Join Date: Feb 2011
Car Year: MY05
Car Model: Forester 2.5 XT
Feedback Score: 0 reviews
I've fitted an up pipe decat as you propose and after fitting the resistor, I had no problems and did not need a remap/tune.
I've also fitted a catback exhaust (so no other cats were touched) and did not require a remap/tune.
I am still on the factory map and been on a rolling road to make sure the fuelling etc was ok - All was good.
If you want to start changing cats in the downpipe or under the floor, you will almost certainly need a remap to be safe. If you run lean you could end up causing piston or valve damage.
I guess in theory, if you knew how the air fuel oxygen sensor responded in terms of resistance to running rich/lean, you could add a resistor in the circuit to fool it to run richer to compensate for a change of downpipe cat...In theory - I don't know anyone who has done that as most simply stay off boost after fitting a sports/decat downpipe etc until you get a remap/tune.
If you fit a decat in the downpipe, you will struggle to pass, or simply flat out fail any emissions testing if that is a concern - Some members on here have reported smells of exhaust gases being very noticeable inside and behind the vehicle after fitting a decat in the downpipe/underfloor and revert back to a sports cat for performance without any noticable exhaust gases
Do you have a particular power goal in mind?