Failed smog check

[omega2]

I got my 91 tested this morning after about 1 hour of driving on the freeway. I have a stock CTSC at 6-7 psi with factory injectors, comptech headers, random tech hi flo cats, and a uni air filter. I already know my car runs on the rich side (AFR approx 11.0 when last tuned), but the failure was at the NOX at 15 mph at 1689 rpm. My car measured at 856 ppm where the max allowed is 785 ppm. Strangely, it passed for CO%, HC and the NOX levels at 25 mph passed too (measured at 609 ppm). In fact, the tech drove a little faster and the car ran clean. They are telling me the cats may be bad, but they are less than a year old and only fail at 15 mph at 1689 rpm. I would think if the cats were bad, they should fail even at higher rpm.

Does anyone have additional recommendations regarding this?

 

[Daedalus]

Are you certain you were running rich for the smog check? Whare were your HC, CO% and O2%?

 

[omega2]

15mph rpm 1689
%CO2 13.8
%O2 1.8
HC (ppm) max 114--avg 31--meas 39
CO% (ppm) max 0.73--avg 0.10--meas 0.08
NO (ppm) max 785--avg 237--meas 856

25 mph rpm 2029
%CO2 13.9
%O2 1.6
HC (ppm) max 88--avg 20--meas 42
CO% (ppm) max 0.61--avg 0.09--meas 0.08
NO (ppm) max 724--avg 199--meas 609

My car was setup to run rich when the SC was installed. In fact the car stunk up their garage during the test. I think the cold weather today may have cooled off my car too quickly even while idling--not sure. That may explain the pass at higher rpm. I am thinking of also going in with new engine oil and air filter maybe an octane booster (using 91 shell gasoline). I assume it's something simple, since I haven't failed a smog test with this car before.

Reading the other post on the forum show more failed HC rather than NOX.

 

[Daedalus]

It's only marginally rich at most in cruise; the HC and O2% say as much. Both being a bit high does suggest the cats weren't working as well as they should have been. Possibly from not being hot enough, but you kept the car running between the drive and the test, correct? You said this is the 1st time you've failed smog, but that you replaced the cats less than a year ago. That's a change. Why did you replace them? HC and CO have very little to do with NOx, except that the cat should reduce all 3.

 

[omega2]

The car had to be shut down for about 10 min while I waited for the next guy to finish. I let the car idle for 5 minutes prior to testing and the engine temp was normal, but the cold morning probably cooled everything off better than I thought.

Decided to switch to the high flow cats when the headers were put in. My OEM cats looked pretty bad when they were removed and I was surprised I passed the first time with them.

 

[SexyRed]

From previous experience, my car pass with 1st gear 15mph, and 3rd gear 25mph. I have short gears w/CTSC.

25mph in 2nd gear was difficult to pass.

Danny

 

[Hugh]

Does anyone have additional recommendations regarding this?

Move. :biggrin:

 

[omega2]

Aside from the oppressive taxes, high cost of living, increasing unemployment, decreasing literacy, and the smog check, California isn't a bad place to live.

I also have the short gears and CTSC, so I'll see what gear they test at. I want to say he was in second gear but I am not confident since I was staring at the ppm readings on the computer monitor.

Ironically, they didn't even look at my engine nor wanted to see if the SC was CARB approved. So I passed visual inspection without the visual inspection.:biggrin:

 

[Hugh]

I'll bet if you posted this in a FI forums you'd have a real answer by now.

 

[SexyRed]

once again,
my car did not pass in 2nd gear 25mph.

 

[macspeed71107]

just move:biggrin:

 

[danny49]

Here in Florida we don't have smog checks, No state income tax, And no helmet laws, I love it here!

 

[Hugh]

Here in Florida we don't have smog checks, No state income tax, And no helmet laws, I love it here!

We need the helmet law reinstated. Since it was repealed, motorcycle deaths are up almost 50%. Some laws are good laws. Helmet laws are amongst those laws.

SexyRed, sorry to hear it. Do the people at the smog stations take bribes? :biggrin:

 

[Daedalus]

The car had to be shut down for about 10 min while I waited for the next guy to finish. I let the car idle for 5 minutes prior to testing and the engine temp was normal, but the cold morning probably cooled everything off better than I thought.

Decided to switch to the high flow cats when the headers were put in. My OEM cats looked pretty bad when they were removed and I was surprised I passed the first time with them.

The "engine temp" is really the coolant temp, which says very little about cat temps. Cats are just thin sheet metal and will cool down hundreds of degrees in 10 minutes, much quicker than the cooling system. It's important to get them hot for smog testing. At 500*F they may only be 50% efficient; they need to be anywhere from 900-1600*F to be 100% effective. I would question whether idling can even get them to 900*F. The steady state incoming pipe temp to the rear cat (external) is only ~400*F at idle (stock). There will be an increasing temperature gradient to the substrate, but it's near certain the entire cat is not at 100% at idle. You need to rev it up.

Also, the effectiveness of a cat is related to its surface area. By definition a high-flow cat will be less effective than a stock cat at any working temperature. If you still have the stock cats it wouldn't hurt to throw them on for the next test. That said, I think it's more important to get the cats nice and hot prior to testing. This is probably why the car performed better at 25mph...the cats were hotter at the start of the 25mph test than they were at any point during the 15mph test.

Based on the test RPMs (plus shorties) they tested in 2nd gear @ 15mph and 3rd @ 25mph.

 

[omega2]

Thanks for the input. I figured it was the cat temp dropping due to only one failure. I will retest on Wednesday or Thursday afternoon where I assume it won't be cold and rainy.

 

[nis350]

Thanks for the input. I figured it was the cat temp dropping due to only one failure. I will retest on Wednesday or Thursday afternoon where I assume it won't be cold and rainy.

Just curious how many miles you have on the RT cats? If you are running rich constantly, I think it is bad for the cats.

 

[Cozmo]

I don't know how your state does the test but here in WA I drove my car on the rollers myself. I don't know if that is normal of if they were afraid to mess up my car or what.

IIRC all they did was test @ idle and 25mph.


I have the short gears and RT cats as well and passed just fine. Of course not having the CTSC is a huge difference.

I never shut my car off before the test though.

 

[nsxotic911]

..This may sound dumb/risky, but if you're running rich, why don't you put a slightly lower octane in the car during that time It won't be at boost...right?

Also, I've had great luck with http://www.rxp.com/

 

[Qucumber]

Cats need to be REALLY hot to be effective. My thought is that cats only deal with NOx emissions. Running rich will affect your HC content. Running lower Octane will not improve HC or NOx.

 

[hypermotard]

Check and make sure the EGR system is functioning properly.