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Thread: Spark Plugs with E85?

  1. #1
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    Spark Plugs with E85?

    So I've got this issue where I'm getting inconsistency with NGK spark plugs. When I first got my car running with the turbo I switched to the popular BKR7E. This worked great on 93 octane up until I hit the dyno with E85 and tried to pass 12 PSI. I swapped at the time to what I thought was a step colder plug, turns out I didn't understand the numbering system and went to a BKR6E. This actually fixed the issue along with new coils. When I realized my mistake recently I swapped back to BKR7E's and the misfire came back.. so I am a bit confused. I would like to find a plug that will idle better as the BKR6E at gapped at 22 or so misfires a little at idle but pulls strong in boost. I'm running my M52B28 with stock compression on E85
    1997 328is - Megasquirt PNP, Holset HX35, Deka 80lb injectors, SPA T3, Precision PW39 WG, Synapse Synchronic BOV, DKM Organic Twin Disc Clutch, Innovate LC-2 W/B, Mishimoto Intercooler, Mishimoto Catch Can, Mishimoto Rad, Devils Own Meth, Porsche 911 calipers with E46 M3 rotors, Corsa Exhaust

  2. #2
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    I’ve only ever ran bkr7e’s. They work fine. If your not fouling plugs the heat range is not your problem. Try gapping down a bit more.


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

  3. #3
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  4. #4
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    Quote Originally Posted by someguy2800 View Post
    I’ve only ever ran bkr7e’s. They work fine. If your not fouling plugs the heat range is not your problem. Try gapping down a bit more.
    The hotter plug works fine for me so far it's just the idle quality that I can't stand.

    Quote Originally Posted by vollosso View Post
    46psi boost
    4554’s
    22thou gaps
    Stock coils
    9:1 compression



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    Am I seeing that those are a shrouded and non resistor plug? May have to give that a shot.
    1997 328is - Megasquirt PNP, Holset HX35, Deka 80lb injectors, SPA T3, Precision PW39 WG, Synapse Synchronic BOV, DKM Organic Twin Disc Clutch, Innovate LC-2 W/B, Mishimoto Intercooler, Mishimoto Catch Can, Mishimoto Rad, Devils Own Meth, Porsche 911 calipers with E46 M3 rotors, Corsa Exhaust

  5. #5
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    Quote Originally Posted by somebody5788 View Post
    So I've got this issue where I'm getting inconsistency with NGK spark plugs. When I first got my car running with the turbo I switched to the popular BKR7E. This worked great on 93 octane up until I hit the dyno with E85 and tried to pass 12 PSI. I swapped at the time to what I thought was a step colder plug, turns out I didn't understand the numbering system and went to a BKR6E. This actually fixed the issue along with new coils. When I realized my mistake recently I swapped back to BKR7E's and the misfire came back.. so I am a bit confused. I would like to find a plug that will idle better as the BKR6E at gapped at 22 or so misfires a little at idle but pulls strong in boost. I'm running my M52B28 with stock compression on E85
    Sounds to me your ignition system is the problem (coils/boots). It is certainly not the NGK plugs that's for sure.

  6. #6
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    Im running the ngk 4554 gapped at 24 and full e85, no issues.
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  7. #7
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    I curious if a non resistor plug helps on an ignition system that is marginal on voltage to keep it from misfiring under high boost. In theory it should but we also know that spark plug resistance doesn't mean as much as we would think because the spark energy travels over the surface of the plug wire conductor not through it.


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

  8. #8
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    Quote Originally Posted by someguy2800 View Post
    I curious if a non resistor plug helps on an ignition system that is marginal on voltage to keep it from misfiring under high boost. In theory it should but we also know that spark plug resistance doesn't mean as much as we would think because the spark energy travels over the surface of the plug wire conductor not through it.
    I see where you're going with this... and maybe the non resistor plugs let you squeeze that little extra out of the ign. system. I've never seen the need to go to non-resistor plugs on any platform so far even @ 1300 whp cars. and I too like you use the 7E (4644) on plenty of cars without any issues.

    But no matter in this situation for the OP... If you can't even get to 1 BAR boost without misfiring plugs are not the issue especially @ 0.022" gap.

  9. #9
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    Quote Originally Posted by NOTORIOUS VR View Post
    I see where you're going with this... and maybe the non resistor plugs let you squeeze that little extra out of the ign. system. I've never seen the need to go to non-resistor plugs on any platform so far even @ 1300 whp cars. and I too like you use the 7E (4644) on plenty of cars without any issues.

    But no matter in this situation for the OP... If you can't even get to 1 BAR boost without misfiring plugs are not the issue especially @ 0.022" gap.
    Yeah I'm curious if the resistor increases the breakdown voltage needed to get an arc started. I have a feeling it wouldn't but I don't know enough about high voltage electricity to know one way or another. I've read a few articles about how the spark energy actually goes through the plugs and wires written by people smarter than me and I know enough to know ignition systems don't quite work the way a guy would think.

    I've never really seen it discussed but I do know there are several different models of the OEM ignition coils. I think I have 3 kinds of OBD1 coils on my shelf. I tested them all a couple years ago using megasquirt to trigger them and a screw in and out ignition tester and there was a big difference between them. The good ones I used on my car were just as good from what I could tell as a GM dis coil, which runs a .060" plug gap even on the supercharged motors.


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

  10. #10
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    I'm really curious what the difference between the 2.7 turbo Audi coil packs and ours is. They look exactly the same.

    I am running a set of Bosch coils, I switched from Bremi's that had 200k on them.

    I was really hoping someone might have some reasoning for why a hotter spark plug would work better than the colder one. At first I thought maybe E85 since it's more knock resistant might need the hotter plug but many get away with the BKR7E on E85 and the higher compression ratio would probably make up for any of those differences. I'd really like to be able to go Iridium like most newer stuff and gap at 24-25.....
    Last edited by somebody5788; 09-20-2018 at 10:00 AM.
    1997 328is - Megasquirt PNP, Holset HX35, Deka 80lb injectors, SPA T3, Precision PW39 WG, Synapse Synchronic BOV, DKM Organic Twin Disc Clutch, Innovate LC-2 W/B, Mishimoto Intercooler, Mishimoto Catch Can, Mishimoto Rad, Devils Own Meth, Porsche 911 calipers with E46 M3 rotors, Corsa Exhaust

  11. #11
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    S4 coils are quite good... plenty making lots of power on then. But the same can be said for the stock M/S5x coils for many. The issue with them both is replacing the coils and boots is quite expensive.

    Really what's happening here is just that you have one or more weak coils or bad boots. I too had misfires on my stock BMW coils above 11 or so PSI... I swapped some boots around and some used CP's and it never really helped...

    I threw them out and changed to the VAG COP's, they're cheap and have a very, very good energy output at low dwell. The VAG CP's are lighting off 2500whp in Lambos, and various other high boost cars all over the place. It's a very common swap for the aftermarket. You're running MS so the swap will be straight forward I'd assume.

  12. #12
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    Like others have said, likely a lazy coilpack.

    As for plugs - I still don't know why you guys don't use iridiums. It's like getting an instant 30-40% headroom on your ignition system for a very low cost (smaller ionized volume to jump the gap with a spark). They also last longer than copper plugs.

  13. #13
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    Quote Originally Posted by Def View Post
    Like others have said, likely a lazy coilpack.

    As for plugs - I still don't know why you guys don't use iridiums. It's like getting an instant 30-40% headroom on your ignition system for a very low cost (smaller ionized volume to jump the gap with a spark). They also last longer than copper plugs.
    Your comment made me think to myself "yeah why haven't I, there must be some reason"

    Pulling up the NGK catalog and the first 4 options for a 3/4" reach 5/8" hex 14 mm spark plug iridium and a non projected electrode are discontinued. So I tried to find a newer than 2010 NGK racing catalog and no luck. I could probably just go the BKR8EIX route but they're 3 times the price.


    I have now given up again. 4554 copper plugs it is. I would really love to find a fine wire iridium non projected plug from the ngk racing line though.

  14. #14
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    I used to get around 2-3k mi (lots of them on track) on a copper plug before the resistance went to shit and I'd get misfiring. I put in a set of iridium plugs and they were going strong for 10k+ mi (again, most on track), and pushed way harder on E85, more boost etc. with no issues.

    I get it, it's like $4-5 more per plug, but you really can just buy a set and not worry about it unless you foul them out. I've never sucked so bad at tuning I've fouled out a set of plugs, even on a basemap... so I can only surmise the people that do that regularly need to be put in a padded rubber room.

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