How well can the ECU cope with a catless down pipe? I am contemplating punching out the cat in mine while I have it off the car, but havent been able to find anything on how/if the stock tune is able to handle this change. Will I throw just a cel that needs deleted or will the ECU throw the car in a "limp mode"?

Any help would be appreciated.

 

Typically, the unmodified (stock) ECU sees too much cross-flow on the rear (post-cat) oxygen sensor, throwing a fault code to the extent of "catalyst system efficiency below threshold".
A Check Engine Light (CEL) will illuminate, but catalyst efficiency faults rarely affect performance...
To override the fault, you'll either have to "trick" the ECU that the catalyst is present and working, or have the ECU tuned to simply deny reading the oxygen sensor value.

- Erik

 

Thanks for the quick reply. I figured I'd ask before I removed the CAT coming from my Subaru which needs a tune when going catless. I figured since I'm in there right now I might as well get the cat out of the way so i don't have to deal with it again since I'm wrapping the down pipe and getting a Pure Tune after winter.

What ways are there in tricking the ECU into thinking there is a CAT? I was just going to run with a code for a while and scan for more every weekend.

 

You will also notice the low end torque will drop when you go catless without a good ECU tune. Your high-end power will be a little better. I went for two years catless w/o proper ECU tuning. A good ECU tune is needed to smooth everything out. If I were you, I would wait out till you got a proper tune to go with the downpipe. It's just going to make more noise for the most part without that crucial piece of the puzzle.

Way Motor Works sells a electronic kit that prevents the downpipe codes from populating.