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Thread: Odd spark plug behavour

  1. #1
    Supporting Member II Turbo Mopar Contributor
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    Odd spark plug behavour

    Hello All,
    using Costco 91 fuel in Ontario
    my 87 CSX with 2.5 TII, stock garrett with two piece and mildly ported head. FMIC worked well on stock type spark plug (Autolite 65)
    After a engine rebuilt, forged Weisco pistons from TU, S60, 3" SV and the rest is as above. After the rebuild, I replace the stock SP wires/cap with an NGK and used NGK 97382 Iridium plug. So far so good. I am only running approx 12 psi at the moment, But I thought I would go back to the 65 plugs. The CEL was good until the engine was warm and then started to flash at times (turbonator flash CEL on knock) and I could feel a loss of power. Never flashed at idle but commonly on low part throttle, like leaving a stop sign in traffic. Many time stayed on under load going up a hill. I decided to try a colder champion 9y and results was the same. Uggg replaced with the NGK 97382 Iridium and we are now good.
    Any ideas why??? even the colder 9 has issue.
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  2. #2
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Odd spark plug behavour

    I've never experienced anything like that. It is very interesting though. Is there a different shape to the electrode between the two styles of plug?

  3. #3
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Odd spark plug behavour

    datalog the knock volts/ cyl retards to see if there are different results.

    listen to the knock sensor?

    https://uprev.com/documentation/Knoc...n%20Device.pdf

    Plus

    https://www.amazon.com/FiiO-A1-Porta...01LYYKP29?th=1 (rather than the fiio e5)

    also, an alternative circuit.... ive used this one on my Honda CR-V to listen to knock. I can hear the gearshift moving around in the transmission with the engine off with this circuit below.

    (KS pin/wire) ------------ (.1uF capacitor) -- (100k ohm resistor) ------ (mic jack tip)
    (engine ground) ------------------------------------------------------------(mic jack base)

    that way you can hear if the CEL turn on is real knock or some other phenomenon.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  4. #4
    Supporting Member II Turbo Mopar Contributor
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    Re: Odd spark plug behavour

    Quote Originally Posted by cordes View Post
    I've never experienced anything like that. It is very interesting though. Is there a different shape to the electrode between the two styles of plug?
    Yes the irdium plug has a narrow electrode
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  5. #5
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Odd spark plug behavour

    thats strange.... the NGK 97382 is a GR4IX.... 4 heat range is hotter than the RN12YC from what i can gather.... I would think it would knock more....

    i assume all the cam/distributor timing is set correctly.

    I dont generally get CEL flash for anything but really high boost but my 2.5 is a Ghead.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  6. #6
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    Re: Odd spark plug behavour

    Quote Originally Posted by Aries_Turbo View Post
    thats strange.... the NGK 97382 is a GR4IX.... 4 heat range is hotter than the RN12YC from what i can gather.... I would think it would knock more....

    i assume all the cam/distributor timing is set correctly.

    I dont generally get CEL flash for anything but really high boost but my 2.5 is a Ghead.

    Brian
    I believe the timing and cam are fine but I will check when things quiet down a bit here at home. Where can I check the heat ratings on the plugs vs others? I searched but did not find this cross reference. NGK does recommend the BPR4ES and GR41X for our application.
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  7. #7
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Odd spark plug behavour

    i saw this chart floating around the internet.

    https://forums.pelicanparts.com/uplo...1393302384.jpg

    not sure how accurate it is. I run BPR6ES

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  8. #8
    ...if you know what I mean... Turbo Mopar Contributor csxtra's Avatar
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    Re: Odd spark plug behavour

    Another data point Miles, I run BR8ES (non-projected tip) in my CSX (2.5 G Head) because the porcelain doesn't break as easily from knock as the projected tip plugs do. Same plugs Reeves uses in his OMNI with no issues (9.99 second-proven spark plugs...lol).
    Warren Hall
    "My Name is Warren and my car is an alcoholic..."
    OVC - SDAC "Our Sh*t Rolls!"
    Cincinnati, OH
    87 CSX # 741
    317WHP - 380 WFt-Lbs (STD-5)
    12.460 @ 113.2 - Race Gas + Methanol Injection
    12.749 @ 109.84 - 91 octane + Methanol Injection (Still tuning...)
    "Illegitimi non carborundum."
    -General Joseph Stillwell
    TD Runlogger Page Has Moved...

  9. #9
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Odd spark plug behavour

    ive ran that plug too from time to time... I had a strange low load miss though when i first tried that plug with my g-head 2.5.... it wanted more timing.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  10. #10
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    Re: Odd spark plug behavour

    Thanks Guys
    Plugs are cheap so I will try 'em
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  11. #11
    turbo addict
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    Re: Odd spark plug behavour

    do you have the support bracket/bar that attaches to the head and neck of the 2 piece intake in place?
    that bar stops false knock readings from happening
    that's why it's there .. it's not a support but rather it eliminates an echo in the manifold that the knock sensor can hear..

  12. #12
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    Re: Odd spark plug behavour

    Thanks Johny, yes I do have this but perhaps I should test it is tight The NGK GR4IX does fix the issue
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  13. #13
    Supporting Member II Turbo Mopar Contributor
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    Re: Odd spark plug behavour

    OK update time.
    I changed the fuel o Exxon 91 as Jamie suggested Costco 91 had quality issues as noted by others. The bottom line .... about the same.
    This car is my summer daily.
    Spark plug trials as follows 2.5 TII CB. ported head/S60/FMIC/3" SV/3" Exhaust/ SMEC/MPFlash with BB stage II (stock injectors/2 bar/ 12 psi max boost.) All was tested on cold engine and ran to work of 25-50 miles each on country roads and highway.
    -Stock like Autolite 65, lots of knock even under vacuum conditions
    -Warren suggestion BR8ES. Could not get this to knock which was a positive, the engine was very sluggish to build power but A/F number looked fine.
    -Brian's suggestion BPR6ES This was a very responsive plug with snappy engine, worked near perfect except for knock on large hills under load.
    -Miles' favourite GR41X This was a very responsive plug with snappy engine and never knocked with many attempts..

    My thought on this. I wonder if the incoming charge is able to cool the small iridium tip down to prevent predetonation on the next engine compression cycle.
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  14. #14
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Odd spark plug behavour

    havent looked at all disclaimer... do they make a GR6IX?

    for big power on things like honda k series they run a BR8EIX or something like that. I figure on a medium boost TM, 6 heat range will be fine and wont be sluggish like the BPR8ES snowmobile plug.....

    Brian
    Last edited by Aries_Turbo; 10-01-2022 at 11:07 PM.

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  15. #15
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Odd spark plug behavour

    did some digging. looks like they make a BPR6EIX NGK 6637 that should work fine. 14mm thread, .75 reach.

    for a less projected option, BKR6EIX NGK 3764 should work.

    the B means 14mm thread, 13/16" hex and the BK means 14mm thread, 5/8" hex, 6 is the heat range, E means 19mm/.75" reach and IX is performance Iridium

    the GR4IX.... G = projected, 13/16" hex, 19mm reach, 14mm thread

    both B, BK plugs can be had in a 5 heat range as well.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  16. #16
    Supporting Member II Turbo Mopar Contributor
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    Re: Odd spark plug behavour

    Hi Brian,
    I had a quick look but thank you for taking to time to figure this out. I was hoping to find the iridium in a 6 heat range, and you figured it out for me!
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  17. #17
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Odd spark plug behavour

    you're welcome. twas fun to poke around and decipher the plug numbers.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  18. #18
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Odd spark plug behavour

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    Here are those plugs.

    the electrode and insulator sticks up the same height on the BPR6EIX and BKR6EIX but the BKR shrouds the insulator closer with the metal plug body.

    I think ill try the BPR for now considering im already running BPR6ES

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  19. #19
    Supporting Member II Turbo Mopar Contributor
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    Re: Odd spark plug behavour

    Darn you beat me to the punch!
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  20. #20
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Odd spark plug behavour

    Wow. You guys have got me itching to try out some new plugs. I have some br9es plugs in most of my cars with now if I'm not mistaken. It seems like that is way too cold for the daily drivers I have.

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