Results 1 to 4 of 4

Thread: Do your Catalytic Coverters work, and how much to they help?

  1. #1
    Join Date
    Jul 2010
    Location
    Ripon, Ca. (That's not England chaps)
    Posts
    1,514

    Do your Catalytic Coverters work, and how much to they help?

    Finally passed the smog check on the farm truck I recently bought. I couldn't find information regarding the improvement between old failed Catalytic Converters vs replacements, so here's my data.

    While this is a non-cool truck, the same effect works on our Land Rovers, so just ignore the F-word that follows.


    1990 Ford Ranger with 6 cyl 2.9 liter engine and 170k miles on the original engine. Runs well and has no codes on the OBD1 system.


    Limits:
    15 mph, 126 ppm HC, 0.76% CO, 1025 ppm NOx.
    25 mph, 74 ppm HC, 0.97% CO, 620 ppm NOx.


    Initial Smog - FAILED:
    15 mph at 1571 rpm, 211 ppm HC, 0.77% O2, 1796 ppm NOx. = Fail
    25 mph at 1763 rpm, 74 ppm HC, 0.27% O2, 377 ppm NOx. = Pass


    Post Tune-up (new Plugs, Ignition Wires, Distributor, Cap, Rotor, and Timed) - FAILED:
    15 mph at 1549 rpm, 211 ppm HC, 0.59% CO, 1510 ppm NOx. = Fail
    25 mph at 1758 rpm, 74 ppm HC, 0.28% CO, 439 ppm NOx. = Pass


    Post new Catalytic Converters - PASSED:
    15 mph at 1568 rpm, 41 ppm HC, 0.02% O2, 4 ppm NOx. = Pass
    25 mph at 1776 rpm, 22 ppm HC, 0.00% O2, 8 ppm NOx. = Pass

    So how did I know I had dead catalytic converters (and why didn't I diagnose it sooner)?
    (A) I performed a thermal test on the exhaust system after the second smog failure. It's simply measuring the exhaust temp as it flows through the system from engine towards the tail pipe. The measurements are made with a laser thermometer - commonly on sale at HF [you can trust some of the HF tools, but you sure would buy a parachute from them].

    In my case, the header had roughly 450* F, the intake to the first Cat was 325* F and its exhaust was 250*, the intake to the second Cat was 225* F and its exhaust was a chilly 175* F.

    (B) I could have caught this sooner (not needing the tune-up) if I would have been more aware of the exhaust smell (rotten eggs) and the water that was always leaking from the "hot" exhaust. It's such a quick/simple test, I'm thinking about doing it more often on older vehicles before smog testing.
    Last edited by Green Achers; 08-20-2016 at 02:36 PM. Reason: Technical improvement

    Bill of Green Achers Farms
    Adventure for fellow Geeks! Geocaching
    Land Rover Repair Manual - Download Site
    1. 1996 Discovery I - Yet to be named
    2. 1998 Discovery I - "Kermit"
    3. 2000 Discovery II - Parts Donor


  2. #2
    Join Date
    Oct 2006
    Location
    Oak Park, CA
    Posts
    2,207
    OK, I am curious, how did the temps change after the cats replacement?
    <DCProven >
    <1977 Land Rover Santana, Series III, 2.25 Diesel>
    <1995 RRC, LWB, 4.2 V8>

    "Information is not knowledge,..." Frank Zappa

  3. #3
    Join Date
    Oct 2011
    Location
    Fremont
    Posts
    349
    Good info.

    Sent from my VS987 using Tapatalk
    I spend more time fixing things than using them. My motto is " If it breaks.... F it I'll weld it"

  4. #4
    Join Date
    Jul 2010
    Location
    Ripon, Ca. (That's not England chaps)
    Posts
    1,514
    Quote Originally Posted by dcproven View Post
    OK, I am curious, how did the temps change after the cats replacement?
    Good question that deserves the correct answer (which I'll redo and post soon). Off the top of my head, it went roughly 450* F, the intake to the first Cat was 325* F and its exhaust was 400*, the intake to the second Cat was 300* F and its exhaust was a chilly 320* F.

    Bill of Green Achers Farms
    Adventure for fellow Geeks! Geocaching
    Land Rover Repair Manual - Download Site
    1. 1996 Discovery I - Yet to be named
    2. 1998 Discovery I - "Kermit"
    3. 2000 Discovery II - Parts Donor


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •