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We've been here; Downpipe for 1.5l

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    We've been here; Downpipe for 1.5l

    Ok, precat started crumbling through my exhaust last night on my way home from class. I've had a CEL for about, ohh, a year, but Mazda dealer told me precat failure is pretty common and thats what's setting off the ECU to report some bs error code (error 420, catalyst system warmup under threashold.)

    So, the precat is totally screwed. I have an aftermarket header coming down from it that replaces the o2 sensor with a bung filling where it was plugged in. I have a resistor mod in the sensor's socket that pretty much overrides the ECU and makes it think the precat runs good all the time.

    Problem is, this has been working all too well for so long, I forgot the precat was burned out and still in there, until it started fluing apart, sounding like marbles running through my exhaust pipe. I'm pretty sure it did damage to my entire exhaust because its not only clogged, but the car runs like **** because it can't emmit fumes. Real bad situation, the car's broken down here at my house and I'm driving my spare car (a 93 Tempo GL) in the mean time, so you see what I'm getting at.

    I need a downpipe, something that REPLACES the honey comb bull**** Mazda stuck in there. Who the hell's idea was it to put TWO catalytic convertors in the car anyway. Supposedly these things are warrantied to 80k, unfortunately I'm way over that.

    Any thoughts on who can make that 12" bypass pipe to fill in the space of a foot long honey comb precat?

    -Tim

    #2
    Depending on what kind of type of new headers that you are getting, you might not need the pre-cat. Some headers' design eliminates it, but some don't. As for fixing your current problem, your catalytic converter thats underneath the car is probably clogged like there is no tomorrow. My only suggestion is to take the entire exhaust off, and shake the hell out it. As for making a downpipe, almost any shop should be able to fabricate you one of those, but you would preferably need to have your car in the shop.
    Goodluck.
    "Probable impossibilities are to be preferred to improbable possibilities."

    Comment


      #3
      thanks for the quick reply. hopefully i can unclog it by shacking out all the beads from the precat, and there is no resulting damage, because a new catback is 350 bucks, and a precat's ~300. 650 bucks on crap that really isn't neccessary doesn't sound too pleasing, especially when I think about how new the catback is (under a year)

      Comment


        #4
        I am not sure, and I am not telling you to do it ...

        But there may be a possibility of taking a broom stick and banging out the internals of the pre-cat.
        If outside wasn't so crappy, I would snap a quick pick of the precat.
        photo album|photo album 2 (pbase)

        dbest1a AT yahoo DOT com

        Comment


          #5
          I dont know if your car is a second gen or a third, but, www.essentialspeed.com has a downpipe for the p5 that eliminates the pre cat.
          If not, and you have a second gen, email them at info@essentialspeed.com and tell them what you need. Your car will not be needed as mine is in there right now for the winter/R&D testing.
          Tell kevin that KRIS FROM WOODSTOCK sent you.

          CLICK HERE FOR PICS
          1.8L 97 LX (CDN)
          Erebuni kit, JDM heads/corners/tails/hood scoop, 17" BSA 259 w/ Khumo Ecstas, KYB GR2 struts, Apex springs, Ractive X-drilled/slotted rotors, KVR C/F pads, EssentialSpeed CAI, Essentialspeed custom cat-back (y-piped with dual Vibrant mufflers), Clutch Masters clutch, touring wing, Vibrant F/R strut bar, AWR 21.5mm rear sway bar, indiglo gauges, Sparco wheel/shift knob, custom interior, TomMotorsports 'BRIDE' seats, Innovatek DVD-0181 DVD/CD/MP3/etc player, Innovatek IN-720 7" indash LCD, 'MZDASPD' plates

          Comment


            #6
            wel since the title says 1.5 that would mean 2nd gen

            Comment


              #7
              essentialspeed is going to consider fabricating a pipe to bypass the precat, provided i mail them back the existing part so they can stick it in a jig and have something to base a design from.

              all thats really important is that the bolt patterns be the same, and the length be close to identical.

              Comment


                #8
                doesn't this precat have a sensor in it? by replacing it with a straight pipe what do you do too fool the ecu?
                real drivers accelerate for the corners

                Comment


                  #9
                  Naomi,
                  If i can help out any, send me an email at events@toprotege.com
                  My car is at ES already for the winter.

                  CLICK HERE FOR PICS
                  1.8L 97 LX (CDN)
                  Erebuni kit, JDM heads/corners/tails/hood scoop, 17" BSA 259 w/ Khumo Ecstas, KYB GR2 struts, Apex springs, Ractive X-drilled/slotted rotors, KVR C/F pads, EssentialSpeed CAI, Essentialspeed custom cat-back (y-piped with dual Vibrant mufflers), Clutch Masters clutch, touring wing, Vibrant F/R strut bar, AWR 21.5mm rear sway bar, indiglo gauges, Sparco wheel/shift knob, custom interior, TomMotorsports 'BRIDE' seats, Innovatek DVD-0181 DVD/CD/MP3/etc player, Innovatek IN-720 7" indash LCD, 'MZDASPD' plates

                  Comment


                    #10
                    ill let you know if i need something kdawg. infact you bring me onto answering labike's question.

                    i need the resistance reading (after engine warmup) from your 2nd o2 sensor, the one in the header pipe that goes from the precat to the primary cat. the reason is simple: with that resistance measured i will be able to get a resistor or make a seriel path of resistors to match that resistance and trick the ecu into thinking the precat is warm and burning hydrocarbons at an acceptable rate.

                    as of now i have never gotten a straight answer about the 2nd o2 sensor in a OBD2 system (cars after 1996) as to what it measures... wether its oxygen content or temperature. i'm just taking a wild guess at it being temperature because the only error codes related to the failure of the obd2 sensor are directed at detecting heat (ie, how hot the cat is... hence u get a error code if the cats burned out saying its not warm enough)

                    if you could take a multimeter to that second o2 sensor and measure resistance, probably in kohms, and let the board know, it would help us all out greatly. do it after driving the car around for awhile so the cats nice and toasty.

                    i'm guessing the less resistance, the hotter the cat is.

                    Comment


                      #11
                      I've been procrastinating on my little downpipe project...mostly because I haven't had the motivation to solve some problems.

                      Using a resistor is an interesting idea...I was just going to have a new bung welded into an exhaust pipe and run the sensor.

                      Now if the resistor is always reading warm in relation to everything else in the car saying its cold, the obd-2 bastard computer isn't going to get huffy and fire off a couple codes (faulty temp sensor, catalyst over threshold or catalyst draining your bank account)?

                      Also the flange for the primaries to the downpipe are particularly ugly...not standard so using a bolt on flange and welding on a 90 mandrel bent pipe insn't an option.

                      I hate the Protege exhaust.

                      alot.
                      Last edited by davens; 12-30-2003, 08:13 AM.

                      Comment


                        #12
                        the o2 sensors aren't used for the obd2 system to determine wether or not the system should enter open loop. the temp sensor is. all that it cares about is when the block hits a certain temperature, then it decides wether its ready to run on its own.

                        when the temp sensor hits ~175' F the systems starts this sequence: block temp sensor 175, if ok, check sensor functions (intake temp, mass airflow, oxygen1, oxygen 2) at which point the oxygen 1 will report back wether lean or rich, and the systems adjusts on the fly. the o2 will report (because of the resistor) that everythings dandy below the pre-cat because the resistor used always returns the same value, for example 96% oxygen or such and such temperature (1000' F.)

                        the system doesn't rely on the oxygen sensors for anything until in open loop, because if they did, you could turn your car off, turn it back on after 10 seconds and it would throw a dozen errors through the ecu because the block would take longer to warm up than the cat's, because the cats would already be warm from the last time the car was turned on 10 seconds ago.

                        resistor kits are sold at many places, including essentialspeed, for about 20 dollars, and are pretty universal across all odb-2 protege's because the ecu has no changes in these sequences.

                        Comment


                          #13
                          Yes, you're getting at what I'm asking...maybe I'm giving the obd-2 system too much credit(or expecting the worst).
                          If all the collective sensors say the engine is stone cold but one lone sensor says it's a balmy 1000 degrees, the ecu isn't going to see that as a possible faulty sensor?

                          The resistor is great idea but has anyone done it yet? Are there any drawbacks? I'm leaning towards doing it just because the damn o2 sensors are so expensive.

                          Comment


                            #14
                            ok, so the sensor reports 1000 degrees even though the systems a chicago 15f on a cold morning... it doesn't matter what the sensor thinks the temp is because the system isn't even looking at it yet. o2 sensors aren't even triggered for readings until the system enters open loop.

                            besides, if it doesn't work, then you can do your bung & sensor idea, all you loose is about an hours worth of time wiring a resistor in their

                            Comment


                              #15
                              Well, essentialspeed didn't have o2 signal simulators...

                              I did find this company:


                              It would involve using the universal retrofit kit but $50 and never having to buy an o2 sensor again is alright by me.

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