can i decat without any issues?
 

S8 has developed a rattle over the last few days. It went on a long run yesterday (100+ miles) and the car was so loud when i got back (didnt really notice with the windows up, another point for build quality!)

Had a look under and the exhaust has come off at the cat. I can see the bolts on the downpipe are loose which was the rattle.

Im going to get my floor ramps out tomorrow and have a look underneath. If i cant save it and have to get it repaired, can i take the cat out without any issues? I.e engine lights on the dash etc.

Must admit it pulled really hard yesterday with in essence just a downpipe, and sounded the dogs danglies. Really tempted for a full exhaust now ha

Your is a late FL (like mine) model so will have lambda sensors before and after the cats - there are two, one on each bank. One is built in to the pipework on the cat itself on one side (the other side is in 2 parts IIRC).

I replaced one of my cats a while back at "significant" cost. The old cat (which had to go back as it's all done on an exchange basis) apparently had effectively nothing inside it.
I bought the car knowing it had a bad/rattly cat on one side and it got worse and noisier until most of it had been spat out of the rear.

No warnings and it still passed the MOT for 2 years! But that's no guarantee yours will be the same.

I had to have one new lambda sensor as well as it just couldn't be removed from the pipe and the wiring had to be cut. Wasn't faulty though and they did get it out eventually with major brute force. Probably ended up on eBay....

I had 100 cell cats (I think?) on my old D2 S8 FL, and they would trigger a post-cat lambda error every 100 miles or so. But no CEL on the dash.
With no cats you may well trigger a CEL on the dash which would be annoying and possibly mask a future issue that would also trigger the CEL.
You could of course take the car to a tuner and have the error codes from rear lambdas coded out permanently.

^ ^ ^ Yep, I get exactly this after fitting sports cats. I reset the light then a few journeys later it's back on. Annoying but I've learnt to live with it. Would be good if it could be coded out though.

If you don't mind splashing some cash, MRC tuning coded out my rear lambdas and SAI electric pump that lives in the airbox for £150+VAT.
I wanted the lambdas coded out in advance because I have two 200-cell cats ready to fit.

Goran I forgot to tell you, I just unpluged and removed my SAI pump blocked the pipe and vacuum pipe of the combi valves. Over a year ago and it works fine.
Dave

Thanks Dave, good to know. I was under the impression that the N112 solenoid valve or whatever its called would keep throwing an error code, (but no dash light). Maybe simply blocking it tricks it?

I went all the way and had all the components removed, even combi valves, N112, blocked off holes in the back of the head. All SAI vacuum pipework gone.

Would a cat rattle (pretty bad now) trigger the engine light?

Might do, if not enough CO2 or that other gas is being reacted away by the mesh (because its partly gone) then it could trigger the post-cat O2 sensors. If you scan it the error codes should reveal the cause.

Ill get it read soon.


Long story short, cats rattling. Cars exhaust note has changed a bit.

Thought it wasnt pulling well today so flicked it to petrol on an open road. Top of third it was struggling to rev and would not go past 6.5k. Obviousely has a 7k redline.



Also the engine light is on and since its been the everage mpg on the dis has gone from 17 to 12. Dont know if its just the dis until i use a tank though.


Any thoughts??