ajsfirehawk

iTrader: (4)

So are you pointing to failing or poor quality O2 sensors? Is one brand versus another noted for shorter switching speeds? I think I'm following the concept, it is back to Jimmyblue's point that the PCM is 'chasing' the slow switching and chasing back and forth between rich and lean. What would be the action plan to fix?

joecar

Ok, I looked at some of my logs (I passed CA smog in Oct 2009)... my front O2's are switching at 0.2-0.3 seconds per cycle.

ajsfirehawk

iTrader: (4)

Are you running long tube headers? What would cause lower switching speeds?

joecar

No, I got the stock manifold at the moment.

WeathermanShawn

iTrader: (1)

OP, I run the Rear Corvette O2 Sensors up front. I also have headers and high-flow cats. When I originally lived in the emissions testing zone I passed with flying colors (220/220 114 cam) utilizing the above O2 sensors.

You will various reviews on differing O2 setups. The bottom line is they tend to get dirty and fail easily. The farther displacement away from the original manifold location, also tends to skew the temperature and switching ability of the O2 sensors.

You just have to replace them more frequently. Not that much money. It may or may nor be the cause of your fail. But, it is an easy fix. If you are running closed-loop you need them to properly maintain stoich anyway.

I would try the easy fix first. Good luck..

ajsfirehawk

iTrader: (4)

What prompted you to use rear Vette O2 sensors on your car?

WeathermanShawn

iTrader: (1)

I think it was the longer harness length..I forget the exact dimensions, but they were easy to hook up and did not require extensions.

Whether their ability to 'heat-up' is really any better than the stock O2's have been widely debated. Primarily convenience..so far they have lasted several years. My only issue is one that is common with long-tube headers..they are just simply farther away from the stock manifold, so they tend to run 'colder' than stock location.

But, the bottom line is that for me they worked.

Hope that helps..

joecar

My LT's are ceramic coated (IDK if this makes a difference), when I run them the O2's seem to switch ok (I'll dig thru my logs... I run mostly OLSD tho, so it may be hard to find some CL logs with the LT's).

ajsfirehawk

iTrader: (4)

My QTPs are ceramic coated as well. Just replaced O2's with Bosch 13111s, new set of NGK TR6's gapped to .055, drove it for about 15 minutes and took it back in. Now I've easily passed the HC and CO2 checks, the limit on NOx is 1.500, I came in a 1.579. Failed me. Huge difference in results, but a whisker short of success.

ajsfirehawk

iTrader: (4)

Since I only failed the g/ml test by .079 on the acceleration portion, would higher octance fuel or an additive buy my even a teensy bit on the NOx??

joecar

Maybe drive it for longer than 15 minutes, get the cats hotter...

Which cats do you have and how many miles on them...?

ajsfirehawk

iTrader: (4)

Magnaflow bullets, metal substrate. About 4K miles on them. 12 months old. Most of those miles on the 2009 Power Tour and the trip I took to Kansas City last week. Complete pain in the a$$ at the testing facility, there is always a wait, so the car cools.

WeathermanShawn

iTrader: (1)

I would call one of the facilities and talk to a manager. Explain that excessive wait time is cooling off your cats and making the test ineffective. Request assistance in scheduling and ask for expedited service.

You will be surprised how a little bit of diplomacy and flexibility on your part will help. If all else fails you can always locate one of Denver's drive-by smog vehicles (Air Care Colorado?) and do a pass-by. Thats always a little harder to successfully pass, but those are some ideas.

If all else fails, get a mail drop..Legally of course.

Good luck. I bet with your cats warm you can pass..

joecar

Show up first thing when they open midweek, leave your engine running while they startup their test equipment (don't let them shut it off).

Schwanke Engines

iTrader: (1)

You could also try topping the tank off with E-85. Not more than 20%. It should lower the NOx, right guys.

joecar

Would that cause combustion chamber temp to be cooler so it will create less NOx, is that what happens..?

WeathermanShawn

iTrader: (1)

Hey its worth a shot. You probably have more experience in knowing how E-85 affects emissions. I have stayed away from it just from the change in stoich AFR, but thats another issue (unrelated).

I really think they will accommodate a reasonable request to keep the car running and keep the cats warm. But, OP any 'trick' you can legitimately use I would go for it..

ajsfirehawk

iTrader: (4)

I gave in and bought the EFI Live tuning software to go with my scan tool. I've contacted the original tuner, he will ship me the stock tune, then I can flip between the factory tune and the performance tune. I'm failing the NOx on acceleration, that is where the AFR goes fat. It normally runs at Stoich, but >65% or 70% throttle position sensor open it drops to 11.3. I suspect the extra fuel has some cooling affect, but still, more fuel will result in more emission. Wish me luck. This way I can tune out the rear O2 sensors, adjust my cooling fan operating range....lots to learn now.

joecar

Don't forget to visit the EFILive forum.

Schwanke Engines

iTrader: (1)

Sounds like your PE enable table needs to be adjusted to 90% for the Test. You could also try to take some spark out of it to keep the cats hot.

Joecar, yes, that would be the theory.