Anybody else have a Y-Pipe put in and then fail smog? I failed smog after installing a Y-Pipe (no codes, or any problems, other than high NOx on my smog test). Ive backtracked the problem to the BPT valve, which doesn't seem to be getting enough backpressure from the exhaust to actuate the valve fully, which ensures full vacuum gets to the EGR to open it. Even after replacing the BPT valve, the EGR isn't opening enough (it works great when the BPT is bypassed). Anyways, since I've read so much about how much power the Y-Pipe creates by reducing backpressure, I guess it makes sense that the calibrated BPT valve now doesn't get enough backpressure from the exhaust to actuate the EGR (the BPT valve spring is calibrated to the original exhaust backpressure). Anybody overcome this by changing the BPT spring rate, or is it just necessary to bolt up the stock pipe to pass smog?

Thanks in advance...

 

Was your car warmed up when you had it tested or was it cold when they ran it through? I have a warpspeed y-pipe and passed in Colorado with really good numbers but the car was running in line for maybe 30 minutes before hand.

 

yeah the the egr system somehow has the twisted effect of ruducing nox emmisions even though nox is created from combustion temps that are too high, so your spot on with what's going wrong. That's why I love the dumb mustang owners who buy egr block-off plates, what a waste, when they could be putting that money towards fixing their ****box. As to a solution, I dunno, I just felt like mentioning this info, but I would definitly have it tested after blasting down the highway with a crap load of fuel injector cleaner, if all else fails figure out a way to bypass the bpt when needed or bolt the stock Y back on. Neither sounds like fun, I'm glad I don't live in Cali!

 

I passed with a ypipe and I have many friends who also passed with a ypipe here in cali. First time I failed because of high nox, I replaced the cat with a hi flow from warpspeed and then passed just fine. Never heard of the ypipe not having enough backpreassure to open the EGR tho. Try bypassing it before you go in for smog.

 

How do you bypass the bpt valve?

 

I can just run the vacuum line around the BPT, but then the EGR valve opens so much, the car runs rough. When I smogged the car, it was fully warmed up, and just had a "pass smog" treatment put in the tank......

Other ideas?

 

swap the old y back on, its not that bad considering the bolts must be somewhat loose since the aftermarket y is on. Once every 2 years isnt that bad. Maybe a New cat behind the y, like vlasic said. That would be a lot more than just swapping the y out though. Maybe an auto rx treatment...but that would take 3500 miles. Just some ideas.
peace

 

Problem Solved.

Vacuum line leading to and / or the BPT valve was bad. The thing that screwed me up was that after I replaced the BPT valve, I also replaced the vacuum hose. Turns out, the new hose was kinked, so the EGR / BPT still didn't work. New hose routing....problem solved.

NOx reduced from 1500 to about 50. Thanks for all the help !

 

Good to hear

1500 -> 50

 

but still, dont' shut off your car even at the inspection shop. keep your car warm and fresh for them to run the smog. if your car gets cold by the time they get to your car, good luck with that smog test. aftermarket y-pipe doesn't have cold start pre-cats, so you'll not pass the smog again.

 

Awesome info for those in cali! Thanks!

 

don't mean to revive an old thread from the grave but didnt wanna have to create another thread regarding the same subject. I changed my Y in Jan and just tested it here at my school, Im getting Nox of like 82 and HC of 241. will that be passable in Cali, im concerned about the Hydro Carbons.

 

* this was at idle only

 

HC is too high. I just got mine done. The limits to pass in cali for me were 39ppm for the 15mph test and 55ppm for the 25mph test

 

you'll fail a smog check with a catless ypipe. On my max i failed the smog test with a ypipe. At first i thought it was the random tech cat i had. So i replaced it with an oem one, still failed. All the numbers were horrible. A soon as i put in my stock ypipe with the stock cat, i passed with flying colors. Same deal also with my brothers, and my friends max. They all failed with a aftermarket y pipe.

 

well wish me luck im goin in January for the first time with my y pipe lol.... ill make sure my main cat is cherry red on the inside(dont know how to tell that lol)

 

depending on the smog machine they have, if it's ESP have them do a manual ASM test. Have them do the ASM15, and ASM25.

They'll input some info from your car like the yr, make, model, then they will run it on the dyno and give them the smog readings. If all the numbers are green, then you're golden. if they're red, you're fuked..

 

dang it, everybody here said that if your car is just warm enough it will pass with the aftermarket y pipe. A lot have passed with the Y tho, did you make sure you drove for atleast 15 min and didnt shut off the car before the test? What numbers were you getting for HC

 

Anyway to reduce the HC, I am no way putting that stock Y back on again lol it was a burden takin it off. IM close to throwing it away its just sitting in my backyard and my dad is gettin mad that its makin the house look like junk haha

 

I found the best thing to do in general even with a bad EGR valve is reset the code then drive it for 35 to 40 miles, then take it in. A mechanic told me to do this and I couldn't believe it, I passed. Even with a Y pipe and all kinds of other mods. I've never failed with the Y pipe but that was a damn good trick to know.

 

what if I aint getting any codes? Should I reset the ecu anyway?

 

No!

 

you wanna sell it?

 

Here in Cali they can tell if all your monitors aren't in sync. So the old reset my computer thing doesn't work here. I just passed my first cali smog last week, I just moved out here from Texas so this was kind of new to me. I put back on factory y pipe, with both orig. Factory cats ( the Y and reg Cat.) original with 349,000 miles I failed Nox. By like 140 ppm. I just ran Guaranteed to Pass through my car and everything worked out, I'm putting after mark. Y pipe back I this weekend.