Need some smog help

Had my introduction to the wonderful world of the CA smog check today. Unfortunately, results were not what I had hoped for. My 1992 Miata is apparently a gross polluter.

Results below - what does this look like to you? It seems to have been close at 25mph, but failed badly at 15? I haven't checked the timing but I have a suspicion that a previous owner advanced it, and I should probably reset it to factory spec.

At 15mph (1844 rpm)-

%CO2 = 14.1

%O2 = 0.8

HC = 231 (max 94)

CO = 0.74 (max 0.58)

NO = 2070 (max 847)

at 25mph (2198 rpm)-

%CO2 = 15.4

%O2 = 0.2

HC = 57 (max 76)

CO = 0.27 (max 0.49)

NO = 1870 (max 786)

New cat? I just did the timing belt and all of the seals, as well as installing a stock header and intake, so it's in decent running shape. Help?

Cat would be my first guess. I had similar NOx numbers last year on my sniffer test and it was due to the hollow cat. 

Oops.  Wrong Thread.  Continue. 

Retarding the timing back to stock will help with the high NOx.  Non-working EGR will also probably high NOx, but IIRC there is no EGR on the 1.6 so that's not a factor.

High HC with non-zero O2 means that the cat isn't working as well as it ought to, because it should be using up all of that O2 to burn off the HCs.  High HC with zero O2 means that it's running too rich, and there isn't enough O2 for the cat to do its job.  You have non-zero O2, so that points to the cat being a problem.

How warmed up was the car when you smogged it?  Cats work better when they're hot, so you stand a better chance of passing if you bring the car to the smog station after a nice long drive and have it smogged immediately (no sitting in the parking lot for an hour).

Try to make it clear with the smog place whether you can come back for a retest. I've found the prices and policies to vary from place to place. Ask if you have to pay the full amount again if you have to come back basically.

In no particular order, basic tune up items are good to do. Either inspect and clean or replace is fine. Spark plugs, wires, air filter, fuel filter, oil + filter, set timing to stock (+/- a few degrees will change the emissions ^HC vNO or vHC ^NO IIRC).

The cat might need replacing, but I think a new cat can also be a band-aid fix to pass even without a tune up. As said earlier run the car on the highway first and leave it idling at the smog place to keep the catalyst as hot as possible.

It just occurred to me that I put a high flow cat in this car last summer. That could have something to do with it?

Thanks for the other suggestions - I will definitely check the timing. Plugs and wires were just changed, along with the air filter when I had it all apart for the timing belt. You're correct that there's no egr on a 1.6.

The car was fully warmed up but definitely not hot - maybe I should autocross tomorrow then drive directly there

cmcgregor said:

It just occurred to me that I put a high flow cat in this car last summer. That could have something to do with it?

 

It will not pass with a high flow cat period. It will pass with some of the replacement cats from some of the miata vendors that are direct replacements.

To get mine to pass I had to go stock cat, OEM timing and new O2 sensor with about the same readings.

Yeah....I had a feeling that would be the case. I forgot about it until I was looking through maintenance records.

Next question - how different are CARB approved cats vs their generic equivalents that cost half as much?

There are ebay test pipe things marketed as cat deletes, spun metallic core high flow cats with different cell densities, and then the standard universal replacement ceramic/precious metal cats which is what I'd consider the Magnaflow high flow universal cat to be. The cost of an OEM cat vs universal replacement has to do with how much valuable metal is used to make it and how long it lasts. As far as the 50 state vs 49 state, I am not aware of what the technical difference is. How well they all work relative to one another I'm not sure.

In reply to cmcgregor :

Probably not any different other than having an EO number etched into it, but EO numbers are required for aftermarket emissions equipment in CA.

The EO simply shows California has done testing on the equipment to ensure its is infact equivalent to the OEM cat. It's required for all aftermarket emissions equipment and you will fail the visual portion of the test if it isn't present. 

Catalyst first, O2 sensor second. The numbers tell me that there isn’t much on that cat since it is almost dead at 15 and kinda dead at 25. 

High flow metallic cats are so overrated to me. They flow a little better but weight a lot more. Let alone are poorly made and barely work. 

GRM did a nice comparison on various cats and a straight pipe. The end result is just put a good normal approved catalyst on the car. Almost no power loss. 

High flow cats are worthless after the first test.  There's a reason why OEM cats costs thousands and high flow ones cost a few hundred.  The high flow ones just don't have enough heavy metal in them to work more than a few months. 

On my LS converted 944, I had to buy the biggest magnaflow cats I could find and I V banded them.  Since that car was mostly a track car I didn't want to melt the cats while on track.  When I put them in, the car would literally fast pass on the rollers when it was smog tested.

The first set of "high flow" cats barely got it to pass the first time and then it failed miserably the second time...

nobody is suggesting the old alcohol in the tank trick?  we used to use that to bring the numbers down because alcohol burns cleaner than gas.  We used to dump in a bottle of rubbing alcohol then drive for a bit and go get tested.  Thankfully IL no longer tests cars older than 96 so we don't need that trick anymore.  Funny thing is, when I had my old carbed Camaro, I had removed all the emission stuff besides the 17 yr old OE cat and had a CAM, intake manifold, and Holley carb on it.  It passed better than most of the new cars, darn near zero emissions.

In reply to Brian :

I've heard of that as well. Interesting, but the bottom line is that I'd like for the emissions equipment to actually function as intended. I'll just get a cat with an EO number - I didn't fail the visual the first time with this high flow cat from a reputable Miata vendor and I do have one free retest within 30 days, but better to just do the right thing now.

I have no idea when the O2 sensor was last changed and this car has 230k on it, so I'll probably do that too just to be safe.

Thanks for all your input - I had assumed that since I was following the letter of the law in my previous state, the car was actually not polluting. Interesting to find that that was not the case.

It does sound like a cat issue, but I disagree that you can't pass with a decent quality high flow cat. I've passed for years on many cars with high flow cats. That fact that it's only a year old has me thinking that you should be able to pass with it, unless you have been running around with misfires that killed it. 

I'd check the plugs and wires, and make sure the car is good and hot  before the test- really beat on it. Is the cat and exhaust larger diameter? I know of lots of people who have had a lot of luck putting a restriction in the exhaust after the cat for the test- usually a plate with a 1" hole instead of a gasket. 

Now, I do agree that aftermarket high flow cats don't last as long as  OEM, but they don't usually wear out in a year. Shouldn't be any problem on an otherwise well running car. The aftermarket cat on one of my cars is over 15 years old and it passed with flying colors last time. 

As for legality- I believe any OBD2 cars are required to have the OE cat or a certified OE replacement. Pre OBD2 cars are grandfathered in, since many cats were replaced before the law went into effect. If you change a cat on a pre OBD2 car today, I believe it's supposed to be OEM, but they really wouldn't know when you replaced it. But it would be tougher to find a shop willing to install it.

Edit: I did some checking, and learned that if you had a cat changed before the 2009 law change that requires the OE numbers, then you are supposed to have a record of when it was changed with a note from the shop on why it was changed. So technically on my 1992 car where the cat was changed in 2000, I should have predicted that the law would change in 2009 and saved my paperwork and had the shop note that the OE cat was damaged by road debris. Good thing no shop really cared during my multiple smog checks since. 

I think a well running engine can burn clean with no cat or just about, and likewise, a dirty engine spitting raw fuel can burn clean with a brand new cat or at least a working one. When we need to pass are the smog numbers are relative, absolute, or arbitrary? In other words I have a hard time believing that an "old" 1.6 L pollutes more than a "new" 5.0 L. You can get into the scientific details of emissions but how much fuel you burn, how much power you make/use, how heavy the vehicle is all translate to CO2 emissions - a major greenhouse gas that raises the temperature of the whole planet. Not to go on some 'political' thing but I think most here that have ever welded understand good and well that more CO2 = more heat. The bottle was left open and the gas doesn't leave it just hangs around in the atmosphere. The globe is going to cook from too much CO2, and smog tests or catalysts bolted to the exhaust aren't going to change that.

I would like to think that the CA cats are somehow better but all I know is a universal cat can be had for around $50 while CA cats are closer to $300 to pass smog. Without evidence to suggest otherwise who knows if that price difference is 100% bureaucratic. My skepticism comes from pushing cars into the crusher to replace them with new regular gas engine vehicles forcing people to spend money under a possible false pretense of the cars being cleaner. Instead, what is more appropriate, an actual overhaul to get with the times and make vehicles be actually zero emissions. Don't dilly dally around basically. Scrap the cars and being in new lightweight electric vehicles that are appropriately sized to mitigate the increasing traffic problem or nothing. Don't pretend like you're saving the environment while making new petroleum engines at the same time. For 2020 we need a 980 pound 2 person transport with 200 mile range for <$15k. People need to appreciate the importance of getting the most amount of value and work for the energy spent, which is pretty much totally counter to 'bigger is better' and wasting oil as fast as you possibly can. We are hesitant to change for various reasons but that's what we need IMO, stop the presses, not a complicit snail's pace. Fix or repair daily are you listening? The 1989 Taurus was way better than the 2005.

I (naively?) think we can still have machines do most of our work but we need to ramp up renewable and taper off the petroleum ASAP. Round up all the fracking equipment and miners and hand each one a windmill or solar panel instead. The investors can get lost but I know they won't go away. Very quickly becomes a geopolitical war issue I suspect which IDK.

Cars won't pass modern smog requirements with no cat.

In reply to cmcgregor :

It's not you it's California's emissions rules and the apes that pass as certified emissions station inspectors in some instances.

Things can get kind of sticky there because, while the rules are clear in some instances, others are left to interpretation. Ever have an argument with someone about if silicon couplers to the intercooler and thick walked vacuum lines count as "modifying emissions controls" (as part of the intake, ECBS, and evap systems)? I have. 

Not saying this is good or bad, I certainly can appreciate what they accomplished there, but some inspection stations will make you want to murder something cute out of spite.

In reply to plain92 :

No well running engine will pass this test without a catalyst. But you are right that a crappy running engine with a new car will also not pass. What you will see is a bias toward CO/HC or to NOx. With all of the gasses high, I see that as mostly a catalyst problem. 

Update time!

I got a replacement CA legal cat from rockauto (much cheaper than expected), replaced the plugs, wires, and 02 sensor, and reset the timing. The timing was a bit of a mess - the marks seem to have slipped on my pulley, so that will be replaced in the near future. It was FULLY advanced - like 20 degrees. As far as I can tell, the car lost zero power moving back to stock timing, and now I can probably run regular gas without the occasional pinging I was experiencing.

It passed easily and the station I went to (Berkeley smog test only) was awesome. Fast, easy, and able to do all of the registration paperwork as well. Now I'm legal!

Excellent news.

I once passed emissions with no cat and 6 year old gas.  Including that time, there has been no rhyme or reason to pass/fail here.  I’ve failed on new everything.  It’s nice to see someone take the proper steps and actually pass for a change.  

In reply to cmcgregor :

Great! The timing probably didn't help things but it's good to hear you were able to do it semi easily and sort of inexpensively. The STAR stations are generally pretty easy to work with and it's always a hassle when you get referred to a referee after failing a few times.

In reply to cmcgregor : if you use gas with high alcohol percentage it helps 

Patrick said:

Excellent news.

I once passed emissions with no cat and 6 year old gas.  Including that time, there has been no rhyme or reason to pass/fail here.  I’ve failed on new everything.  It’s nice to see someone take the proper steps and actually pass for a change.  

It all depends on what the goal is.  For many model years, and many test states, the requirement is basically a good (not great) running engine.  Nothing else.  For this, it was targeting a well aged full emissions set up- working catalyst and all.  That's why it's always important to post not only the results but the limits as well.  All of that helps figuring out what is going on.

frenchyd said:

In reply to cmcgregor : if you use gas with high alcohol percentage it helps 

 

California has very limited fuels available. And gas is all E10.  

(as a side note, I really wish the rest of the country had such limited blend choices available- it would actually benefit the environment as a whole, since there would be no bad fuels out there)