De-Catting - anyone done it? Worthwhile?

M

M@r]{

Senior member
 East Midlands
With previous cars I've had there are some good gains to be had by doing this, not to mention an improvement in noise (if you count an increase as an improvement :evil: )

Has anyone done it? If so how was it? I assume something also has to be done to stop the ECU from throwing a wobbly? And should the car be mapped afterwards or does it deal with the reduction in back pressure etc on its own?
 
Well it keeps the paw prints off and the vet bills down so some gains. The kids also cried so the noise levels were up too. :tumbleweed:
 
Stuart Truman said:
Well it keeps the paw prints off and the vet bills down so some gains. The kids also cried so the noise levels were up too. :tumbleweed:
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LOL I suppose I asked for that. I can certainly see some benefits to de-catting that side of my life too, bloody girlfriends cats drive me insane using the Elises roof as a bed :x
 
On a serious note, isn't that illegal? I'm guessing you'd fail the new MOT in spectacular style.

[edit] Just checked The AA website and found this "A catalytic convertor fitted as original equipment but missing will be a reason for failure."
 
Waste of time and effort unless you're thinking of track use only? As said will fail MOT. Car is fast enough as standard surely and any improvements in noise would be better from a sports exhaust.
 
I know a lot of people who have de-catted. Yes, it will fail an MOT and therefore cannot be declared as a modification and so potentially voiding any policy.

There are however many testing stations where emissions "aren't an issue" or if you can't find one of those, swap your exhaust back, which is the way most people I know avoided it...

In terms of gains, probably, it's less restrictive, but you might gain 0.1 of a second 0-60, so why bother with all the hassle?
 
There's more than one CAT. You can take one out and still pass an MOT.

I de-catted my second car. It made the engine breath far easier above 3,000rpm. EDIT - definite power gain.

Should you do it? You choose sir, you choose :thumbsup:
 
Adamski said:
There's more than one CAT. You can take one out and still pass an MOT.

I de-catted my second car. It made the engine breath far easier above 3,000rpm. EDIT - definite power gain.

Should you do it? You choose sir, you choose :thumbsup:
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We only have 1 set of catalytic converters on European M's. North American Z4M's have an extra set of converters on the headers but all others have just the one set, as in the diagram below. The link shows the full exhaust system. http://www.realoem.com/bmw/partgrp.do?model=DU92&mospid=49422&hg=18

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M@r]{, I've posted my views on the matter on that other M modification thread.

ga41 said:
M@r said:
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and while I'm at it what are these cars like de-catted?..... :roll:
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I was thinking of doing this but decided against it in the end. According to people i've asked they will give a noticeable gain but only at the top 3/4 of the rev range and will lose out on torque at lower revs... A mate who had an E46 M3 decatted it and mentioned this as well.
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ga41 said:
Adamski said:
There's more than one CAT. You can take one out and still pass an MOT.

I de-catted my second car. It made the engine breath far easier above 3,000rpm. EDIT - definite power gain.

Should you do it? You choose sir, you choose :thumbsup:
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We only have 1 set of catalytic converters on European M's. North American Z4M's have an extra set of converters on the headers but all others have just the one set, as in the diagram below. The link shows the full exhaust system. http://www.realoem.com/bmw/partgrp.do?model=DU92&mospid=49422&hg=18

221.png
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Oops. Sorry guys :?

Does indeed explain US power difference.

The other posts also match my experience when I de-catted my previous car. Power gains are at the top end of the rev range
 
Greetings from across the pond. Should anyone in the UK have a set of euro-spec 'middle section' catalytic converters (i.e. "Section 1", under the car, item 1 in above diagram), I would like to purchase them provided they are in serviceable condition. I'll pay the shipping as well, or course.

Please do advise :)

Replies invited on: robclements "at" spamcop "dot" net.


regards,

RC.
 
Decatting is illegal indeed, but what about replacing the OEM catalytic convcerters with "sport catatalytic converters"? Has anyone done that? If you believe the marketing, you get 30% gains in power, which seems a bit much. Or is this only valid for diesel engines?

I can have the cats changed for sport cats with less cells (100 or 200 cells) for about 800 euro (for both cats) all-in. Is it worth the effort?
 
If your purpose in decatting is to make the exhaust system less restrictive than it is in OEM state, then you'll find that gutting the silencers achieves this with the bonus that you don't have the hassle of refitting cats for MOT then refitting decats after MOT.
 
sixspeed said:
Very different gains on a boosted engine compared to standard N/A though...
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agreed...n/a is exoect to loose some Tq.... FI is expect to pick 20hp easily..... the stock CAT is a lovely piece however!!
 
Might not be ideal, but I believe you only have to pass the emissions test on one tailpipe...
 
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