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Thread: Catalytic converter options

  1. #1
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    Default Catalytic converter options

    Posting it also here in the hope that someone has experience with KSP or SARD cats:
    Being 8 years old the cats failed the SMOG test due to high CO at 2500 rpm. They're 300 cells (Prospeed style but a different brand) with a perfect fit for 600 bucks back then. Car has a CTSC system.
    What are the options nowadays? They should keep up with the CTSC but also guarranty SMOG for some years (the more expensive - the more years of course).
    I've seen the ones from SoS, SARD and KSP.
    Last edited by goldnsx; 25-06-2020 at 02:32 PM. Reason: typo: SARD cats, not SARK

  2. #2
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    What is the spec of the upper stream header?
    Please note that the CAT length/spec is different between country/year models.

    Also, what is the fitting spec (number of holes, specific angle, etc) for both the header and the exh back box?

    Do you need specific certificate to be displayed/shown in your country at the time of emission test?

    300 Cells and just 8 years old….. Should be enough to clear the test so question mark on the original structure. Is the honeycomb melted?

    Kaz
    Last edited by Kaz-kzukNA1; 25-06-2020 at 11:10 AM. Reason: format

  3. #3
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    Thanks very much, Kaz, always very helpful.
    I've 97-99 headers plus adapters to mount the 91 cats (3 holes on each side). So any cat for 91-94 should work.
    Those 300 cells are Random Technology cats, they don't seem to like rich fuel mixtures like the CTSC needs. I didn't look at them yet but I think that there's no visible damage. They don't rattle. Power is there too.
    Extended story: last month, they passed an emission test when they were very hot, means idling at 5000 rpm for 2 minutes and test it then at 2500 rpm. But at idle again they cool down after some time. The mechanic said that these cats show their problem under a higher flow. At the MOT station they did test the cats too but they gave up after a while. CO was around 0.4-0.5 %vol. Lambda was 1. So I need new cats.
    A certificate is not really needed but would be nice of course. I know that you have to use OEM cats in California, they have the strictest law regarding emissions of the world. What about Japan? I could image that it's pretty strict too, no? Is it allowed to sell and mount aftermarket cats? Do they have to guarranty passing an emission test?
    OEM cats are crazy $3000, no way. SARD are about half of that but what about their quality. They're based in Japan I've seen. But I'd only go with these if they're good.
    Any other recommendation?
    Thanks in advance.

  4. #4

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    Hi Gold,

    I have SARD cats, they pass SMOG here (Portugal) no problem. Regarding durability I can't comment as I have them installed for only 3 years... they do look very well crafted. SARD cats come with a certificate for emissions but is all in japanese... so probably not very useful here in Europe.

    Regards,
    Bruno

    Quote Originally Posted by goldnsx View Post
    Thanks very much, Kaz, always very helpful.
    I've 97-99 headers plus adapters to mount the 91 cats (3 holes on each side). So any cat for 91-94 should work.
    Those 300 cells are Random Technology cats, they don't seem to like rich fuel mixtures like the CTSC needs. I didn't look at them yet but I think that there's no visible damage. They don't rattle. Power is there too.
    Extended story: last month, they passed an emission test when they were very hot, means idling at 5000 rpm for 2 minutes and test it then at 2500 rpm. But at idle again they cool down after some time. The mechanic said that these cats show their problem under a higher flow. At the MOT station they did test the cats too but they gave up after a while. CO was around 0.4-0.5 %vol. Lambda was 1. So I need new cats.
    A certificate is not really needed but would be nice of course. I know that you have to use OEM cats in California, they have the strictest law regarding emissions of the world. What about Japan? I could image that it's pretty strict too, no? Is it allowed to sell and mount aftermarket cats? Do they have to guarranty passing an emission test?
    OEM cats are crazy $3000, no way. SARD are about half of that but what about their quality. They're based in Japan I've seen. But I'd only go with these if they're good.
    Any other recommendation?
    Thanks in advance.

  5. #5
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    Hi Bruno

    Thanks for your response.

    How does the emissions test in Portugal work? CO at idle and CO at 2500 rpm < 0.1 %vol like we have here? Do you have to heat them up like crazy to pass the test or do they pass it after 10 miles of normal drive?

  6. #6
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    For the CAT to perform well, it requires the efficient redox reaction.

    If your engine requires rich A/F continuously, it will not only reduce the efficiency but also may damage the CAT itself.

    In Japan, MOT is very strict especially the emission test.
    First, the car manufactures can't even register a new model if it doesn't meet the latest regulation. Same in other countries.

    If CAT or Exhaust were replaced by the owner, the MOT place will ask for the specific document showing the test certificate for the noise level, emission, safety, etc and that it has to be specific to the spec of the car.
    Hence, many different certificates required for NSX due to engine size as well as MT/AT differences.
    The emission spec is different between pre/post LEV.
    So, any aftermarket CAT/EXH from major manufactures/shops in Japan would be sold with the certificate document included.

    With NSX V-type engine, it's not hard for the CAT to meet the requirement if designed properly using the good quality parts.
    For pre-LEV, even 100 cell will pass the test because good quality cell and design only need to deal with 3 cyl at each bank instead of 4 - 6cyl on straight inline engine design.
    For LEV, at least 200 cell will be used to keep the length shorter.

    So, any aftermarket CAT from well known Japanese manufactures with test certificate specific to NSX models would be good but you don't want checking the price….
    The one from T3TEC with 100 cell is well over GBP1,500 even before leaving Japan and for 200 cell, over GBP2,000, but designed and tested properly against the requirement of the Japanese emission standard.

    With the normal engine, you don't need replacing the CAT but with your modified spec requiring rich A/F continuously, I don't know the durability on OEM/aftermarket CAT.

    Kaz
    Last edited by Kaz-kzukNA1; 29-06-2020 at 01:13 PM. Reason: format

  7. #7
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    99% of the time, my cats see lambda 1, it's only under boost (CTSC) where AFR is 11-12. I'm driving it quite relaxed these days, so not much boost used.

    Those Random Tech cats for $600 might have cheap cores and won't like an enriched fuel mixture. At least they lasted 7-8 years and 45k miles. That's fine for me. The cats are some kind of a 'consumable' when you boost it up.

    No feedback from the suppliers in the States so far (Corona won't easy the process either). So, I'm willing to go the SARD route. SARD cats are 200 cells. I've found them here: https://www.rhdjapan.com/sard-sports...a1-type-i.html
    I don't know if the supplier is reliable.
    They end up around $1500 imported. So could I expect that these meet the strict Japanese rules and their quality is perfect? If so, they're worth to me.

    What do you think?

  8. #8

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    Quote Originally Posted by goldnsx View Post
    Hi Bruno

    Thanks for your response.

    How does the emissions test in Portugal work? CO at idle and CO at 2500 rpm < 0.1 %vol like we have here? Do you have to heat them up like crazy to pass the test or do they pass it after 10 miles of normal drive?
    Yes It is the same, Idle and 2.500 rpm. I usualy drive the car enough for it to get to the working temperture before SMOG, but the cats didn't need to be heated "like crazy". Sometimes the guy from SMOG just tells me to rev the engine 2 or 3 times... but with all the cars I take there is the same procedure. I did this rev procedure with OEM cats too.

    Since I Have KSP Headers and Exhaust I tried to buy KSP Cats when I bought my Sards, but was told KSP Cats were no longer available...

    Regrads
    Bruno

  9. #9
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    http://www.nsxprime.com/forum/showth...-(on-CTSC-NSX)

    This thread is old but may be helpful....at least the posters are in Europe except for Ryu (his bypass option is an idea with standard cat)

    SS
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  10. #10
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    Thanks for the link to the good old times. Unfortunately, the US forum was not of any help so far. No surprise, with the exception of California they can do whatever they want. That's why I'm not taking the US as a reference.
    200 cells are ok. I'd even consider 400 cells if the flow was higher than stock but they're hard to come by. Back in the days people in Europe even had problems with HJS 100 cells cats and they were the best available option back then.

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