de-cat & lambda sensor ?

[eddieedmo]

I am going to decat my S2 and was wondering if the sensor is needed ?
Any experiences ?
Thanks and a Merry Xmas.

Nick []

 

[sulzeruk]

Yes, you'll need it. Get a decat pipe and weld the old threaded boss in if you can. Someone sells the metal bngs but I can't remember where I saw them,
Alasdair

 

[jonk]

I just had a full system fitted from downpipes back including decat. Wasn't aware they had to bypass any lamda sensor though it is entirely possible they did so without me knowing. It's certainly not thrown up any warning lights....and it seems to breathe much easier now!

 

[robwright]

Not sure but would it not be possible to just change the FQ settings and coding plug? S2s are a bit of a mystery to me.

 

[nick9one1]

I de-catted my own recently and was really easy! (if you have a welder)

I bought a meter of 2.5 inch (I think) tube from eBay for about £20
http://www.ebay.co.uk/itm/T304-1meter-Exhaust-Stainless-Steel-Pipe-Tube-2-5-64mm-/260841085844?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item3cbb571b94

Unbolted the old downpipe/cat
Chopped out the old cat with an angle grinder
Cut the new pipe about 2 inches longer (it just fitted snugly over the other two parts)
Reassemble
Tacked in place with MIG welder
Remove
Weld fully
Refit

overall it took about an hour and a half.

The S2 only has one lambda/O2 and its forward of the cat (engine side). This means removing the cat doesn't change its reading.
When de-catting you only have to worry about lambdas if you have two.. one in front and one behind the cat. Normally they produce different readings (if the cat is still working ok!). When you remove the cat, both lambdas read the same and the ecu thinks the cat is faulty.