Hype

Welp, I'll start off by saying I failed. Here's what I've got:


Driving Test :

HC (ppm) MAX: 199.00 / Average: 28.00 / ME: 153.00 (PASS)

CO (%) MAX: 1.34 / Average: 0.04 / ME: 5.22 (!!) (FAIL)

NO (ppm) MAX: 1971 / Average: 671.00 / ME: 259.00 (PASS)


Idle Test :

HC (ppm) MAX: 348 / Average: 80 / ME: 316 (PASS)

CO (%) MAX: 4.00 / Average 0.03 / ME: 3.13 (PASS)



Well, there you have it. I will note that I am now running SLP headers /w dual exhaust, Y-piping right before the rear axle and exiting through a Borla Muffler. There is no catalytic converter on this vehicle. Last year, with the original exhaust setup in my sig. and rotten-through catalytic converter, I passed, although barely, with the driving test CO coming very close to the limit. (1.32 it was, max 1.34). I have owned 3 different cars with decent cams, no cats, that have all passed before, one with a Holley DP sitting on top of it.

There is no visual inspection here, just the sniffer.

I find it odd how the CO will pass at idle, although it is somewhat higher there is room to spare, where as it is through the roof on the driving test, where they hold the car at 45 KM/HR (30mph or so) on rollers.


I believe the ignition coil is ANCIENT, so I will start there. Will backing off the timing, swapping in stiffer springs etc. help? It seems to me as though an advanced timing curve would help emissions, but thats not how they come from the factory, so...

Will leaner jets help? I have a non-CC Qjet that came stock on this car, as it is a Canadian car. This carb also has 250,000 KM on it, so maybe its time for a rebuild.

Anyone? I have been searching through the archives on this one, but have not found anyone with high CO on the driving test, as opposed to the idle test, which is the more common grounds for failure. My insurance is up in two days, any help would be appreciated.

Thanks,

pauldaniel26

Why not just put cats on? I'm almost positive you'd pass if you put a cat on.

Hype

Well, I am actually leaving the country for a year in 3 weeks, and was planning on letting a friend drive the car for a couple of months.

I don't think slapping one cat on where the y-pipe joins towards the rear axle would be effective, seeing as how it would be placed an additional 3-4 feet back from where the stock cat sits.

Dual cats? $$$$$. I am saving here for my trip. I have got by before without them several times before, I am sure with some tuning I can do it again for less $$$. By the way, besides the car I am driving now, I have never removed a cat from a car before myself, they just seem to come that way, damn hicks. =) There is no SOTP power difference, so to all those out there considering gutting your cats, don't bother.

Mark A Shields

Yup, a cat converts CO to SO2 if I'm not mistaken.

darbleinad

you are mistaken. a catalytic converter converts carbon monoxide (CO) and unburned hydrocarbons to carbon dioxide (CO2) and water. they also convert NOx to elemental nitrogen (N2) and oxygen (O2). sulphur dioxide is a harmfull pollutant as well and diesel powered vehicles emit much more SO2.

Mark A Shields

I'll take your word, but how come I've heard when a cat is working properly overtime, you'll smell an egg smell, thus SO2. or is that just S.?

darbleinad

hmmm...i have never heard the thing about the rotten egg smell, but cars do produce sulphur dioxide as one of their emissions.

rezinn

WTF Mark. Didn't you take chemistry? CO -> SO2? I don't think so buddy. You need sulfur to make sulfur. BUT gas does contain sulfur, so yeah our cars pollute not only with NOx, CO, HC, but also SO2. A catalytic converter will definitely help to get rid of carbon monoxide, it turns that into CO2.

Hype

I understand adding a cat would most likely hack both my HC and CO readings right down, but what I don't understand is why it skims by the idle test, yet only fails the CO test when on the dyno, and not by a little amount, by a HUGE amount.

It's weird. I'm studying my neighbours recent Aircare data on his '72 Camaro, (true duals, no cats) and the maximum allowable is not much higher than what I am allowed, yet his actual readings are FAR lower than what my car records.

Something is out of tune. Exhaust work is the most expensive route out, and does not mask the fact that something in the engine is not running right. It is running far too rich, or the mixture is not being burned properly.

Cap, rotor, leads are new. I guess I will pull plugs and check 'em out for signs of richness. I imagine a new ignition coil will work wonders, seeing as how thats how I managed to get my cat-less '81 T/A to pass, as it failed the same aspect of the test last year.


Can anyone tell me what effect total timing (less the vacuum advance) has on emissions? Seeing as how my car came set stock at 4*, and had springs in the distributor stiff enough to support the weight of the entire car, I would imagine this has some sort of effect, although it seems to me that a more aggressive curve would benefit emissions.

Oh yeah, I forgot to mention that I was running a 160* t-stat. SMACK. I will put the 190* back in tomorrow.

I will post back what I find, hopefully to benefit some poor smogged-out schmuk in the future.

Lates.

Mark A Shields

Well, let's see 10th grade Honors Chem class with a teacher from Boston, so my name was Mac. I left that class early so many times, couldn't stand it.

90Formula-X-F

On the very top of the carb there is a metal plug that gives you access to the metering rods. You can bring down your cruise mixture there "CO" and the "HC's" will come down also. As you do this though the NOX will probley climb due to the fact that your leaning out and increasing your combustion temps. If you have EGR or the ability to run it I would hook it up and that will help keep the NOX down too. This is your best bet to try first. If your going to run a cat, even if its new, an air pump would also be in order to add more oxygen to the burn to keep the unburn't fuel ignited, other that that you'd need to remove it or you'll burn it out right off the bat.

Hype

Am I dense? Where is this plug? I am looking at an exploded diagram of the Qjet and man, is it exploded.

I assume I am going to have to yank the top half of the carb off to get at this thing, or what?

Hopefully I'll learn something out of this.

Lates.

Hype

By the way, thanks for all the replies.

90Formula-X-F

Sorry I'm late, I brought my Firebird back to life tonight after being down a few month's .. Lotsa mods and more horses.. But anyways... As you look at top of the carb in the picture you have. In the front half... top, close to the center and partially covered by the air cleaner housing gasket. A silver plug about the size of a dime.. This is the one.

Find a short self tapping screw.
Then get a drill bit thats alittle smaller than the screw.
Drill a hole in that plug, all the way won't hurt.
Insert the screw the hole.
Use a pair of dikes or something to pop out the plug.

The screw to adjust this might look strange. It's like a pole
with flat edges on 2 sides or what's called a double D....

Since your at home, I would recomend using a long valve core remover for tires. The kind with a screw driver handle. It should be easy to find one.

Turning counter clockwise should lean it out but.. Good luck ....