johny Posted March 18, 2019 Report Share Posted March 18, 2019 Can anyone tell me how the ignition HT circuit is completed? I want to understand the route the spark takes to return to the secondary circuit in the coil after jumping the spark plug gap. It appears it doesnt return via the coil casing but through its 12v +ve terminal as this is connected internally to both the primary AND secondary windings!!!!! Link to comment Share on other sites More sharing options...
NonMember Posted March 18, 2019 Report Share Posted March 18, 2019 I'm sure I've just seen that question on another forum... Yes, the circuit is completed through the +ve terminal. It's possible to run the engine with the coil not bolted down, even stuck in a plastic bag. Link to comment Share on other sites More sharing options...
johny Posted March 18, 2019 Author Report Share Posted March 18, 2019 Thanks yes I didnt think I was going to get a response on the other forum so tried on here and have now had answers on both which fortunately agree! It looks like the car battery is used for the return from the spark plugs and I wonder if thats why many years ago vehicle electrics changed over to -ve earth.... Link to comment Share on other sites More sharing options...
Pete Lewis Posted March 18, 2019 Report Share Posted March 18, 2019 neg earth was more to solve corrosion , pete Link to comment Share on other sites More sharing options...
SpitFire6 Posted March 31, 2019 Report Share Posted March 31, 2019 On 18/03/2019 at 16:49, Pete Lewis said: neg earth was more to solve corrosion , pete Hi Pete, Are you talking about HT electrode corrosion or body corrosion? Would be interested in any available data that confirms that. Cheers, Iain. Link to comment Share on other sites More sharing options...
poppyman Posted March 31, 2019 Report Share Posted March 31, 2019 It was battery and earth to body corrosion Iain. It was common place in the early days of possitive earth cars to have a mound of green stuff growing around the battery.... Boiling water was the only way to clean it off, and then vaseline or grease to try and stop it coming again. Dont know why it does'nt happen to neg earth though? Tony. Link to comment Share on other sites More sharing options...
johny Posted April 1, 2019 Author Report Share Posted April 1, 2019 Believe its to do with the direction of current flow as each electron (which being negatively charged actually flow from -ve to +ve) can take with them a microscopic piece of the metal it leaves. This causes metal to be depleted on one side of the connection and deposited on the other which means one loses its protective surface and is open to corrosion. So by carefully selecting the connector material and having the electrons flow in the right direction using neg earth the effects of this process can be avoided..... Link to comment Share on other sites More sharing options...
Pete Lewis Posted April 1, 2019 Report Share Posted April 1, 2019 easy..............it has a hatred of vaseline having lumps of different metals bolted on like ships , anodes and cathodes all a bit doctor who stuff. pete Link to comment Share on other sites More sharing options...
SpitFire6 Posted April 1, 2019 Report Share Posted April 1, 2019 Hi, sacrificial Anodes on boats & platforms work a treat. Buried pipelines work great with impressed current, like having a battery connected to a car chassis, work well with monitoring. So if you drive your car underwater or underground & get the current flow correct you will have zero corrosion. Not practical for a car? Cheers, Iain. Link to comment Share on other sites More sharing options...
Pete Lewis Posted April 2, 2019 Report Share Posted April 2, 2019 you can get voltage off some tooth fillings ,.................. doesnt help the car much Pete Link to comment Share on other sites More sharing options...
SpitFire6 Posted April 2, 2019 Report Share Posted April 2, 2019 KitKat foil and an amalgam filling. Loverly. 1 Link to comment Share on other sites More sharing options...
SpitFire6 Posted April 2, 2019 Report Share Posted April 2, 2019 On 18/03/2019 at 16:47, johny said: Thanks yes I didnt think I was going to get a response on the other forum so tried on here and have now had answers on both which fortunately agree! It looks like the car battery is used for the return from the spark plugs and I wonder if thats why many years ago vehicle electrics changed over to -ve earth.... Hi, to answer your question about spark plugs. The spark is always designed to jump from the centre as this is the hottest of the two surfaces. Lower HT volts are required. The ignition coil has three terminals but 2 internal coils like the transformer it is. Primary is always the screw or push on terminals. Secondary step-up is the tower & one of the primary terminals. The HT to + or - dictates the coil polarity. Ignition coils are made for positive ground or negative ground vehicles. (Nothing to do with voltage or ballast.) It's good our cars are -ve ground; Better & cheaper automotive electtornic stuff. Cheers, Iain Link to comment Share on other sites More sharing options...
poppyman Posted April 2, 2019 Report Share Posted April 2, 2019 1 hour ago, Spitfire6 said: KitKat foil and an amalgam filling. Loverly. Why did you have to mention that........... Aaaaaargh!! 1 Link to comment Share on other sites More sharing options...
SpitFire6 Posted April 2, 2019 Report Share Posted April 2, 2019 Is it safe? Link to comment Share on other sites More sharing options...
SpitFire6 Posted April 2, 2019 Report Share Posted April 2, 2019 Is it safe? Link to comment Share on other sites More sharing options...
Adrian Cooper Posted April 2, 2019 Report Share Posted April 2, 2019 1 hour ago, Spitfire6 said: Is it safe? This could turn into a marathon... 1 Link to comment Share on other sites More sharing options...
JohnD Posted April 3, 2019 Report Share Posted April 3, 2019 10 hours ago, Spitfire6 said: The spark is always designed to jump from the centre as this is the hottest of the two surfaces. Lower HT volts are required. Cheers, Iain I'd hate to confuse anyone (actually, I love it!) but which way does the spark jump? An electric charge is an accumulation of electrons that are negatively charged. An electric current is the flow of those electrons. But our cars have a negative earth, and the charge applied to a spark plug is an electron 'vacuum', a lack of electrons. When the spark happens, a flood of electrons move onto the centre electrode, from the earthed block. We automatically think of a current moving from plus to minus, but in fact the electrons flow in the opposite direction. John Link to comment Share on other sites More sharing options...
johny Posted April 3, 2019 Author Report Share Posted April 3, 2019 yes it must be electrons jumping from the earth post to the centre electrode of the sparkplugs and subsequently its the earth post that gets gradually eroded away opening up the gap.... Link to comment Share on other sites More sharing options...
NonMember Posted April 3, 2019 Report Share Posted April 3, 2019 No, it's electrons jumping from the centre. Whether the vehicle system is positive or negative earth you always fit the type of coil that produces a NEGATIVE HT. Link to comment Share on other sites More sharing options...
SpitFire6 Posted April 3, 2019 Report Share Posted April 3, 2019 Hi, Forgot to say that the electrons will travel from center to earth electrode on a normal/correct coil. With wasted/spark/ distributor-less system. (But not COP); half the plugs are reverse fired; electrons flow from the ground to center. Plugs firing from the ground electrode will wear out faster & precious metals on the center electrode serve no purpose. Precious metals on both electrodes are available at a cost. Cheers, Iain. 1 Link to comment Share on other sites More sharing options...
NonMember Posted April 3, 2019 Report Share Posted April 3, 2019 Yes, thanks Iain, I remembered about wasted spark just after posting my last reply... Link to comment Share on other sites More sharing options...
johny Posted April 3, 2019 Author Report Share Posted April 3, 2019 Thats interesting as the HT electrons must then flow the opposite way through the battery on their way back to the .coil. Nothing to stop em going both ways through the battery I suppose.... Link to comment Share on other sites More sharing options...
SpitFire6 Posted April 6, 2019 Report Share Posted April 6, 2019 On 03/04/2019 at 11:39, johny said: Thats interesting as the HT electrons must then flow the opposite way through the battery on their way back to the .coil. Nothing to stop em going both ways through the battery I suppose.... Hi Johny, Anode & cathode could be + or -, it depends on what the subject is. But, Electrons Always go from negative to positive. Cheers, Iain. Link to comment Share on other sites More sharing options...
johny Posted April 6, 2019 Author Report Share Posted April 6, 2019 if the theory we have got so far is correct the battery plates must be both anode and cathode at the same time so that the HT electrons can flow from -ve to +ve and 12v electrons go in the opposite direction😵 Link to comment Share on other sites More sharing options...
NonMember Posted April 7, 2019 Report Share Posted April 7, 2019 Normally, a battery "sucks in" electrons at the +ve terminal an pushes them out of the -ve one. This provides the electric current from +ve to -ve that you expect. But what about when you're charging the battery? In this case the current flows into the +ve, meaning electrons are flowing out from it. So yes, batteries can have the electrons going both ways. Link to comment Share on other sites More sharing options...
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