Need your input on bypass pipes
 

For those of you not living in California allow me to explain something about our smog test. The test equipment is connected via modem to a State of California computer such that all readings during a test are sent to this computer. This was an evolution in the smog test saga, and was designed to avoid fraud. In the past it would be common to slip a guy twenty bucks and he would make sure you pass the test, or he would enter your VIN info and then tailpipe a known clean car, rather than your nasty beast.

Now the emission stats are in the CA computer and it is pretty savvy as to what kind of readings to expect from what type of car. So if you are running a big V8 ford and the computer sees readings appropriate for a Pinto – flares are going to go off. And more important – you don’t get do-overs. The State knows you just failed, and now you have to fix your car before you can test again. Yes – it’s all spelled $$$ more than spelled clean air. Ask me about the custom engine I’m getting approved right now, regardless of emissions…

However there is something called a ‘dry board’. This is where they tailpipe you but not connected to Big Brother. It’s a chance to see your readings before a true test. Generally we don’t do this because it runs about fifty bucks, and so we just go with the test and mostly pass. But if you’ve been fussing with your car in some fashion…a dry board is a good thing to do.

I have the four cat exhaust on my 3.2 and want to install the bypass pipes to replace the second set of cats. No headers, and leaving the first cats intact. No O2 sensors on the rear cats, so this is simply going to have an effect on the emissions…but what effect? My engine is clean and just passed its regular smog test nicely, so now is a good time to do a mod and go for the dry board to see if this is going to hang me up next time I do the real thing.

So I’m going to install the bypass pipes (test pipes) and then run a dry smog check to look at my readings. I will know if the elimination of the second cats increased my emissions, and by how much, and if over the limits. If under the limits I might be able to keep the pipes on the car, as they never seem to do a visual check. If over the limits…well then I know for sure I have to make things right before I exhale in Arnold’s face two years from now.

I’ll post my results for your reference. Meanwhile I need some pipes! What do you folks recommend as a good set, reasonably priced, for an ’01 S ?

Dude, it would be most excellent if you could post your smog results. I'm sure many others, myself included, who live in California have considered this modification and also dread the impact on smog. :(

Honestly you're taking out a relatively straight pipe with a cat and a simple bend in it and you want to replace it with a straight pipe, a flange at each end, and that bend in it. This is not rocket science and should NOT cost $500. Go to a local muffler shop and tell them you want some straight pipe/cat deletes for the track. They'll get out a fancy coat hanger, figure out the bend, weld on some flanges, and fab you up a set of pipes. I bet it won't cost you more than $120 or so. I did a muffler delete this way on my WRX and it worked great. You may have to install the pipes yourself though as it wouldn't be legal for the muffler shop to leave them on the car. Just my two cents...

Kirk basically gave you all the input you need. I also plan on doing the bypass pipes for the PCA DE events. I'm doing full course at Pocono Raceway on the 4th of July. In New York we have annual safety & Smog inspections. So I'd be popping my bypass pipes on and off once a year if it didn't pass smog test.

Keep us updated.

I'd pull the trigger on the bypass pipes but I'm afraid I won't pass smog as well... :(

For now this project is on hold.

I installed the Deluboz catback exhaust and took a five hundred mile trip - the drone is just barely tolerable. It isn't so much the volume as the resonance. Around town going through the gears is fine, but on the open road the rev range is right in the wrong spot. I am too concerned that moving to bypass pipes will worsen this situation, and so I'm holding off until I learn more.