Tin foil on HT lead
Discussion
Ok, so I'm slowly getting used to my (new to me) Chim. It currently has B7ECS plugs and after reading all the debates I will be changing them for the BPR6ES plugs (they are really carbon fouled). Nevertheless, my question is about the HT leads. Mine have heat socks and what looks like tin foil wrapped around the plug end (no plug extenders). Anyone seen this sort of set-up before, is it useful? It's currently got what looks like standard Landrover HT leads and I've no idea how old these are. Anyone know what the resistance should be in them? IS there a better upgrade (I haven't read those debates yet, the spark plug took forever 
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)Edited by dalecan on Sunday 3rd April 04:04
SteveR1979 said:
The resistance is in the extenders.
Lose the plug extenders, you need the resistive plugs
Whilst I know this to be the case, I do know that owners don't always follow or even know this, but I don't hear them having any issues either. So, question is, what harm occurs as a result of not fitting resistive plugs?Lose the plug extenders, you need the resistive plugs
Its all a matter of some compromise. Think about it- you have HT leads that are resistive but they are different lengths so have different resistances to start with anyway. The resistance is there to slow down the discharge rate of the coil as the arc is basically a short circuit once it starts. If you have a low resistance path the spark is very short duration and very hot- BUT in the process as the coils magnetic field collapses rapidly on the secondary windings, it also cuts across the primary windings. This makes for a high voltage spike back onto primary coil connection on the 12v side and can glitch both rev counters and surrounding electronics. This could make the difference between say an 80v spike or a 200 v spike and you really dont want high voltages and radio interference - so resistance is added to the secondary circuit . Things like after market ECUS may be more effected by the glitches than the tough old 14CUX so some installations may add extra resistance to stop them being affected by the back EMF.
So hopefully if you don't have daft Magnecore race type leads you should have enough resistance in the HT leads to keep things sweet on their own. You can get away with adding a bit more resistance in the extenders if you wish, but as the resistance goes up the spark looses energy so if you added resistive plugs its likely a step too far and you may end up with a misfire as the engine RPM rises hand the available peak HT from the coil drops as the dwell gets to short for the coil to recover between firing. Its a tall ask for a coil to charge fully on a V8 at over about 5000 RPM as the dwell period is so short.
If you have the inductive type (Magnecore) leads then the overall resistance may become too low, so you have to add back some with R type plugs that completely over rides the idea that expensive low resistance HT leads will some how turn your Lazy V8 into a racing motor of some sort.
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So hopefully if you don't have daft Magnecore race type leads you should have enough resistance in the HT leads to keep things sweet on their own. You can get away with adding a bit more resistance in the extenders if you wish, but as the resistance goes up the spark looses energy so if you added resistive plugs its likely a step too far and you may end up with a misfire as the engine RPM rises hand the available peak HT from the coil drops as the dwell gets to short for the coil to recover between firing. Its a tall ask for a coil to charge fully on a V8 at over about 5000 RPM as the dwell period is so short.
If you have the inductive type (Magnecore) leads then the overall resistance may become too low, so you have to add back some with R type plugs that completely over rides the idea that expensive low resistance HT leads will some how turn your Lazy V8 into a racing motor of some sort.
.Edited by blitzracing on Monday 4th April 19:26
SteveR1979 said:
The resistance is in the extenders.
Lose the plug extenders, you need the resistive plugs
NO, you dont...as the common HT leads already have a resistance built-in....TVR design mistake from the begnning:Lose the plug extenders, you need the resistive plugs
Resistance HT Leads, Resistance plug-extenders, non-resistance plugs.
resistance in the HT circuit is mainly used to suppress electronic-noise, electronic-impact into the car´s other electronic devices, mainly the stereo (radio)
Edited by LLantrisant on Tuesday 5th April 23:30
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