taz90 Posted August 13, 2009 Share Posted August 13, 2009 had the same thing happen to me last month after i put some injector cleaner in the tank. was running on 6-7 pulled off injector plugs made no difference. pulled off plug leads same. stripped fuel rail tested injectors ect still no better. put a new set of plugs in runs fine. was told i had contaminated the plugs and advised to fill up with shell optimax every 3 or 4 fills been as good as gold since Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted August 13, 2009 Author Share Posted August 13, 2009 ^^^^^^^^^^^^^^^^^^ Interesting I shoved Forte injection cleaner though ANyway nice chat with a man who life is plugs, a wealth of info and suggestions, which I'll post up later for others to digest Nige Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 13, 2009 Share Posted August 13, 2009 It's a very informative picture in that you can tell the arcs are directional! Indeed - and as per the welding analogy, one end of the spark erodes the metal and deposits it on the other, so I'd guess the side that erodes the steel body and deposits it on the nice copper electrode would likely be guilty of causing the misfire. Quote Link to comment Share on other sites More sharing options...
Aragorn Posted August 13, 2009 Share Posted August 13, 2009 Interesting. I've just dug out the haynes for our A4, and sure enough on the wasted spark models it shows the two leads coming off different sides of the secondary... I'm pretty sure though, if you pull a lead off on a wasted spark car it only drops one cylinder... Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted August 13, 2009 Share Posted August 13, 2009 Interesting. I'm pretty sure though, if you pull a lead off on a wasted spark car it only drops one cylinder... Sooooo much to learn………….. Yes, if you remove one plug lead on a wasted spark system you just lose one cylinder ………………..because that cylinder will no longer fire on the firing stroke and the exhaust (wasted spark) stroke. Nige, With your engine ………. High volume breathing, large overlap cam, critical timing, & wasted spark ……… I would be inclined to run a slightly colder plug as a lot of your running time is slow moving off road ……….. I would take an educated guess that you are probably exceeding the heat range of the existing plugs which will lead to very early and unexplainable failures. Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted August 13, 2009 Author Share Posted August 13, 2009 Oi BBC You been overdosing on those telephatic tablets again bl**dy druggie ? Yep, having had a VERY long Conv with a Plug Guru (no, not that sort he has said the following 1. Heat range - with a block now 4.5 heat soak is huge, suggested an oil cooler - which was on the cards 2. Plugs are prob working outside the "Approved" Ranges - esp when Red hot plug cermaic shoved in Rocker cover deep ice cold water 3. Gap set at .6 is again at the max for this plug, but would be OK for road use with 40,000 output, but not 1 and 2 added 4. Changing plug temp rnage may cause starting issues but has suggested a alternative, written down here somewhere but way off what I have now 5. Aviod C Plugs (ie BPC etc) as reduces cooling dump via surface area 6. No 6 - Monty Python gag, showing me age 7. Don't bother cleaning, the plug prob is a combo of Cam, fuel fouling on start, Heat and warm up 8. avioding cold starts and short journeys and deep ponds will help 9. Cam causing washing on start up due to Valve overlap, suggested raised start up numbers to reduce the lower RPMs 10. Fit a diesel* - so I shot him, .............even if he was helpful Nige * may have made this up Quote Link to comment Share on other sites More sharing options...
Aragorn Posted August 13, 2009 Share Posted August 13, 2009 Sooooo much to learn………….. Yes, if you remove one plug lead on a wasted spark system you just lose one cylinder ………………..because that cylinder will no longer fire on the firing stroke and the exhaust (wasted spark) stroke. But if the circuit flows current from one plug to the other, and the other is missing, there is no circuit? Therefore both plugs wouldnt spark and you'd drop two cylinders, not just one? Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted August 13, 2009 Share Posted August 13, 2009 Nige, Its more of the case of ………….. been there & done that……………….. and for the younger folk on here ……… experience doesn’t come out of books ! The old A series that I used to build had high volume breathing and a serious overlap cam (idle at 2K +) and generally a plug would expire at the end of each session……….however, you sometimes cannot get a plug that is cold enough ! (heat range still to high) Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted August 13, 2009 Share Posted August 13, 2009 But if the circuit flows current from one plug to the other, and the other is missing, there is no circuit? Therefore both plugs wouldnt spark and you'd drop two cylinders, not just one? No - wrong .............. you need to think about it and understand how the coil driver fires the coil on the firing stoke for any given cylinder . Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted August 13, 2009 Author Share Posted August 13, 2009 experience doesn’t come out of books 'aint that the truth Ian, and with the T'internet is even worse What was it BogMonsterBrush said in his sig a while back ??? "Armchair experts" - Absolute Classic and so true sadly In me "Yoof" I had a Kawka H2 750 triple - now that REALLY ate plugs Between throwing me off into hedges and roads that is Nige Quote Link to comment Share on other sites More sharing options...
Guest otchie1 Posted August 13, 2009 Share Posted August 13, 2009 'aint that the truth Ian, and with the T'internet is even worse What was it BogMonsterBrush said in his sig a while back ??? "Armchair experts" - Absolute Classic and so true sadly In me "Yoof" I had a Kawka H2 750 triple - now that REALLY ate plugs Between throwing me off into hedges and roads that is Nige You TripleK clubber. Wasted spark systems as per loads of Jap multi-cyclinder bikes do eat spark plugs. Twice the number of sparks than a non-wasted plug has to deal with so half the life. Either resign yourself to changing them regularly or maybe fit Bosch plugs at twice the price of the NGKs? How about choking the feed to the coil and so reducing the final spark voltage? Can you do that on MJ? Quote Link to comment Share on other sites More sharing options...
TSD Posted August 13, 2009 Share Posted August 13, 2009 No - wrong .............. you need to think about it and understand how the coil driver fires the coil on the firing stoke for any given cylinder . I'm obviously missing something, explain? Quote Link to comment Share on other sites More sharing options...
Bull Bar Cowboy Posted August 14, 2009 Share Posted August 14, 2009 No Dave, you are not missing anything ………… it just another way of looking at your self explanatory description Quote Link to comment Share on other sites More sharing options...
Aragorn Posted August 14, 2009 Share Posted August 14, 2009 Well i'm lost, your contradicting and agreeing with TMD. TMD stated that a circuit is created that flows current from one side of the coil, thru one plug, across the ground plane (ie the engine block) across the other plug and back to the coil. This means that the current would from from the centre electrode to the ground electrode on one plug, and vice versa on the other. Both plugs fire simultaneously, and twice as often as actually required, alternating between real and wasted on each plug. ie both 1 and 4 fire when 1 is on its compression stroke, and again when 4 is on its compression stroke. If what TMD says is correct, and you disconnected one lead, the entire circuit would be broken and neither plug would fire. You've just said it would only drop one cylinder, but then said TMD's description was correct. It would be beneficial for all involved if you actually explained what you mean, rather than going on about how you cant learn everything from a book etc. I understand how the "coil driver fires the coil for any given cylinder", i just dont quite get the current flow involved, because if its as TMD says (and it seems from the wiring diagram i've looked at that it is), then it should in theory drop two cylinders if you removed a lead, as while one side of the coil was connected to earth via the plug, the other side wouldnt be connected to anything and if the circuit isnt complete no power can flow. Quote Link to comment Share on other sites More sharing options...
errol209 Posted August 14, 2009 Share Posted August 14, 2009 If what TMD says is correct, and you disconnected one lead, the entire circuit would be broken and neither plug would fire Agree strongly. If it continues to work, it can only be because the circuit is completing itself some other way, by arcing from coil terminal to ground somewhere. A diagram to ponder: Quote Link to comment Share on other sites More sharing options...
Aragorn Posted August 14, 2009 Share Posted August 14, 2009 Agree strongly. If it continues to work, it can only be because the circuit is completing itself some other way, by arcing from coil terminal to ground somewhere. A diagram to ponder: Aye, same diagram is in the manual for our Audi A4. I guess i've never had a spark issue with a wasted spark car or diagnosed it too closely to have realised this quirk before! Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 14, 2009 Share Posted August 14, 2009 Can I humbly suggest that since both Dave and Ian are right, we agree it works by magic and worry about something else? Quote Link to comment Share on other sites More sharing options...
Aragorn Posted August 14, 2009 Share Posted August 14, 2009 Lol, i just want to know how it works. I find asking questions and working thru things like this is an excellent way to learn rather than just attributing it to magic! I can see the logic behind what TMD and errol are saying, and i admit i've never actually pulled a plug lead off a wasted spark car to see what would happen. Yet BBC is saying it would only drop 1 cylinder and not the 2 that TMD and errol suggest (and that makes sense from the wiring diagram and the explanation) Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted August 14, 2009 Author Share Posted August 14, 2009 Can I humbly suggest that since both Dave and Ian are right, we agree it works by magic and worry about something else? :rofl: But, on a serious note are you saying ectrix 'aint magic ? And stop there, don't you also start on about how Santa, and the Tooth Fairy not really existing Nige Quote Link to comment Share on other sites More sharing options...
TSD Posted August 14, 2009 Share Posted August 14, 2009 I *think* that I disagree with BBC on the theory, but in practice he's correct. You need to complete the circuit for current to flow, so if you disconnect one end of the coil, you drop two cylinders. But in practice it's very hard to disconnect the coil, all that happens is that it arcs out from the end of the coil to vehicle earth, which can happen externally from the end of the coil body, or internally through the insulation. EDIS has a large margin of spare energy (as evident in the photo Fridge posted), and it's much easier to strike an arc in air at atmospheric pressure than it is in a fuel rich mixture under pressure, so a long spark is quite easy to acheive. When the coil is fired, the terminal voltage continues to rise, until the arc is established (or internal losses use up the available coil energy) Once the arc is ignited, it takes much less voltage to sustain the current path through the ionised air track, so overall spark duration may not change by much, especially as EDIS will ensure the coil is fully charged by extending the coil charge time before the next spark. The coil may arc over internally without apparent damage, either because the manufacturer incorporates a 'failsafe' spark gap into the coil design, which ignites at a voltage much higher than needed to light off the plugs, or by simply punching through the insulation. This isn't usually too much of a problem as the oxide residue created by burning the insulation is also an insulator, but I suspect it makes the coil more likely to break down at reduced voltage - and so become a 'weak' coil. (I don't know if there is a failsafe gap included, but I would if I were designing it, and it's easy to imagine it could be done at zero cost). Dave Quote Link to comment Share on other sites More sharing options...
Jon White Posted August 14, 2009 Share Posted August 14, 2009 If it any help Nige my mini used to do exactly the same with BPR6ES NGK plugs in it. I tried BPR7ES but it didnt make an awful lot of odds. I sold the car before i got to the bottom of it, but I suspect changing to a different brand of plugs would be worth a try. Jon Quote Link to comment Share on other sites More sharing options...
Guest otchie1 Posted August 14, 2009 Share Posted August 14, 2009 Conversely there is a distinct limit to what you can learn from your own experience. Wasted spark ignition coils can come in two varieties; double ended coils and twin tapped coils. Ford's EDIS system I am told uses doubled ended coils. Here, if you remove one plug and hold it insulated from earth then neither plug will fire. With double tapped coils then each HT circuit is independent. Ford's system is interesting in that it relies on good compression to generate a high resistance across the firing spark-plug electrodes and a commensurate low resistance across the wasted spark spark-plug electrodes. Physics then neatly divies up the voltage so you get a bigger spark where the resistance is higher. This means if you either don't have good compression in the firing chamber OR you have too high a compression in the wasted chamber then your spark will be weak. So, maybe check the conditions in the wasted pot? Quote Link to comment Share on other sites More sharing options...
Aragorn Posted August 14, 2009 Share Posted August 14, 2009 TMD: thanks that helps make sense of things otchie: makes sense. I had clearly incorrectly assumed that "twin tapped" coils were the norm, clearly thats not quite the case. Quote Link to comment Share on other sites More sharing options...
SteveRK Posted August 14, 2009 Share Posted August 14, 2009 If the plugs look visibly o.k. then i would break them all apart to check what condition the steel springs (resistor) are in. I would suspect its simply a case of poor quality manufacture or the plug is being subjected to voltages that that BPRE6 model does not normally encounter i.e lower voltage cars - they may say its rated for 40KV - but for how long? Quote Link to comment Share on other sites More sharing options...
TSD Posted August 15, 2009 Share Posted August 15, 2009 If the plugs look visibly o.k. then i would break them all apart to check what condition the steel springs (resistor) are in. I would suspect its simply a case of poor quality manufacture or the plug is being subjected to voltages that that BPRE6 model does not normally encounter i.e lower voltage cars - they may say its rated for 40KV - but for how long? The voltage rating (which I've never seen specc'ed, but never looked either) is irrelevant unless you already have a misfire. The voltage at the plug rises until the spark ignites, then no further, in fact it drops to a sustaining voltage, that required to maintain the arc through the now ionised gas path. Quote Link to comment Share on other sites More sharing options...
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