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| Grimketel |
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gday guys.
went a bought me some autolite 985 sparkplugs today, for the princley sum of 20 bucks for 6 at MTQ in laverton north. No where else i rang had them, including repco, autobarn or bursons. I spent a moment of time instaling them, gapped around the 1.4mm mark (recomended 1.5mm gap on my screamin demon coil pack). all leads on nice and firm, they are the same leads i had on already, not due for replacement yet, so they were not removed, and are correct. started with an initial momentary hesitation before idling perfectly. driving aorund town, smooth as a babies bum, working perfectly as i let the engine warm up a bit. onto the highway onramp, and open the taps to disover what i can only describe as a stuttering missfire on a 2800-3200 rpm band that was not there before installing the autolite plugs. pulls sweetly after that band, and runs smoothly before that band. but everytime you have the throttle opened up at that rpm, is f@rt around and crackles away out the exhaust pipe. whats casuing this problem? any guesses?
_________________ enough isn't enough |
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| 66 coupe |
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close the gaps down to 1.1, you will find that will probably fix it.
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| Kenay |
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well to me tht sounds like a coil pack so check the gaps first then check the coil packs
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| 66 coupe |
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1.4mm with wasted spark, thats near on a 3mm spark gap. chances are its blowing spark out
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| KWIKXR |
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As 66 coupe said, the gap may be a tad too big.
In saying that though, i would of gone with what was recommended too when using the screamin demon coil even though 1.5mm is still quite a big gap. Did you run the screamin demon coilpack with the old plugs at all? If you did, what gap were the old plugs set at? Notice any difference with the demon coilpack? 
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| PIMP_LTD |
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I agree, thats a stupidly huge gap, it'll be blowing out.
Try 1.1mm.
_________________ Commodore australia's favorite car??? What a load of s**t |
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| Grimketel |
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Quote: In saying that though, i would of gone with what was recommended too when using the screamin demon coil even though 1.5mm is still quite a big gap. Did you run the screamin demon coilpack with the old plugs at all? If you did, what gap were the old plugs set at? the gaps no probs, ive had the coil pack for over a year now, and the old ngk were over 1.5mm when i took them out. they had been gapped to 1.5mm when installed and electrode wear has taken them past 1.5mm. Quote: I agree, thats a stupidly huge gap, it'll be blowing out. Try 1.1mm. how is it a stupidly large gap pimp? on a standard coil pack yes, but these things come out with a recomended gap of 1.5mm, and have given no trouble over the past year. Quote: 1.4mm with wasted spark, thats near on a 3mm spark gap. chances are its blowing spark out can you explain 'wasted spark" and how this equates to a 3mm gap? ill try regapping them, but something tells me this could be resulting from the effect of the incresed plug projection having an effect "similar to advancing the timing by 10 degrees". how can it be the gap when its pulling hard above the mark? if spark is going out at 3000rpm, shouldnt it be staying "blown out" above that? and shouldnt it have done so on many occasions in the past year? how will an au2 ecu with its knock sensor respond to the slightly different detonation of the mix with these plugs?
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| 66 coupe |
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wasted spark means one coil within the coil pack is firing two plugs, therefore that coil needs to provide the voltage to spark across double the gap of one plug.
The RPM range its falling over is roughly at peak torque, where cylinder pressures are highest, which is why i suggested it is blowing the spark out. You wont get any more power with a bigger gap. Close them down to 1.1 and see what happens. |
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| Grimketel |
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cheers for the wasted spark education
 as i understand it its the packing of the particles in the chamber that a weak spark doesnt like (compression). it takes more energy to pass through the dense medium to the tip to create the spark. is this what you mean by "blown out"? if i take it literaly its like saying a good gust of wind could blow out a lightning strike, so im trying to nut that one out, since sparks dont follow the same behaviour patern as flame for instance. it passes from particle to particle to reach its groundiing... so im assuming this to mean the density of matter at this rpm is to high for the spark to arc out. plz correct me if im missing anything. another question: could overfueling at that rpm be washing the spark out? it runs as rich as, you can smell it on startup. just got me buggered if it is the gap, as the ones i took out have a larger gap than the ones i put in!  pulling them out is going to mean re-indexing them, and that was a pain in the you know what in a major way...
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| PIMP_LTD |
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Grimketel wrote: Quote: I agree, thats a stupidly huge gap, it'll be blowing out. Try 1.1mm. how is it a stupidly large gap pimp? on a standard coil pack yes, but these things come out with a recomended gap of 1.5mm, and have given no trouble over the past year. From past experiences with different styles of ign systems i've had, i've just never come across that gap before, seems large to me, LOL. On all the cars i've beefed up the ign on, i have only ever used as big as 1.1mm, and one turbo car even used 0.8mm, seemed the best. But just to be sure, i'd try 1.1 if it were me. Just seems odd that they recommend 1.5. Good luck with it mate.
_________________ Commodore australia's favorite car??? What a load of s**t |
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| Grimketel |
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Quote: On all the cars i've beefed up the ign on, i have only ever used as big as 1.1mm, and one turbo car even used 0.8mm, seemed the best. on an AU2 1.1mm is the factory standard gap. they went with a CP that had more kick, hence the larger gap setting. E series was less gap. so 1.1 on an e series would be roughly the equivelant of running 1.4mm on an au CP. or so my twisted logic tells me ill try degapping on the morrow. i think it may be overfueling at that throttle position in the rev range wetting the spark. low throttle position at ANY rpm does not result in any of the symptoms. ie when revving in nuetral, or holding the gear out and using less throttle at high rpm.
_________________ enough isn't enough |
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| Steady ED |
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Low throttle position wouldn't do it, neither would revving in neutral, because a weak spark will blow out under high load at max torque exactly like 66 coupe said.
_________________ ED XR8 Sprint - S-Trim, V500, 249rwkw Last edited by Steady ED on Tue Apr 21, 2009 10:01 pm, edited 1 time in total. |
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| PIMP_LTD |
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Grimketel wrote: i think it may be overfueling at that throttle position in the rev range wetting the spark. low throttle position at ANY rpm does not result in any of the symptoms. ie when revving in nuetral, or holding the gear out and using less throttle at high rpm. When you say you think its the overfuelling, it didn't do this before did it at all? As i know the old I6's can run rich, mine does a bit, but that would be alot of fuel required to do that, and you say it didnt carry on like it before you fitted them.
_________________ Commodore australia's favorite car??? What a load of s**t |
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| TROYMAN |
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are the plugs of a colder range??
maybe there fouling at 3000rpm?? or put your old plugs back in and if the problem goes away its either a bad batch of plugs or they are just crap plugs? |
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| PIMP_LTD |
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TROYMAN wrote: or put your old plugs back in and if the problem goes away its either a bad batch of plugs or they are just crap plugs? I was thinking that myself a bit, as $20 for 6 plugs is cheaper than the standard ngk/champion/whatever plugs
_________________ Commodore australia's favorite car??? What a load of s**t |
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