high rpm misfire

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  1. #1

    Default high rpm misfire

    4.6 4v twin 66mm 10.1 cr. I'm running stock ford 4v pencil coils with 3.0ms dwell. At 14psi and 5200 rpm I get what feels like ignition misfire. I'm running NGK bkr7's at .025". I'm going to put a fresh set in tomorrow and close the gap down to .020" and retry with the stock coils. Using MS3X megasquirt

    Couple questions.
    1. Can I/Should I up the dwell to 3.5-4.0ms? Will the stock coils handle that high of dwell?
    2. If I still have the problem after new plugs and gap, what LS coils to go with? D585 truck coils?
    3. Another possibility is valve float. I am running 04 aviator heads with the stock springs. I'm sure they have 100k or more on them.

    I know some people get 800+ out of the stock ford pencil coils and some get blowout at less. I'll likely get some D585's regardless as i'd rather have an arc welder firing my plugs instead of a triple A battery.

    What springs offer more seat pressure than stock and install without machining the spring seats? I'm looking for the most budget set that offer at or near 100lbs of seat pressure. These are stock 98 cobra cams. This is a low buck project car, so I do not want the most expensive trick coils or springs here.

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  3. #2

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    Coil Stuff

    The OEM pencil cops have a dwell speed limit right around 2ms give or take and I think it is a take situation but I can't recall. If you run them at a 3 ms dwell, like you are, you will likely overheat them, boil the oil in the coil packs and experience a physical failure where the plastic outer cover bursts to release the pressure from the boiling oil. Even if you don't which, I doubt, you are at best still way short of the mark (spark energy-wise) that you need to be at in a boosted engine.

    Brand new OEM pencil cops are only good for about 20mj of spark energy. Just about what it takes to light a naturally aspirated mixture. Once you boost the engine, depending on how used up the cops are, you begin to experience spark blowout. The fix is exactly what you are investigating right now. Ignoring CD coils there are two broad classes of inductive coils available, smart (with igniters built in) and dumb w/o igniters. If you go the dumb route you may need to use igniters along with the coils. If you go the smart route you will not. Smart coils deliver about 103mj oof spark energy, dumb coils deliver about 118mj spark energy — close but not identical.

    The reason igniters are required for the dumb coils is that most aftermarket ECU's are not designed to internally handle the current draw from the dumb coils. There are a couple of notable exceptions to this, one of which is from MegaSquirt. The MS exception is their new Plug and Play (PnP) MS3Pro for Terminators and SN95 cars that uses a stock wiring harness and OEM cops. The circuit board was built to handle the current draw from the stock dumb coils.

    As it turns out the use of dumb coils and external igniter circuitry closely approximates the cost of just the IGN1-A smart coils but adds wiring complexity and additional points of failure, in the igniter electronics, to deal with. As painful as it is, price wise, the name brand IGN1-A coils are a better choice than the cheaper IGN1-A knock-off coils available through Amazon and eBay. The knock off coils not only have a higher failure rate but tend to wilt under load after a short life.

    You might consider setting up the spark at a low dwell (2ms or so) until you are under boost and above some target rpm (4000?). The benefit, with the IGN1-A coils, or any coil for that matter, is a cooler running coil that still fires at high boost and does not overheat or prematurely fail.


    Valve Spring Stuff

    With respect to the valve springs there are basically two manufacturer choices you have and three spring choices between those two. The two manufacturers are PAC and Associated Spring. Pac has two offerings and Associated has one. The Associated spring is sold by Manley as their Nextek spring. The PAC offerings are sold as Pac springs. The Nextek spring is essentially a cop of the PAC 1223 spec-wise.

    The two spring offerings in the PAC line up are the PAC 1223 spring with is an excellent spring that seats at 90 lbs with a 324 #/inch spring rate. The second spring is a PAC 1217X with a 308 3/in spring rate that seats at 135 lbs. The 1217X spring was a three valve spring that is used with a special PAC retainer to increase the installed height to 1.530" if I recall correctly. The PAC retainer is their R346 retainer that adds 0.060" to the installed height allowing you to get to the 1.530" installed height spec. I personally use this spring because of the 135 lbs seat pressure on th intakes. When yo use the 1217X spring on the intake you still use the 1223 spring on the exhaust.

    For a while, although not currently, Pac offered a 1523 spring which was a nitrided version of the 1223 spring. The 1523 spring is a toughened 1223 spring that seats at 101 lbs. To my knowledge they no longer offer this spring but might make a set on a special order basis. By and large the cost does not warrant the effort. The 1223 and 1217X offerings do an excellent job.

    Spring retainers required are PAC because their springs are narrower at the top than OEM. The 1223 springs need a PAC R312 retainer and the 1217X springs need a PAC R346 retainer. The retainers are steel, pretty inexpensive and super light. I believe mine were 5 grams and 6 grams each.


    Ed


    p.s. As a cheapo first step, you might want to try an NGK TR6. I know they send proletariate but they just seem to work everywhere, all the time. If by chance they seem too warm go down one step to a TR7. I think you might be surprised at how well the TR6 plugs perform.
    Last edited by eschaider; 08-19-2019 at 12:28 PM. Reason: Added Postscript

  4. #3

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    I was a bit confused when you said you were using NGK BKR7 plugs. When I looked up the plug to confirm my suspicions, I could not find an NGK BKR7 plug but NGK did show a BKR7E plug that looks like this,

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    This plug does not have a taper seat, does not have a projected tip and is 0.750" long. Additionally the body diameter is larger than the TR6 plug and probably would not properly register in the plug well.

    On the other hand the NGK TR6 plug that looks like this,

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    does have a tapered seat, does have a projected tip and is 0.705" long. The smaller body diameter of the TR6 plugs is designed to properly register in the 4V head's plug well.

    I suspect you are using the wrong plug. Before spending any money on anything else I would put in a set of NGK TR6 plugs and see how the engine behaves.


    Ed

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  6. #4

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    NGK Br7ef (3346), sorry had a brain fart. 7 heat range non projected tip

  7. #5

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    The NGK sparkplug design symbols page image below says a BR7EF plug is ⅝" hex (BR), 7 heat range (7), ¾" reach (E), tapered seat (F) plug. Because of their naming convention the "E" and the "F" in the plug designation could be "EF" which would call out a 0.705" reach plug which is the correct reach for our heads.

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    The non projected tip will hamper combustion efficiency at higher engine speeds. You would be well served to use a projected tip TR6 (preferred) or TR7 (colder) plug. The plugs you are using will not perform as well as the proletariate BR6/BR7 alternatives. It is surprising how helpful the projected tip can actually be in mitigating high speed misses. The plug change is the cheap litmus test that is easy to do — worth the effort.


    Ed

  8. #6

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    I was just a bit leary of projected tip plugs with boost. I ran into problems on a previous sbf e85 RHS headed combo. the strap was so far into the chamber she would det long before peak timing. after putting in non projected plugs I was able to feed it more timing and make an extra chunk of power because of it. Also found non proj plugs dealt better with spark blowout on my sbf and sbc combo's. Obviously the 4v head/chamber is a bit more efficient and likely won't have the same issue. But I plan to push north of 25lb down it's throat and liked the added safety margin of non projected plugs on hot summer days when intake air temp push north of 140-150* on 1/4mile plus pulls and that ground strap is glowing red.

    I might try the tr7's when I put in my next set of plugs and try them out.

    I just got my replacement fuel filter in the mail and installed. Been raining last 2 days, but plan to try the br7ef at .020" on stock coils ramping dwell from around 1.7-2.0ms up to 3.0ms at high boost/high rpm. I going to jump to d585's either way, but if she does ok on these, I will finish out the season the the stock coils.

  9. #7

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    also on the springs. pac said the 1217x at 1.550" is 130lb seat pressure. I'm not sure what the stock installed height on the 04 aviators heads (between 1.420 and 1.470 from what I can find online) So if I get +.060" from the r346 retainers, I would be close if im near the larger end of 1.470 stock (1.530" with retainer) but would be way off if mine are near the bottom end at 1.420". If they end up being to short and are giving me way more seat pressure than i need and also closer to coil bind, what can be done to correct this other than cutting spring seats?

  10. #8

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    Quote Originally Posted by cpask8 View Post
    I was just a bit leary of projected tip plugs with boost. I ran into problems on a previous sbf e85 RHS headed combo. the strap was so far into the chamber she would det long before peak timing. after putting in non projected plugs I was able to feed it more timing and make an extra chunk of power because of it. Also found non proj plugs dealt better with spark blowout on my sbf and sbc combo's. Obviously the 4v head/chamber is a bit more efficient and likely won't have the same issue. But I plan to push north of 25lb down it's throat and liked the added safety margin of non projected plugs on hot summer days when intake air temp push north of 140-150* on 1/4mile plus pulls and that ground strap is glowing red.

    I might try the tr7's when I put in my next set of plugs and try them out.

    I just got my replacement fuel filter in the mail and installed. Been raining last 2 days, but plan to try the br7ef at .020" on stock coils ramping dwell from around 1.7-2.0ms up to 3.0ms at high boost/high rpm. I going to jump to d585's either way, but if she does ok on these, I will finish out the season the the stock coils.

    There are many guys running projected tip plugs in these engines that are well above the boost and power levels you are anticipating running and they do it without any strap induced preignition events. That said it is your engine and you are entitled to do with it as you best see fit.

    A 3 ms dwell time on the stock cops will not improve the coil output. The problem is not a saturation problem it is a design problem. In a coil once the field is created and fully saturates the coil there is no benefit to increasing dwell time. You can not achieve more than a 100% field saturation. The problem is the OEM cop design is at best a 20 mj energy output. That level of spark is unsuitable for a boosted chamber especially with a non projected tip plug. You need more spark energy. The best way to do that is with a higher output coil.

    BTW a 3ms dwell time on OEM cops is self destructive. It will overheat the coil in the cop eventually boil the oil inside bursting the plastic housing encasing the coil and kill the cop while making a mess.

    Coil alternatives are smart with built in igniters or dumb with external igniters. Ford used dumb with the igniters integrated into the ECU electronics. That means the IGN1-A high output coils are not an option with the stock ECU. The dumb IGN1 coil (not 1-A) see pic below

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    will provide 118 mj of spark energy which exceeds even the highly vaunted IGN1-A coils that 'only' produce 103 mj of spark energy. Then of course there is the price, IGN1-A's are $71 and IGN1's are $48.

    As a general rule of thumb if you are causing the side strap to glow red your engine is too lean. Continued operation like that will cost you pistons. Changing to a colder range plug does not impact the side strap temperature, it only impacts the center electrode and porcelain core temperature. If a T/F engine can safely run with projected tip plugs there is no reason why you can not — other than you are doing something wrong in your fueling model.


    Ed
    Last edited by eschaider; 08-27-2019 at 01:26 PM. Reason: Fixed Broken Pic Link

  11. #9

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    Quote Originally Posted by cpask8 View Post
    also on the springs. pac said the 1217x at 1.550" is 130lb seat pressure. I'm not sure what the stock installed height on the 04 aviators heads (between 1.420 and 1.470 from what I can find online) So if I get +.060" from the r346 retainers, I would be close if im near the larger end of 1.470 stock (1.530" with retainer) but would be way off if mine are near the bottom end at 1.420". If they end up being to short and are giving me way more seat pressure than i need and also closer to coil bind, what can be done to correct this other than cutting spring seats?

    Springs can move around a few percent in terms of load from batch to batch. That said, the correct installed height for the 1217X springs is the stock 1.470 spring height plus 0.060" for the PAC R346 retainer, bringing the correct installed height to 1.530".

    Using PAC's published spring rate data from their catalog the 1217X springs have 130 lbs of spring pressure at an installed height of 1.550". When you reduce the spring installed height to 1.500" the spring pressure climbs to 146 lbs — per PAC's published specs. What this means, when they are installed at 1.530", is that you are 40% of the way to 1.500" you will pick up 40% of the incremental pressure increase of 16 lbs. As luck would have it 40% of 16 lbs is 6.4 lbs. When you add 6.4lbs to 130 you get 136 lbs. 'Springs can move around a percent or so in terms of load from batch to batch.'.

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    When you speak with telephone support personnel at a manufacturer you need to be both clear in your questioning and also aware that the person you are talking to is most likely not as smart about what you are inquiring about as you are! In fact he could easily have been packing groceries at Safeway last week and today he is a trusted performance advisor at your vendor of choice.

    You need to learn about the technology you are using, learn how to read and interpret the technical data and specifications that the designers of the products have published for your use and then deploy the product(s) in the manner the original product designers (who you rarely, if ever, get to talk to) intended them to be used.

    If this sort of regimen is a bridge too far, then you need to start looking for a good engine builder to do the work for you. Things as proletariate as valve springs are the tip of a very large ice berg that you are currently on a collision course with. It is best not to hit the iceberg ...



    Ed


    p.s. Your spring seats will come in at 1.470"
    Last edited by eschaider; 08-27-2019 at 03:16 PM. Reason: Added Postscript

  12. #10

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    Man you are a wealth of knowledge, and like a mod motor walking encyclopedia haha, I really appreciate the guidance. I learn as I go with this stuff, but i've put together every piece on this build and have made some mistakes along the way, but have a couple high 9 sec 1/4's timeslip as payoff so far.

    If I had the money to spend, I would for sure have ign-1a's already on it, but i'm trying to have fun and go fast on a shoe string budget. That doesn't always work out, but I promise you I will get this thing lined out and into the 8's by next year.

    I plan to get some junkyard d585 ls truck coils and run them off my ms3x ecu. Springs and retainers will be bought over the course of a month as money permits, and then over the winter ill pull the motor down and and swap springs out. I picked up a th400 to put together w/trans brake vb and a nice converter to go with so come spring next year, i hope to have her running 100% and shooting for 8's.

  13. #11

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    When purchased new, the ING1 coils are about $48 and the wiring pigtail is around another $6 or $7 per coil. New D585 coils go for anywhere between about $26 and $97. I am not familiar enough with the coils to explain the difference. My suspicion is that the lower the price the lower the quality and vice versa. That said I think somewhere in the middle ground you should be able to get good performance and also good life. The upshot is that the d585 coil is very likely a push with the IGN1 coil both from a performance perspective and also from a pricing perspective.

    Two of the guys on the forum have used the d585 coils in the past and in their implementations built extensions to allow them to fit down into the OEM plug wells and connect to the plugs. The coil tops protruded through windows they cut in the top of the coil covers to allow both cooling and electrical connections.

    I would have some reservations about salvage yard coils, especially when you can get brand new GM manufactured coils from Amazon for about $30. I recall seeing one offer below the $30 price point and it was for new original equipment AC Delco branded coils. Be cautious of used salvage yard ignition components. They can be the origin of difficult to track down electrical and performance gremlins.


    Ed

  14. #12

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    Yeah I checked out the 2 threads of people mounting the ls coils. That's pretty neat how he got them down in there almost like the factory ford pencil coils on the 4v. I likely wont get that involved, but build a nice bracket to keep them secure. Can you recommend any particular plug wire? I'll likely need to build my own.


    From what i've read the cheap d585 coils on amazon and ebay are terrible compared to factory installed d585's. The cheap new ones have a black epoxy where as the original gm ones have a white epoxy. Supposedly the black epoxy ones suck and dont put out near the power the good gm ones do. There is a video on youtube somewhere, where a guy was testing the output of one of them cheap amazon type d585's and it was like half or less the output of a gm/delco d585.

    Ive seen some ac delco d585's on amazon for cheap, but in the reviews people said they were receiving the black epoxy/cheap replacement ones and not the white epoxy 585's that the ad shows in the pictures. I can get 8 coils and wiring for around $40 from my local pick n pull. I may grab two sets just to have spares, but the gm coils seem to hold up pretty good.

    Everyone says to keep the dwell under 4.5ms on the d585's to avoid it discharging at the wrong time. So plan to keep em around 4.0ms around peak rpm/boost. I'll give the junkyard coils a go, and if they dont work/hold up, i'll have ya tell me "i told ya so" haha, and i'll somehow work the ign-1a into my budget.

  15. #13

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    Don't forget once the magnetic field is at full strength throwing additional time at the coil charging function does no good only bad and the bad eventually boils the oil and breaks the plastic enclosures. It is better to run more voltage at a 3ms or shorter duration than to crank up the duration at a lower voltage — think Boost-a-Spark.

    The best wires are the MSD Pro-Stock wires for Chrysler and Ford Pro-Stock engines. Here is the link at Jegs, click here => MSD Wires The plug ends are already on and the MSD plastic extraction tubes are length adjustable and make installation and removal a breeze. The coil side uses very robust crimp on ends and corresponding boots.


    Ed

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