De-Catting for the *really* stupid

[telford_mike]

Im interested in getting this done, so heres my question. I understand that there are sensors on a Cat that send information to the ECU (Lambda???). What happens to these when the cat is replaced with a length of drainpipe? Or is there more to a de-cat pipe than I thought?

 

[16V_Matt]

im equaly stupid! ive been thinking of doing it but like how easy is it to do and is it a pain in the ass to replace for tha MOT!

 

[Simon]

My understanding is that you need to cater for the Lambda senors. Drill two holes and weld in Two Mild Steel Nuts so the existing lambda sensors will fit. Nut size for 172 is 18mm with a 1.5 mm thread (from memory). Think I mentioned it in a previous post. Youll need to go to a Fasteners to get the nuts as they are not the sort of thing you find in a DIY shop.

Also cat light only comes on if you rev the car hard while it stands still from cold. It then stays on for a while, maybe 4 hours driving then goes off.

You are best of buying a pipe from K-Tec or Devil and then you wont need to worry about making your own lambda sensor chambers unless that cat only support one Lambda then you have to play about.

 

[Captain Slarty]

first you gotta ask if its even necessary ???.

the highest powered 172s at the rr day recently didnt have decats...

I wouldnt bother really.. too much hassle !



Joe..

 

[Nick Read]

Dont know much about the 172 cat(s). but basically, if the lambda sensor is in the downpipe then you can do whatever you want to the exhaust system from there backwards and it wont affect the lambda readings. The lambda sensor will still read the oxygen and send it up to the ECU, from where the ECU will adjust the injector duration on the fly to keep the mix right. When youre flooring it the lamda signal isnt used anyway, it just reverts to a max power fuel/ignition/timing map. Thats if it works in the same way as the older Clios.

If the lambda sensor is part of the actual cat then surely a decat pipe will include the boss for it.

 

[2 live]

i know the lambda sensor for the willy is b4 the cat pipe so the sensor shouldnt be reading any difrent to what it was with cat in place.

and for the record on the same r/r the highest willy output was also the only one with de-cat pipe fitted .something to think about

cheers

jon

 

[Captain Slarty]

not really Jon.. its purely the age difference in the design..

ancient cats like on the willy, are not a patch on the modern units...

the newer ones flow better.. simple really...

Joe.

 

[BenR]

yup...compare the cell design on a new one to an old cat.......and you wonder why they made it like that in the first place......

 

[2 live]

neva had one in bits mate so wouldnt know about that

as for cats tho the only time ive seen em on my cars is wen im throwin em in the bin lol

jon

 

[MaLicE]

i had my car de catted to day hair every where



no had cat taken off and a k tec bypass put on and OMFG i cant believe it soooo much more noise and quiet a bit more grunt too.





MaLicE