on now and waiting on tune to arrive. __________________ 02 Tiag e46 M3\|6MT\|GC plates\|MCS c.o.\|GC bars\|GC race control arms\|GC bushings\|BW eng. & tran. mounts\|subframe kit\|BW race shifter\|BW Jaffster\|Euro header\|BW exhaust\|K&N c.a.i.\|Epic race tune\|Rouge pulleys\|Seibon CF hood\|CSL bumper\|apr gt 250 & splitter\|ST-40\|XR-2\|SS lines\|half cage\|Recaro profi\|Profi 2 harness\|BMWpedals\|BW studs\|
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08-07-2011, 06:25 AM	#8
Len_Beach Major 186 Rep 1,247 Posts Drives: 435d Join Date: Jun 2011 Location: UK iTrader: (1)	I'll be using the Evolve-R so I'm sure Sal and the boys can accommodate the cat mods. I want to use the secondaries in place if the primaries as I don't want to be in a position where I have to swap pipes each year. My understanding us that the secondaries are 200 cell? Will these provide enough filtration?
	Appreciate 0 Quote