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Thread: Emissions/Cat Help

  1. #26
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    Interesting update.
    Couldnt get into the shop, I wrapped the exhaust all the way to the cat. Drove around for 25 minutes, into boost as much as possible, did a few laps getting into boost near the facility. Went in for my free re-test and drove straight in, no one to wait behind.
    HC hardly budged, down to only 1.48gpm, limit is 1.2.
    CO was 19.25, limit is 15. First failure for CO in 6 tests. Nox is still fine though.

    Theres no way the car wasnt as hot as I can get it.
    Im starting to think I need to check for vacuum leaks again. Maybe the cat is working? Maybe I'm just running really rich. No fuel mixture codes still however.
    '97 BMW M3/4/5, Cosmos Black.

  2. #27
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    That sounds like a capacity issue. Put a bigger cat on it. Or that n55 cat in series to make it pass while you find a bigger one.

    You might have to work on the fuel control but I've been assuming you're running at stoich or very close to it.

  3. #28
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    You can make a dedicated emissions pass tune that is extra retarded on the timing, and runs 'lean' (near stoichiometric), if the problem is keeping the cat hot.

    How far downstream is it?
    -Abel

    - E36 328is ~210-220whp: Lots of Mods.
    - 2000 Z3: Many Mods.
    - 2003 VW Jetta TDI Manual 47-50mpg
    - 1999 S52 Estoril M Coupe
    - 2014 328d Wagon, self-tuned, 270hp/430ft-lbs
    - 2019 M2 Competition, self-tuned, 504whp
    - 2016 Mini Cooper S

  4. #29
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    If you still think the n55 cat would help with both then that'd make me happy bc I should have it in next week, even if it has to be somewhat further away than I want it.

    as far as the tune.. it's been about six revisions to get my CEL to go away, and considering how many codes i got for fuel issues, I think the car is mostly happy where it's at right now. If the new cat doesn't help I will ask the tuner to try. But I think he said he can tune out nox issues, the HC is gunna need to be the cat. Also , I can't currently log afr's, I wish I had a way to, so I think with the limited info I provide, the tune is as good as it can get for now. I can't expect miracles without logging the afr's. However, my ltft still indicates that I'm running rich, and the ltfts don't seem that great right now, still at -7, but my knowledge is limited, and stft are all over the place( based on the printout diagnostic report from the test)
    Let me see if I can post some photos of the exhaust...
    '97 BMW M3/4/5, Cosmos Black.

  5. #30
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    Last edited by Brown9348; 09-01-2018 at 01:15 AM.
    '97 BMW M3/4/5, Cosmos Black.

  6. #31
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    Ok we got a few things going on.

    First that catalyst is way too far downstream. Put it where the flex pipe is and get a real metal heat shield over it or something like this https://www.heatshieldproducts.com/muffler-armor. I usually don't run any sort of flex pipe on the e36.

    Second that O2 sensor is also way too far downstream. You're going to have significant delay and over/ undershoot with a sensor that far away. That's why steady state your output falls.

    Third that output of HC and CO for the extended idle 230-240s (again this is a rich target and should be stoich) shows you don't have enough catalyst. You should get a little spike and almost nothing else. Not idle for 5 seconds then a climb from HC and CO.



    Looking at the outputs I see a vehicle that is running a bias rich off a narrowband sensor. You're pulling significant fuel (10%) at 92s and 146s and you can see a corresponding large jump in HC. You're going to get a spike in NOx at transients because the controller just doesn't have a great ability to respond there.

    You should have your largest outputs at the first 20 seconds, and the big hill at 160s. The fact that inbetween there you've got fuel trims pulling 10% and high output means that fuel control is out to lunch.

    Move the O2 6-8" off the turbo, put the n55 cat where the flex pipe is, clean up fuel trims and you'll pass. I honestly think it'll pass just moving the things upstream and dealing with the crappy fuel control as it will get much better without 4 extra feet of exhaust before the sensor.

  7. #32
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    Thanks man!! That's some really useful information for me. I have a hard time interpreting all the info with my lack of experience.

    that sensor you see isn't the o2, it's the afr. My o2 sensor is very close to the turbo, not shown in the photo though.
    aem recommended putting the afr sensor 36" from the turbo.
    I agree though, the cat is super far away. I will have them take that flex section out and move it somewhere else, and try to get the cat up near flex location, if not in front of it. And since it's so big I'll probably get a test pipe to replace it or else I won't make it over any speed bumps.

    im still wondering if some really hard to find vacuum leak is actually causing the fuel trims to be out. I'm thinking the tune is probably fine, but there may be a leak I just can't find somewhere.
    ive boost leak tested more times than I can count. I think I'll try using a chemical spray and listen for changes at idle to find a leak.. brake cleaner, or maybe propane or something? (I've never tried this method before). Any suggestions on what to use?
    '97 BMW M3/4/5, Cosmos Black.

  8. #33
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    Well make sure the afr is in front of the cat too. Preferable to put it close to the narrow.

    Could be a leak, hard to say. Lots of times people target slightly rich for idle stability and driveability, it's the easy way to smooth a point out.

  9. #34
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    Update: I couldn't get the shop to install the n55 cat. I agree there just isn't enough space to fit it close enough to the turbo.
    They offered to try a larger magnaflow closer to the turbo but for the price of labor and parts, it's cheaper for me to buy a mig welder, saw, and my own parts, so I think that's what I will do. I've always wanted to do the welding myself anyway so even if it doesn't work out with a new cat, I'd rather waste my money on pipes, equipment, and cats than a shop.

    so I'm asking you all, any recommendations on what cat I should use? Considering I can only move the cat up to about the flex pipe section because of the space. I will make a test pipe section for after all of this most likely.
    im looking at the magnaflow 99409HM right now but I'm still undecided.
    thanks!
    '97 BMW M3/4/5, Cosmos Black.

  10. #35
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    Do you have the ability to log your car? i.e. a KKL cable and a copy of romraider?
    If so, follow the same steps that the testers whilst logging the whole thing.

    Can then make recommendations to adjust the tune based on this.

  11. #36
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    Thanks for the advice^ I'm trying to figure out exactly what I need to log afr's, I will look into those for sure!
    '97 BMW M3/4/5, Cosmos Black.

  12. #37
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    Quote Originally Posted by Brown9348 View Post
    Update: I couldn't get the shop to install the n55 cat. I agree there just isn't enough space to fit it close enough to the turbo.
    They offered to try a larger magnaflow closer to the turbo but for the price of labor and parts, it's cheaper for me to buy a mig welder, saw, and my own parts, so I think that's what I will do. I've always wanted to do the welding myself anyway so even if it doesn't work out with a new cat, I'd rather waste my money on pipes, equipment, and cats than a shop.

    so I'm asking you all, any recommendations on what cat I should use? Considering I can only move the cat up to about the flex pipe section because of the space. I will make a test pipe section for after all of this most likely.
    im looking at the magnaflow 99409HM right now but I'm still undecided.
    thanks!
    I got this hoping it can handle turbo heat being ~5-6' from the turbo: https://www.ebay.com/itm/3-Catalytic...!US!-1&vxp=mtr

    Probably not the best for emissions. The flat cats like you mentioned should be fine for ground clearance with no real hit. Looks like you can put a cat there, then the flex right after if you think you need it (stock exhaust doesn't have one, so probably not needed).

    Go for the welder - it's so helpful to have when working on a car. Get a little gun time before you tackle an exhaust though. MIG is pretty easy as long as you concentrate on your gun to workpiece distance (most people have a tendency to pull away as the arc starts) and you make some little cursive e motions to join things together. You can get a small spool of 309L wire for this job, and it's fine with C25 (75% argon, 25% CO2) gas, it'll just have a little less corrosion resistance. I recommend a Hobart 140 plus a 80 cu ft bottle of gas. Go with 0.023" wire for the 120V MIG, as you can max it out on voltage with the wire feed at ~85-90% of max, and it'll run like butter at very low voltage and ~20-30% wirefeed speed. I have a Hobart Handler 125 I've had for a long time and that thing never lets me down. I still find myself favoring it for a lot of automotive stuff even though I have a nice Thermal Arc AC/DC TIG as well.

    With a welder, don't feel like you need to flange the cat either. Just toss the sucker in there with some 4.5" angle grinder + metal cutoff wheel cuts and weld it in. If it fails, well, you have an angle grinder and a welder to fix it!

  13. #38
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    Thanks. That helps a lot. I ordered a new cat, 99009hm magnaflow. Depending on where it'll fit, I might try to put it behind the flex section, it'll be a lot of work to remove the flex and put it there. Vbands will definitely make it more work but I want to have options.
    the cat I have is similar to your link, and obviously too far away.

    I'm looking at maybe a Hobart handler 130 or 140, and the Lincoln 140. Still not sure exactly what'd be best. If the Hobart 130 will suffice, I'll try it because it's the cheapest of those.
    im still trying to figure out how to register the car somewhere emissions aren't required, but I'd rather just pass.
    thank you for the mig setup advice, I will practice a bunch first on the scraps I have.
    '97 BMW M3/4/5, Cosmos Black.

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