Previous owner had straight through from turbo back with lambda sensor still fitted. Very loud, not to my liking.
Anyhoo. I've now refitted the cat downpipe and the cat that immediately follows it and it's much quieter, not noticed a drop in power. The EML has just come on again though. Is this due to putting the cats back on?
It was mapped by Andy Forrest. Should I be expecting to go back to him to remap or can any half decent mapper do the job for me?
I've not yet done a code read as it literally came on 16 miles after refitting the center cat. Lambda sensor is mechanically fine but I'll not rule out a coincidental failure. Thanks in advance.

 

Yes will need map tweak to suit. Could you not of put a bung into backbox or even fitted resonated centre section? It will be down on power either now or after map tweak

 

I am having the same issue on my sti bug eye , it's currently has a Ferral Racing T304 Turbo bac and a Rodger Clarke Motorsport up pipe and the dam thing sound like a Lancaster bomber when popping to the "shops", I would like to fit a miltek resonated system but unsure weather it would fit and worried I would need a re map ?

Any ideas chaps?

 

Id say no, fitting a decat changes the back pressure but by running the decat when mapped Andy would have delt with that via WGDC, fitting a more restrictive exhaust wont cause the same problems as fitting a decat to a none decated car when mapped,

So Shunter will also be fine fitting a res box in the centre section.

hth

 

Cool. I was kinda hoping I wouldn't need a trip to AF, other side of the country.
I read the codes and got P0301, P0302 and P0303. I'm not noticing any sort of misfire but I know the codes don't necessarily mean that I have a misfire at all so have cleared the DTC for now and will monitor for a bit. Could be a large number of things throwing those codes up but I'd like to make sure I'm not doing any damage to the engine.
I feel your pain Shunter. I've come from a nice and quiet E60 M5 which the lass loved, to this banging, popping, squeaking, noise machine. She doesn't love this one as much I have however explained that it's a nice and safe car for the winter.

 

yes it will need a tweak for the cats or at the very least checking, as said will have changed the back pressure.

 

why?
if it was mapped for decat in what way will the pressure change and require a tweek ?

 

as mentioned above, it would be easier to switch to a resonated center pipe and a quieter backbox (prodrive one on mine is quite stealthy but still has a decent note). This will have a smaller impact on the map compared to adding in the cats.

If the cats have been properly removed then there's a chance that the current map on the car will slowly kill them off. The original mapper will be able to tweak the map for you but if you don't mind paying a little more A.N. other mapper should be able to do their own remap on the car (though usually starting from scratch).

 

when you remove the restrictions in the exhaust, less wastegate duty is needed to reach target boost. By adding the restriction into the exhaust in the shape of 2 cats and a bloody awful downpipe mouth your car will now need more wastegate duty to reach target boost. You'll most likely be down on boost which is partly why you feel down on power, once mapped you'll get some of that power back but not all of it. The engine is basically an air pump, the more things you have in the way (either when sucking in or blowing out the exhaust) the harder the engine has to work to get things moving.

 

Well explained