I just went to the smog ref today, and my car's hc and oxides of nitrogen were too high on the 15mph test..Any of you guys have any pointers on how to drop those down to passing levels?
94 ls motor, hc at 101, 89 max to pass, no at 1753, passing for that is 708, less than half of what my car is putting out..
the 25mph test was ok, 45ppm hc and 481ppm NO...wtf..

Can I pour something in the tank..?

 

if i remember correctly HC's r unburnt fuel...try changin ur spark plugs or somethin wit ur spark

 

yeah, make sure your spark plugs is gap correctly. also, use the highest octane rating and clean your throttle plate(the one inside your throttle body). and make sure your o2 is ok and not bad. hope that helped.

 

new plugs, new 02, it's basically a whole new motor, I finally put over 1K miles on it coming back from the ref. He told me my cat might not be broken in enough, since it only has about 100 miles on it. I mentioned to him that I had some concerns about its legitimacy, since it's a kragen special, but he said it should be fine, and he can tell that it is working from the other numbers on the test. So maybe that will break in a little more and solve the HC, but I still have no idea about the oxides of nitrogen. I know that is a function of combustion temp, but I have no idea why my motor would be burning exceptionally hot..wtf.. The ref also said that he sees that all the time with hondas, again wtf. I though hondas were all super ultra low pollution and whatnot. I know how gm solves that though, egr.
My TB is spotless. My timing was supposedly at 17 deg. I might try backing it off to 15..
Any recomendations as far as a brand of nice clean burning gas? I might try that 'guaranteed to pass' **** too..

 

Cat is not warming up quick enough is your problem. Aftermarket cats do take a 30 seconds to warm up at 2000 rpm. If he let your car idle, the cat cools off then he did the test. You probably have more o2 left over at 15 than 25 correct.

Run 87 octane, or what the manufacture specifies is the rule.
Also if where he is testing is over 72 degrees he better be using a fan in front of your car. If he didn't this would raise your temps/Nox and raise your Hc because the ecu is trying to cool off the motor with gas.

There you have it!

 

Any recommendation on what timing to run? High side/low side of the stock spec or in the middle? Or would it even matter that much?

 

You can go retard as much as 2 degrees so if spec is 17? go with 19. But make sure it is 19 exactly.

I would go with spec. My opinion.

And no additives in the tank...Please.

 

thesmogman, I appreciate your responses, so don't take this the wrong way and get offended, but you're saying the car will idle richer than stoichiometric if the motor is hot enough to turn the cooling fan on?? I'm a little skeptical on that. Actually very skeptical..

As far as the 02%, it was 1% at 15mph and 1.6% at 25. So I don't have more 02 left over at 15..and even with the higher leftover 02 % at 25mph, the rest of the emissions were still lower, low enough to pass with some margin.

Also, you just wrote you can retard as much as 2deg, but then you recommend 19, which is 2deg advanced..wtf..?

Maybe my plug wires or injectors are a little retarded..I'm running obd-0 injectors with the factory resistor box my car came with.

And I was running 87, and they did have fan in front of the car. The thing I don't get is anything I do to decrease the nox will increase the HC, by lowering the combustion temp.

 

If he didn't use the fan it would heat up too much for the fan on the radiator to keep it cool so the fan on the radiator would keep running and your temp would be, say 220 when 190 is normal yes the ecu would add gas to try to cool it down.

Your 02 readings are high unless you have an EGR or Air injection. You should see
0.1 at 15 then 0.0 at 25 this is normal for an engine without the EGR and Air inj.

spec is 17 BTDC so 19BTDC would be advanced (I got interupted and just started typing SORRY!)You are right. I am corrected, Damn! But I do recommend spec.

If your O2 readings are correct the cat is the problem unless you have an exhaust leak. Give it another week to cook and see.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thesmogman &raquo;</TD></TR><TR><TD CLASS="quote">If he didn't use the fan it would heat up too much for the fan on the radiator to keep it cool so the fan on the radiator would keep running and your temp would be, say 220 when 190 is normal yes the ecu would add gas to try to cool it down.

Your 02 readings are high unless you have an EGR or Air injection. You should see
0.1 at 15 then 0.0 at 25 this is normal for an engine without the EGR and Air inj.

spec is 17 BTDC so 19BTDC would be advanced (I got interupted and just started typing SORRY!)You are right. I am corrected, Damn! But I do recommend spec.

If your O2 readings are correct the cat is the problem unless you have an exhaust leak. Give it another week to cook and see.

</TD></TR></TABLE>

correction 94ls engine: b18b1 specs: 16 BTDC

at 19 BTDC he is really advanced which the ecu is compensating for the lean condition by adding extra fuel to the mixture.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thesmogman &raquo;</TD></TR><TR><TD CLASS="quote">If he didn't use the fan it would heat up too much for the fan on the radiator to keep it cool so the fan on the radiator would keep running and your temp would be, say 220 when 190 is normal yes the ecu would add gas to try to cool it down.</TD></TR></TABLE>

So in other words the motor would run hotter when being cooled by only the electric fan, ie, not by air being pushed through the radiator when the car is moving? And this would be reflected in my coolant temp guage? I suppose that's why my fan only cycles on and off sporadically, somehow effortlessly keeping my temp needle at the exact same level as when I'm doing 80 down the highway?

 

try fixing your timing, if not retard it some
KNOX= pressure and heat , over advacing timing willgive you high knox, carbon build up. vaccum leaks . also wrong heat range on your plugs will cause high knox ..

and what htey mention is right if the ecu sees to much cylinder tem it will give it more fuel . there raising your HC.
HC's = misfire & unburnt fuel


Modified by Smoke_em at 7:50 AM 6/22/2006


Modified by Smoke_em at 7:51 AM 6/22/2006

 

I think you got it. Most smog shops are caves, mine is to so a fan is necessary above 72 degrees.. I wish I could do the smogcheck at 80 so it would be cool.(temp) Actually your rad fan is not needed at 80 and your thermostat is keeping the guage steady. Its mostly at speeds below 40 your fan is needed. Now try driving at 25 with no wind at all. Or say idling in a closed garage at 125 degrees which is how hot my shop was yesterday with a car in there.

So spec is 16, I would stay there. That is what your computer is believing you have it set at, and designed for.

Don't worry about the questions, I like it! I like to inform everyone that is curious.

 

Maybe you didn't get my rude sarcasm..but I think the smog places use the fans a lot more for their own comfort than for anything to do with the car..

Well, it turns out that all of this discussion might not actually be applied to my car, because I should be out of california in a few weeks..no smog where I'm going. time to start putting my slowly accumulating pile of parts on, starting with that holset turbo yoinked from a cummins diesel..

 

here is something i am wondering about though, has anyone ever noticed different emision levels based on their piston design? I have endyn forced induction rollerwaves.

 

Let me just say first a fan is required above 72 degrees by the state. Not for the smog tech. It has to be 6 ft away from the car too.

Blowing up radiator hoses, and cleaning up the floor with coolant is not fun.

I wish you luck, and enjoy not having to smog, I would.

 

 

every car i test that fails HC and NOx likes the timing retarded as much as possible. i had to pull ALLOT of timing in my car to get the turd to pass....

if the factory spec is 16deg BTDC try setting it around 8-10deg........you will see the readings drop by quite a bit......

 

So very true........ retarded timing does very well with some MTBE additive.

 

How old is the O2 sensor? I had a vehicle that was a gross polluter, checked the signal with a Vantage and sure the signal was dead causing GP levels, put a new O2 sensor passed with flying colors. On OBD1 equiped vehicles if you have a lazy signal or dead O2 you won't get a CEL. you're running lean at 15MPH this is where the dyno puts more load on the rollers. if you need more help email me qfactor85@hotmail.com if you where in Woodland Hills CA, I could personally help you.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rorik &raquo;</TD></TR><TR><TD CLASS="quote">here is something i am wondering about though, has anyone ever noticed different emision levels based on their piston design? I have endyn forced induction rollerwaves.</TD></TR></TABLE>

Yes.