Hybrid_From_Hell Posted August 13, 2009 Share Posted August 13, 2009 Me had big hump time The 90 V8 has had the odd "7" + "1" Misfire now and again, coming home last night it was 7 all the way ....then 6 Me ?....straight into Megasquirt, and all sensors checked out Checked fuel pressure - spot on at 36 PSI, and level running That ruled out pump and PRV Changed coil pack(s) and EDIS8 - Nope Checked known good replacement lead on all 8 plugs - nope checked Injector connectors loose / dirt - nope check sensors - nope checked fuel level Nope Erm, what else is there.... Did full compression check - all fine Checked timing, trigger wheel - all fine Checked earths all ok, and battery voltages - spot on Erm......... Well, that only leaves the spark plugs, ..... and they were new ......6 months or less ago (and they are NGK BPR6ES) I'll change them anyway ..... And sorted......another set of plugs killed ? So, the question is why does this engine eat spark plugs and - on a regualr basis, like 3 sets a YEAR - and thats on a low mileage V8 Is it just the Odd spec / Wild cam / Race engine = killing ?? (BTW Cleaned up the 'old' plugs - and refitted - misfire For those who may be curious and have some thoughts spec is JED (John Eales) 4.5 Ex Flapper system now running 3.9 Injectors and Megasquirt MS1 V3 029v Omega Pistons, whizzy conrods, Ultra Big valve heads - High compression (around 10.2:1) wild High Lift long duration camshaft, Vernier timing gears, Ultra Large Ported 48mm Trumpets and matched inlet Manifolds, Fully Balanced and a load of other internal mods - and Custom 4>2>1 exhaust. I have tried 'hotter' and 'colder' plugs by 1 'grade' each side of 6s, no difference, ....still kills them just makes starting more difficult So, why does it eat plugs ? Thoughts Nige Quote Link to comment Share on other sites More sharing options...
Aragorn Posted August 13, 2009 Share Posted August 13, 2009 Do they actually look worn when they start acting up? Perhaps try a different plug? BPR6EK for instance? Or even a different gap on the stock plugs? Or some from a different manufacturer? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted August 13, 2009 Share Posted August 13, 2009 You sure it's not just the huge EDIS sparks breaking the plug down internally? Might be worth trying non-resistive plugs (BP6ES).... either that or a plug designed to work with EDIS-power sparks.... Poor ickle NGKs.... what have you been doing to them Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted August 13, 2009 Author Share Posted August 13, 2009 In answer to the 2x above posters: 1. No, they look fine, maybe a tad sooty, but normal and no signs of whiteness / leaness / or heavy overfuelling, just "Used" but no wear oir damage The codes for NGks is attached BPR6ES BP is the size R is resistor plug 6 is heat range which I have played with these are projector tipped plugs which are what is needed in an old style 3 wedge head design and the ES is the reach or and depths etc, so playing with that is a no no as you could in therory punch a hole in the crown, more likley just have a problem, as from the gurus I know abd have spoken to NGKs are the best plug to use in a V8, they are known( Rover V8s) to be "Plug Fussy", I have lost count of the number of times the special chavy whizzy plugs people fit cause issues quite soon after fitting http://www.sparkplugs.co.uk/pages/technical/NGK-spark-plug-code.htm I think its a heat rnage issue, which then means a compromise between cold starting and the engine heat rnage running, I do have a contact name for a plug guru in NGK from a fair while ago when I had similar probs which I thought may have been this, I'll try digging his number out 2. I also did some research on plugs and the BPR6ESs are fie for the 40,000 output from the forsd coil packs, the platinium whizzy plugs offer nothing more than longer service intervals, so no gain there, not sure about leaving the "R" out, its a thought, will check with Mr GURUNGK Nige Quote Link to comment Share on other sites More sharing options...
Aragorn Posted August 13, 2009 Share Posted August 13, 2009 The "R" is there to stop interference affecting the ECU/EDIS module. I wouldnt go down that route personally. Your not quite correct on the NGK part numbers... "B" tells you the size (14mm), "P" means it has a projected tip, and "R" that it has a resistor, 6 is the heat range, E tells you the thread reach (19mm), and S (or K) is the electrode style. So switching from a BPR6ES to a BPR6EK simply means your changing from a single electrode to a twin electrode. Might help, but then if your not actually wearing the old plug out then i'm not so sure. Quote Link to comment Share on other sites More sharing options...
Aragorn Posted August 13, 2009 Share Posted August 13, 2009 http://www.highwoodalfa.com/diff_pics/ngk.jpg for reference Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 13, 2009 Share Posted August 13, 2009 What gaps do you have? What gaps do Ford have for EDIS normally? Could be related. Quote Link to comment Share on other sites More sharing options...
Aragorn Posted August 13, 2009 Share Posted August 13, 2009 Zetecs use PTR5A-10 Which is gapped to 1mm Quote Link to comment Share on other sites More sharing options...
Quagmire Posted August 13, 2009 Share Posted August 13, 2009 Its gotta be EDIS related i reckon- i've been running the same Champions since last November with no issues and 12,000 miles or so on them with my crappy dizzy gapped to the upper limit in the book. If you clean them up and they still dont work, then surely its got to be related to a physical change in the property of the plug. What might cause that god only knows... Quote Link to comment Share on other sites More sharing options...
errol209 Posted August 13, 2009 Share Posted August 13, 2009 A bit of thinking aloud (which may may not reach a valid point, or a point at all): The function of the spark plug is to provide a focussed point for an avalanche breakdown of the intervening gas (the air/petrol mixture). In doing so it inevitably gets hot, both from the spark and the ignition cycle itself. To get an avalanche you need volts, but a by-product is amps when the event happens. The 5,000 ohm resistor acts to limit volts when amps rises, damping the spark and therefore limiting the current drawn (in this case from the drive electronics). The rising temperature of the plug will cause the resistance of the resistor to rise, which won't affect the point at which the spark happens, but will quench the spark sooner. Heat will also affect the insulation between the plug core and metal body, but these are fancy ceramic good to a few 1000's of K, so this seems unlikely. That leaves the resistive element, which is also a lump of ceramic. All in all my guess would be mechanical failure of the ceramic insulator (it is quite brittle) under high heat and pressure leading to the centre electrode tracking or arcing to the body. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 13, 2009 Share Posted August 13, 2009 Could it be that stock Rover plugs just can't live with much higher voltage & current provided by EDIS? Might even be worth calling NGK's tech helpline and asking their thoughts on it, they might have seen it before. Quote Link to comment Share on other sites More sharing options...
TSD Posted August 13, 2009 Share Posted August 13, 2009 Over wetting the plugs with fuel can cause them to fail, causeing misfire. I can only guess at the mechanism that causes it, but I saw it several times when messing with the first MS units. When I was working with the prototype EDIS code, I never had any plug failures I could relate to that. Every time I've seen your truck, starting hasn't seemed to be its strong suit, so that might well be part of the problem. The hot spark does tend to increase the erosion of the plug though, and remember that half the plugs are firing reverse polarity, which changes the erosion / metal migration pattern. Ford USA used to spec single platinum plugs for the cylinders firing 'normal' polarity, and double platinum plugs for those running reversed. Maybe worth the price of one set of double platinum plugs to see how long they last? Dave Quote Link to comment Share on other sites More sharing options...
Lara Posted August 13, 2009 Share Posted August 13, 2009 We used to have this problem with one of our engines running a Scintilla Vertex Magneto, NGK BP7ES plugs breaking down every 1500 miles or so, we put it down to the very high voltage that the mags produce, We changed to Bosch Platinum W3CS and never had the problem again. Lara Quote Link to comment Share on other sites More sharing options...
Aragorn Posted August 13, 2009 Share Posted August 13, 2009 TSD: Banks running reverse polarity? huh? Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted August 13, 2009 Share Posted August 13, 2009 EDIS is wasted spark, the spark plugs 'before' the coil get fired the wrong way round. Quote Link to comment Share on other sites More sharing options...
TSD Posted August 13, 2009 Share Posted August 13, 2009 TSD: Banks running reverse polarity? huh? Not different banks, different cylinders running reversed polarity. EDIS is a wasted spark system, using four double ended coils. Two cylinder spark at a time, one on compression, the other on exhaust stroke. The same charge of electricity discharges through both spark plugs, but in opposite directions. The current path is from one end of the coil, from tip of one plug to the body, then through the engine block and the body of the second plug, to the tip and returning to the coil. Because the erosion of the plug is affected by spark polarity (like welding with reverse polarity) the effect is different on 'normal' polarity plugs to the reverse polarity ones. Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted August 13, 2009 Author Share Posted August 13, 2009 starting hasn't seemed to be its strong suit :rofl: Oh yes doesn't it just , combo of the wild Camshaft and Valve overlap, have had to really play with the Cranking, WUE and ASE on MS to get it to where it is now .....which is a lot lot better, .....and has improved so much it could now be called "appalling" I also know my engine gets hot - F hot, being in effect a 3.5 block stroked and linered to 4.5 so the latent heat and heat build up / soak is massive, I also wonder if a hot little plug(s)take a dislike to then being submerged in ice cold rocker deep water ? Have to speak to NGK again later today Ta all for the thoughts Nige Quote Link to comment Share on other sites More sharing options...
Aragorn Posted August 13, 2009 Share Posted August 13, 2009 How can the power possibly discharge from the same coil in more than one direction, when its travelling TO earth.... Both plugs are connected to the same coil and the power flows to earth. It doesnt flow round some crazy loop and back into the coil again... If you disconnect a plug lead, the other bank will still fire. Quote Link to comment Share on other sites More sharing options...
errol209 Posted August 13, 2009 Share Posted August 13, 2009 How can the power possibly discharge from the same coil in more than one direction, when its travelling TO earth.... Both plugs are connected to the same coil and the power flows to earth. It doesnt flow round some crazy loop and back into the coil again... If you disconnect a plug lead, the other bank will still fire. The coil generates a potential difference across its terminals, making one end negative relative to ground and the other is positive relative to ground, so a current flows from ground through the plug to the relatively negative end, and a current flows from the relatively positive coil end to ground through the other plug. So in the first plug the electrode is negative (backwards) and the other is positive (right way round). Tadaaaaaaaaaaa! Quote Link to comment Share on other sites More sharing options...
Aragorn Posted August 13, 2009 Share Posted August 13, 2009 So what then happens in a distributor system where theres only one tap from the coil, or in a wasted spark system when you remove one lead? Quote Link to comment Share on other sites More sharing options...
errol209 Posted August 13, 2009 Share Posted August 13, 2009 So what then happens in a distributor system where theres only one tap from the coil DO you mean what's the circuit? the coil generates the potential difference, with one end of the coil grounded. The distributor then connects the coil live to the appropriate plug (electrode positive), fat spark, flows to ground. You also get a spark between the rotor arm and the contacts, which is why people invented wasted spark (first fitted to 2CVs I think) So what then happens ... in a wasted spark system when you remove one lead? (thinks - is this a trick question? better agree some ground rules before committing ) I have no experience of wasted spark systems personally, but the theory says - nothing works. Quote Link to comment Share on other sites More sharing options...
Lara Posted August 13, 2009 Share Posted August 13, 2009 Strange but true! Lara Quote Link to comment Share on other sites More sharing options...
TSD Posted August 13, 2009 Share Posted August 13, 2009 (thinks - is this a trick question? better agree some ground rules before committing ) I have no experience of wasted spark systems personally, but the theory says - nothing works. One of three things happens :- 1) Nothing 2) The disconnected end arcs out from the end of the coil, and you get a very weak spark on the connected cylinder. 3) The coil arcs out through the internal insulation, and the coil never works properly again, due to reduced breakdown voltage The coil drivers don't really want to be switching a fully charged coil either, so ecu/edis damage is possible (though probably not likely). Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 13, 2009 Share Posted August 13, 2009 For no good reason other than it's a cool picture... Quote Link to comment Share on other sites More sharing options...
ThreeSheds Posted August 13, 2009 Share Posted August 13, 2009 For no good reason other than it's a cool picture... It's a very informative picture in that you can tell the arcs are directional! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.