Decat?

murrayj07

Registered User
Having a little ponder on what mods i can do to my 1.8t 2001? one of the thoughts i had was a decat? love the sound of decat cars so can anyone tell me the ins and outs of fitting/lambda? Also, its a standard backbox i have? will this affect it at all? Thanks!
 

James TQ

Registered User
i have a decat and standard back box, little bit more noise nothing major, had to replace the lambda but it was on the was out anyway so it will be ok
 

murrayj07

Registered User
SO just sticking it on should be sound? possible lambda change though? does it backfire at all? and whats the noise like? like.... loud on acceleration and quiet on cruising?
 

BenJee_S3

Registered User
I may be wrong but I've heard a decat on an S3 is pretty much pointless performance wise? The twin cat setup is so well made, it isn't restrictive enough to make a decat beneficial. That twinned with the hassle of putting the cat back on for mot time is what's deterred me from buying one. So unless you want it purely for the sound, not much point!

Feel free to correct me if I'm wrong, this is just what I've learned from researching it for myself!
 

murrayj07

Registered User
Forgot to ask! is theyre a specific type to get that will just pop straight on? dont want any sort of lambda issues coming up? and i'll just be getting the garage to fit it so does the lambda become affected at all?
 

m19lte

Registered User
Downpipe n decat deffo, just done mine n it sounds sweet :). Turbo spools up quicker and you can now hear the turbo whistling on tick over :) seems to rev much better too.
 

<tuffty/>

Badger 5 Edition...Its all about the flow...
Staff member
Moderator
What is it about the Lambda are you specifically asking? as your A3 is a 2001 it will be an AUM engine code and wideband so the wideband lambda probe (one closest the turbo) MUST be fitted in the right hole... the second lambda (post CAT) will require a spacer (never used one myself so don't know how well they work) or for the post CAT probe to be coded out in the map...

The DP you have linked to seems to have provision for both probes.. on some ebay DP's I have seen the post CAT fitting is capped anyway so doesn't see exhaust gas anyway...

I would advise using an OE gasket for the turbo/DP (4 bolt one) as the supplied gasket are next to useless...

Should also mention they (laughably) advertise this as A3/S3 DP.... it won't fit an S3 (neither will it fit an A3 quattro), completely different beast... :)

<tuffty/>
 

murrayj07

Registered User
Good description, but i was wondering in basic terms, if i order that on ebay, and (for arguements sake) take it to my local garage, theyre would be no issues? obviously there are no gaurentees, but 99%?
 

<tuffty/>

Badger 5 Edition...Its all about the flow...
Staff member
Moderator
Good description, but i was wondering in basic terms, if i order that on ebay, and (for arguements sake) take it to my local garage, theyre would be no issues? obviously there are no gaurentees, but 99%?

Having never fitted one personally I couldn't really comment...

Issues you may have are mating the DP to the existing system... don't know the diameters of the pipework involved so its possible a reducer of some description will be needed..

Only thing I can say about the post cat lambda is that typically without a cat it will throw a CEL and fault code (cat efficiency one normally)... so if it has a capped bung then this 'may' sort it but... on some I have seen the tube extends well into the DP essentially blocking it anyway so seems a bit pointless... just check this...

Only way I know to guaranty no light is coding out...

<tuffty/>
 

vrbob

Thats no Moon, Thats a space station!
After putting my sports cat on my car I got the light on the dash which I could clear but would come back after 10mins.

Got one of the lambda spacers off ebay for not too much money and it made the light stay off. I then got my software upgraded a few months later which coded out the light so have now removed the spacer so can confirm they do work.
 

Tim_Attard

Registered User
Get the decat, the garage wont have a problem fitting it, if they do then you need a new garage, i would strognly recommend doing it yourself tho, its probably one of the easiest jobs ive done on my car to date, your engine light will come on regarding the post cat sensor either get a spacer of ebay or get a map, map would be the more enjoyable route ;)
 
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