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Thread: How to pass smog

  1. #1

    Dr_Snooz's Avatar
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    How to pass smog

    Disclaimer: This thread is intended to help individuals having trouble passing smog. It's meant to help you avoid expensive repairs while still keeping your smog emissions within legal limits. Dr_Snooz encourages you to keep your engine stock and in top running conditionÖalways.

    I know that our cars are getting older. As they age, they emit more smog. Eventually, the car fails a regular smog check and suddenly the shop opens your wallet and empties it. Or at least it tries to. What will most likely happen is that youíll send the car away to the crusher, shell-shocked by how expensive it all got so quickly. It doesn't seem to matter how well the car was running before. Shops know that failed smog checks are their big meal ticket. You don't know what all those controls do and can't call their bluff. So they quote you something obscenely expensive (valve job, new engine, etc.) and you either pay it, or find a new car.

    Some of you want to mod your cars. The smog check frowns on this, so you mod your car and then have an illegal smog check done. This is silly.

    A bit of background
    It's silly because both you and the smog check are on the same team. A properly running engine will produce fewer bad emissions. Most smog controls are designed not only to reduce emissions, but also to help the engine run better and longer. For instance, the PCV system not only reduces crankcase emissions, it helps to prevent sludge from building up in your block. EGR not only reduces NOx, it helps to prevent pinging. It is in both your and the smog checkís interest to keep these controls working well.

    What's more, a typical internal combustion engine runs best within a very narrow fuel mixture range of ~14.7:1. It doesn't matter how much you mod your engine, you still want the fuel mixture being delivered to the combustion chamber to be somewhere around 14.7:1 and you still want that to be burned completely before being blown out the tailpipe. (Forced induction setups, like turbos or superchargers, might require a richer mixture. I donít know much about getting forced induction through smog and suspect the big snag there will be hiding the hardware from the smog tech.)

    Theoretically, if you deliver the right fuel mixture to the engine, burn it thoroughly and have all factory emissions controls working properly, you can pass any smog check, no matter how extensively you have modded. Illegal smogs are counterproductive for two reasons. One, they allow you to run a poor tune. This is bad both for the air and your engine. If youíre running too rich, youíre allowing unburned gas to wash down your cylinder walls, dilute your engine oil and hasten the early death of your engine. Not good. If youíre running too lean, you will get preignition misfires and again, the early death of your engine.

    Two, illegal smogs allow you to mod like crazy. When your shop gets busted, you are suddenly in a world of hurt, unable to go back and unable to get your car registered.

    How to Mod your engine
    You are a man, after all. You can't buy a car without wanting to make it go faster. Even if you arenít a speed demon, sometimes you need to replace a stock part, but a replacement is not available or is too expensive. The factory 3g carb is a case in point. It's okay. You can mod your engine without having to resort to illegal smogs. The California Air Resources Board (CARB) maintains a list of California Smog legal modifications. Before you plan any mod, visit the site and see what smog legal options you have. There are quite a few for most cars.

    http://www.arb.ca.gov/msprog/aftermk...es/amquery.php

    You should use approved parts wherever possible. That isnít always possible though. The good news is that if you buy a non-approved part, you can still pass smog. Itís just more difficult. I feel that it's better to buy a non-approved part and blow clean than to do an illegal smog and blow dirty. Know that if you buy non-approved parts, you have a likelihood of failing smog. You can still pass, but the parts should be pretty incognito.

    How the Smog Check works

    The smog check has two parts.

    1.) Visual inspection - The first part is a visual inspection. In the visual portion of the inspection, the tech will look in your engine bay to ensure that all the factory emissions controls are there and, at least from appearance, still connected and working. The specific components that came on your car are listed on the underhood label. A list of all possible components is available here (http://www.autorepair.ca.gov/80_BARR...quired by law). The tech might also look for non-legal smog parts, but itís not likely he will. Itís even less likely that he will know which parts on your car are not stock, unless you have something really wild, like a green anodized turbo manifold. The tech will also check your timing in this portion of the test.

    In most cases, if your mods arenít really drawing attention to themselves, like painted pink neon or the like, then they will not be noticed in the visual portion of the test.

    2.) Tailpipe sniffer - The next part is the tailpipe test. California tests for three substances in your emissions, HC, CO and NOx at two speeds, 15 and 25 mph. There are specific allowable limits for each of the gases and if you go over on one, you fail the test. These constituents are inter-related. As you reduce one emission, another will go up. For instance, as you reduce HCs, your NOx will go up. This, obviously, allows for a little wiggle room if you are marginal on one gas. If you are just over on HCs, but fine on NOx, you can lean out your mix slightly, pushing up NOx, getting you through the test. You are shooting for a nice balance of the three. As I said, every engine runs optimally with a 14.7:1 air/fuel ratio. It doesnít really matter what mods you install, you will still be delivering a 14.7:1 AFR to the engine, just more of it and faster.

    Very generally:

    - HCs are raw unburned gas in the exhaust stream. A carb running too rich or a bad catalytic converter can cause this.
    - NOx is what you get when there is too little raw unburned gas in the exhaust stream. Most of the time, high NOx is caused by some malfunction in the EGR system.
    - CO is also unburned gas in the exhaust stream, but typically, it comes from sources other than the combustion process, like a dirty crankcase, clogged PCV system or a dirty charcoal canister.

    Tuning
    Proper tuning is vital to passing the tailpipe test. Most mods will require some kind of adjustment to work correctly. Sometimes this is as easy as turning a couple screws on a carburetor. Other times it means a few days with a laptop to tune your standalone engine management system. Knowing what to adjust and by how much is the trick to passing smog. The single most important part of passing your smog check is getting the air/fuel ratio right. If you have made modifications that change the AFR, you need to adjust it back so youíre getting a clean burn again. Youíre helping no one by running overly rich.

    If you are tuning from a laptop, it should be relatively easy to get the AFR right. If you are dealing with more mechanical controls, then you will have to find another way to monitor your AFR. An AFR meter can be an enormous help in tuning. I bought a narrow-band unit from Edelbrock. It had pretty lights that lit up at various times. That was about it. It didnít really help me dial in the tune. Iíve heard that wide-band sensors are much better, but they are way out of my budget.

    A potentially better sensor to use for your AFR is your nose. If your exhaust stinks like gas, youíre rich. Lean it out. When I was tuning my Edelbrock carb, my AFR meter was telling me that I was lean. My nose was telling me that I was rich. I went with my nose and leaned the mix. I passed no problem.

    Most importantly, tune to the test. The California smog check tests emissions at 15 and 25 mph. Make sure your AFR is optimal at those speeds, even if itís a little off in other places. For my Edelbrock, I used a combination of the AFR sensor and the feel of the engine to tune. If you know what lean misfire feels like, then you can richen your mixture until it just stops and youíll probably be right. If you donít know what lean misfire feels like, go lean until the engine starts having trouble. Then youíll know.

    Continued...
    Dr_Snooz

    "I like to take hammers, and just break stuff, just break stuff." - Beavis


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  2. #2

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    Re: How to pass smog

    How to get through it
    First and foremost, keep your car in good working order. If you are not staying current on regular maintenance and/or not using good gas, oil and replacement parts, then you have a much higher likelihood of failing smog. Good maintenance is key to passing the smog check.

    If you have mods, keep them neat and clean. You want your engine bay to look factory stock.

    Request a pre-test before the real test. This is important. If you hit gross polluter on a real test, you will be subject to all the gross polluter restrictions on your next test. If you fail on a pre-test, you will not.

    Just before the test
    There are lots of websites out there with little tricks for preparing. Read them and use them. In the days before the test, change your oil, especially if you are likely to go over on HCs or NOx. Make sure the car is tuned up. This means that the plugs, wires, cap and rotor are not older than is recommended according to your maintenance schedule.

    Immediately before the test, take the car out and drive it vigorously. Get it hot and blow out as much carbon as you can before taking it in. A hot catalytic converter catches a lot more emissions than a cold one. A hot engine runs much leaner than a cold one.

    If you can, watch the tech perform your check. This will give you a lot of insight into how the test conditions might have contributed to a pass or a fail. Did the car sit long enough to cool down before being tested? Did the tech feather the throttle a lot to keep speed in the right testing range? Doing so could cause emissions to spike. If you have dual exhaust, did the tech use the old pipe with all the holes, or the new pipe with no holes and the new catalytic converter? This is all valuable information for getting your car through the next time and the next.

    If you fail
    First, keep your wits about you. The shop might quote you some ridiculous and very frightening figures. Ignore them and start researching. Start with a simple Google search. For instance, “causes of high co” yields some nice results. As you read over possible causes, think about what you already know about your car. If HCs are high and your catalytic converter is 200k miles old, then chances are you need a new one. If you are high on CO and your carbureted car smells up the garage with fresh gas, then you might need a new charcoal canister. The trick is to use your head and come up with the most likely solution.

    Sometimes, the solution is going to be very expensive. If your rings are gone and the car blows blue smoke, it’s going to cost a lot of money to get it past smog.

    The good news is that you can still pass smog, even if your car isn’t factory original or lovingly maintained by the dealer since new. Just be smart and keep loving your 3g!!!
    Dr_Snooz

    "I like to take hammers, and just break stuff, just break stuff." - Beavis


    1989 Honda Accord LX-i Coupe, 220k miles, MT swap, rear disc swap

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  3. #3

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    Re: How to pass smog

    I've noticed that California has been lightening up on the smog requirements around here for older cars. For my last couple tests, they haven't tested for NOx and they didn't dyno my '89 Suburban last time either. Sacramento's decision to revoke the 25-year smog exemption is bumping up against reality apparently. From talking with the smog tech at the shop I go to, the state is having a hard time finding smog shops willing to shell out the big sums to keep up with the testing requirements for older cars. From what he was saying, it costs a shop $5k a year just to be able to test the older cars. If you don't test enough cars, the machine becomes a money suck. The newer cars don't use the old machines, so testing facilities are disappearing. If fate is kind, we could end up with a de facto 25-year exemption again, even though the law remains in force.

    We'll see what happens.
    Dr_Snooz

    "I like to take hammers, and just break stuff, just break stuff." - Beavis


    1989 Honda Accord LX-i Coupe, 220k miles, MT swap, rear disc swap

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  4. #4
    3Geez Veteran Rendon LX-i's Avatar
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    Re: How to pass smog

    Nice . very nice. STICKY THIS


    200+ ALL MOTOR LS VTEC

  5. #5

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    Re: How to pass smog

    Quote Originally Posted by Dr_Snooz View Post
    I've noticed that California has been lightening up on the smog requirements around here for older cars. For my last couple tests, they haven't tested for NOx and they didn't dyno my '89 Suburban last time either. Sacramento's decision to revoke the 25-year smog exemption is bumping up against reality apparently. From talking with the smog tech at the shop I go to, the state is having a hard time finding smog shops willing to shell out the big sums to keep up with the testing requirements for older cars. From what he was saying, it costs a shop $5k a year just to be able to test the older cars. If you don't test enough cars, the machine becomes a money suck. The newer cars don't use the old machines, so testing facilities are disappearing. If fate is kind, we could end up with a de facto 25-year exemption again, even though the law remains in force.

    We'll see what happens.
    That sounds like great news actually. The percentage of the older cars on the road just doesn't make sense to spend the money to smog them. I would be willing to bet the amount of pollution from older cars is such a small percentage. I mean, especially now with that huge gas leak that nobody seems to give a shit about.

  6. #6

    Dr_Snooz's Avatar
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    Re: How to pass smog

    Quote Originally Posted by 2ndGenGuy View Post
    I mean, especially now with that huge gas leak that nobody seems to give a shit about.
    I care. There just isn't much I can do about it.
    Dr_Snooz

    "I like to take hammers, and just break stuff, just break stuff." - Beavis


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  7. #7
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    Re: How to pass smog

    i live in wisonsin and my car is to old to smog test what emission parts
    can i remove with out doin to much harm to my car??

  8. #8

    Dr_Snooz's Avatar
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    Re: How to pass smog

    Short answer, very few. The cat can go, but pretty much everything else increases engine life.
    Dr_Snooz

    "I like to take hammers, and just break stuff, just break stuff." - Beavis


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