Z4M vs E46 M3 Decat

[Martyn]

With the limited number of options I thought I'd try something different, so I sourced a new set of Scorpion decats for an E46 M3, knowing full well they wouldn't fit.

I sourced the Scorpion units for 3 reasons:

1. They are true 2.5" piping.
2. They are cheap.
3. They are stainless, and I already had a bit of 2.5" stainless in the garage.



So off came the stock cats, and a side to side comparison. As you can see, the E46 M3 decats are short by about 80mm, and the 3 bolt flanges are clocked slightly differently.





I chucked one of the pipes on the car just to check they wouldn't foul anything and as suspected, they clear fine.

So out came the chop saw.





I chopped the flange off between the o2 sensor and flange leaving me enough room to add in a small section of pipe to make up the shortfall. Please don't judge my tig welding, I am by no means a welder!



I repeated the process for the second pipe and bolted it all up, I don't have any pictures unfortunately.

The car now sounds like an E46 M3 with the classic rasp between 2-3K, which the Z4M never seemed to have.

I plan on whipping them back off the car and chopping out the fake Scorpion silencers and I'll replace them with a couple of Fabco silencers. I'll update the thread as and when I do that.

I used these silencers on my E46 M3, and they work great.

https://fabco.uk/product/stainless-stee ... th=8-200mm

[warmasice]

Now these are the type of posts that I love reading! Well done!

[Argenta]

Why on earth are people "decatting" everywhere?
Has the level of knowledge sunk so low the kids don't know what a cat does anymore?

[Mister T]

If you're chopping the silencers out anyway why not just fit high flow cats?

[Martyn]

Because a decent high flow cat is ~500 quid per unit.

[Matt.13]

Love seeing mods like this . Thanks for sharing

[NLW73]

good work martyn and keep us posted.

I read that those primary Cats dont do a huge amount and its the secondary that does most of the work ?

it's more for sound muffling

[Martyn]

No secondary cats on euro Z4Ms, only the US guys had the primary cats in their headers.

[maupineda]

I knew this was possible, but had no idea they would be different in length, I always assumed it was only the clocking. I am interested in the mufflers you posted, I have OE X-Pipe, Remus, and DKF 300cells cats and my car is too loud, to the point I have been thinking about putting my OE US Secondary cats, primaries are gone as I have EU headers.

So maybe the design of the OE S pipe helps with muffling sound. everyone says Remus is quite, well, that most be deafened people LOL, is VERY loud, at least in my setup.

[Martyn]

On my old E46 M3 I ran a milltek center, stock backbox and the Fabco silencers on my decat pipes and it was perfect.



Having said that, if you have 300 cell cats, then I've no idea why it's still mega loud.

[maupineda]

Here is video, I have CSL intake, and yet, exhaust dominates mostly the sound experience

https://www.instagram.com/reel/CYe7wMrFDJO/

https://www.instagram.com/reel/CT27PbrFkvv/

Exhaust is very bassy and raspy too.

[Martyn]

Version 2 inbound!



Told you I'm no welder! Hands are waaaaay too shakey for that.



First one fitted.



Will attempt the second pipe tomorrow.

[NLW73]

looks pretty good to me and great work. it's under the car so who is going to look

just admire the noise!!

[john-e89]

Those welds are awesome......take a bow.

[Martyn]

Second pipe done and all bolted up.




Sounds much better on cold start!