Z4 2.5 secondary cat delete kit

wysjoz367 · Post by **wysjoz367** » Fri Dec 02, 2022 12:44 pm

Hello everyone
Im new to this forum as just bought my first Z4. Its a 2004 2.5 engine. Im sure its been discussed many times but can some one send me the link to the disacussion on who to buy the kits from in UK for secondary cat delete kits.
many thanks

Smartbear · Post by **Smartbear** » Fri Dec 02, 2022 1:48 pm

wysjoz367 wrote: ↑Fri Dec 02, 2022 12:44 pm Hello everyone
Im new to this forum as just bought my first Z4. Its a 2004 2.5 engine. Im sure its been discussed many times but can some one send me the link to the disacussion on who to buy the kits from in UK for secondary cat delete kits.
many thanks

Hi, I’m not sure that the m54 cars even have secondary cats - i thought they had one cat in the exhaust manifold?
Rob

wysjoz367 · Post by **wysjoz367** » Fri Dec 02, 2022 2:00 pm

Hi Rob
It does have the 2 cats. first ones are still present i think. i'll try to take a picture

TheDan · Post by **TheDan** » Fri Dec 02, 2022 3:18 pm

Yeah there are 2 cats and 2 mufflers/resonators on the pre-facelift 6 pot exhaust. From memory I am pretty certain the right blob in the picture is the secondary cat and the middle blob is the primary resonator (and the left blob is obviously the secondary resonator/backbox). From what I've seen on here most people just get an exhaust shop to cut off one or both of the middle sections and replace with straight pipes. I have also heard that they pass the emissions MOT test fine without the secondary cat.

Smartbear · Post by **Smartbear** » Fri Dec 02, 2022 3:25 pm

wysjoz367 wrote: ↑Fri Dec 02, 2022 2:00 pm Hi Rob
It does have the 2 cats. first ones are still present i think. i'll try to take a picture

Think I’m getting them mixed up with the n52 cars

Rob

Sidewaze Samm · Post by **Sidewaze Samm** » Fri Dec 02, 2022 9:38 pm

It's possible to open the cover shields for the secondary cats; cut cats open; remove the gubbins; re-weld the cats; and then replace covers. If done with care all looks standard and untouched.
Sounds better though!

viewtopic.php?f=2&t=129420&hilit=cat

patriot66 · Post by **patriot66** » Sat Dec 03, 2022 5:48 pm

Sidewaze Samm wrote: ↑Fri Dec 02, 2022 9:38 pm It's possible to open the cover shields for the secondary cats; cut cats open; remove the gubbins; re-weld the cats; and then replace covers. If done with care all looks standard and untouched.
Sounds better though!

viewtopic.php?f=2&t=129420&hilit=cat

This

At 20 years old the secondary cat ceramic is absolutely shot and serving no purpose whatsoever other than to REALLY hinder gas flow. Get rid ! I did. Vastly improved throttle response and a bit more noise

Sailed through its MOT last January with no issues at all

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