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    Less HP with small dia catalytic converter?

    Hey all.

    I have a 90 stock EX that I use as a daily drive.

    Few months ago I discovered my stock catalytic converter was partially clogged as about half the honeycomb had fused into a lump. I took out the fused portion and planned on replacing the whole cat with a higher grade one before my next smog check.

    Went to replace it last month and found out that the CA lawmakers had passed a new law that says I can only buy an approved cat for a CA registered vehicle. It’s illegal to even ship a non-approved cat into the state. The approved cats must have a 5 year / 50k mile warranty vs the old 2 year. They also must have markings on them that say they are CA approved.

    Because of this, the price for a crappy CA cat is now about double what it was a few months ago and double the price of a non-CA cat. So I didn’t buy the better quality CA (which is also double the price), I just bought the cheapest bolt-in CA approved cat I could find from Napa.

    The approved CA cats of this brand for the EX, DX and LX are all the same model and when I swapped it in I saw the intake of the cat has a smaller diameter than the stock cat. There is a 2”-to-1 ¾” adapter welded on the cat. So that new cat adapter is now a choke point in my larger diameter exhaust.

    My question: Am a losing any power by having the smaller diameter cat on?

    I can easily swap the old, partially empty cat back on after the smog check. Would doing this, or even taking all the remaining honeycomb out and putting the empty old cat back on, give me better performance than the new, smaller diameter cat?


    I was happy to spend my money on a better quality cat but I’m betting the only difference tween a standard cat and the CA approved one is lettering on the cat and maybe additional welds on the seam to prevent rust through and now I’m feeling like the state of CA is screwing me (again).
    90 Accord Ex, F22A4. Slight fire damage.

    #2
    I would say that your loosing both power & probably some MPG ta boot???? I'd like to know what makes a CA approved part 4x more expensive than an OEM or standard replacement part? I've seen carb legal Intakes that are no different than the 3" aluminum tubing that I can pick up on a job site. It's a political farse as far as I'm concerned. But then again I'm a Liberal Canadian, so I'm the F#@K'n enemy to begin with.....,.
    MR Thread
    GhostAccord 2.4L Blog

    by Chappy, on Flickr

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      #3
      I noticed this with aftermarket cats also. Power loss is probably not that much, but is something. But I think it's better to sacrifice 2 horse power than the air quality.

      This new law is retarded. OEM cats from the dealer are still around 500 bucks. I'd rather pay 500 for one that lasts 10 years, than 200 for one that lasts 2 years.

      My swap thread
      Main relay proplems?--DIY

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        #4
        I've got a Random Technology High flow cat. They're pretty decent quality. I passed emissions right after installing it here in AZ, even w/ my H22 w/ the JDM P13 ECU.

        member's ride thread
        93' EX Coupe H22A w/ P2T4 Sir 5spd 191whp 155 wtq
        99' Lexus LS400 157k VVTi V8 gets up & goes...new DD
        91 Accord SE 176k
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          #5
          I'm not 100% but I'm guessing that it's harder to pass emmissions in the totalitarian Schwarzenegger state. Yes being good to our planet is a must. But I want to know how much these CA laws reduce the carbon foot print over the rest of us. What are other states emmissions limits? If this guy in Arizona can put a high flow cat on his car and pass a sniff test.....What's up? I don't have any personal exp. with this. We don't have emissions laws here. Yet! FYI, here where I live, our carbon footprint, including industry, is probably 1/32 that of California's.
          Last edited by GhostAccord; 03-05-2010, 01:35 AM.
          MR Thread
          GhostAccord 2.4L Blog

          by Chappy, on Flickr

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            #6
            Originally posted by 4CYLPOWER92 View Post
            I'd rather pay 500 for one that lasts 10 years, than 200 for one that lasts 2 years.
            Yeah, my 3 year old magnaflow cat failed a year ago, and I can already smell thorugh my current year-old cat

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              #7
              So if I didn't care about air quality (which I do, but now I'm feeling like I'm getting screwed since I can't buy a good quality cat cuz it's too expensive since it has to have "CA APPROVED" stamped on the side) would my car perform better during my daily drive if I:

              1) used the original old OEM cat with half the honeycomb taken out
              2) used the original old OEM and took out the rest of the honeycomb?

              I could still swap in my CA approved cat for smog checks.
              90 Accord Ex, F22A4. Slight fire damage.

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                #8
                Gutting an OEM cat will pass visual but it doubt that it will pass a smog/sniffer test. At least it shouldn't.......I would think that if you reset your ECU & swap the Cali legal Cat a few days before smog you should be GTG. It's all about the ready state ports from the ECU at that point.
                Last edited by GhostAccord; 03-06-2010, 01:02 AM.
                MR Thread
                GhostAccord 2.4L Blog

                by Chappy, on Flickr

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                  #9
                  I passed my stupid Smog using the new, CA approved cat. Also Seafoamed the intake and the oil, changed the oil/filter & air filter, set the valves, new sparks and new spark plug wires.

                  HC was 9 with 31 ave, 118 max.
                  CO was .01 with .10 ave and .75 max
                  NO was 10 with 237 ave and 799 max.

                  I'm yanking the new cat to keep it fresh and replacing it with the old OEM one. Only question remaining is to rod it out for better performance or leave it the way it is with only half the old honeycomb in it.
                  90 Accord Ex, F22A4. Slight fire damage.

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                    #10
                    Omg what will those dumbasses in CA come up with next. If they saw the laws that SC had they would shit a chicken. But yea man, it looks like you are going to have to buy that new cat. Or one of us other fellers can ship you a used one hehe.

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                      #11
                      If you're having a hard time getting your car to pass emissions, try adding acetone to the gas. I usually add 2oz/10gal , to lower emissions you could double that, it just won't improve mpg/power over the lesser amount. I've heard of o2 sensors being cleaned and brought back to life this way as well.

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