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| nannas_ed |
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I was thinking of replacing my standard I6 coil with a coil of an XR8. firstly is there any difference in the two and secondly would there be any benifit from doing this. if any one has done this or knows anything about this please share your thoughts.
thanks
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| Waggin |
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Not really. The V8's cylinder capcity is actually less than the 4L, so theres actually less spark requirement. Maybe the 4L coil is bigger/better, or they could be almost the same.
If you want some serious spark, look aftermarket, like MSD.
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| msman |
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does an after market coil help, on a resonably stock car.
i.e. does it idle smoother rev freer go harder. would the leads and plugs handle the extra spark. i.e. ngk plugs and topgun heavy duty, iknow iknow i couldn't find ngk and evry one was outa boschleads. not tryin to hijack thread.
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| xdv8 |
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essentially what an aftermarket setup will do is produce a bigger spark which in theory burn the fuel quickly and efficiently, so therefore more of the fuel in the combustion chamber is going to burn. this means a more efficient engine. if you upgade to an msd ignition, or any other, you will find they recommend you upgrade the secondary side to the same level(plugs, leads, etc). i dont think you will find a marked improvement on a standard car, but start modifing with a standard setup, then switching to aftermarket, then you will start to notice
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| Bozz |
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xdv8 wrote: essentially what an aftermarket setup will do is produce a bigger spark which in theory burn the fuel quickly and efficiently, so therefore more of the fuel in the combustion chamber is going to burn. this means a more efficient engine. if you upgade to an msd ignition, or any other, you will find they recommend you upgrade the secondary side to the same level(plugs, leads, etc). i dont think you will find a marked improvement on a standard car, but start modifing with a standard setup, then switching to aftermarket, then you will start to notice
Tell me how this is possible? The flame front travels at a constant speed which is approximately two meters per second, give or take for various fuels. So you've ignited the fuel with a 20,000v spark or a 50,000v spark. How is it going to make a difference because it's already burning. Snake oil my friends. You need an upgraded coil if you are running serious revs (7000rpm plus - euro/jap performance motors, not a ford single cam i6) or running very high cylinder pressures (greater than 10:1 CR or forced induction) where a higher voltage is required to break a specific distance. You theoretically could get a performance improvement by widening the spark plug gap more than the 1.1mm factory setting and getting a bigger coil to give sufficient voltage to arc the gap. |
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| xdv8 |
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contrary to popular belief, when the mixture in the cylinder is ignited, not all the fuel gets burnt. also the vehicle manifacturer uses the cheapest option available. so when the mixture is ignited, more of the gases are burnt when using quality aftermarket components. think of it like an amp for your spark. if what you say is true, then why are more and more vehicle brands changing to coil-per-cylinder setup?
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| tickford_6 |
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Posts: 6449 Joined: 11th Nov 2004 |
contrary to popular belief, you coil does not produce it's max voltage all the time.
it only produces the voltage needed to jump the spark gap. so a 20,000v stock coil may perform the same as an expansive 60 000 or 80 000v coil, because the higher voltage coil would be overkill for the engine. you really only need a higher output coil when you stock one can no longer produce enough voltage to jump the gap. things like cylinder pressure and feul type have a bearing on how much voltage is needed |
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| Bozz |
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xdv8 wrote: contrary to popular belief, when the mixture in the cylinder is ignited, not all the fuel gets burnt. also the vehicle manifacturer uses the cheapest option available. so when the mixture is ignited, more of the gases are burnt when using quality aftermarket components. think of it like an amp for your spark. if what you say is true, then why are more and more vehicle brands changing to coil-per-cylinder setup?
tickford_6 is on the money Why do high performance vehicles use multicoil setups? Didn't I outline it in the post above? High revs and high boost - Lets use an engine family i'm very familiar with - the Nissan RB/SR series - these engines rev their tits off, over 7000RPM reliably, daily, out of the box, produce s**t of power out of bugger all capacity and have very high in-cylinder pressures. Ten points for guessing why they use multicoil setups. As tickford_6 said above, an uprated coil will have SFA improvement unless the factory system is inadequate. This only shows up under high cylinder pressures (WOT) and at high RPM when the coil does not physically have enough time to recharge. Neither of these are a problem in the crude 4 litre I6 in the Fords, WRT a high performance engine. |
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| xdv8 |
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ok, lets go to my original statment. i doubt that you would find any improvment in a standard engine, no matter what brand it was. second, i dont think that the chevs in the new commodores are a high reving engine, but still use the coil per cylinder idea. third, just to put the theory to the test, get two batteries, one a 6 volt, the second a 12 volt. connect these to light circuit one at a time. first the 6, the bulb lights up wthout a problem. then the 12. also lights up the bulb, but is alot brighter than the 6 volt battery. the same applies to the aftermarket coils. regardless of what you say, thsi how it is.
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| tickford_6 |
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Posts: 6449 Joined: 11th Nov 2004 |
xdv8 wrote: ok, lets go to my original statment. i doubt that you would find any improvment in a standard engine, no matter what brand it was. second, i dont think that the chevs in the new commodores are a high reving engine, but still use the coil per cylinder idea. third, just to put the theory to the test, get two batteries, one a 6 volt, the second a 12 volt. connect these to light circuit one at a time. first the 6, the bulb lights up wthout a problem. then the 12. also lights up the bulb, but is alot brighter than the 6 volt battery. the same applies to the aftermarket coils. regardless of what you say, thsi how it is.
i don't think you fully understand how the ignition system in a car works a light bulb in no way at all works the same way. if you realy want to test it get some voltage test gear and a few spark plugs. set one with 0.1mm gap and check what voltage the coils makes now set it at 2mm or 3mm and see wat voltage is made. then in stages open the gap up untill the spark no longer jumps the gap. you'll find more voltage is made with bigger gaps. not 20 000v (or what ever your coil is rated) with every gap. the same thing happens in your engine. higher cylinder pressures make it harder for the spark to jump the gap so more voltage is created in the coil. you only need a high out put coil if your stock one can not keep up. but if you think your right finr go out and waste money one someting you might not need. the more you spend in performance parts the more money we make of fools that don't know what they are talking about |
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| Bozz |
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xdv8 I wont insult your stubborn persistance to prove your lack of electrical knowledge but I'll write a bit more to help prevent other people being ripped off.
A spark is an electrical short circuit - maximum current flows through it. As soon as the spark begins to arc the gap, it is completely identical to simply having put a piece of wire from one side to the other. It is obvious what will happen now. The peak voltage has already been acheived a poofteenth of a second BEFORE the spark occured, by having a spark, it immediately drops the voltage a bit and allows a current to flow, how much flows depends on things like leads, coil impedance and a few other factors. Regards, Bozz. Qualified Electronics Engineer. |
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| nannas_ed |
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hey thanks everyone for your input, from what ive read there is very little or no point in changing my coil, so i think i will put my money towards some 9.0mm leads and a set of decent plugs. thanks again
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| 66 coupe |
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Upgrading the Ignition WILL make a difference.
Upgrading to a Multi Spark ignition will make a greater difference such as MSD 6AL or Crane HI-6 or simular - as Waggin suggested. You can use one of these with the standard I6 coil and have excelllent results The standard coil fires a plug with a 1.1mm gap. With CDI you can open the spark plug gaps more, which will result in a more efficient burn. You will notice immediately that the car will idle smoother, and gain some low down torque. It is stated in the majority of the multispark ignition instruction books to retard the timing 1 or 2* when fitting a CD Multispark ignition, because it results in a faster, more powerful burn, it can tend to make the car ping. |
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| Dellboy999 |
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8mm leads are as big as you would possibly ever need to go in a stockish motor any bigger is wasting your money, unless you think they look really cool, and for all the reasons stated above, big leads can carry a big voltage, so if you dont need big voltage dont bother, stock is 6mm leads, so going to 8mm is over kill anyways but some improvement is to be had.
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| 4.9 EF Futura |
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Awesome read guys.
So, regarding the aftermarket ignistion systems - its not actually the increased voltage which benefits a stock engine.... it's the fact that they fire the spark more than once for every ignition stroke? And I guess its fair to assume the extra voltage is merely there for 'headroom' ? So regarding the need for upgraded coil for a high revving engine... is this a result of the fact that coil needs to 'recharge' between firing each spark? (is this dwell?)... ie. if you're engine is going to 8000rpm, there's a good chance the factory coil wont be able to recharge quick enough for each spark?
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