I know it's possible to have a "y-pipe" in the exhaust and make both a "stock" exhaust and a catalytic exhaust...but what I'm wondering is how you could tune this for the car? Is there any aftermarket ECU or other way to quickly switch your tuning settings to accomodate the difference? The idea is, I'd like to have a racing exhaust for obvious reasons but I still have to do smog check every year or so and I don't feel like having to pull the exhaust on and off, etc. Also, sometimes they have road checks for smog so it wouldn't be that easy to get away with. Any ideas?

 

They do have electronic controlled CUT OUT valves.
Have it close to forced the exhaust into the cat, open for straight through.

You only tune for straight through max power.
When I put my cat in for emmisison testing, I only change the idle and low cruise areas for leaner fuel with my PFC commander. Only about 6 cells.

 

hmmmmm that's not too bad - is there any faster way to change 6 cells in the PFC? Like a macro or something?

 

Anyone have a faster idea?...say you want to track your car on weekends - is there any way to have two fuel maps on any ECU for the FD and an easy way to switch between them?

 

If you were using a PFC you could wideband with the y-pipe open and with the y-pipe closed. Then calculate the amount of extra fuel needed. When you want to race, change the PIM voltages to the correct per centages. You would only have to change the PIM voltages in the boost regions, about 4 values.