1. pishta

    pishta I know I'm right....

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    Having trouble passing smog (high NOx) on a carbed pickup that uses EGR. I already cleaned the EGR system and there is no more charcoal in it. I need more EGR or cooler EGR as I milled the head a little more than recommended. Would it make a lick of difference if I ran my EGR through a trans cooler? sort of an Air to air cooler? would it make more sense to just get a larger EGR valve (or hog mine out at the pintle hole) the EGR uses a pretty small opening (maybe 4mm) and a cone seal. diesels have water to air coolers but I have an extra finned trans cooler.
     
  2. 2 Darts

    2 Darts A-body Addicted

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    Are the EGR valve and manifold port(s) clean? Is the EGR valve getting vacuum from the carburetor? EGR tends to get crudded up with carbon preventing proper opening. Best thing I've found for baked on carbon is CLP Break-Free. Works wonders on firearms, too.
     
  3. slantsixdan

    slantsixdan =..=

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    Year, model, engine, transmission, emissions spec (Federal or California], how many miles on it? What mods aside from your head-mill, what carb, what ignition setup, what is your stock or non-stock exhaust system configuration, etc? Details, man, details!

    What are your HC, CO, and NOx numbers vs. the allowable standards?

    And/or less ignition advance...

    Not at all.

    Diesel EGR (diesel emission control at all) is a whole different ballgame vs. gasoline.

    Maybe, maybe not. Need more detailed info on exactly what you're running and how it's failing!
     
  4. pishta

    pishta I know I'm right....

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    Its a 82 Fed. Mazda truck 2.0, carb is a NOS stock Nikki 2bbl, 5sp, spark timing is not changeable as it is checked against specs @8 BTDC. Cam timing is dead on as you count links to line cam cog up. I milled the head .060 to clean up some PO's water coolant only on an AL head for pitting corrosion but Mazda spec says .030 is limit and they sell a shim to correct even that. EGR is clean and functional (cleaned valve, no residue but found loads of crap in the feed tube and intake port from the exhaust, complete blockage but cleaned that completely) pintle moves with engine vacuum..and learned that the feather Duster used a larger EGR valve for part of its package than the normal slant to combat NOx levels with its leaner carb jetting, so I assumed more EGR (or cooler) would assist my quest. Carb was untouched since its last test where is passed with flying colors. Changed since last test were a valve job and milling the head. perhaps my cat is done. NOx failed by about 10% over max (ie. 70 max, I had 77) everything else was in line. 250,000 mile truck with new rings (bores straight and smooth) 2 years ago. runs like new (of course) Wife wants me to scrap it, I need my little truck for hauling Moparts! one concern is that the valve timing may be altered with the head milling, as in the cam is advanced slightly because the head is closer to the crank.
     
  5. slantsixdan

    slantsixdan =..=

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    Good score on the NOS carb. Japanese carburetors from the emission control era are notorious for dying very stubbornly (i.e., once past a certain point they are bound and determined to stay dead no matter how much time, effort, and money you put into 'em).

    You may wind up buying that shim kit (or two of them, LOL) but I don't think you're at that point yet.

    Good...

    Given those numbers and that set of circumstances on that truck, I think it's right to focus primarily on the emission control system at first.

    EGR valve is clean and moves...okeh, but I'd still replace it with a new one. Fun: a whole lot of Mopars use the same valve as your B2000 Mazda. Which means you can swap on the transducer-equipped EGR valve, Standard Motor Products № EGV490 (under $20 at RockAuto). Not only will that get you a smarter valve that's more responsive to changing engine load conditions, but Standard's replacement valves use separate orifice plates so you can dial-in your EGR by swapping the plate. Attached to this post is the breakout chart (Standard's blueprint for the washers). Some valves use the flat plates, some use the cup-shaped ones. Any given valve comes with anywhere from one to several washers; if several, there'll be a sheet listing the correct washer by application. The washers aren't sold as separate parts, but with this breakout chart you can make your own.

    You don't mention your numbers on CO and HC (please spit 'em out), but I'm guessing once I see them I will probably call the catalytic converter a prime suspect. It looks like that truck does not have feedback carburetion (no oxygen sensor), is that correct? If so, the cat (meow!) lives a harder life than if the truck had an O2 sensor. Most aftermarket cats (meow!) are cheap junk that'll get you past a few years' worth of inspections if everything else is in perfect condition; they contain much less catalyst than factory converters and are only rated for a 25,000 mile lifespan. Which is why you go to price a factory converter and it's something ridiculous like a thousand bucks, not worth buying, but Summit will sell you one for $49, equally and oppositely not worth buying. I don't replace a cat (meow!) unless everything upstream of it is in good running condition, otherwise it's just money down the drain because a faulty engine/fuel/ignition system will quickly kill even a brand-new cat (meow!). I buy California-spec converters because the type-approval standards for them are much tougher to meet—they do a better cleanup job on the exhaust and they last a lot longer, so even though they're more expensive to buy, they're worth it in the long run.

    Looks like your truck originally had two cats (MeowMeow!), one directly off the exhaust manifold flange and the other downstream a ways. If both aren't still present, tailpipe emissions are going to be higher than they should be; that's not a terrifically clean-burning engine.

    In your case I'd put in this rear cat (meow!) and this front cat (meow!). With everything else in good running condition and that new-type EGR valve, that should get you plenty of "breathing" room on the emission test, without having to take apart the engine and shim the head.

    [​IMG]

    [​IMG]
     
  6. pishta

    pishta I know I'm right....

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    Dan, thanks for the assistance! I dug up all my paperwork and found a few things I didnt know: first off, I failed most recently because of high CO and HC, not NOx. The high CO was at the 25mph test. I was thinking NOx because my Lexus had the EGR issue (95%clogged), my bad. I cleaned that one too and it passed. The Mazda had a 100% clogged EGR pipe too, I cleaned it after green test. red is most recent test (failed) 2 tests prior are in green and blue (pass)
    15mph

    %CO2 12.1 13.6 13.3
    %O2 0 1.5 1.9
    HC ppm 232 (max allowed 214, gross polluter 395) FAIL 62 96
    CO % 4.33 (max allowed 1.56, gross polluter 3.06) FAIL .23 .57
    NO % 214 (max allowed 1514, gross polluter 2764) PASS 1128 1331

    25mph

    %CO2 14.1 13.9 14.2
    %O2 0 0.9 0.9
    HC ppm 78 (max allowed 130, gross polluter 305) PASS 46 47
    CO % 1.33 (max allowed 1.36, gross polluter 2.86) PASS .14 .20
    NO % 96 (max allowed 1374, gross polluter 2564) PASS 778 916

    So Doc: Whats the verdict? My truck was a fed so it only came with one cat IIRC as it never had one on the manifold end and to my knowledge, the cat has not been changed in 218K but I bought it at 196k. No o2 sensor. My fuel pump was weak and i finally changed it prior to the failing test as it kept failing the "hold" test where he gets it up to RPM then applies a load. the old pump leaned out and caused it to fall out of the parameters of the test RPM's. forgot to mention that but the pump is a facet stock bypass style where it routes whatever the bowl doesnt need back the tank via a return line (loud as hell, I need to isolate it from the frame) . fuel level is spot on thanks to a glass window and idiot line engraved on the side. I wonder if it is running rich with new fuel pump? How would it with the bypass and accurate fuel level...

    PS, ignition system is stock. new plugs and rebuilt electronic distributor with new cap and rotor, plug wires OHM out within spec. Stock coil. I could put an MSD on it as I have an extra if that would aid in combustion. Im allowed +- 3 degrees timing variance.
     
    Last edited: Jul 8, 2016
  7. slantsixdan

    slantsixdan =..=

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    I don't think you'll get anywhere trying to improve the ignition. Your HC and CO are way up from previous tests and your NOx is way down, which suggests you're running rich. I doubt it's from a fuel pump fault -- could be a carb calibration or adjustment fault or a sticking choke or other air restriction. HC is unburned fuel; CO is incomplete combustion. NOx happens when combustion chamber temperatures rise high for whatever reason, particularly with a lean mixture. Rich mixtures burn cold and there's no excess O2 to combine with nitrogen, so NOx doesn't form.

    With this new info, I'm changing my vote: it is still somewhere between "quite possible" and "quite likely" that your cat (meow!) is past due for replacement, but it also looks like you've got a running condition to correct before doing so, or else the new cat (meow!) will be killed to death.

    Pull a spark plug or two — what do the firing ends look like?

    Did the NOS carb get installed between the previous (easy pass) test and the recent (multi-flunk) test?
     
  8. pishta

    pishta I know I'm right....

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    No, NOS carb was on since 1st test as the one I had when I bought it was barely running the motor. You could see light through the throttle shaft. When I got the NOS one put on, the truck ran like new, it idled down to 600 and the mirrors were not even vibrating. Old POS carb wouldnt idle under 900. New rings, valve job with head milling (non issue?) new smog anti-backfire valve, new distributor pot, new fuel pump. Lots of new stuff, just not a new cat (meow!) yet...Hey, I can spend 50 bucks on a Fed cat....Exhaust had a few small leaks in it too right at the muffler that I welded up (wonder if no more dilution of the exhaust at the sniffer made it sense more?) . So for a truck that cant pass smog, this thing runs pretty darn good! New catalytic convertor on order.
     
  9. slantsixdan

    slantsixdan =..=

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    Okeh, but I'm still curious what the spark plugs look like.

    $50 converter = the cheap short-lived junk I was referring to earlier.
     
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