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    M20 cam setup to pass emission test

    Hey guys,

    I was wondering if anyone in here have experience on building a cammed m20 that passes emission idle test.

    My M20 has Schrick 288' cam with Metric Mechanic parts (coated rod bearings, head bolts, head gasket, rocker arms, valve springs & retainers) which was originally built for a racecar, but I've been using it on my street car for few years.

    Up until last year I could get a conditional pass by failing emission test twice with a proof that 'repair' bill would be more than $500.

    As of last year the Ontario government won't issue two conditional passes in a row. So that leaves me with 2 years to change my engine so that it'll pass emission.

    Right now it gets about 1800 ppm HC in idle (test limit is 200ppm) - so changing spark plug gaps, cat or idle speed to at HC isn't going to help much to get it down to 200ppm.

    So I'm planning to swap out the cam to either stock or something milder, and do a top-end work while I'm in there. I like the idea of hotter cam but I was wondering if anyone have experience building a cammed m20 that's mild enough to pass the emission. Looks like aftermarket 'street' cam is 272, which sounds pretty aggressive in terms of emission, and I couldn't find anything less aggressive (Alpina cams) on the market yet.
    sigpic

    #2
    Metric mechanic sport cam might be ok on a stroker anyway.
    89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

    new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

    Comment


      #3
      Originally posted by digger View Post
      Metric mechanic sport cam might be ok on a stroker anyway.

      It's not a stroked m20 - it only has cam and MM valve train parts for track reliability. I believe it has stock pistons & crank.

      If I run a 272 Cam with same stock internal with retuned chip (I have state 1 SSSQUID) and perhaps an MAF, would I pass the smog with less than 200ppm HC? I'm not sure what the limit for California smog test, so if anyone have experience passing Cali smog with 272 cam, I'd love to know the HC value in idle.
      sigpic

      Comment


        #4
        Originally posted by jasonbk View Post
        It's not a stroked m20 - it only has cam and MM valve train parts for track reliability. I believe it has stock pistons & crank.

        If I run a 272 Cam with same stock internal with retuned chip (I have state 1 SSSQUID) and perhaps an MAF, would I pass the smog with less than 200ppm HC? I'm not sure what the limit for California smog test, so if anyone have experience passing Cali smog with 272 cam, I'd love to know the HC value in idle.
        Considering going 272 and I too would like to know how it goes up against Cali smog

        Comment


          #5
          The cam vs compression ratio is the issue. When you have low (stock) compression and a lot of overlap, you run into efficiency problems at idle (low vacuum). When a cam has a lot of overlap, part of the air rich in HC and un-burnt fuel passes right through into the exhaust.

          Do you have a catalyst? If so, how hot did you let the exhaust get?

          Not entirely sure you will be able to get it to pass with your current cam. Even if you were to get a chip to lean it out, you are still bringing in fresh air due to the cam (vacuum leaks also cause high HC).
          john@m20guru.com
          Links:
          Transaction feedback: Here, here and here. Thanks :D

          Comment


            #6
            Originally posted by ForcedFirebird View Post
            The cam vs compression ratio is the issue. When you have low (stock) compression and a lot of overlap, you run into efficiency problems at idle (low vacuum). When a cam has a lot of overlap, part of the air rich in HC and un-burnt fuel passes right through into the exhaust.

            Do you have a catalyst? If so, how hot did you let the exhaust get?

            Not entirely sure you will be able to get it to pass with your current cam. Even if you were to get a chip to lean it out, you are still bringing in fresh air due to the cam (vacuum leaks also cause high HC).
            We did few runs to see how it'd hold up as the exhaust got hotter(with stock 325i catalyst), but it didn't do much. I guess the proper way to get the car running properly in low rpm/idle is to stroke it with milder cam. Still looking to hear from those who run 272 cam with stock piston & crank.
            sigpic

            Comment


              #7
              Originally posted by jasonbk View Post
              It's not a stroked m20 - it only has cam and MM valve train parts for track reliability. I believe it has stock pistons & crank.

              If I run a 272 Cam with same stock internal with retuned chip (I have state 1 SSSQUID) and perhaps an MAF, would I pass the smog with less than 200ppm HC? I'm not sure what the limit for California smog test, so if anyone have experience passing Cali smog with 272 cam, I'd love to know the HC value in idle.
              properly tuned you probably could. one of the guys that did a 2.8L recently passed the test quite easily though failed a few test earlier on so even the smaller engine might be ok.





              IIRC the MM sport cam has less overlap than a 272, no experience with it myself
              89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

              new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

              Comment

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