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CFI and dual exhaust-will it run too lean?

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    #16
    Thats not true, the o2 sensor is located before the cats so that would have no effect. The air system is about emissions thats it.

    You know funny enough my 85 ltd had the flanges cut off and welded too.


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      #17
      You can remove the converters without issue. The non-heated O2 sensor will certainly still heat up with the heat being generated.

      Personally I like having converters mostly due to the smell of un-catted exhaust. You can get away with just capping or welding the tubes shut. I have converters but no Thermactor system since the system was generally inop when I got my car. The smog pump can be removed with a shorter belt run if you desire to keep the A/C (or just don’t have any belt if you’re not fixing/deleting the A/C) and the piping can be removed outright. Just cap off the white and black vacuum lines that run to the solenoids.

      If the CFI cars are similar to the SEFI cars, there’s a smog pipe at the back of the head with a check valve where the Thermactor hoses attach to. You can just leave that alone unless you don’t like looking at it, then you’ll need to block the ports on the back of the heads.

      The only thing I remember being different on CFI cars was the existence of some heat riser or valve on one of the exhaust manifolds? I forget to what extent and purpose its job was.


      My Cars:
      -1964 Comet 202 (116K Miles) - Long Term Project
      -1986 Dodge D-150 Royale SE (112K Miles) - Slowly Getting Put Back Together
      -1987 Grand Marquis Colony Park LS (325K Miles) - April 2017 + September 2019 POTM Winner
      -1997 Grand Marquis LS (240K Miles) - The Daily Workhorse & March 2015 + January 2019 POTM Winner

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        #18
        Its been a while since I had my 85 but I don’t remember it having a crossover to the back of the heads but it still had a diverter valve so maybe it was just set up differently.

        As far as the heat riser goes I believe it was there to heat up the intake charge to shorten warmup time but I could be wrong. My 85 had a broken one so I threw it away and didn’t have an issue. Plus the valve didn’t work anyway so the heated air was funneled into the air cleaner anyway.


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          #19
          If I can just get away with capping them, then that would be fine. I always thought the Thermactor system was to keep the cats from plugging up. I do not want to unnecessarily pollute if I don't have to.

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            #20
            The Thermactor system was designed to primarily heat up the converters faster to get them doing their thing faster. There’s a few members here running around with original style converters and no air system.


            My Cars:
            -1964 Comet 202 (116K Miles) - Long Term Project
            -1986 Dodge D-150 Royale SE (112K Miles) - Slowly Getting Put Back Together
            -1987 Grand Marquis Colony Park LS (325K Miles) - April 2017 + September 2019 POTM Winner
            -1997 Grand Marquis LS (240K Miles) - The Daily Workhorse & March 2015 + January 2019 POTM Winner

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              #21
              Yeah thats a myth, I asked the same question and the concensus was not having the air system hooked up won’t hurt the cats. I have newish walker cats with no air pump and for a while I had bad vacuum signal going to the map sensor so it ran super rich and my cats are fine.


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                #22
                Ok! Well, i will just try that then. If the cats have problems after that, then I will remove them. There is no use fixing something that isn't broke, right?

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                  #23
                  If you live somewhere you're not required to have it, dump the AIR system entirely. It'll clean up a lot of junk from the engine bay and there's really no down side. As others said, i would run cats just to keep the car from being stinky, but otherwise don't give a shit about "emissions". I live in california so if i put a different air filter in the car they send the Gestapo to kill one of my children, it's a bit different here. Free states are much better for older cars.

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                    #24
                    Yeah, it is pretty laid back here in Washington as far as emissions go. At least it is where I live. Olympia and Seattle are another story. But just getting rid of the thermactor system will make everything better under the hood and get rid of that annoying exhaust leak.

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                      #25
                      I put new cats on my car last spring. They came with the AIR tubes, but they were capped with a welded plug. Instructions were to cut the plugs off to attach the AIR system.
                      My guess is they can't tell you to ditch it, but if they were needed to run the car the caps wouldn't be welded in place. There's also nothing in the warranty notes about the AIR needing to be hooked up.
                      These were for non-California cars only.

                      A tailpipe tester found my emissions cleaner after the new catalysts than the old ones (I suspect that had more to do with my new o2 sensors; I replaced the cats because the flanges were rusty and the manifolds and exhaust piping was all new). I haven't tested since then, but maybe I should.
                      Prior to the catalytic replacement, the AIR pump was removed but all the piping left in place. When I did the exhaust I plugged the ports in the heads and removed the vacuum and AIR lines (but left EGR and electronics).

                      My guess is that modern catalytic converters don't need the air injection to stay within their operating range, and so can work without the 3-way arrangement. Older converters with the AIR disconnected don't seem to last so long.
                      California, on the other hand, doesn't allow changes without submitted testing and proof of operation, which is not cost-effective for our cars.

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                        #26
                        Yeah, I thought I had heard that removing the air from the older cats would destroy them in time. I will eventually probably remove them since I will most likely convert it over to a 4 barrel carb in the future. But while the CFI still works and does its job, I would rather retain the cats. Who knows, I may put some aftermarket cats on it at the same time if I feel rich!

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                          #27
                          Only if you only take short trips everywhere. If you drive for more than 5-10 minutes, you should be fine. Just need to get the cats up to operating temp (this is faster than the engine warm-up even without the air injection system) so they can burn off all the excess fuel properly and remain clean... as it were... when you shut off the car. That was my experience with my 88. Put well over 50K miles with zero issues. Cats still smelled like the day I installed them.

                          Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
                          rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
                          Originally posted by gadget73
                          ... and it should all work like magic and unicorns and stuff.
                          Originally posted by dmccaig
                          Overhead, some poor bastards are flying in airplanes.

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                            #28
                            So there's 49-state cats and then there's california cats, which cost about 2-3x as much. Think the 2 i had put on the offroad pipe on the first '90 cost me about $450. 2 cats. Before this state went completely shit nuts i had an entire(single) exhaust system with a high-flow cat and flowmaster done for like $200. I'll allow it was a few(20?) years ago, but seriously. Be smart and don't ever vote for people that seem to be offering way too much. I didn't but everyone else here does, and this is the result.

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